Cotton-fiber germin-like protein. II: Immunolocalization, purification, and functional analysis.
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.
Kim
Hee Jin
HJ
Southern Regional Research Center, US Department of Agriculture, Agricultural Research Service-New Orleans, LA 70124, USA.
Pesacreta
Thomas C
TC
Triplett
Barbara A
BA
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
D000939:Epitopes; D006023:Glycoproteins; D010940:Plant Proteins; C058814:germin