University of Tasmania

File(s) under permanent embargo

Rht18 semidwarfism in wheat Is due to increased GA 2-oxidaseA9 expression and reduced GA content

journal contribution
posted on 2023-05-19, 19:09 authored by Ford, BA, Eloise FooEloise Foo, Sharwood, R, Karafiatova, M, Vrana, J, MacMillan, C, David NicholsDavid Nichols, Steuernagel, B, Uauy, C, Dolezel, J, Chandler, PM, Spielmeyer, W

Semidwarfing genes have improved crop yield by reducing height, improving lodging resistance, and allowing plants to allocate more assimilates to grain growth. In wheat (Triticum aestivum), the Rht18 semidwarfing gene was identified and deployed in durum wheat before it was transferred into bread wheat, where it was shown to have agronomic potential. Rht18, a dominant and gibberellin (GA) responsive mutant, is genetically and functionally distinct from the widely used GA-insensitive semidwarfing genes Rht-B1b and Rht-D1b. In this study, the Rht18 gene was identified by mutagenizing the semidwarf durum cultivar Icaro (Rht18) and generating mutants with a range of tall phenotypes. Isolating and sequencing chromosome 6A of these “overgrowth” mutants showed that they contained independent mutations in the coding region of GA2oxA9. GA2oxA9 is predicted to encode a GA 2-oxidase that metabolizes GA biosynthetic intermediates into inactive products, effectively reducing the amount of bioactive GA (GA1). Functional analysis of the GA2oxA9 protein demonstrated that GA2oxA9 converts the intermediate GA12 to the inactive metabolite GA110. Furthermore, Rht18 showed higher expression of GA2oxA9 and lower GA content compared with its tall parent. These data indicate that the increased expression of GA2oxA9 in Rht18 results in a reduction of both bioactive GA content and plant height. This study describes a height-reducing mechanism that can generate new genetic diversity for semidwarfism in wheat by combining increased expression with mutations of specific amino acid residues in GA2oxA9.


Publication title

Plant Physiology








School of Natural Sciences


Amer Soc Plant Biologists

Place of publication

15501 Monona Drive, Rockville, USA, Md, 20855

Rights statement

?Copyright 2018 American Society of Plant Biologists. All Rights Reserved.

Repository Status

  • Restricted

Socio-economic Objectives

Environmentally sustainable plant production not elsewhere classified

Usage metrics

    University Of Tasmania


    Ref. manager