title: Breadfruit (Artocarpus altilis) gibberellin 2-oxidase genes in stem elongation and abiotic stress response.
abstract: Breadfruit (Artocarpus altilis) is a traditional staple tree crop in the Oceania. Susceptibility to windstorm damage is a primary constraint on breadfruit cultivation. Significant tree loss due to intense tropical windstorm in the past decades has driven a widespread interest in developing breadfruit with dwarf stature. Gibberellin (GA) is one of the most important determinants of plant height. GA 2-oxidase is a key enzyme regulating the flux of GA through deactivating biologically active GAs in plants. As a first step toward understanding the molecular mechanism of growth regulation in the species, we isolated a cohort of four full-length GA2-oxidase cDNAs, AaGA2ox1- AaGA2ox4 from breadfruit. Sequence analysis indicated the deduced proteins encoded by these AaGA2oxs clustered together under the C19 GA2ox group. Transcripts of AaGA2ox1, AaGA2ox2 and AaGA2ox3 were detected in all plant organs, but exhibited highest level in source leaves and stems. In contrast, transcript of AaGA2ox4 was predominantly expressed in roots and flowers, and displayed very low expression in leaves and stems. AaGA2ox1, AaGA2ox2 and AaGA2ox3, but not AaGA2ox4 were subjected to GA feedback regulation where application of exogenous GA3 or gibberellin biosynthesis inhibitor, paclobutrazol was shown to manipulate the first internode elongation of breadfruit. Treatments of drought or high salinity increased the expression of AaGA2ox1, AaGA2ox2 and AaGA2ox4. But AaGA2ox3 was down-regulated under salt stress. The function of AaGA2oxs is discussed with particular reference to their role in stem elongation and involvement in abiotic stress response in breadfruit.
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, University of Queensland, St Lucia, QLD 4072, Australia; Faculty of Science, Education and Engineering, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia. Electronic address: y.zhou1@uq.edu.au.
authors.forename: Yuchan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Queensland Alliance for Agriculture and Food Innovation, University of Queensland, St Lucia, QLD 4072, Australia; Faculty of Science, Education and Engineering, University of the Sunshine Coast, Sippy Downs, QLD 4556, Australia.
authors.forename: Steven J R
authors.initials: SJ
authors.lastname: Underhill
mesh_terms: D000595:Amino Acid Sequence; D031622:Artocarpus / Q000201:enzymology* / Q000254:growth & development / Q000502:physiology; D035264:Flowers / Q000201:enzymology / Q000254:growth & development / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D005875:Gibberellins / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology / Q000254:growth & development / Q000502:physiology; D018517:Plant Roots / Q000201:enzymology / Q000254:growth & development / Q000502:physiology; D018547:Plant Stems / Q000201:enzymology / Q000254:growth & development / Q000502:physiology; D054712:Salinity; D016415:Sequence Alignment; D013312:Stress, Physiological
chemical_list: D005875:Gibberellins; D010937:Plant Growth Regulators; D006899:Mixed Function Oxygenases; C121463:gibberellin 2-dioxygenase
keywords: Breadfruit (Artocarpus altilis); Drought; Dwarfing; Gibberellin 2-oxidase; Salinity; Stem elongation