a mutation in mrh2 kinesin enhances the root hair tip growth defect caused by constitutively activated rop2 small gtpase in arabidopsis突变mrh2驱动蛋白增强了根发梢增长缺陷引起的持续激活rop2小gtpase拟南芥.pdfVIP

A Mutation in MRH2 Kinesin Enhances the Root Hair Tip Growth Defect Caused by Constitutively Activated ROP2 Small GTPase in Arabidopsis 1 1 2 2 1,3 Guohua Yang , Peng Gao , Hua Zhang , Shanjin Huang , Zhi-Liang Zheng * 1 Department of Biological Sciences, Lehman College, City University of New York, Bronx, New York, United States of America, 2 Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Center for Signal Transduction and Metabolomics, Institute of Botany, Chinese Academy of Sciences, Beijing, China, 3 Plant Sciences PhD Subprogram, Graduate School and University Center, City University of New York, New York, United States of America Root hair tip growth provides a unique model system for the study of plant cell polarity. Transgenic plants expressing constitutively active (CA) forms of ROP (Rho-of-plants) GTPases have been shown to cause the disruption of root hair polarity likely as a result of the alteration of actin filaments (AF) and microtubules (MT) organization. Towards understanding the mechanism by which ROP controls the cytoskeletal organization during root hair tip growth, we have screened for CA-rop2 suppressors or enhancers using CA1-1, a transgenic line that expresses CA-rop2 and shows only mild disruption of tip growth. Here, we report the characterization of a CA-rop2 enhancer (cae1-1 CA1-1) that exhibits bulbous root hairs. The cae1-1 mutation on its own caused a waving and branching root hair phenotype. CAE1 encodes the root hair growth-related, ARM domain-containing kinesin-like protein MRH2 (and thus cae1-1 was renamed to mrh2-3). Cortical MT displayed fragmentation and random orientation in mrh2 root hairs. Consistently, the MT-stabilizing drug taxol could partially rescue the wavy root hair phenotype of mrh2-3, and the MT-depolymerizing drug