Fenni Lv1, Mingya Han1, Dongdong Ge1, Hui Dong1, Xiaotong Zhang1, Lifeng Li1, Peipei Zhang1, Zhongqi Zhang1, Jing Sun1, Kang Liu2,3, Youlu Yuan4. 1. Department of Sciences of Seed Industry, College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, The People's Republic of China. 2. Department of Sciences of Seed Industry, College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, The People's Republic of China. kangliu@njau.edu.cn. 3. Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing, The People's Republic of China. kangliu@njau.edu.cn. 4. State Key Laboratory of Cotton Biology, Institute of Cotton Research, The Chinese Academy of Agricultural Sciences, Anyang, 455004, Henan, The People's Republic of China. yuanyl@cricaas.com.cn.
Abstract
MAIN CONCLUSION: GhVLN4 exhibited activity of cross-linking actin filaments into bundles. Overexpression of GhVLN4 increased the abundance of thick actin bundles and resulted in longer cell phenotypes. Actin bundle is a dynamic, higher-order cytoskeleton structure that is essential for cell expansion. Villin is one of the major proteins responsible for crosslinking actin filaments into bundles. However, this kind of actin binding protein has rarely been investigated in cotton. In the present work, a cotton villin gene was molecularly cloned from Upland cotton and denominated as GhVLN4. This gene was more highly expressed in fiber-bearing wild-type cotton TM-1 (Texas Marker-1) than in Ligon lintless-1 mutant (Li-1). Biochemical analysis combined with subcellular localization revealed that GhVLN4 is an actin-binding protein performing actin filament bundling activity in vitro. In line with these findings, a greater abundance of thick actin filament bundles were observed in GhVLN4-overexpressing transgenic plants compared with those in wild-type control. Moreover, ectopic expression of GhVLN4 significantly enhanced the cell length-width ratio of Schizosaccharomyces pombe yeast and increased the length of various Arabidopsis cells, including root cells, root hairs and pollen tubes. Taken together, our results demonstrate that GhVLN4 is involved in the generation of actin filament bundles, suggesting that GhVLN4 may play important roles in regulating plant cell morphogenesis and expansion by remodeling actin cytoskeleton.
MAIN CONCLUSION: GhVLN4 exhibited activity of cross-linking actin filaments into bundles. Overexpression of GhVLN4 increased the abundance of thick actin bundles and resulted in longer cell phenotypes. Actin bundle is a dynamic, higher-order cytoskeleton structure that is essential for cell expansion. Villin is one of the major proteins responsible for crosslinking actin filaments into bundles. However, this kind of actin binding protein has rarely been investigated in cotton. In the present work, a cotton villin gene was molecularly cloned from Upland cotton and denominated as GhVLN4. This gene was more highly expressed in fiber-bearing wild-type cotton TM-1 (Texas Marker-1) than in Ligon lintless-1 mutant (Li-1). Biochemical analysis combined with subcellular localization revealed that GhVLN4 is an actin-binding protein performing actin filament bundling activity in vitro. In line with these findings, a greater abundance of thick actin filament bundles were observed in GhVLN4-overexpressing transgenic plants compared with those in wild-type control. Moreover, ectopic expression of GhVLN4 significantly enhanced the cell length-width ratio of Schizosaccharomyces pombe yeast and increased the length of various Arabidopsis cells, including root cells, root hairs and pollen tubes. Taken together, our results demonstrate that GhVLN4 is involved in the generation of actin filament bundles, suggesting that GhVLN4 may play important roles in regulating plant cell morphogenesis and expansion by remodeling actin cytoskeleton.