Phytoene Synthase 2 Can Compensate for the Absence of Psy1 in Pepper Fruit (Capsicum annuum)

Phytoene synthase 1 (PSY1) and Capsanthin-capsorubin synthase (CCS) are two major genes responsible for fruit color variation in pepper (Capsicum spp.), although fruit colors cannot be explained by variations in these two genes alone. Furthermore, the role of PSY2 in fruit color development in pepper is unknown. Here, we used a systemic approach to discover the genetic factors responsible for the yellow fruit color of C. annuum MicroPep Yellow (MY) and to reveal the role of PSY2 in fruit color. We detected a complete deletion of PSY1 and a retrotransposon insertion in CCS in MY. Despite the loss of PSY1 and CCS function, the MY and mutant F2 plants from a cross between MY and the MicroPep Red (MR) accumulated basal levels of carotenoids, indicating that other PSY genes may complement the loss of PSY1. A qRT-PCR analysis demonstrated that PSY2 is constitutively expressed in both MR and MY fruits, and a color complementation assay using Escherichia coli revealed that PSY2 is capable of biosynthesizing a carotenoid. Virus-induced gene silencing of PSY2 in MY resulted in white fruits. These findings suggest that PSY2 can compensate for the absence of PSY1 in fruit, resulting in the yellow color of MY fruits.\n\nHighlightWe reveal the novel function of PSY2 in the development of yellow pepper fruit coloration using a psy1 knockout mutant. This gene function was not previously identified in solanaceous crops.