Sym2 of Pea Is Involved in a Nodulation Factor-Perception Mechanism That Controls the Infection Process in the...

Area of Science:

• Plant-microbe interactions
• Molecular genetics
• Legume symbiosis

Background:

• Pea (Pisum sativum) exhibits complex symbiotic interactions with Rhizobium bacteria, involving numerous nodulation (Nod) genes.
• Several known pea nodulation mutants are impaired in early symbiotic signaling pathways.

Purpose of the Study:

• To elucidate the function of the sym2 gene in nodulation factor perception in pea.
• To investigate the specificity of Nod factor recognition and its impact on infection thread development.

Main Methods:

• Analysis of pea nodulation mutants, specifically focusing on the sym2A allele.
• Bacterial genetics to manipulate Nod factor production (NodX acetylation) and expression of bacterial nodulation genes (nodO).
• Phenotypic assessment of infection thread growth, early nodulin gene (ENOD12) induction, and nodule primordium formation.

Main Results:

• The sym2A allele restricts infection thread growth when Rhizobium lacks Nod factors acetylated by NodX.
• Early nodulin gene ENOD12 induction and nodule primordium formation were not impaired, indicating alternative perception mechanisms.
• The sym2A-mediated control of infection thread growth is influenced by the bacterial nodO gene.

Conclusions:

• Pea possesses multiple Nod factor perception mechanisms, with sym2A playing a role in a specific pathway.
• Nod factor structure, particularly acetylation, is critical for sym2A-dependent infection thread progression.
• Bacterial factors like nodO modulate the host's perception of symbiotic signals.