Cytoskeletal control of trichome cell shaping: from Arabidopsis trichomes to cotton fibers
作者单位：State Key Laboratory of Plant GenomicsInstitute of MicrobiologyChinese Academy of Sciences
会议名称：《2016年全国植物生物学大会》
会议日期：2016年
学科分类：0710[理学-生物学] 07[理学] 071009[理学-细胞生物学]
关 键 词：trichomes cotton fibers microtubules actin filaments
摘 要：Plant cells assume an amazing diversity of cell shapes that enable these cells to execute unique physiological functions,and the study of plant cell shape determination has remained an intriguing part of plant biology. The plant cytoskeletal system,composed of microtubules(MTs) and actin filaments(F-actin),plays a central role in cell morphogenesis. However,the molecular mechanisms underlying cytoskeletal control of plant cell shaping remain largely unknown. The Arabidopsis thaliana leaf trichome has long been a model system for investigating the role of the cytoskeleton in defining plant cell shape. Using live cell imaging,we observed the spatiotemporal organizations of MTs and F-actin in the Arabidopsis trichomes during development. We found that transverse MT rings encircle the elongating branches but leave a MT-depleted zone at the extreme apex,where precisely forms the transverse cortical F-actin cap. Importantly,we discovered that KCBP,a plant-unique kinesin,forms a gradient in the elongating trichome branch,with the highest density at MT-depleted zone. Further,single-molecule imaging demonstrated that the specific My TH4 domain and FERM domain in the N-terminal tail of KCBP physically bind to MTs and F-actin,respectively. Collectively,our findings revealed that KCBP,a plant-unique kinesin,acts as a hub integrating MTs and actin filaments to assemble the required cytoskeletal configuration for trichome cell morphogenesis. Cotton fiber cell is another intriguing model for studying cytoskeletal regulation of polarized cell elongation and cellulose biosynthesis. Through long-term efforts,we generated stable transgenic cotton lines expressing GFP-labelled actin filaments,and visualized actin architecture and dynamics in living cotton fiber cells. Our findings provide important insights into mechanisms underlying extremely polarized elongation of cotton fiber cells.