Os02g0698800

Please input one-sentence summary here.

Annotated Information

Function

WRKY transcription factors (TFs) are key regulators of many plant processes, including the responses to biotic and abiotic stresses, senescence, seed dormancy and seed germination. For over 15 years, limited evidence has been available suggesting that WRKY TFs may play roles in regulating plant responses to the phytohormone abscisic acid (ABA), notably some WRKY TFs are ABA-inducible repressors of seed germination. However, the roles of WRKY TFs in other aspects of ABA signalling, and the mechanisms involved, have remained unclear. Recent significant progress in ABA research has now placed specific WRKY TFs firmly in ABA-responsive signalling pathways, where they act at multiple levels. In Arabidopsis, WRKY TFs appear to act downstream of at least two ABA receptors: the cytoplasmic PYR/PYL/RCAR-protein phosphatase 2C-ABA complex and the chloroplast envelope-located ABAR-ABA complex. In vivo and in vitro promoter-binding studies show that the target genes for WRKY TFs that are involved in ABA signalling include well-known ABA-responsive genes such as ABF2, ABF4, ABI4, ABI5, MYB2, DREB1a, DREB2a and RAB18. Additional well-characterized stress-inducible genes such as RD29A and COR47 are also found in signalling pathways downstream of WRKY TFs. These new insights also reveal that some WRKY TFs are positive regulators of ABA-mediated stomatal closure and hence drought responses. Conversely, many WRKY TFs are negative regulators of seed germination, and controlling seed germination appears a common function of a subset of WRKY TFs in flowering plants. Taken together, these new data demonstrate that WRKY TFs are key nodes in ABA-responsive signalling networks. The plants during their sessile, autotrophic lifestyle are affected by wide range of environmental signals and regulate complex patterns of gene expression with the help of transcription factors. The WRKY transcription factors are considered as plant-specific, however, are also reported in protist, slime mold, fern and pine. The WRKY name is coined from its highly conserved 60 amino acid long WRKY domain. These TFs show W box specific binding which is also influenced by the W box flanking sequence. During evolution, the family has expanded in different patterns to facilitate distinct cellular, developmental, and physiological role in plants. The WRKY TFs form one of the largest families in flowering plants, and play a broad spectrum regulatory role as positive and negative regulators of plant defense regulation, abiotic stresses and also involved in growth and development of plants.

Expression

WRKY proteins comprise a large family of transcription factors. Despite their dramatic diversification in plants, WRKY genes seem to have originated in early eukaryotes. The cognate DNA-binding site of WRKY factors is well defined, but determining the roles of individual family members in regulating specific transcriptional programs during development or in response to environmental signals remains daunting. This review summarises the recent advances made in starting to unravel the various functions controlled by WRKY proteins. WRKY transcription factors that are unique to plants are the new type transcriptional regulatory factors in which N-terminal ends contain a conserved WRKYGQR amino acids sequences. WRKY transcription factors regulate the target genes expression that contain the W-box elements in the promoter regions by specifically binding to (T)(T)TGAC(C/T) sequence. Therefore, the WRKY transcription factors participate in the plant various kinds defense responses and regulate the plant growth and development. Members of the complex family of WRKY transcription factors have been implicated in the regulation of transcriptional reprogramming associated with plant immune responses. Recently genetic evidence directly proving their significance as positive and negative regulators of disease resistance has accumulated. WRKY genes were shown to be functionally connected forming a transcriptional network composed of positive and negative feedback loops and feed-forward modules. Within a web of partially redundant elements some WRKY factors hold central positions mediating fast and efficient activation of defense programs. A key mechanism triggering strong immune responses appears to be based on the inactivation of defense-suppressing WRKY proteins.

Evolution

New findings illustrate that WRKY proteins often act as repressors as well as activators, and that members of the family play roles in both the repression and de-repression of important plant processes. Furthermore, it is becoming clear that a single WRKY transcription factor might be involved in regulating several seemingly disparate processes. Mechanisms of signalling and transcriptional regulation are being dissected, uncovering WRKY protein functions via interactions with a diverse array of protein partners, including MAP kinases, MAP kinase kinases, 14-3-3 proteins, calmodulin, histone deacetylases, resistance proteins and other WRKY transcription factors. WRKY genes exhibit extensive autoregulation and cross-regulation that facilitates transcriptional reprogramming in a dynamic web with built-in redundancy. reat progress has been made since then in establishing the diverse biological roles of WRKY transcription factors in plant growth, development, and responses to biotic and abiotic stress. Despite the functional diversity, almost all analyzed WRKY proteins recognize the TTGACC/T W-box sequences and, therefore, mechanisms other than mere recognition of the core W-box promoter elements are necessary to achieve the regulatory specificity of WRKY transcription factors. Research over the past several years has revealed that WRKY transcription factors physically interact with a wide range of proteins with roles in signaling, transcription, and chromatin remodeling. Studies of WRKY-interacting proteins have provided important insights into the regulation and mode of action of members of the important family of transcription factors. It has also emerged that the slightly varied WRKY domains and other protein motifs conserved within each of the seven WRKY subfamilies participate in protein-protein interactions and mediate complex functional interactions between WRKY proteins and between WRKY and other regulatory proteins in the modulation of important biological processes. In this review, we summarize studies of protein-protein interactions for WRKY transcription factors and discuss how the interacting partners contribute, at different levels, to the establishment of the complex regulatory and functional network of WRKY transcription factors.

Labs working on this gene

Department of Biology and Microbiology, South Dakota State University, Brookings, SD, USA. Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Yunnan, China. Department of Biology and Microbiology, South Dakota State University, Brookings, SD 57007, USA. Max-Plank-Institute for Plant Breeding Research, Department of Plant-Microbe Interactions, Carl-von-Linné Weg 10, D-50829 Köln, Germany.

References

Tian Y, Lu XY, Peng LS, Fang J.The structure and function of plant WRKY transcription factors.Yi Chuan.2006 Dec;28(12):1607-12. Agarwal P, Reddy MP, Chikara J.WRKY: its structure, evolutionary relationship, DNA-binding selectivity, role in stress tolerance and development of plants.Mol Biol Rep. 2011 Aug;38(6):3883-96. doi: 10.1007/s11033-010-0504-5. Epub 2010 Nov 25. Rushton PJ, Somssich IE, Ringler P, Shen QJ.WRKY transcription factors.Trends Plant Sci. 2010 May;15(5):247-58. doi: 10.1016/j.tplants.2010.02.006. Epub 2010 Mar 19. Chen L, Song Y, Li S, Zhang L, Zou C, Yu D.The role of WRKY transcription factors in plant abiotic stresses.Biochim Biophys Acta. 2012 Feb;1819(2):120-8. doi: 10.1016/j.bbagrm.2011.09.002. Epub 2011 Sep 20. Ulker B, Somssich IE.WRKY transcription factors: from DNA binding towards biological function.Curr Opin Plant Biol. 2004 Oct;7(5):491-8.