Up-regulation of GhPAP1A results in moderate anthocyanin accumulation and pigmentation in sub-red cotton.

Anthocyanins are a group of important secondary metabolites, functioning as colorant in plant organs as well as protective agents against several stresses. Sub-red plant (Rs) cottons, accumulating moderate level of anthocyanins in shoots, had increased photosynthesis efficiency compared to green- (GL) and red-plant (R1) cottons. The present work aimed to clarify the molecular base of anthocyanin regulation in Rs cotton. It was found that GhPAP1A was significantly up-regulated in Rs plants compared to GL cottons, but its expression level is lower than that of GhPAP1D in R1 plants. Virus induced gene silencing of GhPAP1s inhibited the red pigmentation in Rs plants. Comparative cloning revealed a 50-bp tandem repeat in the promoter of GhPAP1A in Rs cotton, which showed stronger activity to drive the expression of downstream genes in petals. Considered that the coding sequence of GhPAP1As from Rs and GL cottons had similar functions to promote anthocyanin biosynthesis in transgenic tobaccos, we attributed moderate anthocyanin accumulation in Rs cotton to increased transcription of GhPAP1A, resulted from varied promoter structure. Our works suggested GhPAP1s as useful tool to manipulate anthocyanin level and several breeding targets, including herbivore- and pathogen- resistance, high photosynthesis efficiency and colored fibers.