The SAP function in pistil development was proved by two allelic mutations in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Abstract

AbstractBackgroundPistil development is a complicated process in plants, and female sterile mutants are ideal material for screening and cloning pistil development-related genes. Using the female sterile mutant (fsm1),BraA04g009730.3Cwas previously predicted as a candidate mutant gene encoding the STERILE APETALA (SAP) transcriptional regulator. In the current study, a parallel female sterile mutant (fsm2) was derived from EMS mutagenesis of a Chinese cabbage DH line ‘FT’ seeds.ResultsBothfsm2andfsm1mutant phenotypes exhibited pistil abortion and smaller floral organs. Genetic analysis indicated that the phenotype of mutantfsm2was also controlled by a single recessive nuclear gene. Allelism testing showed that the mutatedfsm1andfsm2genes were allelic. A single-nucleotide mutation (G-to-A) in the first exon ofBraA04g009730.3Ccaused a missense mutation from GAA (glutamic acid) to GGA (glycine) in mutantfsm2plants. Both allelic mutations ofBraA04g009730.3Cinfsm1andfsm2conferred the similar pistil abortion phenotype, which verified theSAPfunction in pistil development. To probe the mechanism ofSAP-induced pistil abortion, we compared the mutantfsm1and wild-type ‘FT’ pistil transcriptomes. Among the 3855 differentially expressed genes obtained, 29 were related to ovule development and 16 were related to organ size.ConclusionOur study clarified the function ofBraA04g009730.3Cand revealed that it was responsible for ovule development and organ size. These results lay a foundation to elucidate the molecular mechanism of pistil development in Chinese cabbage.