WRKY10 transcriptional regulatory cascades in rice are involved in basal defense and Xa1-mediated resistance

Abstract

WRKY proteins play essential roles as negative or positive regulators of pathogen defense. This study explored the roles of different OsWRKY proteins in basal defense and Xa1-mediated resistance to Xanthomonas oryzae pv. oryzae (Xoo) infection in rice. Assays of disease in OsWRKY10KD and OsWRKY88KD lines following infection with an incompatible Xoo race, which induced Xa1-mediated resistance in wild-type plants, showed that OsWRKY10 and OsWRKY88 were positive regulators of Xa1-mediated resistance. OsWRKY10 also acted as a positive regulator in basal defense by directly or indirectly activating transcription of defense-related genes. OsWRKY10 activated the OsPR1a promoter by binding to specific WRKY binding sites. Two transcriptional regulatory cascades of OsWRKY10 were identified in basal defense and Xa1-mediated resistance. In the first transcriptional regulatory cascade, OsWRKY47 acted downstream of OsWRKY10 whereas OsWRKY51 acted upstream. OsWRKY10 activated OsPR1a in two distinct ways: by binding to its promoter and, at the same time, by indirect activation through OsWRKY47. In the second transcriptional regulatory cascade, OsWRKY47 acted downstream of OsWRKY10, and OsWRKY88 acted upstream. These OsWRKY10 transcriptional regulatory cascades played important roles in basal defense and Xa1-mediated resistance to enable the mounting of a rapid immune response against pathogens.

When rice gets the chills: comparative transcriptome profiling at germination shows WRKY transcription factor responses

“…OsWRKY10 was reported to be upregulated in response to drought, salt, ABA, IAA, MeJA and SA in japonica rice Nipponbare (Ramamoorthy et al 2008). Recently, the role of the OsWRKY10-mediated pathway in basal defence and resistance to pathogens was revealed (Choi et al 2020). Here, we detected OsWRKY10 upregulation in response to chilling in the sensitive genotype.…”

“…5C). The presence of more than one W-box sequence was previously reported in OsWRKY gene promoters (Li et al 2015;Choi et al 2020). Thus, 53% of the OsWRKY genes had at least one W-box sequence in the 1.5 Kb putative promoters.…”

“…Recently, the role of the OsWRKY10‐mediated pathway in basal defence and resistance to pathogens was revealed (Choi et al . 2020). Here, we detected OsWRKY10 upregulation in response to chilling in the sensitive genotype.…”

“…2015; Choi et al . 2020). Thus, 53% of the OsWRKY genes had at least one W‐box sequence in the 1.5 Kb putative promoters.…”

“…OsWRKY10 has a complex regulatory role in two main transcriptional regulatory cascades involving other OsWRKY genes in basal defence against Xoo infection. In one of these, OsWRKY10 positively regulates OsWRKY47 by binding to their W-box; further, OsWRKY47 activates OsPR1a expression, increasing Xoo resistance (Choi et al 2020). In addition, OsWRKY10 is activated by OsWRKY51 that binds to its W-box (Choi et al 2020).…”