A Chimeric Arabinogalactan Protein Promotes Somatic Embryogenesis in Cotton Cell Culture

• Published in: Plant physiology (Bethesda) Vol. 160; no. 2; pp. 684 - 695
• Main Authors: Poon, Simon, Heath, Robyn Louise, Clarke, Adrienne Elizabeth
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.10.2012
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Base Sequence; Bioassay; Biological and medical sciences; CELL BIOLOGY AND SIGNAL TRANSDUCTION; Cell culture techniques; Cell walls; Chromatography, High Pressure Liquid; Cloning, Molecular; Complementary DNA; Culture Media - metabolism; DNA, Complementary - genetics; DNA, Complementary - metabolism; Fundamental and applied biological sciences. Psychology; Genetics and breeding of economic plants; Glycosylation; Gossypium - embryology; Gossypium - genetics; Gossypium - metabolism; Haploidy, in vitro culture applications, somatic hybrids; Hydrophobic and Hydrophilic Interactions; Molecular Sequence Data; Molecules; Mucoproteins - genetics; Mucoproteins - metabolism; Nicotiana - genetics; Nicotiana - metabolism; Plant breeding: fundamental aspects and methodology; Plant cells; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Somatic Embryogenesis Techniques - methods; Plants; Protein Structure, Tertiary; Proteins; Ratios; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sequence Analysis, DNA; Somatic embryogenesis; Transformation, Genetic; Malvaceae; Proteoglycan; Cell culture; Embryonic development; Plant physiology; Dicotyledones; Gossypium; Angiospermae; Tissue culture; Spermatophyta; Fiber crop; Somatic embryo
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.112.203075

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 (Gossypiutn 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 SEpromoting activity resided in a hydrophobic fraction. We cloned a full-length complementary DNA (cotton PHYTOCYANINLIKE 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 GhPLAl 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 GhPLAl, which was bacterially produced, also promoted SE, indicating that the glycosylated AGP domain was unnecessary for in vitro activity.