ABC transporter BrABCG12 mutation results in tender green glossy leaves in Chinese cabbage

Epicuticular wax crystals are synthesized and secreted by the epidermal cells of aerial tissues in terrestrial plants and are transported to the outer surface, where they crystallize on the cuticle. The absence of these wax crystals conferred a glossy phenotype to plant leaves, which is beneficial for enhancing the commercial quality of leafy vegetables. Fourteen glossy leaf mutants were isolated from an EMS-mutagenized doubled haploid line 'FT' of Chinese cabbage. Genetic analysis revealed that the glossy leaf trait in all mutants followed recessive nuclear inheritance. Among them, wdm15 and wdm16 were identified as allelic mutants and were selected for cloning and identification of the glossy leaf gene. MutMap combined with KASP analyses predicted that BrABCG12, encoding an ABC transporter homologous to Arabidopsis ABCG12, was the candidate gene. Sequencing results showed two independent G-to-A substitutions within the second exon of BrABCG12, resulting in a D155N substitution in wdm15 and a G107D substitution in wdm16. These results confirm that BrABCG12 is the gene responsible for the glossy leaf and provide valuable germplasm resources for the genetic improvement of Chinese cabbage.