Phenylpropanoid metabolism and pigmentation show divergent patterns between brown color and green color cottons as revealed by metabolic and gene expression analyses
Abstract Background Naturally colored cotton has become increasingly popular because of their natural properties of color, UV protection, flame retardant, antibacterial activity and anti-mildew. But poor fiber quality and restricted color choices are two key issues that have limited the cultivation of naturally colored cottons. To identify the possible pathways participating in fiber pigmentation in naturally colored cottons, three differently colored cotton (with green, brown and white colored fiber) were chosen for a comprehensive analysis of phenylpropanoid metabolism during fiber development. Results The expression levels of flavonoid biosynthesis pathway genes in brown cotton fibers were significantly higher than in white or green cotton fibers. Total flavonoids and proanthocyanidin (PA) were high in brown cotton fibers but low in white and green cotton fibers, which suggested that flavonoid biosynthesis pathway might not participate in the pigmentation of green cotton fibers. Further expression analysis found that genes encoding enzymes for the synthesis of caffeic acid derivatives, lignin and lignan were activated in 10 DPA (days post-anthesis) and 15 DPA fibers of green cotton. Conclusions Our results strengthen understanding of phenylpropanoid metabolism and pigmentation in different colored cottons, and may provide strategies for improving green color and brown color cottons.