Identification of a new male sterile gene BrATAF1 of Chinese cabbage

A new male sterile gene BrATAF1 was cloned via map-based cloning and verified via Arabidopsis transformation. BrNAC092 was proved as the target gene of BrATAF1 in Chinese cabbage. Chinese cabbage exhibits significant heterosis, and the male sterile lines is crucial for its hybrid seed production. In this study, a male sterile mutant msm1355 was obtained from a EMS-mutagenized population in Chinese cabbage. Cytological analysis indicated that the abnormal tapetum development was the primary cause of the stamen abortion. By using MutMap and KASP techniques, BraA10g000280.3.5C, a homologous gene of ATAF1, was identified as the candidate gene for the male sterility. BrATAF1 encodes a transcriptional activator with a NAC domain. Heterologous complementation and overexpression tests in Arabidopsis thaliana confirmed the role of BrATAF1 in regulating stamen fertility, indicating that it is a key factor causing male sterility in Chinese cabbage. Subcellular localization and transcriptional activation assays demonstrated that BrATAF1 functioned as a nuclear protein with transcriptional activation activity. The downstream target gene BrNAC092 regulated by BrATAF1 was identified by transcriptome data, and the yeast one-hybrid and dual-luciferase assays verified that BrATAF1 could transcriptionally activate the expression of BrNAC092. Heterologous overexpression tests in Arabidopsis thaliana further substantiated the involvement of BrNAC092 in regulating stamen fertility in Chinese cabbage. These findings provided evidences that BrATAF1 regulated male sterility by positively modulating BrNAC092 expression, which presented a valuable genetic resource for the development of male sterile lines in Chinese cabbage.