title: A chimeric arabinogalactan protein promotes somatic embryogenesis in cotton cell culture.
abstract: Arabinogalactan proteins (AGPs) are a family of extracellular plant proteoglycans implicated in many aspects of plant growth and development, including in vitro somatic embryogenesis (SE). We found that specific AGPs were produced by cotton (Gossypium hirsutum) calli undergoing SE and that when these AGPs were isolated and incorporated into tissue culture medium, cotton SE was promoted. When the AGPs were partly or fully deglycosylated, SE-promoting activity was not diminished. Testing of AGPs separated by reverse-phase high-performance liquid chromatography revealed that the SE-promoting activity resided in a hydrophobic fraction. We cloned a full-length complementary DNA (cotton PHYTOCYANIN-LIKE ARABINOGALACTAN-PROTEIN1 [GhPLA1]) that encoded the protein backbone of an AGP in the active fraction. It has a chimeric structure comprising an amino-terminal signal sequence, a phytocyanin-like domain, an AGP-like domain, and a hydrophobic carboxyl-terminal domain. Recombinant production of GhPLA1 in tobacco (Nicotiana tabacum) cells enabled us to purify and analyze a single glycosylated AGP and to demonstrate that this chimeric AGP promotes cotton SE. Furthermore, the nonglycosylated phytocyanin-like domain from GhPLA1, which was bacterially produced, also promoted SE, indicating that the glycosylated AGP domain was unnecessary for in vitro activity.
authors.affiliation: School of Botany, University of Melbourne, Victoria 3010, Australia. s.poon@latrobe.edu.au
authors.forename: Simon
authors.initials: S
authors.lastname: Poon
authors.forename: Robyn Louise
authors.initials: RL
authors.lastname: Heath
authors.forename: Adrienne Elizabeth
authors.initials: AE
authors.lastname: Clarke
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D003470:Culture Media / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D006031:Glycosylation; D003368:Gossypium / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D009088:Mucoproteins / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D058439:Plant Somatic Embryogenesis Techniques / Q000379:methods*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
chemical_list: D003470:Culture Media; D018076:DNA, Complementary; D009088:Mucoproteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C006619:arabinogalactan proteins