title: Cotton-fiber germin-like protein. II: Immunolocalization, purification, and functional analysis.
abstract: Cotton (Gossypium hirsutum L.) contains a germin-like protein (GLP), GhGLP1, that shows tissue-specific accumulation in fiber. The fiber GLP is an oligomeric, glycosylated protein with a subunit size of approximately 25.5 kDa. Accumulation of GhGLP1 occurs during the period of fiber elongation [4-14 days post-anthesis (DPA)]. During early phases of fiber development (2-4 DPA), GhGLP1 localizes to cytoplasmic vesicles as shown by confocal immunofluorescent microscopy. In slightly older fibers (7-10 DPA), GhGLP1 localizes to the apoplast. In other plants, germins and GLPs have been reported to have enzymatic activities including oxalate oxidase (OxO), superoxide dismutase, and ADP-glucose pyrophosphatase. Cotton fiber extracts did not contain OxO activity, nor did intact fibers stain for OxO activity. A four-step purification protocol involving ammonium sulfate precipitation of a 1.0 M NaCl extract, ion-exchange chromatography on DEAE-Trisacryl M, lectin-affinity chromatography, and gel filtration chromatography resulted in electrophoretically pure GhGLP1. While 1.0 M NaCl extracts from 10-14 DPA fiber contained superoxide dismutase and phosphodiesterase activities, GhGLP1 could be separated from both enzyme activities by the purification protocol. Although a GLP accumulates in the cotton fiber apoplast during cell elongation, the function of this protein in fiber growth and development remains unknown.
authors.affiliation: Southern Regional Research Center, US Department of Agriculture, Agricultural Research Service-New Orleans, LA 70124, USA.
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Pesacreta
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Triplett
mesh_terms: D000595:Amino Acid Sequence; D032561:Cotton Fiber; D000939:Epitopes / Q000032:analysis / Q000737:chemistry; D006023:Glycoproteins / Q000032:analysis*; D003368:Gossypium / Q000737:chemistry* / Q000166:cytology; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010940:Plant Proteins / Q000032:analysis
chemical_list: D000939:Epitopes; D006023:Glycoproteins; D010940:Plant Proteins; C058814:germin