Heading date (or flowering time) is one of the most important agronomic traits in rice, which determines the regional adaptability and crop yield. Many major-effect genes have been identified in rice, but they cannot be utilized for molecular breeding in general simply owing to their dramatic effect on heading date. Instead, minor-effect genes are preferred for fine-tuning flowering time as they usually don’t cause significant yield penalty. However, identification of these genes is lagging behind.

Recently, a report entitled “DHD4, A CONSTANS-like Family Transcription Factor, Delays Heading Date through Affecting the Formation of FAC Complex in Rice” was published in Molecular Plant by Prof. Wan Jianmin’s team at ICS-CAAS. In this report, the authors identified a new minor-effect repressor DHD4, which competes with 14-3-3 for interaction with OsFD1, thus affecting formation of the Hd3a-14-3-3-OsFD1 tri-protein FAC complex and causing reduced expression of OsMADS14 and OsMADS15, and ultimately delaying flowering. (https://doi.org/10.1016/j.molp.2020.11.013)

In this study, researchers collected several lines of evidence to support the notion that DHD4 represses flowering by affecting formation of the FAC complex and reducing the expression of OsMADS14 and OsMADS15. First, they showed that overexpression of DHD4 caused a delay in flowering time, while knocking out DHD4 resulted in a slightly earlier flowering phenotype compared with the wild type. Second, molecular and biochemical experiments revealed that DHD4 impacts on interaction of OsFD1 with 14-3-3 proteins through interacting with OsFD1, thus affecting formation of the FAC complex. Third, they showed that DHD4 could repress expression of OsMADS14 and OsMADS15 by affecting formation of the FAC complex. Fourth, their genetic analysis supported the notion that DHD4 acts upstream of OsMADS14 and OsMADS15 in regulating flowering in rice. Together, these results demonstrate a regulatory network in flowering time control and provide a promising target gene for improving regional adaptability of rice by fine-tuning of flowering time.

A proposed working model for DHD4 in regulating rice flowering.

                              By Zhu Shanshan (zhushanshan@caas.cn)