Fine mapping and characterisation of a PV-PUR mediating anthocyanin synthesis in snap bean (Phaseolus vulgaris L.)

Abstract Anthocyanin makes snap bean ( Phaseolus vulgaris L.) pods purple, which is visually attractive and protects against environmental stress. In this study, we characterised the snap bean purple mutant pv-pur , which has purple cotyledon, hypocotyl, stem, leaf vein, flower and pod tissues. Total anthocyanin, delphinidin and malvidin levels in mutant pods were significantly higher than in wild-type plants. We constructed two populations for fine mapping of the PV-PUR purple mutation gene, located in the 243.9-kb region of chromosome 06. We identified Phvul.006g018800.3 , encoding F3'5'H, as a candidate gene for PV-PUR. Six single base mutations occurred in the coding region of this gene, altering protein structure. Phvul.006g018800.3 transcription was measured, and expression levels in the mutant were significantly higher than in wild-type plants in all tissues. The mutant Phvul.006g018800.3 gene was transferred into Arabidopsis thaliana , and the leaf base and internodes of transgenic Arabidopsis T3 plants were purple, verifying the function of the mutant gene. The results demonstrated that PV-PUR is a crucial gene for anthocyanin biosynthesis in snap bean, resulting in purple colouration. The findings lay a foundation for future breeding and improvement of snap bean.