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

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Jager, CE and Symons, GM and Ross, JJ and Smith, JJ and Reid, JB (2005) The brassinosteroid growth response in pea is not mediated by changes in gibberellin content. Planta, 221. pp. 141-148. ISSN 0032-0935

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Abstract

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-BLtreated 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.

Item Type: Article
Journal or Publication Title: Planta
Page Range: pp. 141-148
ISSN: 0032-0935
Identification Number - DOI: 10.1007/s00425-004-1454-8
Additional Information: The final publication is available at http://www.springerlink.com
Date Deposited: 19 Aug 2011 02:34
Last Modified: 18 Nov 2014 04:21
URI: http://eprints.utas.edu.au/id/eprint/11566
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