Epigenetic regulation of JASMONATE ZIM-DOMAIN genes contributes to heat tolerance in the heat-tolerant rice cultivar Nagina 22

Abstract

Extreme hot weather severely limits rice (Oryza sativa) production. Rice cultivars from regions with hot weather are a valuable resource for breeding heat-tolerant rice, but the mechanisms mediating heat tolerance in these cultivars are not fully understood. Here, we investigated heat-tolerance mechanisms in rice using the well-known heat-tolerant cultivar Nagina 22 (N22) and comparing it with the less heat-tolerant cultivar 93–11. Following heat shock (HS) treatment (45 °C for 3 or 24 h), the expression of JASMONATE ZIM-DOMAIN (JAZ) genes spiked during the early stages of HS responses in N22 but not 93–11 and genes related to jasmonic acid (JA) signaling were repressed in N22. Promoting JA signaling in N22 via pretreatment with methyl JA (MeJA) impaired the heat tolerance of N22, measured as survival after HS treatment of 45 °C for 30 h, followed by a 7-d recovery. Furthermore, the N22-specific activation of JAZ genes was associated with increased histone acetylation and decreased DNA methylation. Comparing N22 to 93–11, we propose that the DNA demethylation process, rather than the hypomethylation status per se, is likely associated with JAZ activation. In summary, we revealed epigenetic mechanisms that may contribute to the heat tolerance of N22 via the JA signaling pathway; our findings have implications for improving heat tolerance in rice and other crops.