Wheat lectin as a factor in plant-microbial communication and a stress response protein

Wheat lectin (wheat germ agglutinin, WGA), a representative of a broad group of cereal lectins, is excreted by plant roots into the surrounding medium and interacts with both pathogenic microflora and growth-stimulating rhizobacteria. WGA was found to serve as a molecular signal for the rhizobacterium Azospirillum brasilense, which forms endophytic and associative symbioses with wheat plants. The bacterial response to the lectin was pleiotropic: WGA at concentrations from 10(-10) to 10(-6) M exerted a dose-dependent effect on a range of processes in the bacterium that are important for the establishment and functioning of symbiosis. Plants with different WGA content differed in their responses to severe nitrogen starvation and to seed treatment with Azospirillum.