Maize root lectins mediate the interaction with Herbaspirillum seropedicae via N-acetyl glucosamine residues of lipopolysaccharides

PLoS One. 2013 Oct 9;8(10):e77001. doi: 10.1371/journal.pone.0077001. eCollection 2013.

Abstract

Herbaspirillum seropedicae is a plant growth-promoting diazotrophic betaproteobacterium which associates with important crops, such as maize, wheat, rice and sugar-cane. We have previously reported that intact lipopolysaccharide (LPS) is required for H. seropedicae attachment and endophytic colonization of maize roots. In this study, we present evidence that the LPS biosynthesis gene waaL (codes for the O-antigen ligase) is induced during rhizosphere colonization by H. seropedicae. Furthermore a waaL mutant strain lacking the O-antigen portion of the LPS is severely impaired in colonization. Since N-acetyl glucosamine inhibits H. seropedicae attachment to maize roots, lectin-like proteins from maize roots (MRLs) were isolated and mass spectrometry (MS) analysis showed that MRL-1 and MRL-2 correspond to maize proteins with a jacalin-like lectin domain, while MRL-3 contains a B-chain lectin domain. These proteins showed agglutination activity against wild type H. seropedicae, but failed to agglutinate the waaL mutant strain. The agglutination reaction was severely diminished in the presence of N-acetyl glucosamine. Moreover addition of the MRL proteins as competitors in H. seropedicae attachment assays decreased 80-fold the adhesion of the wild type to maize roots. The results suggest that N-acetyl glucosamine residues of the LPS O-antigen bind to maize root lectins, an essential step for efficient bacterial attachment and colonization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylglucosamine*
  • Bacterial Adhesion
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Gene Expression Regulation, Bacterial
  • Herbaspirillum / genetics
  • Herbaspirillum / metabolism
  • Herbaspirillum / physiology*
  • Host-Pathogen Interactions*
  • Mutagenesis
  • O Antigens / chemistry
  • O Antigens / metabolism*
  • Plant Lectins / metabolism*
  • Plant Roots / metabolism
  • Plant Roots / microbiology*
  • Zea mays / metabolism
  • Zea mays / microbiology*

Substances

  • Bacterial Proteins
  • O Antigens
  • Plant Lectins
  • Acetylglucosamine

Grants and funding

This work was supported by the Brazilian Program of National Institutes of Science and Technology-INCT/Biological Nitrogen Fixation/Brazilian Research Council- CNPq/MCT and Fundação Araucária. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.