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Nodulation Phenotypes of Gibberellin and Brassinosteroid Mutants of Peal


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Ferguson, BJ, Ross, JJ and Reid, JB 2005 , 'Nodulation Phenotypes of Gibberellin and Brassinosteroid Mutants of Peal' , Plant Physiology, vol. 138, no. 4 , pp. 2396-2405 .

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The initiation and development of legume nodules induced by compatible Rhizobium species requires a complex signal
exchange involving both plant and bacterial compounds. Phytohormones have been implicated in this process, although in
many cases direct evidence is lacking. Here, we characterize the root and nodulation phenotypes of various mutant lines of pea
(Pisum sativum) that display alterations in their phytohormone levels and/or perception. Mutants possessing root systems
deficient in gibberellins (GAs) or brassinosteroids (BRs) exhibited a reduction in nodule organogenesis. The question of
whether these reductions represent direct or indirect effects of the hormone deficiency is addressed. For example, the
application of GA to the roots of a GA-deficient mutant completely restored its number of nodules to that of the wild type.
Grafting studies revealed that a wild-type shoot or root also restored the nodule number of a GA-deficient mutant. These
findings suggest that GAs are required for nodulation. In contrast, the shoot controlled the number of nodules that formed
in graft combinations of a Bk-deficient mutant and its wild type. The root levels of auxin and GA were similar among
these latter graft combinations. These results suggest that BRs influence a shoot mechanism that controls nodulation and that
the root levels of auxin and GA are not part of this process. Interestingly, a strong correlation between nodule and lateral root
numbers was observed in all lines assessed, consistent with a possible overlap in the early developmental pathways of the two

Item Type: Article
Authors/Creators:Ferguson, BJ and Ross, JJ and Reid, JB
Journal or Publication Title: Plant Physiology
ISSN: 0032-0889
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