title: Cloning and characterization of two full-length cDNAs, TaGA1 and TaGA2, encoding G-protein alpha subunits expressed differentially in wheat genome.
abstract: In the present study, we identified and characterized two cDNAs, named TaGA1 and TaGA2, encoding alpha subunits of heterotrimeric G proteins synthesized from one-week-old seedling mRNAs of common wheat cv. S615 using RACE PCR and RT-PCR methods. The clone TaGA1 contained an open reading frame that encoded a protein consisting of 383 amino acid residues with a molecular mass of 51.3 kDa, whereas the clone TaGA2 contained an open reading frame encoding 390 amino acids with a molecular mass of 52.5 kDa. At the amino acid level, both cDNAs (TaGA1 and TaGA2) showed 70-96% and 30-40% homologies to plant and animal G-protein alpha (G alpha) subunits, respectively, and 97.7% homology to each other. The regions essential for binding to GTP were conserved among all G alpha subunits in higher plants and mammals examined. However, the C-terminal amino acid sequences of TaGA1 and TaGA2 were similar to those of cereal G alpha subunits (rice and barley) but were different from the analogous sequences of mammalian G alpha subunits as well as from those of the leguminous and Solanaeceous G alpha subunits. Southern analysis revealed that the hexaploid wheat genome contained three major copies of G alpha subunit gene with a few less homologous copies. The analysis of the expression for G alpha subunit genes in wheat showed that both TaGA1 and TaGA2 mRNAs were abundant in one-week-old seedlings, immature seeds harvested one-week after anthesis, young spikes and internodes, indicating constitutive expression patterns in all of the organs tested. Especially, young spikes and internodes exhibited increased levels of mRNA accumulation, suggesting that G alpha subunit gene is highly expressed in actively elongating and fast growing tissues. Moreover, both TaGA1 and TaGA2 showed genome-specific expressions in wheat and may participate in the light-regulated growth and development of the seedlings.
authors.affiliation: Laboratory of Genetics and Plant Breeding, Faculty of Horticulture, Graduate School of Science and Technology, Chiba University, Japan.
authors.forename: Md Shakhawat
authors.initials: MS
authors.lastname: Hossain
authors.forename: Takato
authors.initials: T
authors.lastname: Koba
authors.forename: Kyuya
authors.initials: K
authors.lastname: Harada
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D020869:Gene Expression Profiling; D008969:Molecular Sequence Data; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D014908:Triticum / Q000235:genetics* / Q000378:metabolism
chemical_list: D019204:GTP-Binding Proteins