Abstract
WRKY transcription factors (TFs) are involved in regulating a range of biological processes such as growth, development, and the responses to biotic and abiotic stresses. Genome-wide expression profiling of OsWRKY TF superfamily genes in rice after infection with Xanthomonas oryzae pv. oryzae (Xoo) was performed to elucidate the function of OsWRKY TFs in the interaction between rice and Xoo. Of the 111 OsWRKY TF genes tested, the transcription of 94 genes changed after Xoo infection. The OsWRKY TF genes were classified into eight types according to their expression profiles. Eighty-two genes in Groups I, II, III, IV, VII were up-regulated after exposure to a compatible or an incompatible race of Xoo. Examination of salicylic acid (SA)-deficient rice lines revealed that SA was involved in Xa1-mediated resistance to Xoo infection. OsWRKY TF genes involved in Xa1-mediated resistance were classified according to their SA-dependent or -independent expression. In SA-deficient rice, the expression of 12 of 57 OsWRKY TF genes involved in Xa1-mediated resistance was compromised. Of these six OsWRKY TF genes were induced by SA. OsWRKY88, an example of a gene possibly involved in SA-dependent Xa1-mediated resistance, activated defense related genes and increased resistance to Xoo. Thus, expression profiling of OsWRKY TF genes may help predict the functions of OsWRKY TF genes involved in Xa1-mediated resistance.
Highlights
WRKY transcription factors (TFs) are characterized by the presence of one or two 60-aminoacid WRKY motifs, a very highly conserved WRKYGQK sequence, and zinc finger-like motifs [Cys(2)-His(2) or Cys(2)-HisCys] that bind to the W-box [TTGAC(C/T)] cis-element in target gene promoters (Sun et al, 2003; Cai et al, 2008; Ciolkowski et al, 2008; Pandey and Somssich, 2009)
A recent transcriptome study in rice noted that OsWRKY TF genes were significantly enriched in the group of genes up-regulated during the early defense response to M. oryzae infection and that OsWRKY47 played a critical role in rice blast resistance (Wei et al, 2013)
The roles of OsWRKY TF superfamily genes in the defense pathway mediated by Xa1, a bacterial blight resistance protein (Yoshimura et al, 1998), were investigated using expression profiling
Summary
WRKY transcription factors (TFs) are characterized by the presence of one or two 60-aminoacid WRKY motifs, a very highly conserved WRKYGQK sequence, and zinc finger-like motifs [Cys(2)-His(2) or Cys(2)-HisCys] that bind to the W-box [TTGAC(C/T)] cis-element in target gene promoters (Sun et al, 2003; Cai et al, 2008; Ciolkowski et al, 2008; Pandey and Somssich, 2009). Numerous WRKY TFs are involved in responding to biotic stresses in rice and Arabidopsis (Dong et al, 2003; Ryu et al, 2006; Berri et al, 2009). The first such study examined the expression of 45 OsWRKY TF genes in response to M. oryzae challenge and found that 15 OsWRKYs were up-regulated upon infection (Ryu et al, 2006). A recent transcriptome study in rice noted that OsWRKY TF genes were significantly enriched in the group of genes up-regulated during the early defense response to M. oryzae infection and that OsWRKY47 played a critical role in rice blast resistance (Wei et al, 2013)
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