transcription factors are one of the largest families of
regulators in plants and form integral parts of signalling webs that modulate many plant processes. WRKY proteins often act as repressors as
well as activators, and 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
(Rushton et al., 2010).
Fifteen years have passed since the first reports of WRKY transcription factors and enormous progress
has been achieved since then. The first two reports were of ill-defined DNA binding proteins that played potential
roles in regulation of gene expression by sucrose (SPF1) or during germination (ABF1 and ABF2). A third report
identified WRKY1, -2 and -3 from parsley and coined the name. This paper also provided the first evidence that
WRKY factors play roles in regulating plant responses to pathogens and many reports have since shown this to
be a major role of WRKY transcription factors. The WRKY family is among the ten largest families of
transcription factors in higher plants and is found throughout the green lineage. The family has expanded
during the evolution of plants. Very likely this expansion is associated with the on-going development of
highly sophisticated defence mechanisms co-evolving in land plants together with their adapted pathogens.
However, more recently research has come to focus on additional roles of WRKY factors in plant processes such
as germination, senescence and the responses to abiotic stresses such as drought and cold.
Rushton, D.L., Tripathi, P., Rabara, R.C., Lin, J., Ringler, P., Boken, A.K., Langum, T.J., Smidt, L.,
Boomsma, D.D., Emme, N.J., Chen, X., Finer, J.J., Shen, Q.J., and Rushton P.J. (2011): WRKY
transcription factors: key components in abscisic acid signalling. The Plant Biotechnology Journal, pp. 1-10.
Rushton, P.J., Somssich, I.E., Ringler, P., and Shen, J. (2010): WRKY transcription
factors. Trends in Plant Science, 15(5): p. 247-58.
Eulgem, T., Rushton, P.J., Robatzek, S. and Somssich, I.E. (2000): The WRKY superfamily of
plant transcription factors. Trends in Plant Science, 5: 199-206.
Last updated by Dr. Jeff Chen (Jeff.Chen@igece.org) on July 7, 2011.