OsWRKY80-OsWRKY4 Module as a Positive Regulatory Circuit in Rice Resistance Against Rhizoctonia solani

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.

Understanding sheath blight resistance in rice: the road behind and the road ahead

“…In our recent studies, we have demonstrated the effectiveness of AtNPR1 gene in rice sheath blight tolerance via the activation of several downstream defence genes (Karmakar et al , ; Karmakar et al , ; Molla et al , ). Overexpression of transcription factor genes, WRKY30 and WRKY80 caused improved resistance to ShB by activating JA or JA/ET signalling pathway (Peng et al , , ). Similarly, a transgenic plant expressing the ACS2 ( 1‐aminocyclopropane‐1‐carboxylic acid synthase ) gene, essential for the synthesis of signalling molecule ethylene, showed increased resistance against R. solani (Helliwell et al , ).…”

“…WRKY30 overexpression in transgenic rice plants has been shown to enhance ShB tolerance by activating jasmonate biosynthesis-related genes and subsequent increase of endogenous JA accumulation (Peng et al, 2012). Similarly, WRKY80 was found to confer ShB tolerance through the activation of WRKY4 and JA/ET signalling pathway (Peng et al, 2016). Recent studies indicated the involvement of JA and phenylpropanoid metabolism in ShB disease resistance (Ghosh et al, 2017;Zhang et al, 2017).…”

OsACL‐A2 negatively regulates cell death and disease resistance in rice

“…Chitinase, hydrolytic enzymes in plants, showed in vitro antifungal activity (Karmakar et al, 2016) and many OsWRKY transcription factor were also involved in defence mechanisms in rice (Peng et al, 2016). Pathogenesis-related genes were upregulated by enhanced expression of several OsWRKYs, including OsWRKY77 (Jimmy and Babu, 2015), a transcription factor reported to play important roles in plant pathogen responses by activating the salicylic acid (SA) pathway (Lan et al, 2013).…”

Transcriptome analysis of rice leaves in response to Rhizoctonia solani infection

“…WRKYs are well known for their pivotal roles in plant responses to stress conditions. Several studies illustrated that OsWRKY4, OsWRKY13, OsWRKY30, and OsWRKY80 positively regulates the resistance of rice to ShB (13)(14)(15)(16). In this study, we identified that OsWRKY53 was induced by R. solani, and further genetic study revealed that OsWRKY53 overexpression in the plant rendered it more susceptible to ShB, while Oswrky53 rendered it less susceptible.…”

“…The BR signaling transcription factor RAVL1 activates the key BR and ethylene signaling pathways to modulate the rice defense to ShB (12). OsWRKY4, OsWRKY13, OsWRKY30, and OsWRKY80 have been reported to positively regulate the resistance to ShB (13)(14)(15)(16), and more recently, we identified that sugar will eventually be exported via transporter 11 (SWEET11), which negatively regulates the rice resistance to ShB (17). Although much progress has been made, the knowledge about how rice defend themselves against ShB is still fragmented and limited.…”