Rhizosphere of Maise: Maize root lectins (MRLs) mediate interaction with Herbaspirillum seropedicae via O-GalNAc of Lipopolysaccharides (LPS).

A group from Universidade Federal do Paraná, Curitiba, Paraná, Brazil, etc. has reported that maize root lectins (MRLs) mediate interaction with Herbaspirillum seropedicae via O-GalNAc of Lipopolysaccharides (LPS).
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0077001

The lipopolysaccharides (LPS) are highly complex macromolecules found exclusively as a monolayer on the outer membrane of gram-negative bacteria. These glycoconjugates are composed of three regions: the lipid A that anchors the molecule to the outer cell membrane, the core oligosaccharide, and the O-antigen. The LPS from Herbaspirillum seropedicae strain (wild type) has lipid A-core containing different degrees of O-antigen oligomerization, however, the LPS from the mutant strain LPSEB (waaL) lacks the O-antigen, has only the lipid A-core. Here, H. seropedicae is a plant growth-promoting diazotrophic betaproteobacterium which associates with important crops, such as maize, wheat, rice and sugar-cane.

Maize root colonization of both wild type and mutant strains showed dose-dependent increases (as shown in a figure below A), however, the numbers of the waaL mutant cells attached to the roots were always lower than those of the wild type. Co-inoculation assays revealed a clear predominance of the wild type strain against the waaL mutant for attachment (see the figure below B).

In the figure below, A: maize was inoculated separately with the indicated amount of each bacterial strain, and B: maize was inoculated with a 1∶1 mixture of both strains. H. seropedicae wild-type is shown in black color and waaL mutant strain is shown in gray color.

It is likely that the interaction between LPS O-antigen and the MRLs is a key step for the establishment of the bacteria onto the root enhancing H. seropedicae attachment and conferring a competitive advantage during colonization of root surfaces, to gain access to inner tissues.