A Comprehensive Transcriptional Profiling of the WRKY Gene Family in Rice Under Various Abiotic and Phytohormone Treatments

Abstract

WRKY transcription factors play important roles in the regulation of various biological processes. We have analyzed the publicly available rice genome sequence databases and predicted 103 genes encoding WRKY transcription factors. Among them, the majority of rice WRKY genes (77.7%) were located in duplicated regions; 45.6% of WRKY genes were fragmentally duplicated and 35% of them were tandemly duplicated. These results suggested that genome duplications might be regarded as a major mechanism for expansion of this family in the rice genome. Subsequently, we analyzed their expression profiles under normal and abiotic stress, as well as various hormone treatments. Under normal growth conditions, 65 WRKY genes were expressed differentially either in their transcript abundance or in their expression patterns. Under abiotic (cold, drought and salinity) stresses and various phytohormone treatments, 54 WRKY genes exhibited significant differences in their transcript abundance; among them three genes were expressed only in stressed conditions. Among the stress-inducible genes, 13 genes were regulated only by abiotic stresses, another set of 13 genes were responsive to only phytohormone treatments and the remaining 28 genes were regulated by both factors, suggesting an interaction between abiotic stress and hormone signaling. On the other hand, we have also surveyed the expression divergence of duplicated genes under normal or stressed conditions, and the results showed that high expression divergence has occurred not only among fragmentally but also among tandemly duplicated genes. These results suggested that the high expression divergence could be one of the mechanisms for the retention of these duplicated WRKY genes.

The rice transcription factor OsWRKY47 is a positive regulator of the response to water deficit stress

“…Similar results were obtained when the Glycine Soja GsWRKY20 was expressed in Arabidopsis (Luo et al 2013) and the maize ZmWRKY58 was overexpressed in transgenic rice (Cai et al 2014). In rice, the overexpression of OsWRKY7 (Ramamoorthy et al 2008), OsWRKY05, OsWRKY43, OsWRKY1, OsWRKT2 (Berri et al 2009) and OsWRKY11 ) was shown to improved drought tolerance.…”

“…A third group, group III, is formed by proteins with one WRKY motif and a zinc finger type C 2 -HC(C-X 7 -C-X 23 -H-X 1 -C). Sequence alignment tools and phylogenetic analyses have been used for the identification and classification of WRKY TFs in a few species such as Arabidopsis thaliana (Eulgem et al 2000), Oryza Sativa (Wu et al 2005;Xie et al 2005;Ramamoorthy et al 2008), Hordeum vulgare (Mangelsen et al 2008) and Heilanthus annuus (Giacomelli et al 2010), among others. In rice, the WRKY family comprises 102 proteins (Wu et al 2005).…”

The Role of WRKY Transcription Factors in Plant Immunity

“…The rice genome contains more than 100 WRKY genes, often present in duplicated chromosomal regions, suggesting genome duplications as one of the mechanisms for the expansion of this family in this plant species (Ross et al, 2007;Ramamoorthy et al, 2008). The majority of these genes respond to (a)biotic stresses and various phytohormones (Ryu et al, 2006;Ramamoorthy et al, 2008).…”

Identification of a drought- and cold-stress inducibleWRKYgene in the cold-hardyCitrusrelativePoncirus trifoliata

“…In another study, Ramamoorthy et al (2008) showed that expression of 41 WRKY genes including OsWRKY45 and OsWRKY79 were significantly changed in response to cold, drought and salinity stresses in rice. In addition, expression of 25 WRKY genes, including GmWRKY13, GmWRKY21 and GmWRKY54 was regulated by at least one or a combination of cold, drought and salinity stresses in soybean (Zhou et al 2008).…”