Regulation of the gibberellin pathway by auxin and DELLA proteins

Damian P. O'Neill, Sandra E. Davidson, Victoria C. Clarke, Yukika Yamauchi, Shinjiro Yamaguchi, Yuji Kamiya, James B. Reid, John J. Ross

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    39 Citations (Scopus)

    Abstract

    The synthesis and deactivation of bioactive gibberellins (GA) are regulated by auxin and by GA signalling. The effect of GA on its own pathway is mediated by DELLA proteins. Like auxin, the DELLAs promote GA synthesis and inhibit its deactivation. Here, we investigate the relationships between auxin and DELLA regulation of the GA pathway in stems, using a pea double mutant that is deficient in DELLA proteins. In general terms our results demonstrate that auxin and DELLAs independently regulate the GA pathway, contrary to some previous suggestions. The extent to which DELLA regulation was able to counteract the effects of auxin regulation varied from gene to gene. For Mendel's LE gene (PsGA3ox1) no counteraction was observed. However, for another synthesis gene, a GA 20-oxidase, the effect of auxin was weak and in WT plants appeared to be completely over-ridden by DELLA regulation. For a key GA deactivation (2-oxidase) gene, PsGA2ox1, the up-regulation induced by auxin deficiency was reduced to some extent by DELLA regulation. A second pea 2-oxidase gene, PsGA2ox2, was up-regulated by auxin, in a DELLA-independent manner. In Arabidopsis also, one 2-oxidase gene was down-regulated by auxin while another was up-regulated. Monitoring the metabolism pattern of GA20 showed that in Arabidopsis, as in pea, auxin can promote the accumulation of bioactive GA.

    Original languageEnglish
    Pages (from-to)1141-1149
    Number of pages9
    JournalPlanta
    Volume232
    Issue number5
    DOIs
    Publication statusPublished - 2010 Aug 13

    Keywords

    • Arabidopsis
    • Auxin
    • DELLA protein
    • Gibberellin
    • Pisum

    ASJC Scopus subject areas

    • Genetics
    • Plant Science

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