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Lateral Root Inducible System in Arabidopsis and Maize
Published on: January 14, 2016
Auxin and nitric oxide control indeterminate nodule formation
Youry Pii1, Massimo Crimi, Giorgia Cremonese
1Dipartimento Scientifico Tecnologico, University of Verona, Verona, Italy. pii@sci.univr.it
BMC Plant Biology
|May 10, 2007
Summary
Bacterial auxin (indole-3-acetic acid) and nitric oxide enhance indeterminate root nodule formation in legumes. This suggests a model involving auxin transport regulation and nitric oxide synthesis for successful symbiosis.
Area of Science:
- Plant-microbe interactions
- Molecular biology
- Plant physiology
Background:
- Rhizobia bacteria form symbiotic root nodules with legumes, a process crucial for nitrogen fixation.
- Nodule development depends on localized auxin accumulation, with both plants and bacteria synthesizing this hormone.
- This study investigates the impact of bacterial auxin overproduction on legume nodulation.
Purpose of the Study:
- To determine the effect of increased bacterial indole-3-acetic acid (IAA) synthesis on nodule formation in different legume species.
- To elucidate the role of nitric oxide (NO) in auxin-mediated nodulation.
- To propose a model for nodule formation involving auxin and NO.
Main Methods:
- Genetic engineering of Sinorhizobium meliloti and Rhizobium leguminosarum for enhanced IAA production.
- Comparative analysis of nodulation in Medicago species (indeterminate nodules) and Phaseolus vulgaris (determinate nodules).
- Measurement of nitric oxide (NO) levels and assessment of nodulation inhibition using a specific NO scavenger (cPTIO).
Main Results:
- IAA-overproducing S. meliloti significantly increased nodulation in Medicago species.
- R. leguminosarum with enhanced auxin synthesis did not affect nodulation in Phaseolus vulgaris.
- Indeterminate nodules in Medicago showed increased lateral root development, higher NO levels, and enhanced nodulation with IAA-overproducing rhizobia.
- NO scavenger cPTIO reduced nodulation induced by both wild-type and IAA-overproducing strains.
Conclusions:
- Bacterial-derived auxin (IAA) and nitric oxide (NO) positively regulate indeterminate nodule formation.
- Increased expression of an auxin efflux carrier in roots with higher IAA and NO content was observed.
- A model is proposed where nodule formation involves coordinated regulation of auxin transport and NO synthesis.
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