OsMAINTENANCE OF MERISTEM LIKE 1 controls style number at high temperatures in rice

OsMAIL1 encodes for a rice protein of the Plant Mobile Domain (PMD) family and is strongly upregulated during floral induction in response to the presence of the florigens Heading date 3a (Hd3a) and RICE FLOWERING LOCUS T1 (RFT1). Although OsMAIL1 expression depends on the florigens, osmail1 null mutants do not show delay in flowering time, rather OsMAIL1 participates in ensuring successful reproduction. Indeed, when day temperatures reach 35 °C (7 °C higher than standard greenhouse conditions), osmail1 mutants show increased sterility due to abnormal pistil development with about half of the plants developing three styles topped by stigmas. OsMAIL1 expression correlates with that of carpel identity genes and RNA-seq of osmail1-1 mutant compared to the wt during inflorescence development showed that OsMAIL1 is required to activate carpel identity genes expression when floral meristems are about to be initiated. OsMAIL1 is a newly characterized rice gene that specifically controls carpel development under heat stress, ensuring plant female fertility in these conditions.