Molecular analysis of caffeoyl residues related to pigmentation in green cotton fibers

The pigment components in green cotton fibers were isolated and identified as 22-O-caffeoyl-22-hydroxymonodocosanoin and 22-O-caffeoyl-22-hydroxydocosanoic acid. The concentration of 22-O-caffeoyl-22-hydroxymonodocosanoin was correlated positively with the degree of green fibers of color, indicating a role of caffeoyl derivatives in pigmentation of green cotton fibers. Upland cotton (Gossypium hirsutum L.) contains four genes (Gh4CL1 to Gh4CL4) encoding 4-coumarate:CoA ligase (4CL), key enzymes of the phenylpropanoid biosynthesis pathway. In 15 to 24 days-post anthesis fibers, the expression level of Gh4CL1 was very low, Gh4CL3 had a similar expression level between the white and green cottons, Gh4CL2 had a significantly higher expression level in the green fibers than in the white fibers, whereas Gh4CL4 seemed to have a higher expression level in the white fibers than in the green fibers. According to enzyme kinetics analysis, Gh4CL1 displayed a preference for 4-coumarate, Gh4CL3 and G...