title: Characterization of a gene encoding a single-subunit bacteriophage-type RNA polymerase from maize which is alternatively spliced.
abstract: Single-subunit RNA polymerases belonging to the T3/T7 bacteriophage family are thought to be common throughout eukaryotes. We report the isolation and characterization of a nucleus-encoded single-subunit RNA polymerase gene from maize. This gene is highly homologous to other single-subunit RNA polymerase genes from Arabidopsis, Chenopodium. yeast and Neurospora crassa involved in organellar transcription. Genomic Southern analysis reveals 10 to 15 hybridising fragments, suggesting that maize contains a small gene family. The isolated gene contains 19 exons and its genomic structure is highly conserved when compared to the three Arabidopsis homologues. Unlike the case in Arabidopsis, intron-12 of the maize bacteriophage-type RNA polymerase gene is alternatively spliced. Quantitative RT-PCR revealed that the resultant alternatively spliced transcript represents approximately 21 to 26% of the total polymerase mRNA in maize coleoptiles. The orthologous wheat bacteriophage-type RNA polymerase is also alternatively spliced and the intron exhibits 78% identity to maize intron-12. The conservation in alternative splicing between wheat and maize and its absence from Arabidopsis suggest a functional requirement for the alternatively spliced product.
authors.affiliation: Department of Molecular Genetics, John Innes Centre, Colney, Norwich, UK.
authors.forename: D A
authors.initials: DA
authors.lastname: Young
authors.forename: R L
authors.initials: RL
authors.lastname: Allen
authors.forename: A J
authors.initials: AJ
authors.lastname: Harvey
authors.forename: D M
authors.initials: DM
authors.lastname: Lonsdale
mesh_terms: D017398:Alternative Splicing; D001483:Base Sequence; D002736:Chloroplasts / Q000201:enzymology / Q000235:genetics; D003001:Cloning, Molecular; D017124:Conserved Sequence; D012321:DNA-Directed RNA Polymerases / Q000145:classification / Q000235:genetics*; D017343:Genes, Plant; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D010442:Peptide Chain Initiation, Translational; D017422:Sequence Analysis, DNA; D013604:T-Phages / Q000201:enzymology / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics; D003313:Zea mays / Q000201:enzymology / Q000235:genetics*
chemical_list: D014764:Viral Proteins; D012321:DNA-Directed RNA Polymerases