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

Eduardo Balsanelli,Thalita Regina Tuleski,Valter Antonio De Baura,Marshall Geoffrey Yates,Emanuel Maltempi De Souza,Rose Adele Monteiro,Leda Satie Chubatsu,Fabio De Oliveira Pedrosa,Eric Cascales

doi:10.1371/journal.pone.0077001

Eduardo Balsanelli, Thalita Regina Tuleski + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0077001

Copy DOI

Journal: PloS one	Publication Date: Oct 9, 2013
Citations: 78	License type: CC BY 4.0

Affiliation: Federal University of Paraná

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.

Highlights

H. seropedicae is a plant growth-promoting diazotrophic betaproteobacterium found in association with maize, sugarcane, rice, sorghum and wheat [1,2,3,4,5]
Results was named H. seropedicae LPSEB (waaL) mutagenesis The waaL gene was chosen for mutagenesis since the O-antigen ligase is specific for LPS biosynthesis; contrasting phenotypes between wild type and mutant strains would reflect the lack of O-antigen
We previously reported that intact LPS is required for H. seropedicae attachment and endophytic colonization of maize roots, and suggested that it is necessary for the bacteria to bind to plant receptors and to resist plant chemical defenses [19]

Summary

Introduction

H. seropedicae is a plant growth-promoting diazotrophic betaproteobacterium found in association with maize, sugarcane, rice, sorghum and wheat [1,2,3,4,5]. The mechanisms of establishment of interaction between associative endophytes and plants are not fully understood. The lipopolysaccharides (LPS) are highly complex macromolecules found exclusively as a monolayer on the outer membrane of gram-negative bacteria [10]. 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 [11,12]. The biogenesis of Oantigen can be divided in four stages: 1) initiation, 2) elongation/ translocation/polymerization of O-antigen repeating subunits; 3) ligation of O-antigen repeating subunits to the lipid A-core, and 4)

Methods

Results

Conclusion