Fine-mapping and transcriptome analysis of BoGL-3, a wax-less gene in cabbage (Brassica oleracea L. var. capitata)

The great majority of terrestrial plants produce epicuticular wax that is used to protect plants from a variety of biotic and abiotic stresses. Cabbage epicuticular wax is a white crystalline compound of various lipids. Wax-less cabbage has the characteristics of lustrous green leaves and beautiful exterior, which facilitates the brilliant green cabbage breeding. CGL-3 is a spontaneous wax-less mutant identified from cabbage. Genetic analysis indicated that the waxy deficiency of the mutant was controlled by a single dominant gene. To clarify the mechanism of the waxy deficiency, fine-mapping and transcriptome analysis of the wax-less gene, BoGL-3, were carried out in this study. The result of fine mapping showed that the wax-less gene, BoGL-3, was delimited in a 33.5-kb interval which is between the flanking marker C08-98 and the end of chromosome 8. Two cDNA libraries, constructed with wax-less cabbage CGL-3 and the wild-type cabbage WT, were sequenced for screening of the target gene BoGL-3. A total of 8340 genes were identified with significant differential expression between CGL-3 and WT. Among these genes, 3187 were up-regulated and 5153 were down-regulated in CGL-3. With homologous analysis, four differential expressed genes related to wax metabolism were obtained. Among these four genes, only Bol018504 is located within the region of fine-mapping. Bol08504 is homologous to CER1, which encodes fatty acid hydroxylase and plays an important role in wax synthesis in Arabidopsis. However, there was no difference of Bol08504 sequence between CGL-3 and WT. We suggested that Bol018504 was regulated by BoGL-3. The suppression of Bol018504 leads to the reduction of wax. These findings will be helpful to reveal the mechanism of the wax metabolism in cabbage and develop lustrous green cabbage germplasm material.