Abstract
Pod color is a major economic trait of snap beans (Phaseolus vulgaris 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 ‘pv-pur’ via 60Co-γ radiation. Transcriptome analysis showed that three genes in the anthocyanin biosynthetic pathway were differentially expressed, among which the expression level of F3′5′H (Phvul.006G018800) was increased in the mutant ‘pv-pur’, while expression of F3′H (Phvul.004G021200) and ANS (Phvul.002G152700) 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 Phvul.006G024700, Phvul.002G152700, and Phvul.006G018800. Based on the levels of six anthocyanins in wild type and mutant plants, we speculative that the purple appearance of the mutant ‘pv-pur’ is caused by the increased expression of F3′5′H (Phvul.006G018800), 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.
Highlights
There are rich and colorful colors in the plant world
In order to study the genetic behavior of the purple mutant, we used wild type ‘A18-1’ and purple mutant ‘pv-pur’ as parents to generate a six-generation cross population, and investigated the phenotype of each generation
We examined the purple mutant of snap bean induced by artificial mutation
Summary
There are rich and colorful colors in the plant world. The existence of these colors is due to the existence of a variety of plant pigments in the plant tissues, including chlorophyll, carotenoids, photosensitive pigments, flavonoids and some algal pigments. Flavonoids are widely distributed in higher plants; they are a group of water-soluble phenolic compounds which mainly exist in the vacuoles and play an important role in signal transmission and the stress resistance of plants [1]. The variety and content of anthocyanins are the main factors that cause the color changes of fruits, flowers and vegetative tissues in different plants. Anthocyanins are the main bioactive substances for plants to resist biotic and abiotic stresses such as low temperature, drought, strong light, and ultraviolet radiation [2,3]
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