Cenchrus setigerus Vahl. secretes root agglutinins to promote colonization by plant growth-promoting rhizobacteria

Authors: Subramanyam, Subhashree; SARDESAI, NAGESH - Corteva Agriscience; BABU, CHERUKERI - University Of Delhi

Submitted to: Global Ecology and Biogeography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2022
Publication Date: 2/22/2022
Citation: Subramanyam, S., Sardesai, N., Babu, C.R. 2022. Cenchrus setigerus Vahl. secretes root agglutinins to promote colonization by plant growth-promoting rhizobacteria. Brazilian Journal of Botany. 45: 819-832. https://doi.org/10.1007/s40415-022-00794-4.
DOI: https://doi.org/10.1007/s40415-022-00794-4

Interpretive Summary: Grasses are extremely important not only as forage crops but also in the redevelopment of degraded lands. Bacteria associated with the roots of grasses, play an important role in promoting plant growth. However, the mechanism by which bacteria attach to the plant roots is not well understood. In this work we discovered a plant cell wall protein, known as a lectin, that plays an important role in binding growth promoting bacteria to the roots of grasses. This work is significant because it will help devise new ways to increase the growth of grasses, so they can be more effective as forage grasses for livestock and ecological restoration of derelict lands.

Technical Abstract: Grasses constitute a key taxonomic group that is of immense ecological value in ecosystem redevelopment. Plant growth-promoting rhizobacteria (PGPR) associated with the rhizosphere of the grasses play a significant role by aiding the development of the plant or by controlling phytopathogens. Cenchrus setigerus is a forage grass that is tolerant to heat and saline soils. Biochemical and physiological characterization of PGPR isolated from the rhizosphere of C. setigerus was carried out and diazotrophs were identified as belonging to the genera Azospirillum and Pseudomonas. An N-acetylglucosamine-binding agglutinin (Cenchrus root agglutinin: CRA) was isolated from the roots of C. setigerus, by affinity chromatography, that agglutinated buffalo erythrocytes. Immunoblot analyses of CRA indicated that it shared no similarity with other monocot and dicot lectins tested. Hemagglutination assays with buffalo erythrocytes were competitively inhibited by CRA in the presence of either Azospirillum or Pseudomonas, indicating that CRA specifically binds to surface antigens of these rhizobacteria. Further, lipopolysaccharides (LPS) were isolated from the rhizobacteria and used in a double diffusion assay to show that CRA reacted specifically with the LPS from Azospirillum and Pseudomonas. Our data illustrate the mechanism by which attachment of rhizobacteria to roots of C. setigerus is mediated through the interaction of bacterial LPS and CRA.