title: Regulation of the gibberellin pathway by auxin and DELLA proteins.
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 GA(20) showed that in Arabidopsis, as in pea, auxin can promote the accumulation of bioactive GA.
authors: Agilent Technologies Australia, Forest Hill, Australia. damian_oneill@agilent.com
authors: Damian P
authors: DP
authors: O'Neill
authors: Sandra E
authors: SE
authors: Davidson
authors: Victoria C
authors: VC
authors: Clarke
authors: Yukika
authors: Y
authors: Yamauchi
authors: Shinjiro
authors: S
authors: Yamaguchi
authors: Yuji
authors: Y
authors: Kamiya
authors: James B
authors: JB
authors: Reid
authors: John J
authors: JJ
authors: Ross
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics; D005875:Gibberellins / Q000235:genetics / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000494:pharmacology*; D018532:Pisum sativum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018547:Plant Stems / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D005875:Gibberellins; D007210:Indoleacetic Acids; D010940:Plant Proteins