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


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Jager, CE, Symons, GM, Ross, JJ, Smith, JJ and Reid, JB 2005 , 'The brassinosteroid growth response in pea is not mediated by changes in gibberellin content' , Planta, vol. 221 , pp. 141-148 , doi: 10.1007/s00425-004-1454-8.

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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-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
Authors/Creators:Jager, CE and Symons, GM and Ross, JJ and Smith, JJ and Reid, JB
Journal or Publication Title: Planta
ISSN: 0032-0935
DOI / ID Number: 10.1007/s00425-004-1454-8
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