Development of novel plant phenotypes using plant pigment-associated genes (c)

A number of flavonoids produced by plants impart specific flower and fruit color. The R2R3-Myb transcription factors are key regulatory genes involved in flavonoid biosynthesis. Such transcription factors can be potentially used in the development of new plant phenotypes via genetic engineering. In the current study, anthocyanin biosynthesis-related genes from Citrus (RUBY), grapevine (VvMybA1), and maize(leaf color-LC) were isolated and placed along with a NPTII gene under the control of a CaMV35S-derived promoter complex. Embryogenic cultures of Vitis vinifera 'Thompson Seedless' were initiated from leaves and floral explants. Somatic embryos at the mid-cotyledonary stage of development were co-cultivated with Agrobacterium harboring individual candidate genes to regenerate modified plants. Leaf discs of tobacco cultivar 'Samsun' and petunia cultivar 'Mitcham' were also transformed to produce modified plants. Regenerated plants were transferred to potting mix, hardened under conditions of high humidity and transferred to a greenhouse. Transient anthocyanin expression from various genes was evidenced by bright red spots on explants after 3-5 d of co-cultivation with Agrobacterium. Stable gene expression was observed in callus and shoot cultures after 4-8 weeks on regeneration medium. Modified ` Thompson Seedless' plants were recovered after 16 weeks of co-cultivation while 'Samson' and 'Mitcham' produced plants in 4-6 weeks. Regenerated plants exhibited varied patterns and intensity of red pigmentation in mature tissues. While some plant lines exhibited uniform red pigmentation on leaves and shoots, other lines exhibited patchy or interveinal accumulation of the anthocyanin pigment. Normal growth and flowering was observed in all plants. Such plants expressing anthocyanin pigments with varied patterns and intensities could be used as breeding lines for the development of ornamental phenotypes with unique coloration.