Functional analysis of GhCHS, GhANR and GhLAR in colored fiber formation of Gossypium hirsutum L

Background: The formation of natural colored fibers mainly results from the accumulation of different anthocyanidins and their derivatives in the fibers of Gossypium hirsutum L. Chalcone synthase (CHS) is the first committed enzyme of flavonoid biosynthesis, and anthocyanidins are transported into fiber cells after biosynthesis mainly by Anthocyanidin reductase (ANR) and Leucoanthocyanidin reductase (LAR) to present diverse colors with distinct stability. The biochemical and molecular mechanism of pigment formation in natural colored cotton fiber is not clear. Results: The three key genes of GhCHS, GhANR and GhLAR were predominantly expressed in the developing fibers of colored cotton. In the GhCHSi, GhANRi and GhLARi transgenic cottons, the expression levels of GhCHS, GhANR and GhLAR significantly decreased in the developing cotton fiber, negatively correlated with the content of anthocyanidins and the color depth of cotton fiber. In colored cotton Zongxu1 (ZX1) and the GhCHSi, GhANRi and GhLARi transgenic lines of ZX1, HZ and ZH, the anthocyanidin contents of the leaves, cotton kernels, the mixture of fiber and seedcoat were all changed and positively correlated with the fiber color. Conclusion: The three genes of GhCHS, GhANR and GhLAR were predominantly expressed early in developing colored cotton fibers and identified to be a key genes of cotton fiber color formation. The expression levels of the three genes affected the anthocyanidin contents and fiber color depth. So the three genes played a crucial part in cotton fiber color formation and has important significant to improve natural colored cotton quality and create new colored cotton germplasm resources by genetic engineering.