Publications by authors named "Guan-Feng Wang"

21 Publications

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The novel pathogen-responsive glycosyltransferase UGT73C7 mediates the redirection of phenylpropanoid metabolism and promotes SNC1-dependent Arabidopsis immunity.

Plant J 2021 Apr 18. Epub 2021 Apr 18.

The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, 266237, China.

Recent studies have shown that global metabolic reprogramming is a common event in plant innate immunity; however, the relevant molecular mechanisms remain largely unknown. Here, we identified a pathogen-induced glycosyltransferase, UGT73C7, that plays a critical role in Arabidopsis disease resistance through mediating redirection of the phenylpropanoid pathway. Loss of UGT73C7 function resulted in significantly decreased resistance to Pseudomonas syringae pv. tomato DC3000, whereas constitutive overexpression of UGT73C7 led to an enhanced defense response. UGT73C7-activated immunity was demonstrated to be dependent on the upregulated expression of SNC1, a Toll/interleukin 1 receptor-type NLR gene. Furthermore, in vitro and in vivo assays indicated that UGT73C7 could glycosylate p-coumaric acid and ferulic acid, the upstream metabolites in the phenylpropanoid pathway. Mutations that lead to the loss of UGT73C7 enzyme activities resulted in the failure to induce SNC1 expression. Moreover, glycosylation activity of UGT73C7 resulted in the redirection of phenylpropanoid metabolic flux to biosynthesis of hydroxycinnamic acids and coumarins. The disruption of the phenylpropanoid pathway suppressed UGT73C7-promoted SNC1 expression and the immune response. This study not only identified UGT73C7 as an important regulator that adjusts phenylpropanoid metabolism upon pathogen challenge, but also provided a link between phenylpropanoid metabolism and an NLR gene.
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http://dx.doi.org/10.1111/tpj.15280DOI Listing
April 2021

The potential roles of different metacaspases in maize defense response.

Plant Signal Behav 2021 Jun 12;16(6):1906574. Epub 2021 Apr 12.

The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, Shandong, PR China.

Metacaspases (MCs), a class of cysteine-dependent proteases, act as important regulators in plant defense response. In maize genome, there are 11 which have been categorized into two types (type I and II) based on their structural differences. In this study, we investigated the different transcript patterns of 11 in maize defense response mediated by the nucleotide-binding, leucine-rich-repeat protein Rp1-D21. We further predicted that many -elements responsive to salicylic acid (SA), methyl jasmonate (MeJA), abscisic acid (ABA) and auxin were identified in the promoter regions of , and several different transcription factors were predicted to bind to their promoters. We analyzed the localization of with previously identified quantitative trait loci (QTLs) in maize disease resistance, and found that all other , except for , are co-located with at least one QTL associated with disease resistance to southern leaf blight, northern leaf blight, gray leaf spot or ear rot. Based on previous RNA-seq analysis, different display different transcript levels in response to and . All the results imply that the members of might have differential functions to different maize diseases. This study lays the basis for further investigating the roles of in maize disease resistance.
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http://dx.doi.org/10.1080/15592324.2021.1906574DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8143262PMC
June 2021

Maize nicotinate N-methyltransferase interacts with the NLR protein Rp1-D21 and modulates the hypersensitive response.

Mol Plant Pathol 2021 May 6;22(5):564-579. Epub 2021 Mar 6.

The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, China.

Most plant intracellular immune receptors belong to nucleotide-binding, leucine-rich repeat (NLR) proteins. The recognition between NLRs and their corresponding pathogen effectors often triggers a hypersensitive response (HR) at the pathogen infection sites. The nicotinate N-methyltransferase (NANMT) is responsible for the conversion of nicotinate to trigonelline in plants. However, the role of NANMT in plant defence response is unknown. In this study, we demonstrated that the maize ZmNANMT, but not its close homolog ZmCOMT, an enzyme in the lignin biosynthesis pathway, suppresses the HR mediated by the autoactive NLR protein Rp1-D21 and its N-terminal coiled-coil signalling domain (CC ). ZmNANMT, but not ZmCOMT, interacts with CC , and they form a complex with HCT1806 and CCoAOMT2, two key enzymes in lignin biosynthesis, which can also suppress the autoactive HR mediated by Rp1-D21. ZmNANMT is mainly localized in the cytoplasm and nucleus, and either localization is important for suppressing the HR phenotype. These results lay the foundation for further elucidating the molecular mechanism of NANMTs in plant disease resistance.
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http://dx.doi.org/10.1111/mpp.13044DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8035639PMC
May 2021

Analysis of the transcriptomic, metabolomic, and gene regulatory responses to Puccinia sorghi in maize.

Mol Plant Pathol 2021 Apr 28;22(4):465-479. Epub 2021 Feb 28.

Department of Entomology and Plant Pathology, NC State University, Raleigh, North Carolina, USA.

Common rust, caused by Puccinia sorghi, is a widespread and destructive disease of maize. The Rp1-D gene confers resistance to the P. sorghi IN2 isolate, mediating a hypersensitive cell death response (HR). To identify differentially expressed genes (DEGs) and metabolites associated with the compatible (susceptible) interaction and with Rp1-D-mediated resistance in maize, we performed transcriptomics and targeted metabolome analyses of P. sorghi IN2-infected leaves from the near-isogenic lines H95 and H95:Rp1-D, which differed for the presence of Rp1-D. We observed up-regulation of genes involved in the defence response and secondary metabolism, including the phenylpropanoid, flavonoid, and terpenoid pathways. Metabolome analyses confirmed that intermediates from several transcriptionally up-regulated pathways accumulated during the defence response. We identified a common response in H95:Rp1-D and H95 with an additional H95:Rp1-D-specific resistance response observed at early time points at both transcriptional and metabolic levels. To better understand the mechanisms underlying Rp1-D-mediated resistance, we inferred gene regulatory networks occurring in response to P. sorghi infection. A number of transcription factors including WRKY53, BHLH124, NKD1, BZIP84, and MYB100 were identified as potentially important signalling hubs in the resistance-specific response. Overall, this study provides a novel and multifaceted understanding of the maize susceptible and resistance-specific responses to P. sorghi.
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http://dx.doi.org/10.1111/mpp.13040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7938627PMC
April 2021

Maize metacaspases modulate the defense response mediated by the NLR protein Rp1-D21 likely by affecting its subcellular localization.

Plant J 2021 01 20;105(1):151-166. Epub 2020 Nov 20.

The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, Shandong, 266237, PR China.

Plants usually employ resistance (R) genes to defend against the infection of pathogens, and most R genes encode intracellular nucleotide-binding, leucine-rich repeat (NLR) proteins. The recognition between R proteins and their cognate pathogens often triggers a rapid localized cell death at the pathogen infection sites, termed the hypersensitive response (HR). Metacaspases (MCs) belong to a cysteine protease family, structurally related to metazoan caspases. MCs play crucial roles in plant immunity. However, the underlying molecular mechanism and the link between MCs and NLR-mediated HR are not clear. In this study, we systematically investigated the MC gene family in maize and identified 11 ZmMCs belonging to two types. Further functional analysis showed that the type I ZmMC1 and ZmMC2, but not the type II ZmMC9, suppress the HR-inducing activity of the autoactive NLR protein Rp1-D21 and of its N-terminal coiled-coil (CC ) signaling domain when transiently expressed in Nicotiana benthamiana. ZmMC1 and ZmMC2 physically associate with CC in vivo. We further showed that ZmMC1 and ZmMC2, but not ZmMC9, are predominantly localized in a punctate distribution in both N. benthamiana and maize (Zea mays) protoplasts. Furthermore, the co-expression of ZmMC1 and ZmMC2 with Rp1-D21 and CC causes their re-distribution from being uniformly distributed in the nucleocytoplasm to a punctate distribution co-localizing with ZmMC1 and ZmMC2. We reveal a novel role of plant MCs in modulating the NLR-mediated defense response and derive a model to explain it.
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http://dx.doi.org/10.1111/tpj.15047DOI Listing
January 2021

Genome-wide identification of the maize 2OGD superfamily genes and their response to Fusarium verticillioides and Fusarium graminearum.

Gene 2021 Jan 25;764:145078. Epub 2020 Aug 25.

The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, Shandong 266237, PR China. Electronic address:

In maize, eat rot and stalk rot caused by Fusarium verticillioides and Fusarium graminearum lead to contamination of moldy grains to produce mycotoxins. Identification of resistance genes against these pathogens for maize breeding is an effective way for disease control. Several 2-oxoglutarate-dependent dioxygenase (2OGD) proteins have been found to confer resistance to different pathogens in diverse plant species. However, little is known about the 2OGD superfamily in maize. Here, we identified 103 putative 2OGD genes in maize from a genome-wide analysis, and divided them into three classes - DOXA, DOXB, and DOXC. We further comprehensively investigated their gene structure, chromosome distribution, phylogenetic tree, gene-function enrichment, and expression profiles among different tissues. The genes encoding three 2OGD proteins, ACO, F3H, and NCS involved in ethylene biosynthesis, flavonoids biosynthesis, and alkaloids biosynthesis pathways, respectively, were identified to be induced by F. verticillioides and F. graminearum. The promoters of the three genes contain the binding sites for the transcription factor ZmDOF and ZmHSF, which are also induced by the two pathogens. The results imply that the three 2OGDs and the two transcription factors might be involved in the resistance to the two pathogens. This study provided a comprehensive understanding of the 2OGD superfamily in maize and laid the foundation for the further functional analysis of their roles in maize resistance to eat rot and stalk rot.
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http://dx.doi.org/10.1016/j.gene.2020.145078DOI Listing
January 2021

Fine-Tuning Immunity: Players and Regulators for Plant NLRs.

Trends Plant Sci 2020 07 17;25(7):695-713. Epub 2020 Mar 17.

The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, Shandong 266237, PR China. Electronic address:

Plants have evolved a sophisticated innate immune system to defend against pathogen infection, and intracellular nucleotide-binding, leucine-rich repeat (NLR or NB-LRR) immune receptors are one of the main components of this system. NLR activity is fine-tuned by intra- and intermolecular interactions. We survey what is known about the conservation and diversity of NLR-interacting proteins, and divide them into seven major categories. We discuss the molecular mechanisms by which NLR activities are regulated and how understanding this regulation has potential to facilitate the engineering of NLRs for crop improvement.
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http://dx.doi.org/10.1016/j.tplants.2020.02.008DOI Listing
July 2020

Maize ZmFNSI Homologs Interact with an NLR Protein to Modulate Hypersensitive Response.

Int J Mol Sci 2020 Apr 5;21(7). Epub 2020 Apr 5.

The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao 266237, China.

Nucleotide binding, leucine-rich-repeat (NLR) proteins are the major class of resistance (R) proteins used by plants to defend against pathogen infection. The recognition between NLRs and their cognate pathogen effectors usually triggers a rapid localized cell death, termed the hypersensitive response (HR). Flavone synthase I (FNSI) is one of the key enzymes in the flavone biosynthesis pathway. It also displays salicylic acid (SA) 5-hydroxylase (S5H) activity. A close homolog of FNSI/S5H displays SA 3-hydroxylase (S3H) activity. Both FNSI/S5H and S3H play important roles in plant innate immunity. However, the underlying molecular mechanisms and the relationship between S5H and S3H with the NLR-mediated HR are not known in any plant species. In this study, we identified three genes encoding ZmFNSI-1, ZmFNSI-2 and ZmS3H that are significantly upregulated in a maize line carrying an autoactive NLR mutant. Functional analysis showed that ZmFNSI-1 and ZmFNSI-2, but not ZmS3H, suppressed HR conferred by Rp1-D21 and its signaling domain CC when transiently expressed in . ZmFNSI-1 and ZmFNSI-2 physically interacted with CC. Furthermore, ZmFNSI-1 and ZmFNSI-2 interacted with HCT, a key enzyme in lignin biosynthesis pathway, which can also suppress Rp1-D21-mediated HR. These results lay the foundation for the further functional analysis of the roles of FNSI in plant innate immunity.
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http://dx.doi.org/10.3390/ijms21072529DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7177559PMC
April 2020

Protective effects of lipoic acid-niacin dimers against blue light-induced oxidative damage to retinal pigment epithelium cells.

Int J Ophthalmol 2019 18;12(8):1262-1271. Epub 2019 Aug 18.

Department of Ophthalmology, General Hospital of Southern Theatre Command of PLA, Guangzhou 510010, Guangdong Province, China.

Aim: To evaluate the protective effects of lipoic acid-niacin (N2L) dimers against blue light (BL)-induced oxidative damage to human retinal pigment epithelium (hRPE) cells

Methods: hRPE cells were divided into a control group (CG), a BL group, an N2L plus BL irradiation group, an α-lipoic acid (ALA) plus BL group, an ALA-only group, and an N2L-only group. hRPE cellular viability was detected by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) bromide assays, and apoptosis was evaluated by annexin-V-PE/7-AAD staining followed by flow cytometry. Ultrastructural changes in subcellular organelles were observed by transmission electron microscopy. Reactive oxygen species formation was assayed by flow cytometry. The expression levels of the apoptosis-related proteins BCL-2 associated X protein (BAX), B-cell leukmia/lymphoma 2 (BCL-2), and caspase-3 were quantified by Western blot analysis.

Results: BL exposure with a light density of 4±0.5 mW/cm exceeding 6h caused hRPE toxicity, whereas treatment with a high dose of N2L (100 mol/L) or ALA (150 mol/L) maintained cell viability at control levels. BL exposure caused vacuole-like degeneration, mitochondrial swelling, and reduced microvillus formation; however, a high dose of N2L or ALA maintained the ultrastructure of hRPE cells and their organelles. High doses of N2L and ALA also protected hRPE cells from BL-induced apoptosis, which was confirmed by Western blot analysis: BCL-2 expression significantly increased, while BAX and caspase-3 expression slightly decreased compared to the CG.

Conclusion: High-dose N2L treatment (>100 mol/L) can reduce oxidative damage in degenerating hRPE cells exposed to BL with an efficacy similar to ALA.
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http://dx.doi.org/10.18240/ijo.2019.08.05DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6694045PMC
August 2019

Protection of tight junction between RPE cells with tissue factor targeting peptide.

Int J Ophthalmol 2018 18;11(10):1594-1599. Epub 2018 Oct 18.

General Surgery, Aviation General Hospital, Beijing 100012, China.

Aim: To investigate the effect of tissue factor targeting peptide (TF-TP) on retinal pigment epithelium (RPE) cells tight junctions.

Methods: Cell counting kit-8 (CCK-8) was used to measure the proliferation of ARPE-19 cells. Expression of tight junction, ZO-1 in ARPE-19 cells was measured by Western blot and immunofluorescent staining. Western blot was also used to detect the expression of tissue factor (TF). CEC Transmigration Assay was used to measure the migration of ARPE-19 cells. The transport of fluorescent markers [fluorescein isothiocyanate dextrans of 4, 10, 20 (FD4, FD10, FD20)] and the transepithelial electrical resistance (TEER) were used to measure in ARPE-19 cell.

Results: CCK-8 assay showed that 5 µmol/L TF-TP can inhibit ARPE-19 cells abnormally proliferation stimulated by lipopolysaccharide (LPS; <0.05). LPS increased the transport of fluorescent markers (FD4, FD10, FD20) and decreased TEER levels in ARPE-19 cells, respectively, which were prevented by 5 µmol/L TF-TP pretreatment (<0.05). Furthermore, LPS significantly up-regulated the expression of TF and downregulated the expression of ZO-1 (<0.05) in ARPE-19 cell which was inhibited by the TF-TP (<0.05). In addition, TF-TP inhibited the abnormal migration induced by LPS in ARPE-19 cell (<0.05).

Conclusion: Our findings suggest that TF-TP suppressed proliferation and migration of ARPE-19 cells induced by LPS, and maintained the RPE tight junctions through inhibition of TF expression and increased expression of ZO-1.
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http://dx.doi.org/10.18240/ijo.2018.10.04DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6192970PMC
October 2018

Maize Homologs of CCoAOMT and HCT, Two Key Enzymes in Lignin Biosynthesis, Form Complexes with the NLR Rp1 Protein to Modulate the Defense Response.

Plant Physiol 2016 07 10;171(3):2166-77. Epub 2016 May 10.

Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina 27695 (G.-F.W., P.J.B.-K.)Key Laboratory of Plant Cell Engineering and Germplasm Innovation, Ministry of Education, School of Life Sciences, Shandong University, Jinan, Shandong 250100, P.R. China (G.-F.W.); U.S. Department of Agriculture-Agricultural Research Service, Plant Science Research Unit, Raleigh, North Carolina 27695 (P.J.B.-K.).

Disease resistance (R) genes encode nucleotide binding Leu-rich-repeat (NLR) proteins that confer resistance to specific pathogens. Upon pathogen recognition they trigger a defense response that usually includes a so-called hypersensitive response (HR), a rapid localized cell death at the site of pathogen infection. Intragenic recombination between two maize (Zea mays) NLRs, Rp1-D and Rp1-dp2, resulted in the formation of a hybrid NLR, Rp1-D21, which confers an autoactive HR in the absence of pathogen infection. From a previous quantitative trait loci and genome-wide association study, we identified genes encoding two key enzymes in lignin biosynthesis, hydroxycinnamoyltransferase (HCT) and caffeoyl CoA O-methyltransferase (CCoAOMT), adjacent to the nucleotide polymorphisms that were highly associated with variation in the severity of Rp1-D21-induced HR We have previously shown that the two maize HCT homologs suppress the HR conferred by Rp1-D21 in a heterologous system, very likely through physical interaction. Here, we show, similarly, that CCoAOMT2 suppresses the HR induced by either the full-length or by the N-terminal coiled-coil domain of Rp1-D21 also likely via physical interaction and that the metabolic activity of CCoAOMT2 is unlikely to be necessary for its role in suppressing HR. We also demonstrate that CCoAOMT2, HCTs, and Rp1 proteins can form in the same complexes. A model is derived to explain the roles of CCoAOMT and HCT in Rp1-mediated defense resistance.
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http://dx.doi.org/10.1104/pp.16.00224DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4936554PMC
July 2016

Maize Homologs of Hydroxycinnamoyltransferase, a Key Enzyme in Lignin Biosynthesis, Bind the Nucleotide Binding Leucine-Rich Repeat Rp1 Proteins to Modulate the Defense Response.

Plant Physiol 2015 Nov 15;169(3):2230-43. Epub 2015 Sep 15.

Departments of Plant Pathology (G.-F.W., Y.H., B.A.O., P.J.B.-K.),Plant and Microbial Biology (R.S., X.L.), andBiological Sciences (D.N.), North Carolina State University, Raleigh, North Carolina 27695;Plants for Human Health Institute, North Carolina State University, Kannapolis, North Carolina 28081 (R.S., X.L.); andPlant Science Research Unit, United States Department of Agriculture-Agricultural Research Service, Raleigh, North Carolina 27695 (P.J.B.-K.)

In plants, most disease resistance genes encode nucleotide binding Leu-rich repeat (NLR) proteins that trigger a rapid localized cell death called a hypersensitive response (HR) upon pathogen recognition. The maize (Zea mays) NLR protein Rp1-D21 derives from an intragenic recombination between two NLRs, Rp1-D and Rp1-dp2, and confers an autoactive HR in the absence of pathogen infection. From a previous quantitative trait loci and genome-wide association study, we identified a single-nucleotide polymorphism locus highly associated with variation in the severity of Rp1-D21-induced HR. Two maize genes encoding hydroxycinnamoyltransferase (HCT; a key enzyme involved in lignin biosynthesis) homologs, termed HCT1806 and HCT4918, were adjacent to this single-nucleotide polymorphism. Here, we show that both HCT1806 and HCT4918 physically interact with and suppress the HR conferred by Rp1-D21 but not other autoactive NLRs when transiently coexpressed in Nicotiana benthamiana. Other maize HCT homologs are unable to confer the same level of suppression on Rp1-D21-induced HR. The metabolic activity of HCT1806 and HCT4918 is unlikely to be necessary for their role in suppressing HR. We show that the lignin pathway is activated by Rp1-D21 at both the transcriptional and metabolic levels. We derive a model to explain the roles of HCT1806 and HCT4918 in Rp1-mediated disease resistance.
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http://dx.doi.org/10.1104/pp.15.00703DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4634058PMC
November 2015

Cytoplasmic and Nuclear Localizations Are Important for the Hypersensitive Response Conferred by Maize Autoactive Rp1-D21 Protein.

Mol Plant Microbe Interact 2015 Sep 25;28(9):1023-31. Epub 2015 Aug 25.

1 Dept. of Plant Pathology, North Carolina State University, Raleigh, NC 27695, U.S.A.;

Disease resistance (R) genes have been isolated from many plant species. Most encode nucleotide binding leucine-rich repeat (NLR) proteins that trigger a rapid localized programmed cell death called the hypersensitive response (HR) upon pathogen recognition. Despite their structural similarities, different NLR are distributed in a range of subcellular locations, and analogous domains play diverse functional roles. The autoactive maize NLR gene Rp1-D21 derives from an intragenic recombination between two NLR genes, Rp1-D and Rp1-dp2, and confers a HR independent of the presence of a pathogen. Rp1-D21 and its N-terminal coiled coil (CC) domain (CCD21) confer autoactive HR when transiently expressed in Nicotiana benthamiana. Rp1-D21 was predominantly localized in cytoplasm with a small amount in the nucleus, while CCD21 was localized in both nucleus and cytoplasm. Targeting of Rp1-D21 or CCD21 predominantly to either the nucleus or the cytoplasm abolished HR-inducing activity. Coexpression of Rp1-D21 or CCD21 constructs confined, respectively, to the nucleus and cytoplasm did not rescue full activity, suggesting nucleocytoplasmic movement was important for HR induction. This work emphasizes the diverse structural and subcellular localization requirements for activity found among plant NLR R genes.
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http://dx.doi.org/10.1094/MPMI-01-15-0014-RDOI Listing
September 2015

Molecular and functional analyses of a maize autoactive NB-LRR protein identify precise structural requirements for activity.

PLoS Pathog 2015 Feb 26;11(2):e1004674. Epub 2015 Feb 26.

Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America; USDA-ARS Plant Science Research Unit, Raleigh, North Carolina, United States of America.

Plant disease resistance is often mediated by nucleotide binding-leucine rich repeat (NLR) proteins which remain auto-inhibited until recognition of specific pathogen-derived molecules causes their activation, triggering a rapid, localized cell death called a hypersensitive response (HR). Three domains are recognized in one of the major classes of NLR proteins: a coiled-coil (CC), a nucleotide binding (NB-ARC) and a leucine rich repeat (LRR) domains. The maize NLR gene Rp1-D21 derives from an intergenic recombination event between two NLR genes, Rp1-D and Rp1-dp2 and confers an autoactive HR. We report systematic structural and functional analyses of Rp1 proteins in maize and N. benthamiana to characterize the molecular mechanism of NLR activation/auto-inhibition. We derive a model comprising the following three main features: Rp1 proteins appear to self-associate to become competent for activity. The CC domain is signaling-competent and is sufficient to induce HR. This can be suppressed by the NB-ARC domain through direct interaction. In autoactive proteins, the interaction of the LRR domain with the NB-ARC domain causes de-repression and thus disrupts the inhibition of HR. Further, we identify specific amino acids and combinations thereof that are important for the auto-inhibition/activity of Rp1 proteins. We also provide evidence for the function of MHD2, a previously uncharacterized, though widely conserved NLR motif. This work reports several novel insights into the precise structural requirement for NLR function and informs efforts towards utilizing these proteins for engineering disease resistance.
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http://dx.doi.org/10.1371/journal.ppat.1004674DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4342346PMC
February 2015

TaRAR1 and TaSGT1 associate with TaHsp90 to function in bread wheat (Triticum aestivum L.) seedling growth and stripe rust resistance.

Plant Mol Biol 2015 Apr 20;87(6):577-89. Epub 2015 Feb 20.

The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China,

RAR1 and SGT1 are important co-chaperones of Hsp90. We previously showed that TaHsp90.1 is required for wheat seedling growth, and that TaHsp90.2 and TaHsp90.3 are essential for resistance (R) gene mediated resistance to stripe rust fungus. Here, we report the characterization of TaRAR1 and TaSGT1 genes in bread wheat. TaRAR1 and TaSGT1 each had three homoeologs, which were located on wheat groups 2 and 3 chromosomes, respectively. Strong inhibition of seedling growth was observed after silencing TaSGT1 but not TaRAR1. In contrast, decreasing the expression of TaRAR1 or TaSGT1 could all compromise R gene mediated resistance to stripe rust fungus infection. Protein-protein interactions were found among TaRAR1, TaSGT1 and TaHsp90. The N-terminus of TaHsp90, the CHORD-I and CHORD-II domains of TaRAR1 and the CS domain of TaSGT1 may be instrumental for the interactions among the three proteins. Based on this work and our previous study on TaHsp90, we speculate that the TaSGT1-TaHsp90.1 interaction is important for maintaining bread wheat seedling growth. The TaRAR1-TaSGT1-TaHsp90.2 and TaRAR1-TaSGT1-TaHsp90.3 interactions are involved in controlling the resistance to stripe rust disease. The new information obtained here should aid further functional investigations of TaRAR1-TaSGT1-TaHsp90 complexes in regulating bread wheat growth and disease resistance.
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http://dx.doi.org/10.1007/s11103-015-0298-xDOI Listing
April 2015

A genome-wide association study of the maize hypersensitive defense response identifies genes that cluster in related pathways.

PLoS Genet 2014 Aug 28;10(8):e1004562. Epub 2014 Aug 28.

Department of Botany and Plant Pathology, Purdue University, Lilly Hall, West Lafayette, Indiana, United States of America.

Much remains unknown of molecular events controlling the plant hypersensitive defense response (HR), a rapid localized cell death that limits pathogen spread and is mediated by resistance (R-) genes. Genetic control of the HR is hard to quantify due to its microscopic and rapid nature. Natural modifiers of the ectopic HR phenotype induced by an aberrant auto-active R-gene (Rp1-D21), were mapped in a population of 3,381 recombinant inbred lines from the maize nested association mapping population. Joint linkage analysis was conducted to identify 32 additive but no epistatic quantitative trait loci (QTL) using a linkage map based on more than 7000 single nucleotide polymorphisms (SNPs). Genome-wide association (GWA) analysis of 26.5 million SNPs was conducted after adjusting for background QTL. GWA identified associated SNPs that colocalized with 44 candidate genes. Thirty-six of these genes colocalized within 23 of the 32 QTL identified by joint linkage analysis. The candidate genes included genes predicted to be in involved programmed cell death, defense response, ubiquitination, redox homeostasis, autophagy, calcium signalling, lignin biosynthesis and cell wall modification. Twelve of the candidate genes showed significant differential expression between isogenic lines differing for the presence of Rp1-D21. Low but significant correlations between HR-related traits and several previously-measured disease resistance traits suggested that the genetic control of these traits was substantially, though not entirely, independent. This study provides the first system-wide analysis of natural variation that modulates the HR response in plants.
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http://dx.doi.org/10.1371/journal.pgen.1004562DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4148229PMC
August 2014

Characterization of temperature and light effects on the defense response phenotypes associated with the maize Rp1-D21 autoactive resistance gene.

BMC Plant Biol 2013 Jul 26;13:106. Epub 2013 Jul 26.

Department of Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA.

Background: Rp1 is a complex locus of maize, which carries a set of genes controlling race-specific resistance to the common rust fungus, Puccinia sorghi. The resistance response includes the "Hypersensitive response" (HR), a rapid response triggered by a pathogen recognition event that includes localized cell death at the point of pathogen penetration and the induction of pathogenesis associated genes. The Rp1-D21gene is an autoactive allelic variant at the Rp1 locus, causing spontaneous activation of the HR response, in the absence of pathogenesis. Previously we have shown that the severity of the phenotype conferred by Rp1-D21 is highly dependent on genetic background.

Results: In this study we show that the phenotype conferred by Rp1-D21 is highly dependent on temperature, with lower temperatures favoring the expression of the HR lesion phenotype. This temperature effect was observed in all the 14 genetic backgrounds tested. Significant interactions between the temperature effects and genetic background were observed. When plants were grown at temperatures above 30°C, the spontaneous HR phenotype conferred by Rp1-D21 was entirely suppressed. Furthermore, this phenotype could be restored or suppressed by alternately reducing and increasing the temperature appropriately. Light was also required for the expression of this phenotype. By examining the expression of genes associated with the defense response we showed that, at temperatures above 30°C, the Rp1-D21 phenotype was suppressed at both the phenotypic and molecular level.

Conclusions: We have shown that the lesion phenotype conferred by maize autoactive resistance gene Rp1-D21 is temperature sensitive in a reversible manner, that the temperature-sensitivity phenotype interacts with genetic background and that the phenotype is light sensitive. This is the first detailed demonstration of this phenomenon in monocots and also the first demonstration of the interaction of this effect with genetic background. The use of temperature shifts to induce a massive and synchronous HR in plants carrying the Rp1-D21 genes will be valuable in identifying components of the defense response pathway.
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http://dx.doi.org/10.1186/1471-2229-13-106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3733612PMC
July 2013

Tissue factor with age-related macular degeneration.

Int J Ophthalmol 2012 18;5(5):609-13. Epub 2012 Oct 18.

Department of Ophthalmology, Guangzhou General Hospital of Guangzhou Military Command, Guangzhou 510010, Guangdong Province, China ; Jinan University, Guangzhou 510630, Guangdong Province, China.

Wet age-related macular degeneration which incidence increases year by year is a blinding eye disease, but current clinical methods of treatment on this disease are limited and the outcome is not ideal. Recent studies have found abnormally high expression of tissue factors which are targets for the treatment of wet age-related macular degeneration to achieve a certain effect in the choroidal neovascularization. Related literatures are reviewed as following.
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http://dx.doi.org/10.3980/j.issn.2222-3959.2012.05.13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3484712PMC
November 2012

Multiple roles of WIN3 in regulating disease resistance, cell death, and flowering time in Arabidopsis.

Plant Physiol 2011 Jul 4;156(3):1508-19. Epub 2011 May 4.

Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21250, USA.

The salicylic acid (SA) regulatory gene HOPW1-1-INTERACTING3 (WIN3) was previously shown to confer resistance to the biotrophic pathogen Pseudomonas syringae. Here, we report that WIN3 controls broad-spectrum disease resistance to the necrotrophic pathogen Botrytis cinerea and contributes to basal defense induced by flg22, a 22-amino acid peptide derived from the conserved region of bacterial flagellin proteins. Genetic analysis indicates that WIN3 acts additively with several known SA regulators, including PHYTOALEXIN DEFICIENT4, NONEXPRESSOR OF PR GENES1 (NPR1), and SA INDUCTION-DEFICIENT2, in regulating SA accumulation, cell death, and/or disease resistance in the Arabidopsis (Arabidopsis thaliana) mutant acd6-1. Interestingly, expression of WIN3 is also dependent on these SA regulators and can be activated by cell death, suggesting that WIN3-mediated signaling is interconnected with those derived from other SA regulators and cell death. Surprisingly, we found that WIN3 and NPR1 synergistically affect flowering time via influencing the expression of flowering regulatory genes FLOWERING LOCUS C and FLOWERING LOCUS T. Taken together, our data reveal that WIN3 represents a novel node in the SA signaling networks to regulate plant defense and flowering time. They also highlight that plant innate immunity and development are closely connected processes, precise regulation of which should be important for the fitness of plants.
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http://dx.doi.org/10.1104/pp.111.176776DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3135961PMC
July 2011

Molecular analysis of common wheat genes encoding three types of cytosolic heat shock protein 90 (Hsp90): functional involvement of cytosolic Hsp90s in the control of wheat seedling growth and disease resistance.

New Phytol 2011 Jul 13;191(2):418-431. Epub 2011 Apr 13.

The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.

Heat shock protein 90 (Hsp90) molecular chaperones play important roles in plant growth and responses to environmental stimuli. However, little is known about the genes encoding Hsp90s in common wheat. Here, we report genetic and functional analysis of the genes specifying cytosolic Hsp90s in this species. Three groups of homoeologous genes (TaHsp90.1, TaHsp90.2 and TaHsp90.3), encoding three types of cytosolic Hsp90, were isolated. The loci containing TaHsp90.1, TaHsp90.2 and TaHsp90.3 genes were assigned to groups 2, 7 and 5 chromosomes, respectively. TaHsp90.1 genes exhibited higher transcript levels in the stamen than in the leaf, root and culm. TaHsp90.2 and TaHsp90.3 genes were more ubiquitously transcribed in the vegetative and reproductive organs examined. Decreasing the expression of TaHsp90.1 genes through virus-induced gene silencing (VIGS) caused pronounced inhibition of wheat seedling growth, whereas the suppression of TaHsp90.2 or TaHsp90.3 genes via VIGS compromised the hypersensitive resistance response of the wheat variety Suwon 11 to stripe rust fungus. Our work represents the first systematic determination of wheat genes encoding cytosolic Hsp90s, and provides useful evidence for the functional involvement of cytosolic Hsp90s in the control of seedling growth and disease resistance in common wheat.
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http://dx.doi.org/10.1111/j.1469-8137.2011.03715.xDOI Listing
July 2011