RESUMEN
Cytoplasmic linker-associated proteins (CLASPs) are microtubule-associated proteins (MAPs) involved in regulation of dynamics of microtubules (MTs) that play an important role in plant growth and development. In this study, we identified cotton CLASP genes and investigated the function of GhCLASP2. GhCLASP2 was mainly expressed in stem and developing fibers, especially in fibers of the secondary cell wall deposition stage. Ectopic expression of GhCLASP2 in Arabidopsis increased the branching number of leaf trichomes and rescued the defective phenotypes of clasp-1. In cotton, overexpression of GhCLASP2 increased fiber strength, probably related to enhanced expression levels of tubulin, cellulose synthase, and expansin genes. Suppression of GhCLASP2 caused shorter internodes and semi-dwarfism, abnormal flower stigma, aborted anthers without pollen grains, and sterility. These changed phenotypes were similar to those observed in the Arabidopsis clasp-1 mutant. GhCLASP2 was co-localized with MTs according to transient experiment. These results suggest that GhCLASP2 functions similarly as AtCLASP, acting as a MAP and controlling cotton growth and development by regulating MTs.
RESUMEN
BACKGROUND: Cotton fiber, a natural fiber widely used in the textile industry, is differentiated from single cell of ovule epidermis. A large number of genes are believed to be involved in fiber formation, but so far only a few fiber genes have been isolated and functionally characterized in this developmental process. The Kinesin13 subfamily was found to play key roles during cell division and cell elongation, and was considered to be involved in the regulation of cotton fiber development. RESULTS: The full length of coding sequence of GhKIS13A1 was cloned using cDNA from cotton fiber for functional characterization. Expression pattern analysis showed that GhKIS13A1 maintained a lower expression level during cotton fiber development. Biochemical assay showed that GhKIS13A1 has microtubule binding activity and basal ATPase activity that can be activated significantly by the presence of microtubules. Overexpression of GhKIS13A1 in Arabidopsis reduced leaf trichomes and the percentage of three-branch trichomes, and increased two-branch and shriveled trichomes compared to wild-type. Additionally, the expression of GhKIS13A1 in the Arabidopsis Kinesin-13a-1 mutant rescued the defective trichome branching pattern of the mutant, making its overall trichome branching pattern back to normal. CONCLUSIONS: Our results suggested that GhKIS13A1 is functionally compatible with AtKinesin-13A regarding their role in regulating the number and branching pattern of leaf trichomes. Given the developmental similarities between cotton fibers and Arabidopsis trichomes, it is speculated that GhKIS13A1 may also be involved in the regulation of cotton fiber development.