Publications by authors named "Catherine Colas des Francs-Small"

31 Publications

A synthetic RNA editing factor edits its target site in chloroplasts and bacteria.

Commun Biol 2021 May 10;4(1):545. Epub 2021 May 10.

Australian Research Council Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Crawley, WA, Australia.

Members of the pentatricopeptide repeat (PPR) protein family act as specificity factors in C-to-U RNA editing. The expansion of the PPR superfamily in plants provides the sequence variation required for design of consensus-based RNA-binding proteins. We used this approach to design a synthetic RNA editing factor to target one of the sites in the Arabidopsis chloroplast transcriptome recognised by the natural editing factor CHLOROPLAST BIOGENESIS 19 (CLB19). We show that our synthetic editing factor specifically recognises the target sequence in in vitro binding assays. The designed factor is equally specific for the target rpoA site when expressed in chloroplasts and in the bacterium E. coli. This study serves as a successful pilot into the design and application of programmable RNA editing factors based on plant PPR proteins.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s42003-021-02062-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8110955PMC
May 2021

The Pentatricopeptide Repeat Protein MEF100 Is Required for the Editing of Four Mitochondrial Editing Sites in .

Cells 2021 Feb 22;10(2). Epub 2021 Feb 22.

Australian Research Council Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Crawley, WA 6009, Australia.

In there are more than 600 C-to-U RNA editing events in the mitochondria and at least 44 in the chloroplasts. Pentatricopeptide repeat (PPR) proteins provide the specificity for these reactions. They recognize RNA sequences in a partially predictable fashion via key amino acids at the fifth and last position in each PPR motif that bind to individual ribonucleotides. A combined approach of RNA-Seq, mutant complementation, electrophoresis of mitochondrial protein complexes and Western blotting allowed us to show that MEF100, a PPR protein identified in a genetic screen for mutants resistant to an inhibitor of γ -glutamylcysteine synthetase, is required for the editing of -493, -403, -698 and -356 sites in Arabidopsis mitochondria. The absence of editing in leads to a decrease in mitochondrial Complex I activity, which probably explains the physiological phenotype. Some plants have lost the requirement for MEF100 at one or more of these sites through mutations in the mitochondrial genome. We show that loss of the requirement for MEF100 editing leads to divergence in the MEF100 binding site.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/cells10020468DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7926422PMC
February 2021

Deconvoluting apocarotenoid-mediated retrograde signaling networks regulating plastid translation and leaf development.

Plant J 2021 Mar 8;105(6):1582-1599. Epub 2021 Mar 8.

Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos, 62210, Mexico.

Signals originating within plastids modulate organelle differentiation by transcriptionally regulating nuclear-encoded genes. These retrograde signals are also integral regulators of plant development, including leaf morphology. The clb5 mutant displays severe leaf morphology defects due to Apocarotenoid Signal 1 (ACS1) accumulation in the developmentally arrested plastid. Transcriptomic analysis of clb5 validates that ACS1 accumulation deregulates hundreds of nuclear genes, including the suppression of most genes encoding plastid ribosomal proteins. Herein, we order the molecular events causing the leaf phenotype associated with the accumulation of ACS1, which includes two consecutive retrograde signaling cascades. Firstly, ACS1 originating in the plastid drives inhibition of plastid translation (IPT) via nuclear transcriptome remodeling of chlororibosomal proteins, requiring light as an essential component. Subsequently, IPT results in leaf morphological defects via a GUN1-dependent pathway shared with seedlings undergoing chemical IPT treatments and is restricted to an early window of the leaf development. Collectively, this work advances our understanding of the complexity within plastid retrograde signaling exemplified by sequential signal exchange and consequences that in a particular temporal and spatial context contribute to the modulation of leaf development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/tpj.15134DOI Listing
March 2021

The coordinated action of PPR4 and EMB2654 on each intron half mediates trans-splicing of rps12 transcripts in plant chloroplasts.

Plant J 2019 12 25;100(6):1193-1207. Epub 2019 Sep 25.

Department of Applied Biology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, 61186, Korea.

The pentatricopeptide repeat proteins PPR4 and EMB2654 have been shown to be required for the trans-splicing of plastid rps12 transcripts in Zea mays (maize) and Arabidopsis, respectively, but their roles in this process are not well understood. We investigated the functions of the Arabidopsis and Oryza sativa (rice) orthologs of PPR4, designated AtPPR4 (At5g04810) and OsPPR4 (Os4g58780). Arabidopsis atppr4 and rice osppr4 mutants are embryo-lethal and seedling-lethal 3 weeks after germination, respectively, showing that PPR4 is essential in the development of both dicot and monocot plants. Artificial microRNA-mediated mutants of AtPPR4 displayed a specific defect in rps12 trans-splicing, with pale-green, yellowish or albino phenotypes, according to the degree of knock-down of AtPPR4 expression. Comparison of RNA footprints in atppr4 and emb2654 mutants showed a similar concordant loss of extensive footprints at the 3' end of intron 1a and at the 5' end of intron 1b in both cases. EMB2654 is known to bind within the footprint region in intron 1a and we show that AtPPR4 binds to the footprint region in intron 1b, via its PPR motifs. Binding of both PPR4 and EMB2654 is essential to juxtapose the two intron halves and to maintain the RNAs in a splicing-competent structure for the efficient trans-splicing of rps12 intron 1, which is crucial for chloroplast biogenesis and plant development. The similarity of EMB2654 and PPR4 orthologs and their respective binding sites across land plant phylogeny indicates that their coordinate function in rps12 trans-splicing has probably been conserved for 500 million years.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/tpj.14509DOI Listing
December 2019

Targeted cleavage of mRNA induced by a modified pentatricopeptide repeat protein in plant mitochondria.

Commun Biol 2018 11;1:166. Epub 2018 Oct 11.

Australian Research Council Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Crawley, WA, 6009, Australia.

Mitochondrial genes encode key components of the cellular energy machinery, but their genetic analysis is difficult or impossible in most organisms (including plants) because of the lack of viable transformation approaches. We report here a method to block the expression of the mitochondrial gene encoding a subunit of respiratory complex I in , via the modification of the specificity of the RNA-binding protein RNA PROCESSING FACTOR 2 (RPF2). We show that the modified RPF2 binds and specifically induces cleavage of RNA, almost eliminating expression of the Nad6 protein and consequently complex I accumulation and activity. To our knowledge, this is the first example of a targeted block in expression of a specific mitochondrial transcript by a custom-designed RNA-binding protein. This opens the path to reverse genetics studies on mitochondrial gene functions and leads to potential applications in agriculture.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s42003-018-0166-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6181959PMC
October 2018

The Mitochondrial DNA-Associated Protein SWIB5 Influences mtDNA Architecture and Homologous Recombination.

Plant Cell 2017 May 18;29(5):1137-1156. Epub 2017 Apr 18.

Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium.

In addition to the nucleus, mitochondria and chloroplasts in plant cells also contain genomes. Efficient DNA repair pathways are crucial in these organelles to fix damage resulting from endogenous and exogenous factors. Plant organellar genomes are complex compared with their animal counterparts, and although several plant-specific mediators of organelle DNA repair have been reported, many regulators remain to be identified. Here, we show that a mitochondrial SWI/SNF (nucleosome remodeling) complex B protein, SWIB5, is capable of associating with mitochondrial DNA (mtDNA) in Gain- and loss-of-function mutants provided evidence for a role of SWIB5 in influencing mtDNA architecture and homologous recombination at specific intermediate-sized repeats both under normal and genotoxic conditions. SWIB5 interacts with other mitochondrial SWIB proteins. Gene expression and mutant phenotypic analysis of and family members suggests a link between organellar genome maintenance and cell proliferation. Taken together, our work presents a protein family that influences mtDNA architecture and homologous recombination in plants and suggests a link between organelle functioning and plant development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1105/tpc.16.00899DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466028PMC
May 2017

The mitochondrial pentatricopeptide repeat protein PPR19 is involved in the stabilization of NADH dehydrogenase 1 transcripts and is crucial for mitochondrial function and Arabidopsis thaliana development.

New Phytol 2017 Jul 23;215(1):202-216. Epub 2017 Mar 23.

Department of Plant Biotechnology, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, 61186, Korea.

Despite the importance of pentatricopeptide repeat (PPR) proteins in organellar RNA metabolism and plant development, the functions of many PPR proteins remain unknown. Here, we determined the role of a mitochondrial PPR protein (At1g52620) comprising 19 PPR motifs, thus named PPR19, in Arabidopsis thaliana. The ppr19 mutant displayed abnormal seed development, reduced seed yield, delayed seed germination, and retarded growth, indicating that PPR19 is indispensable for normal growth and development of Arabidopsis thaliana. Splicing pattern analysis of mitochondrial genes revealed that PPR19 specifically binds to the specific sequence in the 3'-terminus of the NADH dehydrogenase 1 (nad1) transcript and stabilizes transcripts containing the second and third exons of nad1. Loss of these transcripts in ppr19 leads to multiple secondary effects on accumulation and splicing of other nad1 transcripts, from which we can infer the order in which cis- and trans-spliced nad1 transcripts are normally processed. Improper splicing of nad1 transcripts leads to the absence of mitochondrial complex I and alteration of the nuclear transcriptome, notably influencing the alternative splicing of a variety of nuclear genes. Our results indicate that the mitochondrial PPR19 is an essential component in the splicing of nad1 transcripts, which is crucial for mitochondrial function and plant development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/nph.14528DOI Listing
July 2017

In Arabidopsis thaliana distinct alleles encoding mitochondrial RNA PROCESSING FACTOR 4 support the generation of additional 5' termini of ccmB transcripts.

Plant Mol Biol 2017 Apr 22;93(6):659-668. Epub 2017 Feb 22.

Institut Molekulare Botanik, Universität Ulm, Albert-Einstein-Allee 11, 89069, Ulm, Germany.

In plant mitochondria, the 5' ends of many transcripts are generated post-transcriptionally. We show that the pentatricopeptide repeat (PPR) protein RNA PROCESSING FACTOR 4 (RPF4) supports the generation of extra 5' ends of ccmB transcripts in Landsberg erecta (Ler) and a number of other Arabidopsis thaliana ecotypes. RPF4 was identified in Ler applying a forward genetic approach supported by complementation studies of ecotype Columbia (Col), which generates the Ler-type extra ccmB 5' termini only after the introduction of the RPF4 allele from Ler. Studies with chimeric RPF4 proteins composed of various parts of the RPF4 proteins from Ler and Col identified differences in the N-terminal and central PPR motifs that explain ecotype-specific variations in ccmB processing. These results fit well with binding site predictions in ccmB transcripts based on the known determinants of nucleotide base recognition by PPR motifs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11103-017-0591-yDOI Listing
April 2017

The Pentatricopeptide Repeat Protein EMB2654 Is Essential for Trans-Splicing of a Chloroplast Small Ribosomal Subunit Transcript.

Plant Physiol 2017 02 23;173(2):1164-1176. Epub 2016 Dec 23.

Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009 Western Australia, Australia (N.A., H.R., L.V.P.S., L.E., J.D.B., K.A.H., I.S., C.C.d.F.-S.); and

We report the partial complementation and subsequent comparative molecular analysis of two nonviable mutants impaired in chloroplast translation, one (emb2394) lacking the RPL6 protein, and the other (emb2654) carrying a mutation in a gene encoding a P-class pentatricopeptide repeat protein. We show that EMB2654 is required for the trans-splicing of the plastid rps12 transcript and that therefore the emb2654 mutant lacks Rps12 protein and fails to assemble the small subunit of the plastid ribosome, explaining the loss of plastid translation and consequent embryo-lethal phenotype. Predictions of the EMB2654 binding site match a small RNA "footprint" located on the 5' half of the trans-spliced intron that is almost absent in the partially complemented mutant. EMB2654 binds sequence specifically to this target sequence in vitro. Altered patterns in nuclease-protected small RNA fragments in emb2654 show that EMB2654 binding must be an early step in, or prior to, the formation of a large protein-RNA complex covering the free ends of the two rps12 intron halves.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.16.01840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5291019PMC
February 2017

The MTL1 Pentatricopeptide Repeat Protein Is Required for Both Translation and Splicing of the Mitochondrial NADH DEHYDROGENASE SUBUNIT7 mRNA in Arabidopsis.

Plant Physiol 2016 Jan 4;170(1):354-66. Epub 2015 Nov 4.

Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, AgroParisTech, Centre National de la Recherche Scientifique, Université Paris-Saclay, 78026 Versailles cedex, France (N.H., N.P., N.A., M.Q., N.V., J.D., H.M.);Université Paris-Sud, Université Paris-Saclay, 91405 Orsay cedex, France (N.H., N.P.); andAustralian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, Western Australia 6009, Australia (C.C.d.F.-S.)

Mitochondrial translation involves a complex interplay of ancient bacteria-like features and host-derived functionalities. Although the basic components of the mitochondrial translation apparatus have been recognized, very few protein factors aiding in recruiting ribosomes on mitochondria-encoded messenger RNA (mRNAs) have been identified in higher plants. In this study, we describe the identification of the Arabidopsis (Arabidopsis thaliana) MITOCHONDRIAL TRANSLATION FACTOR1 (MTL1) protein, a new member of the Pentatricopeptide Repeat family, and show that it is essential for the translation of the mitochondrial NADH dehydrogenase subunit7 (nad7) mRNA. We demonstrate that mtl1 mutant plants fail to accumulate the Nad7 protein, even though the nad7 mature mRNA is produced and bears the same 5' and 3' extremities as in wild-type plants. We next observed that polysome association of nad7 mature mRNA is specifically disrupted in mtl1 mutants, indicating that the absence of Nad7 results from a lack of translation of nad7 mRNA. These findings illustrate that mitochondrial translation requires the intervention of gene-specific nucleus-encoded PPR trans-factors and that their action does not necessarily involve the 5' processing of their target mRNA, as observed previously. Interestingly, a partial decrease in nad7 intron 2 splicing was also detected in mtl1 mutants, suggesting that MTL1 is also involved in group II intron splicing. However, this second function appears to be less essential for nad7 expression than its role in translation. MTL1 will be instrumental to understand the multifunctionality of PPR proteins and the mechanisms governing mRNA translation and intron splicing in plant mitochondria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.15.01591DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4704600PMC
January 2016

AEF1/MPR25 is implicated in RNA editing of plastid atpF and mitochondrial nad5, and also promotes atpF splicing in Arabidopsis and rice.

Plant J 2015 Mar;81(5):661-9

Australian Research Council Centre of Excellence in Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.

RNA editing is an essential mechanism that modifies target cytidines to uridine in both mitochondrial and plastid mRNA. Target sites are recognized by pentatricopeptide repeat (PPR) proteins. Using bioinformatics predictions based on the code describing sequence recognition by PPR proteins, we have identified an Arabidopsis editing factor required for editing of atpF in plastids. A loss-of-function mutation in ATPF EDITING FACTOR 1 (AEF1, AT3G22150) results in severe variegation, presumably due to decreased plastid ATP synthase levels. Loss of editing at the atpF site is coupled with a large decrease in splicing of the atpF transcript, even though the editing site is within an exon and 53 nucleotides distant from the splice site. The rice orthologue of AEF1, MPR25, has been reported to be required for editing of a site in mitochondrial nad5 transcripts, and we confirm that editing of the same site is affected in the Arabidopsis aef1 mutant. We also show that splicing of chloroplast atpF transcripts is affected in the rice mpr25 mutant. AEF1 is thus highly unusual for an RNA editing specificity factor in that it has functions in both organelles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/tpj.12756DOI Listing
March 2015

Decreasing electron flux through the cytochrome and/or alternative respiratory pathways triggers common and distinct cellular responses dependent on growth conditions.

Plant Physiol 2015 Jan 6;167(1):228-50. Epub 2014 Nov 6.

Molekulare Zellbiologie der Pflanzen, Institut für Biologie, Humboldt-Universität zu Berlin, D-10115 Berlin, Germany (K.K.);Australian Research Council Centre of Excellence in Plant Energy Biology (G.Y., O.D., S.K.-J., C.C.d.F.S.) andCentre for Plant Genetics and Breeding (P.K.), University of Western Australia, Crawley, Western Australia 6009, Australia;National Genebank, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China (G.Y.);Australian Research Council Centre of Excellence in Plant Energy Biology, School of Life Science, La Trobe University, Bundoora, Victoria 3083, Australia (S.R.L., Y.W., R.N., J.W.);Department of Organelle Biology and Biotechnology, Max-Planck-Institut für Molekulare Pflanzenphysiologie, D-14476 Potsdam-Golm, Germany (E.M.); andIllumina, Inc., Scoresby, Victoria 3179, Australia (E.G.)

Diverse signaling pathways are activated by perturbation of mitochondrial function under different growth conditions.Mitochondria have emerged as an important organelle for sensing and coping with stress in addition to being the sites of important metabolic pathways. Here, responses to moderate light and drought stress were examined in different Arabidopsis (Arabidopsis thaliana) mutant plants lacking a functional alternative oxidase (alternative oxidase1a [aox1a]), those with reduced cytochrome electron transport chain capacity (T3/T7 bacteriophage-type RNA polymerase, mitochondrial, and plastidial [rpoTmp]), and double mutants impaired in both pathways (aox1a:rpoTmp). Under conditions considered optimal for growth, transcriptomes of aox1a and rpoTmp were distinct. Under adverse growth conditions, however, transcriptome changes in aox1a and rpoTmp displayed a highly significant overlap and were indicative of a common mitochondrial stress response and down-regulation of photosynthesis. This suggests that the role of mitochondria to support photosynthesis is provided through either the alternative pathway or the cytochrome pathway, and when either pathway is inhibited, such as under environmental stress, a common, dramatic, and succinct mitochondrial signal is activated to alter energy metabolism in both organelles. aox1a:rpoTmp double mutants grown under optimal conditions showed dramatic reductions in biomass production compared with aox1a and rpoTmp and a transcriptome that was distinct from aox1a or rpoTmp. Transcript data indicating activation of mitochondrial biogenesis in aox1a:rpoTmp were supported by a proteomic analysis of over 200 proteins. Under optimal conditions, aox1a:rpoTmp plants seemed to switch on many of the typical mitochondrial stress regulators. Under adverse conditions, aox1a:rpoTmp turned off these responses and displayed a biotic stress response. Taken together, these results highlight the diverse signaling pathways activated by the perturbation of mitochondrial function under different growth conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.114.249946DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4281006PMC
January 2015

The Pentatricopeptide Repeat Proteins TANG2 and ORGANELLE TRANSCRIPT PROCESSING439 Are Involved in the Splicing of the Multipartite nad5 Transcript Encoding a Subunit of Mitochondrial Complex I.

Plant Physiol 2014 Aug 23;165(4):1409-1416. Epub 2014 Jun 23.

Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, Western Australia 6009, Australia (C.C.d.F.-S., A.F.d.L., E.L., S.K.T., I.S.); andDepartment of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom (Y.L., C.S., M.W.B.).

Pentatricopeptide repeat proteins constitute a large family of RNA-binding proteins in higher plants (around 450 genes in Arabidopsis [Arabidopsis thaliana]), mostly targeted to chloroplasts and mitochondria. Many of them are involved in organelle posttranscriptional processes, in a very specific manner. Splicing is necessary to remove the group II introns, which interrupt the coding sequences of several genes encoding components of the mitochondrial respiratory chain. The nad5 gene is fragmented in five exons, belonging to three distinct transcription units. Its maturation requires two cis- and two trans-splicing events. These steps need to be performed in a very precise order to generate a functional transcript. Here, we characterize two pentatricopeptide repeat proteins, ORGANELLE TRANSCRIPT PROCESSING439 and TANG2, and show that they are involved in the removal of nad5 introns 2 and 3, respectively. To our knowledge, they are the first two specific nad5 splicing factors found in plants so far.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.114.244616DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4119027PMC
August 2014

Group II intron splicing factors in plant mitochondria.

Front Plant Sci 2014 18;5:35. Epub 2014 Feb 18.

Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem Jerusalem, Israel.

Group II introns are large catalytic RNAs (ribozymes) which are found in bacteria and organellar genomes of several lower eukaryotes, but are particularly prevalent within the mitochondrial genomes (mtDNA) in plants, where they reside in numerous critical genes. Their excision is therefore essential for mitochondria biogenesis and respiratory functions, and is facilitated in vivo by various protein cofactors. Typical group II introns are classified as mobile genetic elements, consisting of the self-splicing ribozyme and its intron-encoded maturase protein. A hallmark of maturases is that they are intron specific, acting as cofactors which bind their own cognate containing pre-mRNAs to facilitate splicing. However, the plant organellar introns have diverged considerably from their bacterial ancestors, such as they lack many regions which are necessary for splicing and also lost their evolutionary related maturase ORFs. In fact, only a single maturase has been retained in the mtDNA of various angiosperms: the matR gene encoded in the fourth intron of the NADH-dehydrogenase subunit 1 (nad1 intron 4). Their degeneracy and the absence of cognate ORFs suggest that the splicing of plant mitochondria introns is assisted by trans-acting cofactors. Interestingly, in addition to MatR, the nuclear genomes of angiosperms also harbor four genes (nMat 1-4), which are closely related to maturases and contain N-terminal mitochondrial localization signals. Recently, we established the roles of two of these paralogs in Arabidopsis, nMAT1 and nMAT2, in the splicing of mitochondrial introns. In addition to the nMATs, genetic screens led to the identification of other genes encoding various factors, which are required for the splicing and processing of mitochondrial introns in plants. In this review we will summarize recent data on the splicing and processing of mitochondrial introns and their implication in plant development and physiology, with a focus on maturases and their accessory splicing cofactors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fpls.2014.00035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3927076PMC
April 2014

nMAT4, a maturase factor required for nad1 pre-mRNA processing and maturation, is essential for holocomplex I biogenesis in Arabidopsis mitochondria.

Plant J 2014 Apr 26;78(2):253-68. Epub 2014 Mar 26.

Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem, 91904, Israel.

Group II introns are large catalytic RNAs that are found in bacteria and organellar genomes of lower eukaryotes, but are particularly prevalent within mitochondria in plants, where they are present in many critical genes. The excision of plant mitochondrial introns is essential for respiratory functions, and is facilitated in vivo by various protein cofactors. Typical group II introns are classified as mobile genetic elements, consisting of the self-splicing ribozyme and its own intron-encoded maturase protein. A hallmark of maturases is that they are intron-specific, acting as cofactors that bind their intron-containing pre-RNAs to facilitate splicing. However, the degeneracy of the mitochondrial introns in plants and the absence of cognate intron-encoded maturase open reading frames suggest that their splicing in vivo is assisted by 'trans'-acting protein factors. Interestingly, angiosperms harbor several nuclear-encoded maturase-related (nMat) genes that contain N-terminal mitochondrial localization signals. Recently, we established the roles of two of these paralogs in Arabidopsis, nMAT1 and nMAT2, in the splicing of mitochondrial introns. Here we show that nMAT4 (At1g74350) is required for RNA processing and maturation of nad1 introns 1, 3 and 4 in Arabidopsis mitochondria. Seed germination, seedling establishment and development are strongly affected in homozygous nmat4 mutants, which also show modified respiration phenotypes that are tightly associated with complex I defects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/tpj.12466DOI Listing
April 2014

Surrogate mutants for studying mitochondrially encoded functions.

Biochimie 2014 May 29;100:234-42. Epub 2013 Aug 29.

Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. Electronic address:

Although chloroplast transformation is possible in some plant species, it is extremely difficult to create or select mutations in plant mitochondrial genomes, explaining why few genetic studies of mitochondrially encoded functions exist. In recent years it has become clear that many nuclear genes encode factors with key functions in organelle gene expression, and that often their action is restricted to a single organelle gene or transcript. Mutations in one of these nuclear genes thus leads to a specific primary defect in expression of a single organelle gene, and the nuclear mutation can be used as a surrogate for a phenotypically equivalent mutation in the organelle genome. These surrogate mutations often result in defective assembly of respiratory complexes, and lead to severe phenotypes including reduced growth and fertility, or even embryo-lethality. A wide collection of such mutants is now available, and this review summarises the progress in basic knowledge of mitochondrial biogenesis they have contributed to and points out areas where this resource has not been exploited yet.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biochi.2013.08.019DOI Listing
May 2014

The pentatricopeptide repeat MTSF1 protein stabilizes the nad4 mRNA in Arabidopsis mitochondria.

Nucleic Acids Res 2013 Jul 8;41(13):6650-63. Epub 2013 May 8.

INRA, UMR1318, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France, AgroParisTech, Institut Jean-Pierre Bourgin, RD10, F-78000 Versailles, France.

Gene expression in plant mitochondria involves a complex collaboration of transcription initiation and termination, as well as subsequent mRNA processing to produce mature mRNAs. In this study, we describe the function of the Arabidopsis mitochondrial stability factor 1 (MTSF1) gene and show that it encodes a pentatricopeptide repeat protein essential for the 3'-processing of mitochondrial nad4 mRNA and its stability. The nad4 mRNA is highly destabilized in Arabidopsis mtsf1 mutant plants, which consequently accumulates low amounts of a truncated form of respiratory complex I. Biochemical and genetic analyses demonstrated that MTSF1 binds with high affinity to the last 20 nucleotides of nad4 mRNA. Our data support a model for MTSF1 functioning in which its association with the last nucleotides of the nad4 3' untranslated region stabilizes nad4 mRNA. Additionally, strict conservation of the MTSF1-binding sites strongly suggests that the protective function of MTSF1 on nad4 mRNA is conserved in dicots. These results demonstrate that the mRNA stabilization process initially identified in plastids, whereby proteins bound to RNA extremities constitute barriers to exoribonuclease progression occur in plant mitochondria to protect and concomitantly define the 3' end of mature mitochondrial mRNAs. Our study also reveals that short RNA molecules corresponding to pentatricopeptide repeat-binding sites accumulate also in plant mitochondria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/nar/gkt337DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3711453PMC
July 2013

mCSF1, a nucleus-encoded CRM protein required for the processing of many mitochondrial introns, is involved in the biogenesis of respiratory complexes I and IV in Arabidopsis.

New Phytol 2013 Jul 7;199(2):379-394. Epub 2013 May 7.

Institute of Plant Sciences, Agricultural Research Organization (ARO), Volcani Center, Bet Dagan, 50250, Israel.

The coding regions of many mitochondrial genes in plants are interrupted by intervening sequences that are classified as group II introns. Their splicing is essential for the expression of the genes they interrupt and hence for respiratory function, and is facilitated by various protein cofactors. Despite the importance of these cofactors, only a few of them have been characterized. CRS1-YhbY domain (CRM) is a recently recognized RNA-binding domain that is present in several characterized splicing factors in plant chloroplasts. The Arabidopsis genome encodes 16 CRM proteins, but these are largely uncharacterized. Here, we analyzed the intracellular location of one of these hypothetical proteins in Arabidopsis, mitochondrial CAF-like splicing factor 1 (mCSF1; At4 g31010), and analyzed the growth phenotypes and organellar activities associated with mcsf1 mutants in plants. Our data indicated that mCSF1 resides within mitochondria and its functions are essential during embryogenesis. Mutant plants with reduced mCSF1 displayed inhibited germination and retarded growth phenotypes that were tightly associated with reduced complex I and IV activities. Analogously to the functions of plastid-localized CRM proteins, analysis of the RNA profiles in wildtype and mcsf1 plants showed that mCSF1 acts in the splicing of many of the group II intron RNAs in Arabidopsis mitochondria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/nph.12282DOI Listing
July 2013

The E domains of pentatricopeptide repeat proteins from different organelles are not functionally equivalent for RNA editing.

Plant J 2013 Jun 25;74(6):935-45. Epub 2013 Apr 25.

Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, WA 6009, Australia.

RNA editing in plants is an essential post-transcriptional process that modifies the genetic information encoded in organelle genomes. Forward and reverse genetics approaches have revealed the prevalent role of pentatricopeptide repeat (PPR) proteins in editing in both plastids and mitochondria, confirming the shared origin of this process in both organelles. The E domain at or near the C terminus of these proteins has been shown to be essential for editing, and is presumed to recruit the enzyme that deaminates the target cytidine residue. Here, we describe two mutants, otp71 and otp72, disrupted in genes encoding mitochondrial E-type PPR proteins with single editing defects in ccmFN 2 and rpl16 transcripts, respectively. Comparisons between the E domains of these proteins and previously reported editing factors from chloroplasts suggested that there are characteristic differences in the proteins between the two organelles. To test this, we swapped E domains between two mitochondrial and two chloroplast editing factors. In all cases investigated, E domains from the same organelle (chloroplast or mitochondria) were found to be exchangeable; however, swapping the E domain between organelles led to non-functional editing factors. We conclude that the E domains of mitochondrial and plastid PPR proteins are not functionally equivalent, and therefore that an important component of the putative editing complexes in the two organelles may be different.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/tpj.12180DOI Listing
June 2013

Mutations in an Arabidopsis mitochondrial transcription termination factor-related protein enhance thermotolerance in the absence of the major molecular chaperone HSP101.

Plant Cell 2012 Aug 31;24(8):3349-65. Epub 2012 Aug 31.

School of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.

The molecular chaperone heat shock protein101 (HSP101) is required for acquired thermotolerance in plants and other organisms. To identify factors that interact with HSP101 or that are involved in thermotolerance, we screened for extragenic suppressors of a dominant-negative allele of Arabidopsis thaliana HSP101, hot1-4. One suppressor, shot1 (for suppressor of hot1-4 1), encodes a mitochondrial transcription termination factor (mTERF)-related protein, one of 35 Arabidopsis mTERFs about which there is limited functional data. Missense (shot1-1) and T-DNA insertion (shot1-2) mutants suppress the hot1-4 heat-hypersensitive phenotype. Furthermore, shot1-2 suppresses other heat-sensitive mutants, and shot1-2 alone is more heat tolerant than the wild type. SHOT1 resides in mitochondria, indicating it functions independently of cytosolic/nuclear HSP101. Microarray analysis suggests altered mitochondrial function and/or retrograde signaling in shot1-2 increases transcripts of other HSPs and alters expression of redox-related genes. Reduced oxidative damage is the likely cause of shot1 thermotolerance, indicating HSP101 repairs protein oxidative damage and/or reduced oxidative damage allows recovery in the absence of HSP101. Changes in organelle-encoded transcripts in shot1 demonstrate that SHOT1 is involved in organelle gene regulation. The heat tolerance of shot1 emphasizes the importance of mitochondria in stress tolerance, and defining its function may provide insights into control of oxidative damage for engineering stress-resistant plants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1105/tpc.112.101006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3462636PMC
August 2012

A PORR domain protein required for rpl2 and ccmF(C) intron splicing and for the biogenesis of c-type cytochromes in Arabidopsis mitochondria.

Plant J 2012 Mar 28;69(6):996-1005. Epub 2011 Dec 28.

Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009 WA, Australia.

Angiosperm mitochondria encode approximately 20 group II introns, which interrupt genes involved in the biogenesis and function of the respiratory chain. Nucleus-encoded splicing factors have been identified for approximately half of these introns. The splicing factors derive from several protein families defined by atypical RNA binding domains that function primarily in organelles. We show here that the Arabidopsis protein WTF9 is essential for the splicing of group II introns in two mitochondrial genes for which splicing factors had not previously been identified: rpl2 and ccmF(C). WTF9 harbors a recently recognized RNA binding domain, the PORR domain, which was originally characterized in the chloroplast splicing factor WTF1. These findings show that the PORR domain family also functions in plant mitochondria, and highlight the parallels between the machineries for group II intron splicing in plant mitochondria and chloroplasts. In addition, we used the splicing defects in wtf9 mutants as a means to functionally characterize the mitochondrial rpl2 and ccmF(C) genes. Loss of ccmF(C) expression correlates with the loss of cytochromes c and c₁, confirming a role for ccmF(C) in cytochrome biogenesis. By contrast, our results strongly suggest that splicing is not essential for the function of the mitochondrial rpl2 gene, and imply that the Rpl2 fragment encoded by rpl2 exon 1 functions in concert with a nuclear gene product that provides the remainder of this essential ribosomal protein in trans.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-313X.2011.04849.xDOI Listing
March 2012

The RCC1 family protein RUG3 is required for splicing of nad2 and complex I biogenesis in mitochondria of Arabidopsis thaliana.

Plant J 2011 Sep 6;67(6):1067-80. Epub 2011 Jul 6.

Australian Research Council Centre of Excellence in Plant Energy Biology, M316, University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia.

We have identified a mitochondrial protein (RUG3) that is required for accumulation of mitochondrial respiratory chain complex I. RUG3 is related to human REGULATOR OF CHROMOSOME CONDENSATION 1 (RCC1) and Arabidopsis UV-B RESISTANCE 8 (UVR8). Although the family of RCC1-like proteins in Arabidopsis has over 20 members, UVR8 is the sole plant representative of this family to have been functionally characterized. Mitochondria from Arabidopsis plants lacking a functional RUG3 gene showed greatly reduced complex I abundance and activity. In contrast, accumulation of complexes III, IV and V of the oxidative phosphorylation system and the capacity for succinate-dependent respiration were unaffected. A comprehensive study of processes contributing to complex I biogenesis in rug3 mutants revealed that RUG3 is required for efficient splicing of the nad2 mRNA, which encodes a complex I subunit. A comparison of the formation of complex I assembly intermediates between rug3 and wild type mitochondria indicated that NAD2 enters the assembly pathway at an early stage. Remarkably, rug3 mutants displayed increased capacities for import of nucleus-encoded mitochondrial proteins into the organelle and showed moderately increased mitochondrial transcript levels. This observation is consistent with global transcript changes indicating enhanced mitochondrial biogenesis in the rug3 mutant in response to the complex I defect.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-313X.2011.04658.xDOI Listing
September 2011

The pentatricopeptide repeat protein OTP87 is essential for RNA editing of nad7 and atp1 transcripts in Arabidopsis mitochondria.

J Biol Chem 2011 Jun 19;286(24):21361-71. Epub 2011 Apr 19.

Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009 Western Australia, Australia.

In plant organelles, RNA editing is a post-transcriptional mechanism that converts specific cytidines to uridines in RNA of both mitochondria and plastids, altering the information encoded by the gene. The cytidine to be edited is determined by a cis-element surrounding the editing site that is specifically recognized and bound by a trans-acting factor. All the trans-acting editing factors identified so far in plant organelles are members of a large protein family, the pentatricopeptide repeat (PPR) proteins. We have identified the Organelle Transcript Processing 87 (OTP87) gene, which is required for RNA editing of the nad7-C24 and atp1-C1178 sites in Arabidopsis mitochondria. OTP87 encodes an E-subclass PPR protein with an unusually short E-domain. The recombinant protein expressed in Escherichia coli specifically binds to RNAs comprising 30 nucleotides upstream and 10 nucleotides downstream of the nad7-C24 and atp1-C1178 editing sites. The loss-of-function of OTP87 results in small plants with growth and developmental delays. In the otp87 mutant, the amount of assembled respiratory complex V (ATP synthase) is highly reduced compared with the wild type suggesting that the amino acid alteration in ATP1 caused by loss of editing at the atp1-C1178 site affects complex V assembly in mitochondria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M111.230516DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3122196PMC
June 2011

Albinism does not correlate with biparental inheritance of plastid DNA in interspecific hybrids in Cicer species.

Plant Sci 2011 Apr 19;180(4):628-33. Epub 2011 Jan 19.

Centre for Legumes in Mediterranean Agriculture, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley, WA 6009, Australia.

Cultivated chickpea (Cicer arietinum) was crossed with its wild relatives from the genus Cicer to transfer favorable genes from the wider gene pool into the cultivar. Post-hybridization barriers led to yellowing and subsequent senescence from as early as 5 days after fertilization, however, the ovules of hybrid embryos could be rescued in vitro. Hybrids were classified as green, partially green or albino. The hybrid status of regenerated plantlets in vitro was confirmed by amplification of nuclear DNA markers. To check whether chloroplast development correlated with plastid DNA inheritance in these crosses, primers were designed using conserved plastid gene sequences from wild and cultivated species. All three possible plastid inheritance patterns were observed: paternal, maternal and biparental. This is the first report of biparental inheritance of plastid DNA in Cicer. No correlation was observed between parental origin of the plastid genome and degree of albinism, indicating that chloroplast development in hybrid genotypes was mostly influenced by nuclear factors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.plantsci.2011.01.003DOI Listing
April 2011

Rampant gene loss in the underground orchid Rhizanthella gardneri highlights evolutionary constraints on plastid genomes.

Mol Biol Evol 2011 Jul 2;28(7):2077-86. Epub 2011 Feb 2.

Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Perth, Australia.

Since the endosymbiotic origin of chloroplasts from cyanobacteria 2 billion years ago, the evolution of plastids has been characterized by massive loss of genes. Most plants and algae depend on photosynthesis for energy and have retained ∼110 genes in their chloroplast genome that encode components of the gene expression machinery and subunits of the photosystems. However, nonphotosynthetic parasitic plants have retained a reduced plastid genome, showing that plastids have other essential functions besides photosynthesis. We sequenced the complete plastid genome of the underground orchid, Rhizanthella gardneri. This remarkable parasitic subterranean orchid possesses the smallest organelle genome yet described in land plants. With only 20 proteins, 4 rRNAs, and 9 tRNAs encoded in 59,190 bp, it is the least gene-rich plastid genome known to date apart from the fragmented plastid genome of some dinoflagellates. Despite numerous differences, striking similarities with plastid genomes from unrelated parasitic plants identify a minimal set of protein-encoding and tRNA genes required to reside in plant plastids. This prime example of convergent evolution implies shared selective constraints on gene loss or transfer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/molbev/msr028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3112369PMC
July 2011

OTP70 is a pentatricopeptide repeat protein of the E subgroup involved in splicing of the plastid transcript rpoC1.

Plant J 2011 Feb 4;65(4):532-42. Epub 2011 Jan 4.

Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009 WA, Australia.

Over 20 proteins of the pentatricopeptide repeat (PPR) family have been demonstrated to be involved in RNA editing in plant mitochondria and chloroplasts. All of these editing factors contain a so-called 'E' domain that has been shown to be essential for editing to occur. The presumption has been that this domain recruits the (unknown) editing enzyme to the RNA. In this report, we show that not all putative E-class PPR proteins are directly involved in RNA editing. Disruption of the OTP70 gene leads to a strong defect in splicing of the plastid transcript rpoC1, leading to a virescent phenotype. The mutant has a chloroplast transcript pattern characteristic of a reduction in plastid-encoded RNA polymerase activity. The E domain of OTP70 is not required for splicing, and can be deleted or replaced by the E domain from the known editing factor CRR4 without loss of rpoC1 splicing. Furthermore, the E domain of OTP70 is incapable of inducing RNA editing when fused to the RNA binding domain of CRR4. We conclude that the truncated E domain of OTP70 is no longer functional in RNA editing, and that the protein has acquired a new function in promoting RNA splicing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-313X.2010.04441.xDOI Listing
February 2011

Identification of a pentatricopeptide repeat protein implicated in splicing of intron 1 of mitochondrial nad7 transcripts.

J Biol Chem 2010 Oct 3;285(42):32192-9. Epub 2010 Aug 3.

Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom.

Splicing of plant organellar transcripts is facilitated by members of a large protein family, the pentatricopeptide repeat proteins. We have identified a pentatricopeptide repeat protein in a genetic screen for mutants resistant to inhibition of root growth by buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis and consequently named BIR6 (BSO-insensitive roots 6). BIR6 is involved in splicing of intron 1 of the mitochondrial nad7 transcript. Loss-of-function mutations in BIR6 result in a strongly reduced accumulation of fully processed nad7 transcript. This affects assembly of Complex I and results in moderate growth retardation. In agreement with disruption of Complex I function, the genes encoding alternative NADH oxidizing enzymes are induced in the mutant, and the mutant plants are less sensitive to mannitol and salt stress. Mutation in the BIR6 gene allowed normal root growth in presence of BSO and strongly attenuated depletion of glutathione content at these conditions. The same phenotype was observed with other mutants affected in function of Complex I, thus reinforcing the importance of Complex I function for cellular redox homeostasis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M110.147603DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2952220PMC
October 2010

Three highly similar formate dehydrogenase genes located in the vicinity of the B4 resistance gene cluster are differentially expressed under biotic and abiotic stresses in Phaseolus vulgaris.

Theor Appl Genet 2010 Jun 25;121(1):87-103. Epub 2010 Feb 25.

Institut de Biotechnologie des Plantes, UMR-CNRS 8618, bât. 630, Université Paris-Sud, 91405, Orsay, France.

In higher plants, formate dehydrogenase (FDH, EC1.2.1.2.) catalyzes the NAD-linked oxidation of formate to CO(2), and FDH transcript accumulation has been reported after various abiotic stresses. By sequencing a Phaseolus vulgaris BAC clone encompassing a CC-NBS-LRR gene rich region of the B4 resistance gene cluster, we identified three FDH-encoding genes. FDH is present as a single copy gene in the Arabidopsis thaliana genome, and public database searches confirm that FDH is a low copy gene in plant genomes, since only 33 FDH homologs were identified from 27 plant species. Three independent prediction programs (Predotar, TargetP and Mitoprot) used on this large subset of 33 plant FDHs, revealed that mitochondrial localization of FDH might be the rule in higher plants. A phylogenetic analysis suggests a scenario of local FDH gene duplication in an ancestor of the Phaseoleae followed by another more recent duplication event after bean/soybean divergence. The expression levels of two common bean FDH genes under different treatments were investigated by quantitative RT-PCR analysis. FDH genes are differentially up-regulated after biotic and abiotic stresses (infection with the fungus Colletotrichum lindemuthianum, and dark treatment, respectively). The present study provides the first report of FDH transcript accumulation after biotic stress, suggesting the involvement of FDH in the pathogen resistance process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s00122-010-1293-xDOI Listing
June 2010

Repression of formate dehydrogenase in Solanum tuberosum increases steady-state levels of formate and accelerates the accumulation of proline in response to osmotic stress.

Plant Mol Biol 2003 Aug;52(6):1153-68

Institut de Biotechnologie des Plantes UMR CNRS 8618, Université Paris-Sud, 91405 Orsay cedex, France.

Formate dehydrogenase (FDH, EC 1.2.1.2.) is a soluble mitochondrial enzyme capable of oxidizing formate into CO2 in the presence of NAD+. It is abundant in non-green tissues and scarce in photosynthetic tissues. Under stress, FDH transcripts (and protein) accumulate in leaves, and leaf mitochondria acquire the ability to use formate as a respiratory substrate. In this paper, we describe the analysis of transgenic potato plants under-expressing FDH, obtained in order to understand the physiological function of FDH. Plants expressing low FDH activities were selected and the study was focused on a line (AS23) showing no detectable FDH activity. AS23 plants were morphologically indistinguishable from control plants, and grew normally under standard conditions. However, mitochondria isolated from AS23 tubers could not use formate as a respiratory substrate. Steady-state levels of formate were higher in AS23 leaves and tubers than in control plants. Tubers of untransformed plants oxidized 14C formate into 14CO2 but AS23 tubers accumulated it. In order to reveal a possible phenotype under stress conditions, control and AS23 plants were submitted to drought and cold. These treatments dramatically induced FDH transcripts in control plants but, whatever the growth conditions, no 1.4 kb FDH transcripts were detected in leaves of AS23 plants. Amongst various biochemical and molecular differences between stressed AS23 and control plants, the most striking was a dramatically faster accumulation of proline in the leaves of drought-stressed plants under-expressing FDH.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1023/b:plan.0000004306.96945.efDOI Listing
August 2003