title: A Gly65Val substitution in an actin, GhACT_LI1, disrupts cell polarity and F-actin organization resulting in dwarf, lintless cotton plants.
abstract: Actin polymerizes to form part of the cytoskeleton and organize polar growth in all eukaryotic cells. Species with numerous actin genes are especially useful for the dissection of actin molecular function due to redundancy and neofunctionalization. Here, we investigated the role of a cotton (Gossypium hirsutum) actin gene in the organization of actin filaments in lobed cotyledon pavement cells and the highly elongated single-celled trichomes that comprise cotton lint fibers. Using mapping-by-sequencing, virus-induced gene silencing, and molecular modeling, we identified the causative mutation of the dominant dwarf Ligon lintless Li1short fiber mutant as a single Gly65Val amino acid substitution in a polymerization domain of an actin gene, GhACT_LI1 (Gh_D04G0865). We observed altered cell morphology and disrupted organization of F-actin in Li1plant cells by confocal microscopy. Mutant leaf cells lacked interdigitation of lobes and F-actin did not uniformly decorate the nuclear envelope. While wild-type lint fiber trichome cells contained long longitudinal actin cables, the short Li1fiber cells accumulated disoriented transverse cables. The polymerization-defective Gly65Val allele in Li1plants likely disrupts processive elongation of F-actin, resulting in a disorganized cytoskeleton and reduced cell polarity, which likely accounts for the dominant gene action and diverse pleiotropic effects associated with the Li1mutation. Lastly, we propose a model to account for these effects, and underscore the roles of actin organization in determining plant cell polarity, shape and plant growth.
authors.affiliation: Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), 1100 Robert E. Lee Blvd, New Orleans, LA, 70124, USA.|Cotton Chemistry and Utilization Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA, 70124, USA.
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Thyssen
authors.affiliation: Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), 1100 Robert E. Lee Blvd, New Orleans, LA, 70124, USA.
authors.forename: David D
authors.initials: DD
authors.lastname: Fang
authors.affiliation: Crop Genetics Research Unit, USDA-ARS, 141 Experiment Station Road, Stoneville, MS, 38776, USA.
authors.forename: Rickie B
authors.initials: RB
authors.lastname: Turley
authors.affiliation: Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), 1100 Robert E. Lee Blvd, New Orleans, LA, 70124, USA.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Florane
authors.affiliation: Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), 1100 Robert E. Lee Blvd, New Orleans, LA, 70124, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.affiliation: Food Processing and Sensory Quality Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA, 70124, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Mattison
authors.affiliation: Cotton Fiber Bioscience Research Unit, United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Southern Regional Research Center (SRRC), 1100 Robert E. Lee Blvd, New Orleans, LA, 70124, USA.
authors.forename: Marina
authors.initials: M
authors.lastname: Naoumkina
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D003368:Gossypium / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D010940:Plant Proteins
keywords: Ligon lintless Li1; actin; cell polarity; cotton fiber; cytoskeleton; mapping-by-sequencing; virus-induced gene silencing