OsWRKY13

Rice transcription regulator OsWRKY13 influences the functioning of more than 500 genes in multiple signalling pathways, with roles in disease resistance, redox homeostasis,abiotic stress responses, and development[1].

Annotated Information

Expression

Comparative analysis of the genomic and cDNA sequences of OsWRKY13 (GenBank accession number EF143611) from resistant cultivar Minghui 63 (Oryza sativa subsp. indica) showed that the gene was 1,505 bp in length and had a coding region interrupted by two introns. The putative encoding product of OsWRKY13 consisted of 316 amino acids, which contained a WRKY motif, a zinc-finger motif, and a potential nuclear localization signal (Fig. 2A). According to the classification of the WRKY superfamily (Eulgem et al. 2000), OsWRKY13 belongs to group II[2]. OsWRKY13 was overexpressed in cultivar Mudanjiang 8 (O.sativa subsp. japonica).

Function

Rice OsWRKY13 is a potentially important transcriptional regulator involved in multiple physiological processes. It mediates disease resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) and fungal blast caused by Magnaporthe grisea through activation of salicylic acid (SA)-dependent pathways and suppression of jasmonic acid (JA)-dependent pathways(FIG1); OsWRKY13 can bind to the W-box and W-box like cis-elements that are present in the promoters of some pathogen-induced defence-responsive genes [2,3]. Furthermore, genomewide analyses of the expression profiling of OsWRKY13-activated lines reveal that OsWRKY13 directly or indirectly regulates the expression of more than 500 genes [4].

FIG1

Fig. 1. Defense signaling model for the roles of OsWRKY13 in regulation of salicylic acid (SA)- and jasmonic acid (JA)-dependent pathways. Thick solid lines indicate direct action of OsWRKY13 has been confirmed by protein-DNA binding assays; thin solid lines, regulation may be executed by direct or indirect action; dotted lines, regulation has been confirmed in rice or other plant species; the line ending with arrow, activation; and the line ending with perpendicular short line indicates suppression.

OsWRKY13 is also a potential regulator of other physiological processes during pathogen infection. It activates redox homeostasis by the glutathione/glutaredoxin system as well as the flavonoid biosynthesis pathway, which may enhance the biosynthesis of antimicrobial flavonoid phytoalexins [4]. OsWRKY13 inhibits the SNAC1-mediated abiotic stress defence pathway and terpenoid metabolism pathway to suppress salt and cold defence responses as well as to putatively retard rice growth and development[4]. Compared to the large number of differentially expressed genes in OsWRKY13-activated plants, however,most OsWRKY13-regulated pathways have yet to be elucidated. To understand the transcriptional regulation of OsWRKY13, the types of transcription factors and conserved motifs in the promoter regions of the genes differentially expressed in OsWRKY13-activated plants were analyzed. The results suggest that the actions of OsWRKY13 on the expression of more than 500 genes are partitioned by different types of transcription factors through binding to distinctly distributed cis-acting elements in the promoters of OsWRKY13-upregulated and -downregulated genes. Furthermore, OsWRKY13 appears to bind preferentially to the promoters of downregulated genes in vitro, suggesting that it may function more as a negative transcriptional regulator[1].

FIG2

Fig. 1. Product and function of the OsWRKY13 gene. A, Schematic diagrams of conserved motifs of OsWRKY13. NLS = nuclear localization signal, WRKY =WRKY motif, and zinc finger = zinc-finger motif. Conserved sequences of these structures are presented, and numbers indicate the amino acid position of each structure in OsWRKY13. B, OsWRKY13-overexpressing plants show enhanced resistance to Xanthomonas oryzae pv. oryzae PXO61 at both the seedling and booting stages. The T2 transgenic plants (1-1, 7-2, 18-10) are from T0 plants D11UM1, D11UM7, and D11UM18. 7-2N is a transgene-negative plant segregated in the D11UM7-2 family. C, Expression analysis of OsWRKY13 in noninoculated T0 transgenic plants, wild type, mock (water)-inoculated Minghui 63 (donor of OsWRKY13, M), and PXO61-inoculated Minghui 63 (P) by RNA gel blot analysis. D, Enhanced resistance to PXO61 cosegregates with overexpression of OsWRKY13 in T2 families D11UM1-4 and D11UM7-2. E, Growth of PXO61 in leaves of T3 OsWRKY13-overexpressing (D11UM1) and wild-type plants. Bacterial populations were determined from three leaves at each timepoint by counting CFUs. Similar results were obtained in two independent biological experiments. F, Resistance of OsWRKY13-overexpressing plants for Blast. The T1 negative (D11UM18-1N) and positive (D11UM18-4)plants were from T0 plant D11UM18. Similar results were obtained in two independent biological experiments. ck = Mudanjiang 8 (wild type).

Labs working on this gene

Deyun Qiu, Jun Xiao, Weibo Xie

References

1.Deyun Qiu, Jun Xiao, Weibo Xie:Exploring transcriptional signalling mediated by OsWRKY13, a potential regulator of multiple physiological processes in rice.BMC Plant Biology 2009, 9:74 2.Qiu D, Xiao J, Ding X, Xiong M, Cai M, Cao Y, Li X, Xu C, Wang S: OsWRKY13 mediates rice disease resistance by regulating defense-related genes in salicylate- and jasmonate-dependent signaling. Mol Plant Microbe Interact 2007, 20:492-499. 3.Cai M, Qiu D, Yuan T, Ding X, Li H, Duan L, Xu C, Li X, Wang S: Identification of novel pathogen-responsive cis-elements and their binding proteins in the promoter of OsWRKY13, a gene regulating rice disease resistance. Plant Cell Environ 2008,31:86-96. 4.Qiu D, Xiao J, Xie W, Liu H, Li X, Xiong L, Wang S: Rice gene network inferred from expression profiling of plants overexpressing OsWRKY13, a positive regulator of disease resistance. Mol Plant 2008, 1:538-551.