Comprehensive analysis of VQ motif-containing gene expression in rice defense responses to three pathogens

Expression levels of rice VQ motif-containing genes in response to pathogen infection vary among pathogens, and some of the genes are co-expressed with defense-response WRKY genes. Recent studies have revealed that some VQ (FxxxVQxLTG) motif-containing proteins in plants partner with WRKY transcription factors to participate in their functions. Accumulating information suggests that WRKY proteins play important roles in the response of rice plants to pathogen infection. However, the functions of rice VQ motif-containing proteins are unknown. To explore whether VQ motif-containing proteins are involved in defense against pathogens in rice, we performed a comprehensive expression analysis of the genes for these proteins. The rice VQ motif-containing family consists of 40 genes, all of which encode proteins harboring a 21-amino acid VQ-containing motif, which in turn contains the known VQ motif. On the basis of their phylogenetic relationships and tissue-specific and developmental stage-specific expression characteristics, we transcriptionally analyzed 13 representative genes in rice responses to three pathogens: Xanthomonas oryzae pv. oryzae, which causes bacterial blight disease; X. oryzae pv. oryzicola, which causes bacterial streak disease; and Magnaporthe oryzae, which causes fungal blast disease. The expression of some of the genes changed markedly in response to infection by at least one of the pathogen species, and some of the genes also showed markedly different expression in resistant and susceptible reactions. In addition, some defense-responsive VQ motif-containing genes were co-expressed with defense-response WRKY genes. These results provide a new perspective on the putative roles of rice VQ motif-containing proteins and their putative WRKY partners in rice-pathogen interactions.