title: Changes in expansin activity and gene expression during ethylene-promoted leaflet abscission in Sambucus nigra.
abstract: During ethylene-promoted leaflet abscission in Sambucus nigra a 7-fold increase in expansin activity was detected specifically in tissues undergoing cell separation, whilst only low levels of activity were seen in adjacent non-abscising tissues. An RT-PCR strategy was used to amplify expansin fragments from a cDNA library generated from mRNA extracted from ethylene-treated leaflet abscission-zone tissue. Two different full-length expansin-encoding cDNAs were isolated with sizes of 1190 bp and 1169 bp and named SniExp2 and SniExp4, respectively. The deduced protein sequences of SniExp2 and SniExp4 exhibited 67% homology and comprised 256 and 249 amino acids, respectively. Both putative proteins contained signal sequences at their N terminal ends, suggesting that they were likely to encode secreted or transmembrane proteins. Northern analyses with probes specific for each gene revealed that transcripts for both of these cDNAs accumulated specifically in abscission zone tissues in response to ethylene treatment, with no expression being apparent in either freshly excised material or non-separating tissues. These data support a role for expansins in ethylene-stimulated abscission and provide evidence that specific family members contribute to the cell separation process that takes place during organ shedding.
authors.affiliation: Plant Sciences Division, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire LE12 5 RD, UK.
authors.forename: Eric John
authors.initials: EJ
authors.lastname: Belfield
authors.forename: Benedetto
authors.initials: B
authors.lastname: Ruperti
authors.forename: Jeremy Alan
authors.initials: JA
authors.lastname: Roberts
authors.forename: Simon
authors.initials: S
authors.lastname: McQueen-Mason
mesh_terms: D000595:Amino Acid Sequence; D018076:DNA, Complementary; D005030:Ethylenes / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology*; D010940:Plant Proteins / Q000096:biosynthesis / Q000502:physiology*; D027924:Sambucus nigra / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment
chemical_list: D018076:DNA, Complementary; D005030:Ethylenes; D010937:Plant Growth Regulators; D010940:Plant Proteins; C095825:expansin protein, plant; C036216:ethylene