BrCER1 intron mutation causing a wax deficient phenotype in Chinese cabbage.

Background: Cuticular wax is one of the most important substances that cover the aerial parts of most plants and protect them from biotic and abiotic stresses. Plants lacking wax powder on their surface are more popular in terms of appearance and quality. Although most wax deficiency mutants are of high commercial value, most genetic and biochemical studies have been conducted in Arabidopsis, and only a few studies have been conducted in Chinese cabbage (Brassica rapa L. ssp. pekinensis).

Results: In the present study, we described a glossy leaf mutant from the ethyl methanesulfonate mutagenesis population of Chinese cabbage doubled haploid line 'FT'. In the M5075 mutant leaves, wax crystals were completely absent and leaf cuticular permeability was increased. Genetic analysis indicated that the glossy phenotype of M5075 is controlled by a single recessive gene. MutMap detected the responsible gene BrCER1 in the 4.76 Mb region on chromosome A09. BrCER1 shares homology with AtCER1 encoding a key enzyme responsible for biosynthesis of cuticular wax. Sequencing revealed the presence of only one nucleotide substitution at the 4th exon boundary, leading to a alternative splicing of BrCER1 in M5075. Our results showed that the mutation of BrCER1 would severely reduce wax crystals, thereby conferring a glossy phenotype on M5075.

Conclusion: This study describes the known functions and molecular characterization of Chinese cabbage cuticular wax biosynthesis to elucidate its potential use in crop improvement. It not only provides important information for the functional study of BrCER1, but also provides a basis for the study of Chinese cabbage wax synthesis pathway.