The female-specific Cs-ACS1G gene of cucumber. A case of gene duplication and recombination between the non-sex-specific 1-aminocyclopropane-1-carboxylate synthase gene and a branched-chain amino acid transaminase gene.
Cucumber (Cucumis sativus L.) is a monoecious plant in which female sex expression (gynoecy) is controlled by the Female (F) locus that can be modified by other sex-determining genes as well as by environmental and hormonal factors. As in many other cucurbits, ethylene is the major plant hormone regulating female sex expression. Previously we isolated the Cs-ACS1 (ACS, 1-aminocyclopropane-1-carboxylate synthase) gene that encodes the rate-limiting enzyme in the ethylene biosynthetic pathway. We proposed that Cs-ACS1 is present in a single copy in monoecious (ffMM) plants whereas gynoecious plants (FFMM) contain an additional copy Cs-ACS1G that was mapped to the F locus. To study the origin of Cs-ACS1G, we cloned and analyzed both the gynoecious-specific Cs-ACS1G gene and the non-sex-specific Cs-ACS1 gene. Our results indicate that Cs-ACS1G is the result of a relatively recent gene duplication and recombination, between Cs-ACS1 and a branched-chain amino acid transaminase (BCAT) gene. Taking into consideration that the Cs-ACS1G gene was mapped to the F locus, we propose that this duplication event gave rise to the F locus and to gynoecious cucumber plants. Computer analysis of the 1 kb region upstream of the transcription initiation site revealed several putative cis-acting regulatory elements that can potentially confer the responsiveness of Cs-ACS1G to developmental and hormonal factors and thereby control female sex determination in cucumber. These findings lead us to a model explaining the action of Cs-ACS1 and Cs-ACS1G in cucumber floral sex determination.
Knopf
Ronit Rimon
RR
Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, Beer-Sheva 85105, Israel.
Trebitsh
Tova
T
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018553:Cucumis sativus / Q000201:enzymology / Q000235:genetics*; D020440:Gene Duplication; D017343:Genes, Plant; D018745:Genome, Plant; D008190:Lyases / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D011995:Recombination, Genetic; D016415:Sequence Alignment; D000637:Transaminases / Q000737:chemistry / Q000235:genetics*
D000637:Transaminases; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase