SbWRKY62 Coordinates With SbERF096 to Activate Pterostilbene Biosynthesis and Targets a Xylanase Inhibitor Protein for Anthracnose Resistance in Sorghum
Yajing Li, Bofu Deng, Yiming Gan, Nan Lin, Dan Zhou, Clive LoABSTRACT
Sorghum anthracnose caused by Colletotrichum sublineola ( C. sublineola ) is a destructive disease leading to severe crop damages. Pterostilbene is a phytoalexin that contributes to defence responses in sorghum, but the transcriptional regulation of its biosynthesis remained poorly understood. Here, we characterised two transcription factors, SbERF096 and SbWRKY62, that are induced upon C. sublineola infection, with significantly higher expression levels in the resistant cultivar SC748‐5 than the susceptible cultivar BTx623. SbERF096 directly activates SbSTS1 , which encodes stilbene synthase, via binding to GCC box, while SbWRKY62 directly activates SbSOMT , which encodes stilbene O ‐methyltransferase (SOMT), via binding to W‐box motifs, marking the first transcription factor known to regulate a SOMT gene. Transient co‐expression of SbERF096 and SbWRKY62 promoted SbSTS1 and SbSOMT expressions from their native promoters, respectively, resulting in elevated pterostilbene accumulation in Nicotiana benthamiana which does not produce stilbenes inherently. Furthermore, SbWRKY62 directly targets SbXIP1 which is predicted to encode a xylanase inhibitor protein, a cell wall defence‐related protein that may reinforce physical barriers. These findings suggested that SbWRKY62 could confer anthracnose resistance with dual defence pathways to induce phytoalexin with SbERF096 and activate XIP production. Our work provides new molecular targets for breeding sorghum with enhanced anthracnose resistance.