Epigenetic regulation of ISPL10 enhances regional adaptability of rice varieties.

Suppressing the heading date of rice under short-day (SD) conditions while promoting it under long-day (LD) conditions can significantly enhance the regional adaptability of rice varieties. However, rice germplasm resources with these traits are scarce. In this study, we report the Jumonji C (jmjC) protein-encoding gene ISPL10. The ispl10 mutant exhibited heading 7 days later under SD and 14 days earlier under LD compared with the wild type (WT). ISPL10 decreased H3 lysine 9 dimethylation (H3K9me2) levels at the OsMADS51 locus and activated the expression of OsMADS51, which then enhanced the expression of Ehd1 and up-regulated Hd3a under SD conditions. By contrast, ISPL10 is directly bound to the promoter of OsVIL2 to suppress its expression, thereby inhibiting Ehd1 expression and reducing RFT1 expression under LD conditions. Additionally, ISPL10 interacted with Se14, another jmjC protein that controlled H3K4me3 states in the RFT1 chromatin. The field tests showed that the ispl10 mutant not only extended the growth period in low-latitude regions but also shortened the maturity duration in high-latitude regions, and thus significantly increased grain yield in both low- and high-latitude regions compared with WT. Therefore, the ISPL10 locus could be a crucial factor in improving the regional adaptability of rice varieties.