The synergistic effect of fiber quality by proanthocyanidins and lignins in cotton fibers.

High quality naturally colored cotton fibers, coupled with rich colors, have become essentially desirable in current textile market to meet demands on the increasing standard of living and ecological textile industry. Both proanthocyanidins (PAs) and lignin originate from phenylpropanoid metabolism, our findings demonstrated that these two secondary metabolites synchronously regulate the color and quality of brown cotton fibers. From the fibers with different color types, the color depth of brown fiber was darkening with PAs accumulated more in a certain rang. When the PAs content in brown cotton fiber reached a certain threshold, the fiber color remained unchanged despite an increase in PAs content. Simultaneously, the cellulose content in the secondary cell wall (SCW) decreased when the lignin content synchronously increased, and the ratio of different types of lignin monomers changed. The changes of SCW compositions resulted in the reduced quality of mature brown cotton fibers that characterized with thin secondary cell walls, shorter length, lower micronaire values, and lower maturity. This discovery helps us understand the biochemical and molecular mechanisms of coloration and quality composition in brown cotton fibers, and will provide insights for genetic manipulation on NCCs in order to produce high quality multi-colored fibers. ● The changes of cellulose and lignin content in SCW resulted in the reduced quality of mature brown cotton fibers. ● PAs in BCF reached a certain threshold, the fiber color remained unchanged, accompanied lignin increase in SCW and fiber quality deteriorated. ● PAs and lignin are parallel originated from phenylpropanoid metabolism, synchronously regulated BCF color and quality. [ABSTRACT FROM AUTHOR]