Coordination between two cis-elements of WRKY33, bound by the same transcription factor, confers humid adaption in Arabidopsis thaliana.

To cope with flooding-induced hypoxia, plants have evolved different strategies. Molecular strategies, such as the N-degron pathway and transcriptional regulation, are known to be crucial for Arabidopsis thaliana's hypoxia response. Our study uncovered a novel molecular strategy that involves a single transcription factor interacting with two identical cis-elements, one located in the promoter region and the other within the intron. This unique double-element adjustment mechanism has seldom been reported in previous studies. In humid areas, WRKY70 plays a crucial role in A. thaliana's adaptation to submergence-induced hypoxia by binding to identical cis-elements in both the promoter and intron regions of WRKY33. This dual binding enhances WRKY33 expression and the activation of hypoxia-related genes. Conversely, in arid regions lacking the promoter cis-element, WRKY70 only binds to the intron cis-element, resulting in limited WRKY33 expression during submergence stress. The presence of a critical promoter cis-element in humid accessions, but not in dry accessions, indicates a coordinated regulation enabling A. thaliana to adapt and thrive in humid habitats.

SUMO enables substrate selectivity by mitogen-activated protein kinases to regulate immunity in plants.

The versatility of mitogen-activated protein kinases (MAPKs) in translating exogenous and endogenous stimuli into appropriate cellular responses depends on its substrate specificity. In animals, several mechanisms have been proposed about how MAPKs maintain specificity to regulate distinct functional pathways. However, little is known of mechanisms that enable substrate selectivity in plant MAPKs. Small ubiquitin-like modifier (SUMO), a posttranslational modification system, plays an important role in plant development and defense by rapid reprogramming of cellular events. In this study we identified a functional SUMO interaction motif (SIM) in Arabidopsis MPK3 and MPK6 that reveals a mechanism for selective interaction of MPK3/6 with SUMO-conjugated WRKY33, during defense. We show that WRKY33 is rapidly SUMOylated in response to Botrytis cinerea infection and flg22 elicitor treatment. SUMOylation mediates WRKY33 phosphorylation by MPKs and consequent transcription factor activity. Disruption of either WRKY33 SUMO or MPK3/6 SIM sites attenuates their interaction and inactivates WRKY33-mediated defense. However, MPK3/6 SIM mutants show normal interaction with a non-SUMOylated form of another transcription factor, SPEECHLESS, unraveling a role for SUMOylation in differential substrate selectivity by MPKs. We reveal that the SUMO proteases, SUMO PROTEASE RELATED TO FERTILITY1 (SPF1) and SPF2 control WRKY33 SUMOylation and demonstrate a role for these SUMO proteases in defense. Our data reveal a mechanism by which MPK3/6 prioritize molecular pathways by differentially selecting substrates using the SUMO-SIM module during defense responses.

Regulatory module WRKY33-ATL31-IRT1 mediates cadmium tolerance in Arabidopsis.

Cadmium (Cd) is one of the most dangerous environmental pollutants among heavy metals, and threatens food safety and human health by accumulating in plant sink tissues. Here, we report a novel regulatory cascade that profoundly influences Cd tolerance in Arabidopsis. Phenotypic analysis showed that an insertional knockdown mutation at the Arabidopsis Tóxicos en Levadura 31 (ATL31) locus resulted in hypersensitivity to Cd stress, most likely due to a significant increase in Cd accumulation. Consistently, ATL31-overexpressing lines exhibited enhanced Cd stress tolerance and reduced Cd accumulation. Further, IRON-REGULATED TRANSPORTER 1 (IRT1) was identified, and yeast two-hybrid, co-immunoprecipitation and bimolecular fluorescence complementation assays demonstrated its interaction with ATL31. Biochemical, molecular, and genetic analyses showed that IRT1 is targeted by ATL31 for ubiquitin-conjugated degradation in response to Cd stress. Intriguingly, transcription of ATL31 was strongly induced by Cd stress. In addition, transgenic and molecular analyses showed that WRKY33 directly activated the transcription of ATL31 in response to Cd stress and positively regulated Cd tolerance. Genetic analysis indicated that ATL31 acts upstream of IRT1 and downstream of WRKY33 to regulate Cd tolerance. Our study revealed that the WRKY33-ATL31-IRT1 module plays a crucial role in timely blocking Cd absorption to prevent metal toxicity in Arabidopsis.

A single-nucleotide polymorphism in WRKY33 promoter is associated with the cold sensitivity in cultivated tomato.

Natural variations in cis-regulatory regions often affect crop phenotypes by altering gene expression. However, the mechanism of how promoter mutations affect gene expression and crop stress tolerance is still poorly understood. In this study, by analyzing RNA-sequencing (RNA-Seq) data and reverse transcription quantitative real-time PCR validation in the cultivated tomato and its wild relatives, we reveal that the transcripts of WRKY33 are almost unchanged in cold-sensitive cultivated tomato Solanum lycopersicum L. 'Ailsa Craig' but are significantly induced in cold-tolerant wild tomato relatives Solanum habrochaites LA1777 and Solanum pennellii LA0716 under cold stress. Overexpression of SlWRKY33 or ShWRKY33 positively regulates cold tolerance in tomato. Variant of the critical W-box in SlWRKY33 promoter results in the loss of self-transcription function of SlWRKY33 under cold stress. Analysis integrating RNA-Seq and chromatin immunoprecipitation sequencing data reveals that SlWRKY33 directly targets and induces multiple kinases, transcription factors, and molecular chaperone genes, such as CDPK11, MYBS3, and BAG6, thus enhancing cold tolerance. In addition, heat- and Botrytis-induced WRKY33s expression in both wild and cultivated tomatoes are independent of the critical W-box variation. Our findings suggest nucleotide polymorphism in cis-regulatory regions is crucial for different cold sensitivity between cultivated and wild tomato plants.

MPK3/MPK6-mediated phosphorylation of ERF72 positively regulates resistance to Botrytis cinerea through directly and indirectly activating the transcription of camalexin biosynthesis enzymes.

Ethylene response factor (ERF) Group VII members generally function in regulating plant growth and development, abiotic stress responses, and plant immunity in Arabidopsis; however, the details of the regulatory mechanism by which Group VII ERFs mediate plant immune responses remain elusive. Here, we characterized one such member, ERF72, as a positive regulator that mediates resistance to the necrotrophic pathogen Botrytis cinerea. Compared with the wild-type (WT), the erf72 mutant showed lower camalexin concentration and was more susceptible to B. cinerea, while complementation of ERF72 in erf72 rescued the susceptibility phenotype. Moreover, overexpression of ERF72 in the WT promoted camalexin biosynthesis and increased resistance to B. cinerea. We identified the camalexin-biosynthesis genes PAD3 and CYP71A13 and the transcription factor WRKY33 as target genes of ERF72. We also determined that MPK3 and MPK6 phosphorylated ERF72 at Ser151 and improved its transactivation activity, resulting in increased camalexin concentration and increased resistance to B. cinerea. Thus, ERF72 acts in plant immunity to coordinate camalexin biosynthesis both directly by regulating the expression of biosynthetic genes and indirectly by targeting WRKK33.

WRKY33-mediated indolic glucosinolate metabolic pathway confers resistance against Alternaria brassicicola in Arabidopsis and Brassica crops.

The tryptophan (Trp)-derived plant secondary metabolites, including camalexin, 4-hydroxy-indole-3-carbonylnitrile, and indolic glucosinolate (IGS), show broad-spectrum antifungal activity. However, the distinct regulations of these metabolic pathways among different plant species in response to fungus infection are rarely studied. In this study, our results revealed that WRKY33 directly regulates IGS biosynthesis, notably the production of 4-methoxyindole-3-ylmethyl glucosinolate (4MI3G), conferring resistance to Alternaria brassicicola, an important pathogen which causes black spot in Brassica crops. WRKY33 directly activates the expression of CYP81F2, IGMT1, and IGMT2 to drive side-chain modification of indole-3-ylmethyl glucosinolate (I3G) to 4MI3G, in both Arabidopsis and Chinese kale (Brassica oleracea var. alboglabra Bailey). However, Chinese kale showed a more severe symptom than Arabidopsis when infected by Alternaria brassicicola. Comparative analyses of the origin and evolution of Trp metabolism indicate that the loss of camalexin biosynthesis in Brassica crops during evolution might attenuate the resistance of crops to Alternaria brassicicola. As a result, the IGS metabolic pathway mediated by WRKY33 becomes essential for Chinese kale to deter Alternaria brassicicola. Our results highlight the differential regulation of Trp-derived camalexin and IGS biosynthetic pathways in plant immunity between Arabidopsis and Brassica crops.

ERECTA signaling regulates plant immune responses via chromatin-mediated promotion of WRKY33 binding to target genes.

The signaling pathway mediated by the receptor-like kinase ERECTA (ER) plays important roles in plant immune responses, but the underlying mechanism is unclear. Genetic interactions between ER signaling and the chromatin remodeling complex SWR1 in the control of plant immune responses were studied. Electrophoretic mobility shift assay and yeast one-hybrid analysis were applied to identify ER-WRKY33 downstream components. Chromatin immunoprecipitation analyses were further investigated. In this study, we show that the chromatin remodeling complex SWR1 enhances resistance to the white mold fungus Sclerotinia sclerotiorum in Arabidopsis thaliana via a process mediated by ER signaling. We identify a series of WRKY33 target YODA DOWNSTREAM (YDD) genes and demonstrate that SWR1 and ER signaling are required to enrich H2A.Z histone variant and H3K4me3 histone modification at YDDs and the binding of WRKY33 to YDD promoters upon S. sclerotiorum infection. We also reveal that the binding of WRKY33 to YDD promoters in turn promotes the enrichment of H2A.Z and H3K4me3 at YDD genes, thereby forming a positive regulatory loop to activate YDDs expression. Our study reveals how H2A.Z, H3K4me3 and ER signaling mutually regulate YDDs gene expression upon pathogen infection, highlighting the critical role of chromatin structure in ER-signaling-mediated plant immune responses.

WRKY33 interacts with WRKY12 protein to up-regulate RAP2.2 during submergence induced hypoxia response in Arabidopsis thaliana.

Tolerance of hypoxia is essential for most plants, but the underlying mechanisms are largely unknown. Here we show that adaptation to submergence induced hypoxia in Arabidopsis involves up-regulation of RAP2.2 through interactive action of WRKY33 and WRKY12. WRKY33- or WRKY12-overexpressing plants showed enhanced resistance to hypoxia. Y2H, BiFC, Co-IP and pull-down experiments confirmed the interaction of WRKY33 with WRKY12. Genetic experiments showed that RAP2.2 acts downstream of WRKY33/WRKY12. WRKY33 and WRKY12 can bind to and activate RAP2.2 individually. Genetic and molecular experiments demonstrate that the two WRKYs can synergistically enhance activation towards RAP2.2 to increase hypoxia tolerance. WRKY33 expression is increased in RAP2.2-overexpressing plants, indicating a feedback regulation by RAP2.2 during submergence process, which was corroborated by EMSA, ChIP, dual-LUC and genetic experiments. Our results show that a regulatory cascade module involving WRKY33, WRKY12 and RAP2.2 plays a key role in submergence induced hypoxia response of Arabidopsis and illuminate functions of WRKYs in hypoxia tolerance.

Transcriptomics reveal new insights into molecular regulation of nitrogen use efficiency in Solanum melongena.

Nitrogen-use efficiency (NUE) is a complex trait of great interest in breeding programs because through its improvement, high crop yields can be maintained whilst N supply is reduced. In this study, we report a transcriptomic analysis of four NUE-contrasting eggplant (Solanum melongena) genotypes following short- and long-term exposure to low N, to identify key genes related to NUE in the roots and shoots. The differentially expressed genes in the high-NUE genotypes are involved in the light-harvesting complex and receptor, a ferredoxin-NADP reductase, a catalase and WRKY33. These genes were then used as bait for a co-expression gene network analysis in order to identify genes with the same trends in expression. This showed that up-regulation of WRKY33 triggered higher expression of a cluster of 21 genes and also of other genes, many of which were related to N-metabolism, that were able to improve both nitrogen uptake efficiency and nitrogen utilization efficiency, the two components of NUE. We also conducted an independent de novo experiment to validate the significantly higher expression of WRKY33 and its gene cluster in the high-NUE genotypes. Finally, examination of an Arabidopsis transgenic 35S::AtWRKY33 overexpression line showed that it had a bigger root system and was more efficient at taking up N from the soil, confirming the pivotal role of WRKY33 for NUE improvement.

WRKY33-PIF4 loop is required for the regulation of H2O2 homeostasis.

The reactive oxygen species (ROS) are continuously produced and are essential for mediating the growth and development of plants. However too much accumulation of ROS can result in the oxidative damage to cells, especially under the adverse environmental conditions. Plants have evolved sophisticated strategies to regulate the homeostasis of H2O2. In this study, we generated transgenic Arabidopsis plants in the Ws ecotype (Ws) background in which WRKY33 is co-suppressed (csWRKY33/Ws). Compared with Ws, csWRKY33/Ws plants accumulate more H2O2. RNA-seq analysis indicated that in csWRKY33/Ws plants, expression of oxidative stress related genes such as ascorbate peroxidase 2 (APX2) is affected. Over-expression of APX2 can rescue the phenotype of csWRKY33/Ws, suggesting that the changes in the growth of csWRKY33/Ws is duo to the higher accumulation of H2O2. Analysis of the CHIP-seq data suggested that WRKY33 can directly regulate the expression of PIF4, vice versa. qPCR analysis also confirmed that the mutual regulation between WRKY33 and PIF4. Similar to that of csWRKY33/Ws, and the accumulation of H2O2 in pif4 also increased. Taken together, our results reveal a WRKY33-PIF4 regulatory loop that appears to play an important role in regulating the growth and development of seedlings by mediating H2O2 homeostasis.

Reactive oxygen species dosage in Arabidopsis chloroplasts can improve resistance towards Colletotrichum higginsianum by the induction of WRKY33.

Arabidopsis plants overexpressing glycolate oxidase in chloroplasts (GO5) and loss-of-function mutants of the major peroxisomal catalase isoform, cat2-2, produce increased hydrogen peroxide (H2 O2 ) amounts from the respective organelles when subjected to photorespiratory conditions like increased light intensity. Here, we have investigated if and how the signaling processes triggered by H2 O2 production in response to shifts in environmental conditions and the concomitant induction of indole phytoalexin biosynthesis in GO5 affect susceptibility towards the hemibiotrophic fungus Colletotrichum higginsianum. Combining histological, biochemical, and molecular assays, we found that the accumulation of the phytoalexin camalexin was comparable between GO genotypes and cat2-2 in the absence of pathogen. Compared with wild-type, GO5 showed improved resistance after light-shift-mediated production of H2 O2 , whereas cat2-2 became more susceptible and allowed significantly more pathogen entry. Unlike GO5, cat2-2 suffered from severe oxidative stress after light shifts, as indicated by glutathione pool size and oxidation state. We discuss a connection between elevated oxidative stress and dampened induction of salicylic acid mediated defense in cat2-2. Genetic analyses demonstrated that induced resistance of GO5 is dependent on WRKY33, but not on camalexin production. We propose that indole carbonyl nitriles might play a role in defense against C. higginsianum.

The Arabidopsis CCCH protein C3H14 contributes to basal defense against Botrytis cinerea mainly through the WRKY33-dependent pathway.

Necrotrophic pathogens such as Botrytis cinerea cause significant crop yield losses. Plant CCCH proteins play important roles in pathogen resistance responses. However, the CCCH-mediated defense mechanisms against necrotrophic pathogens are unclear. Here, we report that the Arabidopsis CCCH protein C3H14 positively regulates basal defense against B. cinerea mainly by WRKY33 signaling. Simultaneous mutation of C3H14 and its paralog C3H15 resulted in enhanced susceptibility to B. cinerea, while C3H14 or C3H15 overexpression lines exhibited reduced susceptibility. A large number of differentially expressed genes (DEGs) were present in the c3h14c3h15 double mutant and C3H14 overexpression plants compared with wild-type plants at 24 hr post infection. These DEGs covered over one third of B. cinerea-responsive WRKY33 targets, including genes involved in jasmonic acid (JA)/ethylene (ET) signaling, and camalexin biosynthesis. Genetic analysis indicated that C3H14 mainly depended on WRKY33 to modulate defense against B. cinerea. Moreover, C3H14 activated the WRKY33-ORA59 and -PAD3 cascades to correspondingly control JA/ET- and camalexin-mediated defense responses. However, C3H14 was essential for B. cinerea-induced production of 12-oxo-phytodienoic acid and it also directly mediated ORA59-dependent JA/ET signaling after infection. Therefore, C3H14 may act as a novel transcriptional regulator of the WRKY33-mediated defense pathway.

Characterization of the promoter and extended C-terminal domain of Arabidopsis WRKY33 and functional analysis of tomato WRKY33 homologues in plant stress responses.

Arabidopsis AtWRKY33 plays a critical role in broad plant stress responses. Whether there are evolutionarily conserved homologues of AtWRKY33 in other plants and what make AtWRKY33 such an important protein in plant stress responses are largely unknown. We compared AtWRKY33 with its close homologues to identify AtWRKY33-specific regulatory and structural elements, which were then functionally analysed through complementation. We also performed phylogenetic analysis to identify structural AtWRKY33 homologues in other plants and functionally analysed two tomato homologues through complementation and gene silencing. AtWRKY33 has an extended C-terminal domain (CTD) absent in its close homologue AtWRKY25. Both its CTD and the strong pathogen/stress-responsive expression of AtWRKY33 are necessary to complement the critical phenotypes of atwrky33. Structural AtWRKY33 homologues were identified in both dicot and monocot plants including two (SlWRKY33A and SlWRKY33B) in tomato. Molecular complementation and gene silencing confirmed that the two tomato WRKY genes play a critical role similar to that of AtWRKY33 in plant stress responses. Thus, WRKY33 proteins are evolutionarily conserved with a critical role in broad plant stress responses. Both its CTD and promoter are critical for the uniquely important roles of WRKY33 in plant stress responses.

WRKY33 negatively regulates anthocyanin biosynthesis and cooperates with PHR1 to mediate acclimation to phosphate starvation.

Anthocyanin accumulation is acknowledged as a phenotypic indicator of phosphate (Pi) starvation. However, negative regulators of this process and their molecular mechanisms remain largely unexplored. In this study, we demonstrate that WRKY33 acts as a negative regulator of phosphorus-status-dependent anthocyanin biosynthesis. WRKY33 regulates the expression of the gene encoding dihydroflavonol 4-reductase (DFR), a rate-limiting enzyme in anthocyanin production, both directly and indirectly. WRKY33 binds directly to the DFR promoter to repress its expression and also interferes with the MBW complex through interacting with PAP1 to indirectly influence DFR transcriptional activation. Under -Pi conditions, PHR1 interacts with WRKY33, and the protein level of WRKY33 decreases; the repression of DFR expression by WRKY33 is thus attenuated, leading to anthocyanin accumulation in Arabidopsis. Further genetic and biochemical assays suggest that PHR1 is also involved in regulating factors that affect WRKY33 protein turnover. Taken together, our findings reveal that Pi starvation represses WRKY33, a repressor of anthocyanin biosynthesis, to finely tune anthocyanin biosynthesis. This "double-negative logic" regulation of phosphorus-status-dependent anthocyanin biosynthesis is required for the maintenance of plant metabolic homeostasis during acclimation to Pi starvation.

Transcription factor NtWRKY33a modulates the biosynthesis of polyphenols by targeting NtMYB4 and NtHCT genes in tobacco.

There are abundant polyphenols in tobacco leaves mainly including chlorogenic acid (CGA), rutin, and scopoletin, which not only influence plant growth, development, and environmental adaptation, but also have a great impact on the industrial utilization of tobacco leaves. Few transcription factors regulating the biosynthesis of polyphenols have been identified in tobacco so far. In this study, two NtWRKY33 genes were identified from N. tabacum genome. NtWRKY33a showed higher transcriptional activity than NtWRKY33b, and encoded a nuclear localized protein. Overexpression and knock-out of NtWRKY33a gene revealed that NtWRKY33a inhibited the accumulation of rutin, scopoletin, and total polyphenols, but meanwhile promoted the biosynthesis of CGA. Chromatin immunoprecipitation and Dual-Luc assays indicated that NtWRKY33a could directly bind to the promoters of NtMYB4 and NtHCT, and thus induced the transcription of these two genes. The contents of polyphenols in ntwrky33a, ntmy4, and ntwrky33a/ntmyb4 mutants further confirmed that the repression of NtWRKY33a on the biosynthesis of rutin, scopoletin, and total polyphenols depends on the activity of NtMYB4. Moreover, the promotion of NtHCT by NtWRKY33a modulates the distribution of metabolism flux into the synthesis of CGA. Ectopic expression of NtWRKY33a inhibit the expression of NtSAUR14, NtSAUR59, NtSAUR66, NtIAA4, NtIAA17, and NtIAA19 genes, indicating that NtWRKY33a might be involved in the regulation of plant auxin response. Our study revealed new functions of NtWRKY33a in regulating the synthesis of polyphenols, and provided a promising target for manipulating polyphenols contents in tobacco.

Genome-wide (ChIP-seq) identification of target genes regulated by WRKY33 during submergence stress in Arabidopsis.

BACKGROUND: Hypoxia induced by flooding causes significant losses to crop production almost every year. However, the molecular network of submergence signaling pathway is still poorly understood. According to previous studies, transgenic plants overexpressing the WRKY33 gene showed enhanced resistance to submergence stress. Thus, this transcription factor may regulate a series of target genes in response to submergence. Here, to determine putative downstream targets of WRKY33 at a genome-wide scale in Arabidopsis thaliana, we performed the chromatin immunoprecipitation sequencing (ChIP-seq) using 35S:FLAG-WRKY33 overexpression transgenic lines (WRKY33-OE) after 24 h of submergence treatment. RESULTS: Using ChIP-seq data, we identified a total of 104 WRKY33-binding genes under submergence stress (WRKY33BGSs). Most WRKY33BGSs are involved in the oxidation-reduction process, programmed cell death in response to reactive oxygen species, lipid biosynthesis process, and other processes related to stress responses. Moreover, the major motif identified in the WRKY33BGSs promoters is a new cis-element, TCTCTC (named here as "TC box"). This cis-element differs from the previously known W box for WRKY33. Further qPCR experiments verified that genes carrying this motif in their promoters could be regulated by WRKY33 upon submergence treatment. CONCLUSIONS: Our study has identified a new putative binding motif of WRKY33 and recovered numerous previously unknown target genes of WRKY33 during submergence stress. The WRKY33 gene positively participates in flooding response probably by transcriptional regulation of the downstream submergence-related target genes via a "TC box".

Roles of single gene in plant hypoxia and pathogen responses.

Hypoxia stress can be caused by submergence or pathogen infection. These two stresses often occur sequentially or at the same time in nature. Therefore, plants have evolved economical and efficient strategies to deal with them, such as "single-gene multi-functions", that is, one gene could play roles in hypoxia or pathogen responses at the corresponding stress. This review mainly introduces the ERF-VII (ethylene response factor VII) and WRKYs (WRKY transcription factors) that can play roles in these two stresses. Meanwhile, the relationship between hypoxia and pathology has certain similarities in animals and plants, so we can learn from their related studies and develop new ideas for disease therapy and breeding.

A whitefly effector Bsp9 targets host immunity regulator WRKY33 to promote performance.

Whiteflies, Bemisia tabaci (Hemiptera), are pests causing economic damage to many crops, capable of transmitting hundreds of plant vector-borne viruses. They are believed to secrete salivary protein effectors that can improve vector colonization and reproductive fitness in host plants. However, little is known about effector biology and the precise mechanism of action of whitefly effectors. Here, we report a functional screening of B. tabaci salivary effector proteins (Bsp) capable of modulating plant innate immunity triggered by plant endogenous pattern peptide Pep1. Four immunity suppressors and two elicitors were identified. Bsp9, the most effective immunity suppressor, was further identified to directly interact with an immunity regulator WRKY33. We provide evidence that Bsp9 may suppress plant immune signalling by interfering with the interaction between WRKY33 and a central regulator in the MAPK cascade. The interference by Bsp9 therefore reduces plant resistance to whitefly by inhibiting activation of WRKY33-regulated immunity-related genes. Further detailed analysis based on transgenic plants found that whitefly effector Bsp9 could promote whitefly preference and performance, increasing virus transmission. This study enriches our knowledge on insect effector biology. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.

Molecular modeling and simulation of three important components of Plant Pathogen Interaction cascade in Vigna mungo.

Plant pathogen interaction plays a great role in plant immunity. The regulation of various components of plant pathogen interactions is quite complicated and is very important in establishing relationship among components of this system. Yellow Mosaic Disease is common among legumes such as Vigna mungo. Mungbean Yellow Mosaic India Virus (MYMIV) and whitefly (Bemisia tabaci) is a vector causing the disease. Therefore, it is of interest to document the molecule models of three different components of Plant Pathogen interaction cascade- MAP kinase1, MAP kinase 2 and WRKY33 from V. mungo resistant to MYMIV. Both the MAP kinases were sequenced for this study while WRKY 33 was extracted and modeled from transcripts generated from two different transcriptome libraries, one set MYMIV- challenged, the other fed with aviruliferous whitefly. Post simulation studies revealed that MAPKs contained less percentage of disordered residues and were structurally more stable and than WRKY33.

Negative regulation of ABA signaling by WRKY33 is critical for Arabidopsis immunity towards Botrytis cinerea 2100.

The Arabidopsis mutant wrky33 is highly susceptible to Botrytis cinerea. We identified >1680 Botrytis-induced WRKY33 binding sites associated with 1576 Arabidopsis genes. Transcriptional profiling defined 318 functional direct target genes at 14 hr post inoculation. Comparative analyses revealed that WRKY33 possesses dual functionality acting either as a repressor or as an activator in a promoter-context dependent manner. We confirmed known WRKY33 targets involved in hormone signaling and phytoalexin biosynthesis, but also uncovered a novel negative role of abscisic acid (ABA) in resistance towards B. cinerea 2100. The ABA biosynthesis genes NCED3 and NCED5 were identified as direct targets required for WRKY33-mediated resistance. Loss-of-WRKY33 function resulted in elevated ABA levels and genetic studies confirmed that WRKY33 acts upstream of NCED3/NCED5 to negatively regulate ABA biosynthesis. This study provides the first detailed view of the genome-wide contribution of a specific plant transcription factor in modulating the transcriptional network associated with plant immunity.