Auxin-Gibberellin Interactions in Pea: Integrating the Old with the New

Ross, John J.; O'Neill, Damian; Rathbone, Damien A.

doi:10.1007/s00344-003-0021-z

Cited by 50 publications

(25 citation statements)

References 54 publications

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“…Elongation data refer to the difference between the initial and final lengths of the internodes, measured to a mark. GA 1 levels from this experiment were reported previously (Ross et al 2003), and did not exceed the very low level of 0.15 ng gFW -1 However, as in pea, there were opposite effects on the two GA 2-oxidase genes monitored: AtGA2ox1 was up-regulated while AtGA2ox2 was down-regulated (Table 3). The effect of auxin on all genes was statistically significant as shown by ratio t tests (PRISM GraphPad Software Inc., La Jolla, CA 92037, USA).…”

Section: Effects Of Iaa Status On Ga Gene Expression In Arabidopsismentioning

confidence: 49%

Regulation of the gibberellin pathway by auxin and DELLA proteins

O'Neill

Davidson

Clarke

et al. 2010

Planta

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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.

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Section: Effects Of Iaa Status On Ga Gene Expression In Arabidopsismentioning

confidence: 49%

Regulation of the gibberellin pathway by auxin and DELLA proteins

O'Neill

Davidson

Clarke

et al. 2010

Planta

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“…However, an auxin requirement in gibberellin‐induced growth is not shown consistently in all the plant species studied. For example, Ross, O’Neill & Rathbone (2003) showed that the decapitated internodes of Pisum sativum , which are auxin‐deficient, responded strongly to gibberellin application.…”

Section: Discussionmentioning

confidence: 99%

The stimulating effects of ethylene and auxin on petiole elongation and on hyponastic curvature are independent processes in submerged Rumex palustris

Cox

Peeters

Voesenek

2005

Plant Cell & Environment

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The flooding-tolerant plant species Rumex palustris (Sm.) responds to complete submergence with stimulation of petiole elongation mediated by the gaseous hormone ethylene. We examined the involvement of auxin in petiole elongation. The manipulation of petiolar auxin levels by removing the leaf blade, or by addition of synthetic auxins or auxin transport inhibitors, led to the finding that auxin plays an important role in submergence-induced petiole elongation in R. palustris . A detailed kinetic analysis revealed a transient effect of removing the auxin source (leaf blade), explaining why earlier studies in which less frequent measurements were taken failed to identify any role for auxin in petiole elongation. We previously showed that the onset of stimulated petiole elongation depends on a more upright petiole angle being reached by means of hyponastic (upward) curvature, a differential growth process that is also regulated by ethylene and auxin. This raised the possibility that both ethylene and auxin stimulate elongation only indirectly by influencing hyponastic growth. We show here that the action of ethylene and auxin in promoting petiole elongation in submerged R. palustris is independent of the promoting effect that these hormones also exert on the hyponastic curvature of the same petiole.

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“…The results of Bouquin et al (2001) indicate that this similarity might extend to regulation of the GA pathway. Ross et al (2003b) presented evidence that in pea, auxin promotes internode elongation (at least in part) by increasing the content of the bioactive GA, GA 1 . An implication of the Bouquin et al (2001) paper is that BRs might also act in this manner.…”

Section: Introductionmentioning

confidence: 98%

The brassinosteroid growth response in pea is not mediated by changes in gibberellin content

Jager

Symons

Ross

et al. 2004

Planta

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The objective of this study was to increase our understanding of the relationship between brassinosteroids (BRs) and gibberellins (GAs) by examining the effects of BR deficiency on the GA biosynthesis pathway in several tissue types of pea (Pisum sativum L.). It was suggested recently that, in Arabidopsis, BRs act as positive regulators of GA 20-oxidation, a key step in GA biosynthesis [Bouquin et al. (2001) Plant Physiol 127:450-458]. However, this may not be the case in pea as GA20 levels were consistently higher in all shoot tissues of BR-deficient (lk and lkb) and BR-response (lka) mutants. The application of brassinolide (BL) to lkb plants reduced GA20 levels, and metabolism studies revealed a reduced conversion of GA19 to GA20 in epi-BL-treated lkb plants. These results indicate that BRs actually negatively regulate GA20 levels in pea. Although GA20 levels are affected by BR levels, this does not result in consistent changes in the level of the bioactive GA, GA1. Therefore, even though a clear interaction exists between endogenous BR levels and the level of GA20, this interaction may not be biologically significant. In addition to the effect of BRs on GA levels, the effect of altered GA1 levels on endogenous BR levels was examined. There was no significant difference in BR levels between the GA mutants and the wild type (wt), indicating that altered GA1 levels have no effect on BR levels in pea. It appears that the BR growth response is not mediated by changes in bioactive GA levels, thus providing further evidence that BRs are important regulators of stem elongation.

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Auxin-Gibberellin Interactions in Pea: Integrating the Old with the New

Cited by 50 publications

References 54 publications

Regulation of the gibberellin pathway by auxin and DELLA proteins

Regulation of the gibberellin pathway by auxin and DELLA proteins

The stimulating effects of ethylene and auxin on petiole elongation and on hyponastic curvature are independent processes in submerged Rumex palustris

The brassinosteroid growth response in pea is not mediated by changes in gibberellin content

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