Location: Cotton Fiber Bioscience ResearchTitle: A Gly65Val substitution in an actin, GhACT_LI1, disrupts cell polarity and F-actin organization resulting in dwarf, lintless cotton plants
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2017
Publication Date: 1/12/2017
Citation: Thyssen, G.N., Fang, D.D., Turley, R.B., Florane, C.B., Li, P., Mattison, C.P., Naoumkina, M.A. 2017. A Gly65Val substitution in an actin, GhACT_LI1, disrupts cell polarity and F-actin organization resulting in dwarf, lintless cotton plants. Plant Journal. 90(1):111-121. https://doi.org/10.1111/tpj.13477.
Interpretive Summary: Actin forms the cytoskeleton of all plant, animal and fungal cells, which gives them shape and directs cell growth. We discovered that a single mutation in one of the 36 actin genes in cotton can alter the cytoskeleton of the plant cells resulting in dwarf plants that lack the long seed-hairs that make up cotton lint. Cotton lint is the major economic product of the cotton plant and is the world's most important source of natural fibers for textiles. Understanding the detailed molecular mechanisms of how the actin cytoskeleton attaches to membranes inside of cells, coordinates directional cell growth, and gives cells their shape is important broadly, and may also lead to improvements in cotton fibers.
Technical Abstract: • Actin polymerizes to form 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 membrane-anchoring of actin filaments in lobed leaf 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 Li1 short 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 membrane-association of F-actin in Li1 plant cells by confocal microscopy.¬¬ • Mutant leaf cells lacked interdigitation of lobes and F-actin did not decorate the nuclear envelope. While wild-type fiber cells contain long longitudinal actin cables, the short Li1 fiber cells accumulated unanchored, axial cables. • GhACT_LI1 is involved in membrane anchoring of F-actin filaments. The polymerization-defective Gly65Val allele in Li1 plants likely disrupts processive elongation of membrane-anchored F-actin, resulting in a disorganized cytoskeleton and reduced cell polarity.