Publications by authors named "Marcelo Menossi"

49 Publications

Amino Acid and Carbohydrate Metabolism Are Coordinated to Maintain Energetic Balance during Drought in Sugarcane.

Int J Mol Sci 2020 Nov 30;21(23). Epub 2020 Nov 30.

Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP 05508-000, Brazil.

The ability to expand crop plantations without irrigation is a major goal to increase agriculture sustainability. To achieve this end, we need to understand the mechanisms that govern plant growth responses under drought conditions. In this study, we combined physiological, transcriptomic, and genomic data to provide a comprehensive picture of drought and recovery responses in the leaves and roots of sugarcane. Transcriptomic profiling using oligoarrays and RNA-seq identified 2898 (out of 21,902) and 46,062 (out of 373,869) transcripts as differentially expressed, respectively. Co-expression analysis revealed modules enriched in photosynthesis, small molecule metabolism, alpha-amino acid metabolism, trehalose biosynthesis, serine family amino acid metabolism, and carbohydrate transport. Together, our findings reveal that carbohydrate metabolism is coordinated with the degradation of amino acids to provide carbon skeletons to the tricarboxylic acid cycle. This coordination may help to maintain energetic balance during drought stress adaptation, facilitating recovery after the stress is alleviated. Our results shed light on candidate regulatory elements and pave the way to biotechnology strategies towards the development of drought-tolerant sugarcane plants.
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http://dx.doi.org/10.3390/ijms21239124DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7729667PMC
November 2020

Plant 3' Regulatory Regions From mRNA-Encoding Genes and Their Uses to Modulate Expression.

Front Plant Sci 2020 14;11:1252. Epub 2020 Aug 14.

Functional Genome Laboratory, Department of Genetics, Evolution, Microbiology, and Immunology, Institute of Biology, University of Campinas - UNICAMP, Campinas, Brazil.

Molecular biotechnology has made it possible to explore the potential of plants for different purposes. The 3' regulatory regions have a great diversity of -regulatory elements directly involved in polyadenylation, stability, transport and mRNA translation, essential to achieve the desired levels of gene expression. A complex interaction between the cleavage and polyadenylation molecular complex and -elements determine the polyadenylation site, which may result in the choice of non-canonical sites, resulting in alternative polyadenylation events, involved in the regulation of more than 80% of the genes expressed in plants. In addition, after transcription, a wide array of RNA-binding proteins interacts with -acting elements located mainly in the 3' untranslated region, determining the fate of mRNAs in eukaryotic cells. Although a small number of 3' regulatory regions have been identified and validated so far, many studies have shown that plant 3' regulatory regions have a higher potential to regulate gene expression in plants compared to widely used 3' regulatory regions, such as and from and from cauliflower mosaic virus. In this review, we discuss the role of 3' regulatory regions in gene expression, and the superior potential that plant 3' regulatory regions have compared to and 3' regulatory regions.
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http://dx.doi.org/10.3389/fpls.2020.01252DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7457121PMC
August 2020

Bringing to light the molecular evolution of GUX genes in plants.

Genet Mol Biol 2020 23;43(1):e20180208. Epub 2020 Mar 23.

Universidade Estadual de Campinas, Instituto de Biologia, Departamento de Genética, Evolução, Microbiologia e Imunologia, Campinas, SP, Brazil.

Hemicellulose and cellulose are essential polysaccharides for plant development and major components of cell wall. They are also an important energy source for the production of ethanol from plant biomass, but their conversion to fermentable sugars is hindered by the complex structure of cell walls. The glucuronic acid substitution of xylan (GUX) enzymes attach glucuronic acid to xylan, a major component of hemicellulose, decreasing the efficiency of enzymes used for ethanol production. Since loss-of-function gux mutants of Arabidopsis thaliana enhance enzyme accessibility and cell wall digestion without adverse phenotypes, GUX genes are potential targets for genetically improving energy crops. However, comprehensive identification of GUX in important species and their evolutionary history are largely lacking. Here, we identified putative GUX proteins using hidden Markov model searches with the GT8 domain and a GUX-specific motif, and inferred the phylogenetic relationship of 18 species with Maximum likelihood and Bayesian approaches. Each species presented a variable number of GUX, and their evolution can be explained by a mixture of divergent, concerted and birth-and-death evolutionary models. This is the first broad insight into the evolution of GUX gene family in plants and will potentially guide genetic and functional studies in species used for biofuel production.
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http://dx.doi.org/10.1590/1678-4685-GMB-2018-0208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7198009PMC
March 2020

The C-Terminal Domains SnRK2 Box and ABA Box Have a Role in Sugarcane SnRK2s Auto-Activation and Activity.

Front Plant Sci 2019 17;10:1105. Epub 2019 Sep 17.

Centro de Química Medicinal (CQMED), Centro de Biologia Molecular e Engenharia Genética (CBMEG), Universidade Estadual de Campinas (UNICAMP), Campinas, Brazil.

Resistance to drought stress is fundamental to plant survival and development. Abscisic acid (ABA) is one of the major hormones involved in different types of abiotic and biotic stress responses. ABA intracellular signaling has been extensively explored in and occurs a phosphorylation cascade mediated by three related protein kinases, denominated SnRK2s (SNF1-related protein kinases). However, the role of ABA signaling and the biochemistry of SnRK2 in crop plants remains underexplored. Considering the importance of the ABA hormone in abiotic stress tolerance, here we investigated the regulatory mechanism of sugarcane SnRK2s-known as stress/ABA-activated protein kinases (SAPKs). The crystal structure of ScSAPK10 revealed the characteristic SnRK2 family architecture, in which the regulatory SnRK2 box interacts with the kinase domain αC helix. To study sugarcane SnRK2 regulation, we produced a series of mutants for the protein regulatory domains SnRK2 box and ABA box. Mutations in ScSAPK8 SnRK2 box aimed at perturbing its interaction with the protein kinase domain reduced protein kinase activity . On the other hand, mutations to ScSAPK ABA box did not impact protein kinase activity but did alter the protein autophosphorylation pattern. Taken together, our results demonstrate that both SnRK2 and ABA boxes might play a role in sugarcane SnRK2 function.
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http://dx.doi.org/10.3389/fpls.2019.01105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6759772PMC
September 2019

Overexpression of an evolutionarily conserved drought-responsive sugarcane gene enhances salinity and drought resilience.

Ann Bot 2019 10;124(4):691-700

Laboratório de Genoma Funcional, Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brazil.

Background And Aims: Improving drought adaptation is more pressing for crops such as sugarcane, rice, wheat and maize, given the high dependence of these crops on irrigation. One option for enhancing adaptation to water limitation in plants is by transgenic approaches. An increasing number of genes that are associated with mechanisms used by plants to cope with water scarcity have been discovered. Genes encoding proteins with unknown functions comprise a relevant fraction of the genes that are modulated by drought. We characterized a gene in response to environmental stresses to gain insight into the unknown fraction of the sugarcane genome. Scdr2 (Sugarcane drought-responsive 2) encodes a small protein and shares highly conserved sequences within monocots, dicots, algae and fungi.

Methods: Plants overexpressing the Scdr2 sugarcane gene were examined in response to salinity and drought. Measurements of the gas exchange parameters, germination rate, water content, dry mass and oxidative damage were performed. Seeds as well as juvenile plants were used to explore the resilience level of the transgenic plants when compared with wild-type plants.

Key Results: Overexpression of Scdr2 enhanced germination rates in tobacco seeds under drought and salinity conditions. Juvenile transgenic plants overexpressing Scdr2 and subjected to drought and salinity stresses showed higher photosynthesis levels, internal CO2 concentration and stomatal conductance, reduced accumulation of hydrogen peroxide in the leaves, no penalty for photosystem II and faster recovery after submission to both stress conditions. Respiration was not strongly affected by both stresses in the Scdr2 transgenic plants, whereas wild-type plants exhibited increased respiration rates.

Conclusions: Scdr2 is involved in the response mechanism to abiotic stresses. Higher levels of Scdr2 enhanced resilience to salinity and drought, and this protection correlated with reduced oxidative damage. Scdr2 confers, at the physiological level, advantages to climate limitations. Therefore, Scdr2 is a potential target for improving sugarcane resilience to abiotic stress.
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http://dx.doi.org/10.1093/aob/mcz044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6821327PMC
October 2019

Brassinosteroids, the Sixth Class of Phytohormones: A Molecular View from the Discovery to Hormonal Interactions in Plant Development and Stress Adaptation.

Int J Mol Sci 2019 Jan 15;20(2). Epub 2019 Jan 15.

Functional Genome Laboratory, Department of Genetics, Evolution, Microbiology and Immunology, Institute of Biology, State University of Campinas, Campinas 13083-970, Brazil.

Phytohormones are natural chemical messengers that play critical roles in the regulation of plant growth and development as well as responses to biotic and abiotic stress factors, maintaining plant homeostasis, and allowing adaptation to environmental changes. The discovery of a new class of phytohormones, the brassinosteroids (BRs), almost 40 years ago opened a new era for the studies of plant growth and development and introduced new perspectives in the regulation of agronomic traits through their use in agriculture. BRs are a group of hormones with significant growth regulatory activity that act independently and in conjunction with other phytohormones to control different BR-regulated activities. Genetic and molecular research has increased our understanding of how BRs and their cross-talk with other phytohormones control several physiological and developmental processes. The present article provides an overview of BRs' discovery as well as recent findings on their interactions with other phytohormones at the transcriptional and post-transcriptional levels, in addition to clarifying how their network works to modulate plant growth, development, and responses to biotic and abiotic stresses.
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http://dx.doi.org/10.3390/ijms20020331DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6359644PMC
January 2019

Transgenic Nicotiana tabacum seeds expressing the Mycobacterium tuberculosis Alanine- and Proline-rich antigen.

AMB Express 2018 Oct 31;8(1):178. Epub 2018 Oct 31.

Laboratório de Genoma Funcional, Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Rua Monteiro Lobato, 255, Barão Geraldo, PO. Box: 6109, Campinas, SP, 13083-970, Brazil.

The glycoprotein APA (Alanine- and Proline-rich Antigen, a 45/47 kDa antigen complex, Rv1860) is considered as a major immunodominant antigen secreted by M. tuberculosis. This antigen has proved to be highly immunogenic in experimental models and humans, presenting a significant potential for further development of a new vaccine for tuberculosis. Glycosylation plays a key role in the immunogenicity of the APA protein. Because plants are known to promote post-translational modification such as glycosylation and to be one of the most economic and safe hosts for recombinant protein expression, we have over expressed the APA protein in transgenic tobacco plants aiming to produce a glycosylated version of the protein. Seeds are known to be a well-suited organ to accumulate recombinant proteins, due to low protease activity and higher protein stability. We used a seed-specific promoter from sorghum, a signal peptide to target the protein to the endoplasmic reticulum and ultimately in the protein storage vacuoles. We show that the recombinant protein accumulated in the seeds had similar isoelectric point and molecular weight compared with the native protein. These findings demonstrate the ability of tobacco plants to produce glycosylated APA protein, opening the way for the development of secure, effective and versatile vaccines or therapeutic proteins against tuberculosis.
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http://dx.doi.org/10.1186/s13568-018-0708-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6209126PMC
October 2018

pGVG: a new Gateway-compatible vector for transformation of sugarcane and other monocot crops.

Genet Mol Biol 2018 Apr./Jun;41(2):450-454. Epub 2018 Jun 11.

Laboratório de Genoma Funcional, Universidade Estadual de Campinas, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Campinas, SP, Brazil.

The successful development of genetically engineered monocots using Agrobacterium-mediated transformation has created an increasing demand for compatible vectors. We have developed a new expression vector, pGVG, for efficient transformation and expression of different constructs for gene overexpression and silencing in sugarcane. The pCAMBIA2300 binary vector was modified by adding Gateway recombination sites for fast gene transfer between vectors and the maize polyubiquitin promoter Ubi-1 (ZmUbi1), which is known to drive high gene expression levels in monocots. Transformation efficiency using the pGVG vector reached up to 14 transgenic events per gram of transformed callus. Transgenic plants expressing the β-glucuronidase (GUS) reporter gene from pGVG showed high levels of GUS activity. qRT-PCR evaluations demonstrated success for both overexpression and hairpin-based silencing cassettes. Therefore, pGVG is suitable for plant transformation and subsequent applications for high-throughput production of stable transgenic sugarcane. The use of an expression cassette based on the ZmUbi1 promoter opens the possibility of using pGVG in other monocot species.
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http://dx.doi.org/10.1590/1678-4685-GMB-2017-0262DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6082244PMC
June 2018

ScGAI is a key regulator of culm development in sugarcane.

J Exp Bot 2018 07;69(16):3823-3837

Functional Genome Laboratory, Department of Genetics, Evolution and Bioagents, Institute of Biology, State University of Campinas, Campinas, Brazil.

Sugarcane contributes more than 70% of sugar production and is the second largest feedstock for ethanol production globally. Since sugar accumulates in sugarcane culms, culm biomass and sucrose content are the most commercially important traits. Despite extensive breeding, progress in both cane yield and sugar content remains very slow in most countries. We hypothesize that manipulating the genetic elements controlling culm growth will alter source-sink regulation and help break down the yield barriers. In this study, we investigate the role of sugarcane ScGAI, an ortholog of SLR1/D8/RHT1/GAI, on culm development and source-sink regulation through a combination of molecular techniques and transgenic strategies. We show that ScGAI is a key molecular regulator of culm growth and development. Changing ScGAI activity created substantial culm growth and carbon allocation changes for structural molecules and storage. ScGAI regulates spatio-temporal growth of sugarcane culm and leaf by interacting with ScPIF3/PIF4 and ethylene signaling elements ScEIN3/ScEIL1, and its action appears to be regulated by SUMOylation in leaf but not in the culm. Collectively, the remarkable culm growth variation observed suggests that ScGAI could be used as an effective molecular breeding target for breaking the slow yield gain in sugarcane.
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http://dx.doi.org/10.1093/jxb/ery180DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6054169PMC
July 2018

The FBH family of bHLH transcription factors controls ACC synthase expression in sugarcane.

J Exp Bot 2018 04;69(10):2511-2525

Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, CP, Campinas, SP, Brazil.

Ethylene is a phytohormone involved in the regulation of several aspects of plant development and in responses to biotic and abiotic stress. The effects of exogenous application of ethylene to sugarcane plants are well characterized as growth inhibition of immature internodes and stimulation of sucrose accumulation. However, the molecular network underlying the control of ethylene biosynthesis in sugarcane remains largely unknown. The chemical reaction catalyzed by 1-aminocyclopropane-1-carboxylic acid synthase (ACS) is an important rate-limiting step that regulates ethylene production in plants. In this work, using a yeast one-hybrid approach, we identified three basic helix-loop-helix (bHLH) transcription factors, homologs of Arabidopsis FBH (FLOWERING BHLH), that bind to the promoter of ScACS2 (Sugarcane ACS2), a sugarcane type 3 ACS isozyme gene. Protein-protein interaction assays showed that sugarcane FBH1 (ScFBH1), ScFBH2, and ScFBH3 form homo- and heterodimers in the nucleus. Gene expression analysis revealed that ScFBHs and ScACS2 transcripts are more abundant in maturing internodes during afternoon and night. In addition, Arabidopsis functional analysis demonstrated that FBH controls ethylene production by regulating transcript levels of ACS7, a homolog of ScACS2. These results indicate that ScFBHs transcriptionally regulate ethylene biosynthesis in maturing internodes of sugarcane.
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http://dx.doi.org/10.1093/jxb/ery083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5920332PMC
April 2018

Crystal structure and insights into the oligomeric state of UDP-glucose pyrophosphorylase from sugarcane.

PLoS One 2018 1;13(3):e0193667. Epub 2018 Mar 1.

Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.

UDP-glucose pyrophosphorylase (UGPase) is found in all organisms and catalyses the formation of UDP-glucose. In sugarcane, UDP-glucose is a branch-point in the carbon channelling into other carbohydrates, such as sucrose and cellulose, which are the major factors for sugarcane productivity. In most plants, UGPase has been described to be enzymatically active in the monomeric form, while in human and yeast, homo-octamers represent the active form of the protein. Here, we present the crystal structure of UGPase from sugarcane (ScUGPase-1) at resolution of 2.0 Å. The crystals of ScUGPase-1 reveal the presence of two molecules in the asymmetric unit and the multi-angle light scattering analysis shows that ScUGPase-1 forms a mixture of species ranging from monomers to larger oligomers in solution, suggesting similarities with the orthologs from yeast and human.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193667PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5832301PMC
June 2018

Nitrogen supply influences photosynthesis establishment along the sugarcane leaf.

Sci Rep 2018 02 2;8(1):2327. Epub 2018 Feb 2.

Departamento de Genética, Evolução, Microbiologia e Imunologia, Instituto de Biologia, Universidade Estadual de Campinas, 13083-862, Campinas, Brazil.

Nitrogen (N) is a major component of the photosynthetic apparatus and is widely used as a fertilizer in crops. However, to the best of our knowledge, the dynamic of photosynthesis establishment due to differential N supply in the bioenergy crop sugarcane has not been reported to date. To address this question, we evaluated physiological and metabolic alterations along the sugarcane leaf in two contrasting genotypes, responsive (R) and nonresponsive (NR), grown under high- and low-N conditions. We found that the N supply and the responsiveness of the genotype determined the degree of senescence, the carboxylation process mediated by phosphoenolpyruvate carboxylase (PEPcase) and differential accumulation of soluble sugars. The metabolite profiles indicated that the NR genotype had a higher respiration rate in the youngest tissues after exposure to high N. We observed elevated levels of metabolites related to photosynthesis in almost all leaf segments from the R genotype under high-N conditions, suggesting that N supply and the ability to respond to N influenced photosynthesis. Therefore, we observed that N influence on photosynthesis and other pathways is dependent on the genotype and the leaf region.
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http://dx.doi.org/10.1038/s41598-018-20653-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5797232PMC
February 2018

Sugarcane Water Stress Tolerance Mechanisms and Its Implications on Developing Biotechnology Solutions.

Front Plant Sci 2017 23;8:1077. Epub 2017 Jun 23.

Functional Genome Laboratory, Department of Genetics, Evolution and Bioagents, Institute of Biology, State University of CampinasCampinas, Brazil.

Sugarcane is a unique crop with the ability to accumulate high levels of sugar and is a commercially viable source of biomass for bioelectricity and second-generation bioethanol. Water deficit is the single largest abiotic stress affecting sugarcane productivity and the development of water use efficient and drought tolerant cultivars is an imperative for all major sugarcane producing countries. This review summarizes the physiological and molecular studies on water deficit stress in sugarcane, with the aim to help formulate more effective research strategies for advancing our knowledge on genes and mechanisms underpinning plant response to water stress. We also overview transgenic studies in sugarcane, with an emphasis on the potential strategies to develop superior sugarcane varieties that improve crop productivity in drought-prone environments.
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http://dx.doi.org/10.3389/fpls.2017.01077DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481406PMC
June 2017

Ethylene-induced transcriptional and hormonal responses at the onset of sugarcane ripening.

Sci Rep 2017 03 7;7:43364. Epub 2017 Mar 7.

Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, 13083-862, Campinas, Brasil.

The effects of ethephon as a sugarcane ripener are attributed to ethylene. However, the role of this phytohormone at the molecular level is unknown. We performed a transcriptome analysis combined with the evaluation of sucrose metabolism and hormone profiling of sugarcane plants sprayed with ethephon or aminoethoxyvinylglycine (AVG), an ethylene inhibitor, at the onset of ripening. The differential response between ethephon and AVG on sucrose level and sucrose synthase activity in internodes indicates ethylene as a potential regulator of sink strength. The correlation between hormone levels and transcriptional changes suggests ethylene as a trigger of multiple hormone signal cascades, with approximately 18% of differentially expressed genes involved in hormone biosynthesis, metabolism, signalling, and response. A defence response elicited in leaves favoured salicylic acid over the ethylene/jasmonic acid pathway, while the upper internode was prone to respond to ethylene with strong stimuli on ethylene biosynthesis and signalling genes. Besides, ethylene acted synergistically with abscisic acid, another ripening factor, and antagonistically with gibberellin and auxin. We identified potential ethylene target genes and characterized the hormonal status during ripening, providing insights into the action of ethylene at the site of sucrose accumulation. A molecular model of ethylene interplay with other hormones is proposed.
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http://dx.doi.org/10.1038/srep43364DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5339719PMC
March 2017

Integrated analysis of recombinant BPV-1 L1 protein for the production of a bovine papillomavirus VLP vaccine.

Vaccine 2017 03 17;35(12):1590-1593. Epub 2017 Feb 17.

Laboratório de Genética, Instituto Butantan, São Paulo, SP, Brazil. Electronic address:

Bovine papillomatosis is an infectious disease that is caused by bovine papillomavirus (BPV), which results in important economic losses. However, no BPV vaccines or effective treatment methods are commercially available to date. Moreover, the absence of papillomavirus replication in vitro makes the use of recombinant protein a promising candidate for vaccine formulations. Hence, we developed an integrated study on the L1 capsid protein of BPV-1, obtained from a bacterial expression system, regarding its purification, biosafety, thermostability and immunogenicity. The results indicated an absence of genotoxicity of the purified recombinant L1 protein, β-sheet prevalence of secondary structure folding, protein stability under high temperatures as well as the presence of capsomeres and VLPs. In addition, preliminary experimental vaccination of calves showed the production of specific antibodies against BPV-1 L1.
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http://dx.doi.org/10.1016/j.vaccine.2017.02.007DOI Listing
March 2017

Physiological and transcriptional analyses of developmental stages along sugarcane leaf.

BMC Plant Biol 2015 Dec 29;15:300. Epub 2015 Dec 29.

Laboratório de Genoma Funcional, Instituto de Biologia, Universidade Estadual de Campinas Campinas, Caixa Postal 6109, Campinas, 13083-862, SP, Brazil.

Background: Sugarcane is one of the major crops worldwide. It is cultivated in over 100 countries on 22 million ha. The complex genetic architecture and the lack of a complete genomic sequence in sugarcane hamper the adoption of molecular approaches to study its physiology and to develop new varieties. Investments on the development of new sugarcane varieties have been made to maximize sucrose yield, a trait dependent on photosynthetic capacity. However, detailed studies on sugarcane leaves are scarce. In this work, we report the first molecular and physiological characterization of events taking place along a leaf developmental gradient in sugarcane.

Results: Photosynthetic response to CO2 indicated divergence in photosynthetic capacity based on PEPcase activity, corroborated by activity quantification (both in vivo and in vitro) and distinct levels of carbon discrimination on different segments along leaf length. Additionally, leaf segments had contrasting amount of chlorophyll, nitrogen and sugars. RNA-Seq data indicated a plethora of biochemical pathways differentially expressed along the leaf. Some transcription factors families were enriched on each segment and their putative functions corroborate with the distinct developmental stages. Several genes with higher expression in the middle segment, the one with the highest photosynthetic rates, were identified and their role in sugarcane productivity is discussed. Interestingly, sugarcane leaf segments had a different transcriptional behavior compared to previously published data from maize.

Conclusion: This is the first report of leaf developmental analysis in sugarcane. Our data on sugarcane is another source of information for further studies aiming to understand and/or improve C4 photosynthesis. The segments used in this work were distinct in their physiological status allowing deeper molecular analysis. Although limited in some aspects, the comparison to maize indicates that all data acquired on one C4 species cannot always be easily extrapolated to other species. However, our data indicates that some transcriptional factors were segment-specific and the sugarcane leaf undergoes through the process of suberizarion, photosynthesis establishment and senescence.
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http://dx.doi.org/10.1186/s12870-015-0694-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4696237PMC
December 2015

MicroRNAs and drought responses in sugarcane.

Front Plant Sci 2015 23;6:58. Epub 2015 Feb 23.

Laboratório de Genoma Funcional, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas Campinas, São Paulo, Brazil.

There is a growing demand for renewable energy, and sugarcane is a promising bioenergy crop. In Brazil, the largest sugarcane producer in the world, sugarcane plantations are expanding into areas where severe droughts are common. Recent evidence has highlighted the role of miRNAs in regulating drought responses in several species, including sugarcane. This review summarizes the data from miRNA expression profiles observed in a wide array of experimental conditions using different sugarcane cultivars that differ in their tolerance to drought. We uncovered a complex regulation of sugarcane miRNAs in response to drought and discussed these data with the miRNA profiles observed in other plant species. The predicted miRNA targets revealed different transcription factors, proteins involved in tolerance to oxidative stress, cell modification, as well as hormone signaling. Some of these proteins might regulate sugarcane responses to drought, such as reduction of internode growth and shoot branching and increased leaf senescence. A better understanding on the regulatory network from miRNAs and their targets under drought stress has a great potential to contribute to sugarcane improvement, either as molecular markers as well as by using biotechnological approaches.
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http://dx.doi.org/10.3389/fpls.2015.00058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4337329PMC
March 2015

Oligomerization, membrane association, and in vivo phosphorylation of sugarcane UDP-glucose pyrophosphorylase.

J Biol Chem 2014 Nov 15;289(48):33364-77. Epub 2014 Oct 15.

From the Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Rua Monteiro Lobato, 255, C.P. 6109, Campinas, SP, Brazil,

Sugarcane is a monocot plant that accumulates sucrose to levels of up to 50% of dry weight in the stalk. The mechanisms that are involved in sucrose accumulation in sugarcane are not well understood, and little is known with regard to factors that control the extent of sucrose storage in the stalks. UDP-glucose pyrophosphorylase (UGPase; EC 2.7.7.9) is an enzyme that produces UDP-glucose, a key precursor for sucrose metabolism and cell wall biosynthesis. The objective of this work was to gain insights into the ScUGPase-1 expression pattern and regulatory mechanisms that control protein activity. ScUGPase-1 expression was negatively correlated with the sucrose content in the internodes during development, and only slight differences in the expression patterns were observed between two cultivars that differ in sucrose content. The intracellular localization of ScUGPase-1 indicated partial membrane association of this soluble protein in both the leaves and internodes. Using a phospho-specific antibody, we observed that ScUGPase-1 was phosphorylated in vivo at the Ser-419 site in the soluble and membrane fractions from the leaves but not from the internodes. The purified recombinant enzyme was kinetically characterized in the direction of UDP-glucose formation, and the enzyme activity was affected by redox modification. Preincubation with H2O2 strongly inhibited this activity, which could be reversed by DTT. Small angle x-ray scattering analysis indicated that the dimer interface is located at the C terminus and provided the first structural model of the dimer of sugarcane UGPase in solution.
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http://dx.doi.org/10.1074/jbc.M114.590125DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4246093PMC
November 2014

Transcriptome analysis highlights changes in the leaves of maize plants cultivated in acidic soil containing toxic levels of Al(3+).

Mol Biol Rep 2014 Dec 10;41(12):8107-16. Epub 2014 Sep 10.

Laboratório Nacional de Ciência e Tecnologia do Bioetanol, CTBE/CNPEM, Campinas, SP, Brazil,

Soil acidity limits crop yields worldwide and is a common result of aluminum (Al) phytotoxicity, which is known to inhibit root growth. Here, we compared the transcriptome of leaves from maize seedlings grown under control conditions (soil without free Al) and under acidic soil containing toxic levels of Al. This study reports, for the first time, the complex transcriptional changes that occur in the leaves of maize plants grown in acidic soil with phytotoxic levels of Al. Our data indicate that 668 genes were differentially expressed in the leaves of plants grown in acidic soil, which is significantly greater than that observed in our previous work with roots. Genes encoding TCA cycle enzymes were upregulated, although no specific transporter of organic acids was differentially expressed in leaves. We also provide evidence for positive roles for auxin and brassinosteroids in Al tolerance, whereas gibberellin and jasmonate may have negative roles. Our data indicate that plant responses to acidic soil with high Al content are not restricted to the root; tolerance mechanisms are also displayed in the aerial parts of the plant, thus indicating that the entire plant responds to stress.
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http://dx.doi.org/10.1007/s11033-014-3709-1DOI Listing
December 2014

Differentially delayed root proteome responses to salt stress in sugar cane varieties.

J Proteome Res 2013 Dec 19;12(12):5681-95. Epub 2013 Nov 19.

Laboratory of Plant Genomics and Proteomics, Department of Genetics, Center for Biological Sciences, Universidade Federal de Pernambuco , Recife, PE, Brazil.

Soil salinity is a limiting factor to sugar cane crop development, although in general plants present variable mechanisms of tolerance to salinity stress. The molecular basis underlying these mechanisms can be inferred by using proteomic analysis. Thus, the objective of this work was to identify differentially expressed proteins in sugar cane plants submitted to salinity stress. For that, a greenhouse experiment was established with four sugar cane varieties and two salt conditions, 0 mM (control) and 200 mM NaCl. Physiological and proteomics analyses were performed after 2 and 72 h of stress induction by salt. Distinct physiological responses to salinity stress were observed in the varieties and linked to tolerance mechanisms. In proteomic analysis, the roots soluble protein fraction was extracted, quantified, and analyzed through bidimensional electrophoresis. Gel images analyses were done computationally, where in each contrast only one variable was considered (salinity condition or variety). Differential spots were excised, digested by trypsin, and identified via mass spectrometry. The tolerant variety RB867515 showed the highest accumulation of proteins involved in growth, development, carbohydrate and energy metabolism, reactive oxygen species metabolization, protein protection, and membrane stabilization after 2 h of stress. On the other hand, the presence of these proteins in the sensitive variety was verified only in stress treatment after 72 h. These data indicate that these stress responses pathways play a role in the tolerance to salinity in sugar cane, and their effectiveness for phenotypical tolerance depends on early stress detection and activation of the coding genes expression.
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http://dx.doi.org/10.1021/pr400654aDOI Listing
December 2013

Effects of drought on the microtranscriptome of field-grown sugarcane plants.

Planta 2013 Mar 6;237(3):783-98. Epub 2012 Nov 6.

Laboratório de Genoma Funcional, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.

Sugarcane (Saccharum spp.) is the most promising crop for renewable energy. Among the diverse stresses that affect plant productivity, drought stress frequently causes losses in sugarcane fields. Although several studies have addressed plant responses to drought using controlled environments, plant responses under field conditions are largely unknown. Recently, microRNA (miRNA)-mediated post-transcriptional regulation has been described as an important and decisive component in vegetal development and stress resistance modulation. The role of miRNAs in sugarcane responses to drought under field conditions is currently not known. Two sugarcane cultivars differing in drought tolerance were grown in the field with and without irrigation (rainfed) for 7 months. By using small RNA deep sequencing, we were able to identify 18 miRNA families comprising 30 mature miRNA sequences. Among these families, we found 13 mature miRNAs that were differentially expressed in drought-stressed plants. Seven miRNAs were differentially expressed in both cultivars. The target genes for many of the differentially expressed mature miRNAs were predicted, and some of them were validated by quantitative reverse transcription PCR. Among the targets, we found transcription factors, transporters, proteins associated with senescence, and proteins involved with flower development. All of these data increase our understanding of the role of miRNAs in the complex regulation of drought stress in field-grown sugarcane, providing valuable tools to develop new sugarcane cultivars tolerant to drought stress.
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http://dx.doi.org/10.1007/s00425-012-1795-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3579473PMC
March 2013

microRNAs associated with drought response in the bioenergy crop sugarcane (Saccharum spp.).

PLoS One 2012 11;7(10):e46703. Epub 2012 Oct 11.

Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil.

Sugarcane (Saccharum spp.) is one of the most important crops in the world. Drought stress is a major abiotic stress factor that significantly reduces sugarcane yields. However the gene network that mediates plant responses to water stress remains largely unknown in several crop species. Although several microRNAs that mediate post-transcriptional regulation during water stress have been described in other species, the role of the sugarcane microRNAs during drought stress has not been studied. The objective of this work was to identify sugarcane miRNAs that are differentially expressed under drought stress and to correlate this expression with the behavior of two sugarcane cultivars with different drought tolerances. The sugarcane cultivars RB867515 (higher drought tolerance) and RB855536 (lower drought tolerance) were cultivated in a greenhouse for three months and then subjected to drought for 2, 4, 6 or 8 days. By deep sequencing of small RNAs, we were able to identify 18 miRNA families. Among all of the miRNAs thus identified, seven were differentially expressed during drought. Six of these miRNAs were differentially expressed at two days of stress, and five miRNAs were differentially expressed at four days. The expression levels of five miRNAs (ssp-miR164, ssp-miR394, ssp-miR397, ssp-miR399-seq 1 and miR528) were validated by RT-qPCR (quantitative reverse transcriptase PCR). Six precursors and the targets of the differentially expressed miRNA were predicted using an in silico approach and validated by RT-qPCR; many of these targets may play important roles in drought tolerance. These findings constitute a significant increase in the number of identified miRNAs in sugarcane and contribute to the elucidation of the complex regulatory network that is activated by drought stress.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0046703PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3469577PMC
April 2013

A novel stress-induced sugarcane gene confers tolerance to drought, salt and oxidative stress in transgenic tobacco plants.

PLoS One 2012 11;7(9):e44697. Epub 2012 Sep 11.

Laboratório de Genoma Funcional, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brazil.

Background: Drought is a major abiotic stress that affects crop productivity worldwide. Sugarcane can withstand periods of water scarcity during the final stage of culm maturation, during which sucrose accumulation occurs. Meanwhile, prolonged periods of drought can cause severe plant losses.

Methodology/principal Findings: In a previous study, we evaluated the transcriptome of drought-stressed plants to better understand sugarcane responses to drought. Among the up-regulated genes was Scdr1 (sugarcane drought-responsive 1). The aim of the research reported here was to characterize this gene. Scdr1 encodes a putative protein containing 248 amino acids with a large number of proline (19%) and cysteine (13%) residues. Phylogenetic analysis showed that ScDR1is in a clade with homologs from other monocotyledonous plants, separate from those of dicotyledonous plants. The expression of Scdr1 in different varieties of sugarcane plants has not shown a clear association with drought tolerance.

Conclusions/significance: The overexpression of Scdr1 in transgenic tobacco plants increased their tolerance to drought, salinity and oxidative stress, as demonstrated by increased photosynthesis, water content, biomass, germination rate, chlorophyll content and reduced accumulation of ROS. Physiological parameters, such as transpiration rate (E), net photosynthesis (A), stomatal conductance (gs) and internal leaf CO(2) concentration, were less affected by abiotic stresses in transgenic Scdr1 plants compared with wild-type plants. Overall, our results indicated that Scdr1 conferred tolerance to multiple abiotic stresses, highlighting the potential of this gene for biotechnological applications.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044697PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3439409PMC
March 2013

Linking microarray data to QTLs highlights new genes related to Al tolerance in maize.

Plant Sci 2012 Aug 25;191-192:8-15. Epub 2012 Apr 25.

Laboratório Genoma Funcional, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.

The presence of aluminum (Al) is one of the main factors limiting crop yield in Brazil and worldwide. Plant responses to Al are complex, and the use of techniques such as microarrays can facilitate their comprehension. In a previous work, we evaluated the transcriptome of two maize lines, Cat100-6 and S1587-17, after growing the plants for 1 or 3 days in acid soil (pH 4.1) or alkaline soil with Ca(OH)₂ (pH 5.5), and we identified genes that likely contribute to Al tolerance. The mapping of these genes to the chromosomes allowed the identification of the genes that are localized in maize QTLs previously reported in the literature as associated with the tolerant phenotype. We were able to map genes encoding proteins possibly involved with acid soil tolerance, such as the ones encoding an RNA binding protein, a protease inhibitor, replication factors, xyloglucan endotransglycosylase and cyclins, inside QTLs known to be important for the Al-tolerant phenotype.
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http://dx.doi.org/10.1016/j.plantsci.2012.04.009DOI Listing
August 2012

An Arabidopsis mitochondrial uncoupling protein confers tolerance to drought and salt stress in transgenic tobacco plants.

PLoS One 2011 30;6(8):e23776. Epub 2011 Aug 30.

Laboratório de Genoma Funcional, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, Brazil.

Background: Plants are challenged by a large number of environmental stresses that reduce productivity and even cause death. Both chloroplasts and mitochondria produce reactive oxygen species under normal conditions; however, stress causes an imbalance in these species that leads to deviations from normal cellular conditions and a variety of toxic effects. Mitochondria have uncoupling proteins (UCPs) that uncouple electron transport from ATP synthesis. There is evidence that UCPs play a role in alleviating stress caused by reactive oxygen species overproduction. However, direct evidence that UCPs protect plants from abiotic stress is lacking.

Methodology/principal Findings: Tolerances to salt and water deficit were analyzed in transgenic tobacco plants that overexpress a UCP (AtUCP1) from Arabidopsis thaliana. Seeds of AtUCP1 transgenic lines germinated faster, and adult plants showed better responses to drought and salt stress than wild-type (WT) plants. These phenotypes correlated with increased water retention and higher gas exchange parameters in transgenic plants that overexpress AtUCP1. WT plants exhibited increased respiration under stress, while transgenic plants were only slightly affected. Furthermore, the transgenic plants showed reduced accumulation of hydrogen peroxide in stressed leaves compared with WT plants.

Conclusions/significance: Higher levels of AtUCP1 improved tolerance to multiple abiotic stresses, and this protection was correlated with lower oxidative stress. Our data support previous assumptions that UCPs reduce the imbalance of reactive oxygen species. Our data also suggest that UCPs may play a role in stomatal closure, which agrees with other evidence of a direct relationship between these proteins and photosynthesis. Manipulation of the UCP protein expression in mitochondria is a new avenue for crop improvement and may lead to crops with greater tolerance for challenging environmental conditions.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0023776PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166057PMC
December 2011

A transcriptomic analysis of gene expression in the venom gland of the snake Bothrops alternatus (urutu).

BMC Genomics 2010 Oct 26;11:605. Epub 2010 Oct 26.

Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, CP 6111, 13083-970, Campinas, SP, Brazil.

Background: The genus Bothrops is widespread throughout Central and South America and is the principal cause of snakebite in these regions. Transcriptomic and proteomic studies have examined the venom composition of several species in this genus, but many others remain to be studied. In this work, we used a transcriptomic approach to examine the venom gland genes of Bothrops alternatus, a clinically important species found in southeastern and southern Brazil, Uruguay, northern Argentina and eastern Paraguay.

Results: A cDNA library of 5,350 expressed sequence tags (ESTs) was produced and assembled into 838 contigs and 4512 singletons. BLAST searches of relevant databases showed 30% hits and 70% no-hits, with toxin-related transcripts accounting for 23% and 78% of the total transcripts and hits, respectively. Gene ontology analysis identified non-toxin genes related to general metabolism, transcription and translation, processing and sorting, (polypeptide) degradation, structural functions and cell regulation. The major groups of toxin transcripts identified were metalloproteinases (81%), bradykinin-potentiating peptides/C-type natriuretic peptides (8.8%), phospholipases A2 (5.6%), serine proteinases (1.9%) and C-type lectins (1.5%). Metalloproteinases were almost exclusively type PIII proteins, with few type PII and no type PI proteins. Phospholipases A2 were essentially acidic; no basic PLA2 were detected. Minor toxin transcripts were related to L-amino acid oxidase, cysteine-rich secretory proteins, dipeptidylpeptidase IV, hyaluronidase, three-finger toxins and ohanin. Two non-toxic proteins, thioredoxin and double-specificity phosphatase Dusp6, showed high sequence identity to similar proteins from other snakes. In addition to the above features, single-nucleotide polymorphisms, microsatellites, transposable elements and inverted repeats that could contribute to toxin diversity were observed.

Conclusions: Bothrops alternatus venom gland contains the major toxin classes described for other Bothrops venoms based on trancriptomic and proteomic studies. The predominance of type PIII metalloproteinases agrees with the well-known hemorrhagic activity of this venom, whereas the lower content of serine proteases and C-type lectins could contribute to less marked coagulopathy following envenoming by this species. The lack of basic PLA2 agrees with the lower myotoxicity of this venom compared to other Bothrops species with these toxins. Together, these results contribute to our understanding of the physiopathology of envenoming by this species.
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http://dx.doi.org/10.1186/1471-2164-11-605DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017861PMC
October 2010

Molecular characterization of a miraculin-like gene differentially expressed during coffee development and coffee leaf miner infestation.

Planta 2011 Jan 8;233(1):123-37. Epub 2010 Oct 8.

Laboratório de Genoma Funcional Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.

The characterization of a coffee gene encoding a protein similar to miraculin-like proteins, which are members of the plant Kunitz serine trypsin inhibitor (STI) family of proteinase inhibitors (PIs), is described. PIs are important proteins in plant defence against insects and in the regulation of proteolysis during plant development. This gene has high identity with the Richadella dulcifica taste-modifying protein miraculin and with the tomato protein LeMir; and was named as CoMir (Coffea miraculin). Structural protein modelling indicated that CoMir had structural similarities with the Kunitz STI proteins, but suggested specific folding structures. CoMir was up-regulated after coffee leaf miner (Leucoptera coffella) oviposition in resistant plants of a progeny derived from crosses between C. racemosa (resistant) and C. arabica (susceptible). Interestingly, this gene was down-regulated during coffee leaf miner herbivory in susceptible plants. CoMir expression was up-regulated after abscisic acid application and wounding stress and was prominent during the early stages of flower and fruit development. In situ hybridization revealed that CoMir transcripts accumulated in the anther tissues that display programmed cell death (tapetum, endothecium and stomium) and in the metaxylem vessels of the petals, stigma and leaves. In addition, the recombinant protein CoMir shows inhibitory activity against trypsin. According to the present results CoMir may act in proteolytic regulation during coffee development and in the defence against L. coffeella. The similarity of CoMir with other Kunitz STI proteins and the role of CoMir in plant development and plant stress are discussed.
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http://dx.doi.org/10.1007/s00425-010-1284-9DOI Listing
January 2011

Transcriptional profile of maize roots under acid soil growth.

BMC Plant Biol 2010 Sep 9;10:196. Epub 2010 Sep 9.

Laboratório de Genoma Funcional, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.

Background: Aluminum (Al) toxicity is one of the most important yield-limiting factors of many crops worldwide. The primary symptom of Al toxicity syndrome is the inhibition of root growth leading to poor water and nutrient absorption. Al tolerance has been extensively studied using hydroponic experiments. However, unlike soil conditions, this method does not address all of the components that are necessary for proper root growth and development. In the present study, we grew two maize genotypes with contrasting tolerance to Al in soil containing toxic levels of Al and then compared their transcriptomic responses.

Results: When grown in acid soil containing toxic levels of Al, the Al-sensitive genotype (S1587-17) showed greater root growth inhibition, more Al accumulation and more callose deposition in root tips than did the tolerant genotype (Cat100-6). Transcriptome profiling showed a higher number of genes differentially expressed in S1587-17 grown in acid soil, probably due to secondary effects of Al toxicity. Genes involved in the biosynthesis of organic acids, which are frequently associated with an Al tolerance response, were not differentially regulated in both genotypes after acid soil exposure. However, genes related to the biosynthesis of auxin, ethylene and lignin were up-regulated in the Al-sensitive genotype, indicating that these pathways might be associated with root growth inhibition. By comparing the two maize lines, we were able to discover genes up-regulated only in the Al-tolerant line that also presented higher absolute levels than those observed in the Al-sensitive line. These genes encoded a lipase hydrolase, a retinol dehydrogenase, a glycine-rich protein, a member of the WRKY transcriptional family and two unknown proteins.

Conclusions: This work provides the first characterization of the physiological and transcriptional responses of maize roots when grown in acid soil containing toxic levels of Al. The transcriptome profiles highlighted several pathways that are related to Al toxicity and tolerance during growth in acid soil. We found several genes that were not found in previous studies using hydroponic experiments, increasing our understanding of plant responses to acid soil. The use of two germplasms with markedly different Al tolerances allowed the identification of genes that are a valuable tool for assessing the mechanisms of Al tolerance in maize in acid soil.
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http://dx.doi.org/10.1186/1471-2229-10-196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2956545PMC
September 2010

Molecular characterization of ScTFIIAgamma, encoding the putative TFIIA small subunit from sugarcane.

Plant Cell Rep 2010 Aug 18;29(8):857-64. Epub 2010 May 18.

Laboratório de Genoma Funcional, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, 13083-875 Campinas, São Paulo 6109, Brazil.

Transcription mediated by RNA polymerase II depends on a set of different transcription factors to form the pre-initiation complex. TFIIA is involved in the construction of this complex and increases the affinity of TBP for the DNA union region in vitro. In this study, we characterized the ScTFIIAgamma gene, which encodes a homolog of the smaller subunit (gamma) of transcription factor TFIIA in sugarcane. RNA blot analysis showed that ScTFIIAgamma transcripts accumulate in all tissues evaluated, with higher levels in leaf roll and flowers. In situ hybridization showed that ScTFIIAgamma was expressed in different cells of the reproductive meristem. In sugarcane plantlets, methyl jasmonate and absicic acid treatments as well as phosphate starvation had no influence on ScTFIIAgamma transcript accumulation. The subcelullar localization assay demonstrates that ScTFIIAgamma protein is directed to the cell nucleus. The phylogenetic analysis, the expression in several tissues and under different treatments and the nuclear localization are in line with the putative role of ScTFIIAgamma as a subunit of basal transcription factor.
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http://dx.doi.org/10.1007/s00299-010-0871-3DOI Listing
August 2010

Sugarcane genes associated with sucrose content.

BMC Genomics 2009 Mar 21;10:120. Epub 2009 Mar 21.

Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil.

Background: Sucrose content is a highly desirable trait in sugarcane as the worldwide demand for cost-effective biofuels surges. Sugarcane cultivars differ in their capacity to accumulate sucrose and breeding programs routinely perform crosses to identify genotypes able to produce more sucrose. Sucrose content in the mature internodes reach around 20% of the culms dry weight. Genotypes in the populations reflect their genetic program and may display contrasting growth, development, and physiology, all of which affect carbohydrate metabolism. Few studies have profiled gene expression related to sugarcane's sugar content. The identification of signal transduction components and transcription factors that might regulate sugar accumulation is highly desirable if we are to improve this characteristic of sugarcane plants.

Results: We have evaluated thirty genotypes that have different Brix (sugar) levels and identified genes differentially expressed in internodes using cDNA microarrays. These genes were compared to existing gene expression data for sugarcane plants subjected to diverse stress and hormone treatments. The comparisons revealed a strong overlap between the drought and sucrose-content datasets and a limited overlap with ABA signaling. Genes associated with sucrose content were extensively validated by qRT-PCR, which highlighted several protein kinases and transcription factors that are likely to be regulators of sucrose accumulation. The data also indicate that aquaporins, as well as lignin biosynthesis and cell wall metabolism genes, are strongly related to sucrose accumulation. Moreover, sucrose-associated genes were shown to be directly responsive to short term sucrose stimuli, confirming their role in sugar-related pathways.

Conclusion: Gene expression analysis of sugarcane populations contrasting for sucrose content indicated a possible overlap with drought and cell wall metabolism processes and suggested signaling and transcriptional regulators to be used as molecular markers in breeding programs. Transgenic research is necessary to further clarify the role of the genes and define targets useful for sugarcane improvement programs based on transgenic plants.
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http://dx.doi.org/10.1186/1471-2164-10-120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2666766PMC
March 2009