title: Silencing of the ACC synthase gene ACACS2 causes delayed flowering in pineapple [Ananas comosus (L.) Merr.].
abstract: Flowering is a crucial developmental stage in the plant life cycle. A number of different factors, from environmental to chemical, can trigger flowering. In pineapple, and other bromeliads, it has been proposed that flowering is triggered by a small burst of ethylene production in the meristem in response to environmental cues. A 1-amino-cyclopropane-1-carboxylate synthase (ACC synthase) gene has been cloned from pineapple (ACACS2), which is induced in the meristem under the same environmental conditions that induce flowering. Two transgenic pineapple lines have been produced containing co-suppression constructs designed to down-regulate the expression of the ACACS2 gene. Northern analysis revealed that the ACACS2 gene was silenced in a number of transgenic plants in both lines. Southern hybridization revealed clear differences in the methylation status of silenced versus non-silenced plants by the inability of a methylation-sensitive enzyme to digest within the ACACS2 DNA extracted from silenced plants, indicating that methylation is the cause of the observed co-suppression of the ACACS2 gene. Flowering characteristics of the transgenic plants were studied under field conditions in South East Queensland, Australia. Flowering dynamics studies revealed significant differences in flowering behaviour, with transgenic plants exhibiting silencing showing a marked delay in flowering when compared with non-silenced transgenic plants and control non-transformed plants. It is argued that the ACACS2 gene is one of the key contributors towards triggering 'natural flowering' in mature pineapples under commercial field conditions.
authors.affiliation: Plant Genetic Engineering Laboratory, Department of Botany, School of Integrative Biology, University of Queensland, Brisbane 4072, Australia.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Trusov
authors.forename: José Ramón
authors.initials: JR
authors.lastname: Botella
mesh_terms: D031230:Ananas / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D005030:Ethylenes / Q000037:antagonists & inhibitors; D035264:Flowers / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D020868:Gene Silencing; D008190:Lyases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D008745:Methylation; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000254:growth & development
chemical_list: D005030:Ethylenes; C036216:ethylene; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase