OsWRKY67 positively regulates blast and bacteria blight resistance by direct activation of PR genes in rice.

BACKGROUND: WRKY proteins are one of the largest gene families and are well-known for their regulatory roles in many aspects of plant development, including plant response to both biotic and abiotic stresses. Although the roles of WRKY proteins in leaf blast resistance have been well-documented in rice, their functions in panicle blast, the most destructive type of blast disease, are still largely unknown.

RESULTS: Here, we identified that the transcription of OsWRKY67 was strongly activated by leaf and panicle blast infection. OsWRKY67 is ubiquitously expressed and sub-localized in the nucleus. Rice plants overexpressing OsWRKY67 showed quantitatively enhanced resistance to leaf blast, panicle blast and bacterial blight. In contrast, silencing of OsWRKY67 increased the susceptibility to blast and bacterial blight diseases. RNA-seq analysis indicated that OsWRKY67 induces the transcription of a set of defense-related genes including the ones involved in the salicylic acid (SA)-dependent pathway. Consistent with this, the OsWRKY67-overexpressing plants accumulated higher amounts of endogenous SA, whereas lower endogenous SA levels were observed in OsWRKY67-silenced plants relative to wild-type Nipponbare plants before and after pathogen attack. Moreover, we also observed that OsWRKY67 directly binds to the promoters of PR1a and PR10 to activate their expression.

CONCLUSIONS: These results together suggest the positive role of OsWRKY67 in regulating rice responses to leaf blast, panicle blast and bacterial blight disease. Furthermore, conferring resistance to two major diseases makes it a good target of molecular breeding for crop improvement in rice.