Yuchan Zhou
University of the Sunshine Coast, Australia
Title: Breadfruit (Artocarpus altilis) gibberellin metabolic genes: Stem elongation and abiotic stress response
Biography
Biography: Yuchan Zhou
Abstract
Breadfruit (Artocarpus altilis) is a traditional staple tree crop in the Oceania. Susceptibility to tropical windstorm damage has driven an interest in developing breadfruit with dwarf stature. Gibberellin (GA) is one of the most important determinants of plant height. As a first step toward understanding the molecular mechanism of growth regulation in the species, we investigated the role of GA and the regulation of GA20-oxidase and GA2-oxidase genes in breadfruit. We provided first evidence that the stem elongation in breadfruit could be manipulated by exogenous gibberellin-related growth regulators. We then cloned six GA20-oxidase cDNAs, AaGA20ox1- AaGA20ox6, and four GA2-oxidase cDNAs, AaGA2ox1- AaGA2ox4 in full-length from breadfruit. AaGA20ox1, AaGA20ox3 and AaGA20ox4 were predominantly expressed in green vegetative organs, but displayed different expression pattern in roots and reproductive organs. AaGA20ox2, AaGA20ox5 and AaGA20ox6 were expressed mainly in leaves at low level. On the other hand, 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. AaGA20ox1, AaGA20ox3 - AaGA20ox6 and AaGA2ox1 - AaGA2ox3, were subjected to GA feedback regulation following treatment of exogenous gibberellin and/or gibberellin biosynthesis inhibitors. Members of AaGA20oxs and AsGA2oxs were also regulated under drought and salinity stress. The function of these genes is discussed with particular reference to their role in stem elongation and the opportunities of breadfruit dwarfing