title: Temporal and spatial expression of a polygalacturonase during leaf and flower abscission in oilseed rape and Arabidopsis.
abstract: During leaf abscission in oilseed rape (Brassica napus), cell wall degradation is brought about by the action of several hydrolytic enzymes. One of these is thought to be polygalacturonase (PG). Degenerate primers were used to isolate a PG cDNA fragment by reverse transcriptase-polymerase chain reaction from RNA extracted from ethylene-promoted leaf abscission zones (AZs), and in turn a full-length clone (CAW471) from an oilseed rape AZ cDNA library. The highest homology of this cDNA (82%) was to an Arabidopsis sequence that was predicted to encode a PG protein. Analysis of expression revealed that CAW471 mRNA accumulated in the AZ of leaves and reached a peak 24 h after ethylene treatment. Ethylene-promoted leaf abscission in oilseed rape was not apparent until 42 h after exposure to the gas, reaching 50% at 48 h and 100% by 56 h. In floral organ abscission, expression of CAW471 correlated with cell separation. Genomic libraries from oilseed rape and Arabidopsis were screened with CAW471 and the respective genomic clones PGAZBRAN and PGAZAT isolated. Characterization of these PG genes revealed that they had substantial homology within both the coding regions and in the 5'-upstream sequences. Fusion of a 1,476-bp 5'-upstream sequence of PGAZAT to beta-glucuronidase or green fluorescent protein and transformation of Arabidopsis revealed that this fragment was sufficient to drive expression of these reporter genes in the AZs at the base of the anther filaments, petals, and sepals.
authors.affiliation: Plant Science Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire LE12 5RD, United Kingdom.
authors.forename: Zinnia Haydé
authors.initials: ZH
authors.lastname: González-Carranza
authors.forename: Catherine Ann
authors.initials: CA
authors.lastname: Whitelaw
authors.forename: Ranjan
authors.initials: R
authors.lastname: Swarup
authors.forename: Jeremy Alan
authors.initials: JA
authors.lastname: Roberts
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D001937:Brassica / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018744:DNA, Plant / Q000737:chemistry / Q000235:genetics; D005030:Ethylenes / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008969:Molecular Sequence Data; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D018547:Plant Stems / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D011096:Polygalacturonase / Q000235:genetics* / Q000378:metabolism; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D018076:DNA, Complementary; D018744:DNA, Plant; D005030:Ethylenes; D010937:Plant Growth Regulators; C036216:ethylene; D011096:Polygalacturonase