Mutation in BrEPCR1 Led to Early Flowering in Chinese Cabbage

Flowering time is a critical trait in Chinese cabbage, particularly in stalk-type cultivars. In this study, we characterized two allelic early flowering mutants efm1 and efm2 of Chinese cabbage whose mutant characteristics were similar and insensitive to photoperiod, vernalization, and also GA₃ treatments. Genetic analysis revealed that the early flowering trait was controlled by a single recessive nuclear gene. The causal gene, BrEPCR1, was identified via MutMap and KASP techniques, and its function was further validated by sequencing analysis of allelic mutants and transient transformation. BrEPCR1 was a homologue of Arabidopsis thaliana EPCR1, a polycomb-related protein involved in histone deacetylation and heterochromatin silencing. ChIP-qPCR revealed that H4K5ac levels decreased at BrFLC2/3 in the efm1 mutant. The lost part of BrEPCR1, the EPL domain, was necessary for the interaction between BrEPCR1 and BrMBD9. Brepcr1 had the application potential to promote the early maturity in stalk type of Chinese cabbage.