Abstract
BackgroundPlant WRKY transcription factors play pivotal roles in diverse biological processes but most notably in plant defense response to pathogens. Sheath blight represents one of the predominant diseases in rice. However, our knowledge about the functions of WRKY proteins in rice defense against sheath blight is rather limited.ResultsHere we demonstrate that the expression of Oryza sativa WRKY80 gene (OsWRKY80) is rapidly and strongly induced upon infection of Rhizoctonia solani, the causal agent of rice sheath blight disease. OsWRKY80 expression is also induced by exogenous jasmonic acid (JA) and ethylene (ET), but not by salicylic acid (SA). OsWRKY80-GFP is localized in the nuclei of onion epidermal cells in a transient expression assay. Consistently, OsWRKY80 exhibits transcriptional activation activity in a GAL4 assay in yeast cells. Overexpression of OsWRKY80 in rice plants significantly enhanced disease resistance to R. solani, concomitant with elevated expression of OsWRKY4, another positive regulator in rice defense against R. solani. Suppression of OsWRKY80 by RNA interference (RNAi), on the other hand, compromised disease resistance to R. solani. Results of yeast one-hybrid assay and transient expression assay in tobacco cells have revealed that OsWRKY80 specifically binds to the promoter regions of OsWRKY4, which contain W-box (TTGAC[C/T]) or W-box like (TGAC[C/T]) cis-elements.ConclusionsWe propose that OsWRKY80 functions upstream of OsWRKY4 as an important positive regulatory circuit that is implicated in rice defense response to sheath blight pathogen R. solani.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0137-y) contains supplementary material, which is available to authorized users.
Highlights
Plant WRKY transcription factors play pivotal roles in diverse biological processes but most notably in plant defense response to pathogens
Our findings suggest that OsWRKY80 functions upstream of OsWRKY4 and together this module acts as a positive regulatory circuit in the rice defense response against sheath blight disease
Structure analysis revealed that the deduced OsWRKY80 consisted of one classic conserved WRKY domain with a zinc finger motif of CX5-C-X23-H-X1-H, indicating that it belongs to the WRKY group II-e family (Eulgem et al 2000)
Summary
Plant WRKY transcription factors play pivotal roles in diverse biological processes but most notably in plant defense response to pathogens. Our knowledge about the functions of WRKY proteins in rice defense against sheath blight is rather limited. PTI- and ETI-mediated defense responses in plants are modulated mainly by three signaling hormone molecules, salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) (Tsuda et al 2009). There are both synergistic and antagonistic interactions between SA and JA/ET signaling pathways during plant immune progression (Kunkel and Brooks 2002; Mur et al 2006). This apparent discrepancy reflects the complexity of plant defense mechanisms (Kim et al 2006).
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