title: Isolation of Lhcb3 sequences from Brassica napus: evidence for conserved genes encoding LHCII type III chlorophyll a/b binding proteins.
abstract: Three closely related sequences were isolated from Brassica napus genomic DNA and were identified as Lhcb3 (genes encoding type III chlorophyll a/b binding proteins of LHCII, the major light-harvesting complex of photosystem II). These genes, as was observed for a tomato Lhcb3, contain two introns and yield both divergent and conserved predicted amino acid segments as compared with type I and type II polypeptides. One of the B. napus genes, designated Lhcb3*1, is transcribed in vivo, since it is identical to corresponding sequences in a cDNA clone. The protein deduced from another sequence, Lhcb3*2, appears as the most divergent type III so far characterized. The partial sequence of a third gene, Lhcb3*3, was also recovered. The 5' noncoding sequences of Lhcb3*1 and Lhcb3*2, in the far upstream region, are characterized by an extremely high AT content and extensive direct repeats. In the near upstream region, two long Lhcb3*2 segments are very similar to a segment proposed as containing regulatory signals in Lhcb3*1. Specific binding of nuclear proteins to Lhcb3*1 promoter fragments was detected by electrophoretic mobility-shift assays. The evolutionary relationship between genes for type III polypeptides and the other types present in LHCII is discussed.
authors.affiliation: Département de biochimie, Faculté des sciences et de génie, Université Laval, Québec, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Boivin
authors.forename: D
authors.initials: D
authors.lastname: Beauseigle
authors.forename: C L
authors.initials: CL
authors.lastname: Baszczynski
authors.forename: G
authors.initials: G
authors.lastname: Bellemare
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001937:Brassica / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002734:Chlorophyll / Q000378:metabolism; D016384:Consensus Sequence; D017124:Conserved Sequence; D004247:DNA / Q000235:genetics; D017343:Genes, Plant; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D045332:Photosystem II Protein Complex; D010944:Plants / Q000235:genetics*; D015183:Restriction Mapping
chemical_list: D002352:Carrier Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D004247:DNA