Genome- wide characterization, expression profile analysis of WRKY family genes in Santalum album  and functional identification of their role in abiotic stress

Abstract

Background: WRKY proteins are a large superfamily of transcription factors that are involved in diverse biological processes including development, as well as biotic and abiotic stress responses in plants. WRKY family proteins have been extensively characterized and analyzed in many plant species, including Arabidopsis , rice and poplar. However, knowledge on WRKY transcription factors in S antalum album is scarce. Results: Based on S . albu m genome and transcriptome data, 64 SaWRKY genes were identified in this study. A phylogenetic analysis based on the structures of WRKY protein sequences divided these genes into three major groups (I, II, III) together with WRKY protein sequences from Arabidopsis . Tissue-specific expression patterns showed that 37 SaWRKY genes were expressed in at least one of five tissues (leaves, roots, heartwood, sapwood, or the transition zone) while the remaining four genes were weakly expressed in all of these tissues. Analysis of the expression profiles of the 42 SaWRKY genes after callus was stimulated by salicylic acid (SA) and methyl jasmonate (MeJA) revealed that 34 and 19 SaWRKY genes, respectively were significantly induced. The function of SaWRKY1 , which was significantly up-regulated by SA and MeJA, was analyzed. SaWRKY1 was localized in the nucleus and its overexpression improved salt tolerance in transgenic Arabidopsis . Conclusions: Our study provides important information to further identify the functions of SaWRKY genes and to understand the roles of SaWRKY family genes involved in development and in SA- and MeJA-mediated stress responses.