Cotton green fiber promotes suberin synthesis interfering cellulose deposition in the secondary cell wall

Naturally green cotton (NGC) represents one of two commercialized naturally colored cottons, but its application is limited in the textile industry for inferior productivity and fiber quality of NGC cultivars. NGC fiber deposits substantial suberin at maturation, possibly related to fiber green coloration. The effects of suberin deposition on fiber development and fiber yield and quality are still to be elucidated. In the present study, the green fiber gene (Lg) in upland cotton (Gossypium hirsutum L.) was cloned using map-based method. It was found that Lg encoded an R2R3-MYB transcription factor, promoting suberin synthesis and deposition in cotton fiber via regulating multiple suberin structural genes. Suberin accumulated in green fibers continuously from the beginning of the secondary cell wall synthesis, along with significantly inhibited cellulose deposition, leading to dramatically decreased fiber strength and lint percentage. Our data demonstrated that suberin accumulation significantly interfered with cellulose deposition in fiber secondary cell wall, which conferred low yield and inferior fiber quality to green-fiber cottons.