Identification and Characterization of a Mutant PV-PUR Gene Responsible for the Purple Phenotype of Snap Bean ( Phaseolus vulgaris L.)

Pod color is a major economic trait of snap beans ( L.), among which the pod with a purple stripe is more attractive to people. A stable purple mutant with purple stripes on the pods was obtained by artificial mutagenesis with the high generation snap bean inbred line 'A18-1'. In order to reveal the genetic factors and pathways responsible for the purple appearance in snap bean, we performed transcriptome and metabolome analyses using the green stem and yellow pod cultivar 'A18-1' and its purple mutant ' ' via Co-γ radiation. Transcriptome analysis showed that three genes in the anthocyanin biosynthetic pathway were differentially expressed, among which the expression level of ( ) was increased in the mutant ' ', while expression of ( ) and ( ) was downregulated. Anthocyanin-targeted metabonomics analysis showed significant differences in the contents of 10 metabolites between the wild type and mutant plants. Combined analysis of transcriptome and metabolomics showed that one differential metabolite, delphinidin, was related to the differential expression of , , and . Based on the levels of six anthocyanins in wild type and mutant plants, we speculative that the purple appearance of the mutant ' ' is caused by the increased expression of ( ), the key enzyme in the transformation from dihydroflavanol (DHK) to dihydromyricetone (DHM) in the anthocyanin biosynthetic pathway. The results lay a foundation for further studies on the molecular mechanism of anthocyanin synthesis in snap bean, and provide a framework for breeding different colors of snap bean.