Molecular Biology of the Rhizobium - Legume Symbiosis

Background on Nodule Development

Symbiotic defect of Rhizobium purine auxotrophs

Mutants are unable to infect in the absence of intermediate AICA riboside

Hypothesis - AICA riboside is a precursor of a cytokinin-type signal molecule that suppresses defense responses.
*****Theoretical model for symbiotic defect*****

Potential projects

1. Clone green fluorescent protein into Rhizobium to track infection.
2. Microscopic analysis of defense responses before and during infection.
3. Analysis of plant defense gene expression
4. Effect of defense induction on infection by wild-type Rhizobium.

Nodule Determination

Earlier experiments indicate that cells become committed to nodule development about 6 days after inoculation with Rhizobium.

Potential projects

1. Microscopic analysis of infection thread development - time course.
2. Changes in gene expression during commitment to nodule development.
3. Construction and analysis of Rhizobium loti purine auxotrophs.

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