Ethylene-dependent and -independent pathways controlling floral abscission are revealed to converge using promoter::reporter gene constructs in the ida abscission mutant.
The process of floral organ abscission in Arabidopsis thaliana can be modulated by ethylene and involves numerous genes contributing to cell separation. One gene that is absolutely required for abscission is INFLORESCENCE DEFICIENT IN ABSCISSION, IDA, as the ida mutant is completely blocked in abscission. To elucidate the genetic pathways regulating floral abscission, molecular markers expressed in the floral abscission zone have been studied in an ida mutant background. Using plants with promoter-reporter gene constructs including promoters of a novel FLORAL ABSCISSION ASSOCIATED gene (FAA) encoding a putative single-stranded binding protein (BASIL), chitinase (CHIT::GUS) and cellulase (BAC::GUS), it is shown that IDA acts in the last steps of the abscission process. These markers, as well as HAESA, encoding a receptor-like kinase, were unaffected in their temporal expression patterns in ida compared with wild-type plants; thus showing that different regulatory pathways are active in the abscission process. In contrast to BASIL, CHIT::GUS and BAC::GUS showed, however, much weaker induction of expression in an ida background, consistent with a reduction in pathogen-associated responses and a lack of total dissolution of cell walls in the mutant. IDA, encoding a putative secreted peptide ligand, and HAESA appeared to have identical patterns of expression in floral abscission zones. Lastly, to address the role of ethylene, IDA::GUS expression in the wild type and the ethylene-insensitive mutant etr1-1 was compared. Similar temporal patterns, yet restricted spatial expression patterns were observed in etr1-1, suggesting that the pathways regulated by IDA and by ethylene act in parallel, but are, to some degree, interdependent.
Butenko
Melinka A
MA
Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, N-0316 Oslo, Norway.
Stenvik
Grethe-Elisabeth
GE
Alm
Vibeke
V
Saether
Barbro
B
Patterson
Sara E
SE
Aalen
Reidunn B
RB
D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism*; D035264:Flowers / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000032:analysis; D017403:In Situ Hybridization; D009154:Mutation; D027805:Phaseolus / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000032:analysis; D013025:Glycine max / Q000235:genetics
D029681:Arabidopsis Proteins; D005030:Ethylenes; C512213:IDA protein, Arabidopsis; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C036216:ethylene; C089427:RLK5 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases