Tyrosine Kinase Self-Phosphorylation Controls Exopolysaccharide Biosynthesis in Gluconacetobacter diazotrophicus Strain Pal5.

Katyanne Wanderley,Gabriel Silva,José Baldani,Dayse Sousa,Josemir Maia,Maria Silva,Marcia Vidal,Carlos Meneses

doi:10.3390/life11111231

Katyanne Wanderley, Gabriel Silva + Show 6 more

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https://doi.org/10.3390/life11111231

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Abstract

The biosynthesis of exopolysaccharides (EPSs) is essential for endophytic bacterial colonisation in plants bacause this exopolymer both protects bacterial cells against the defence and oxidative systems of plants and acts on the plant colonisation mechanism in Gluconacetobacter diazotrophicus. The pathway involved in the biosynthesis of bacterial EPS has not been fully elucidated, and several areas related to its molecular regulation mechanisms are still lacking. G. diazotrophicus relies heavily on EPS for survival indirectly by protecting plants from pathogen attack as well as for endophytic maintenance and adhesion in plant tissues. Here, we report that EPS from G. diazotrophicus strain Pal5 is a signal polymer that controls its own biosynthesis. EPS production depends on a bacterial tyrosine (BY) kinase (Wzc) that consists of a component that is able to phosphorylate a glycosyltranferase or to self-phosphorylate. EPS interacts with the extracellular domain of Wzc, which regulates kinase activity. In G. diazotrophicus strains that are deficient in EPS production, the Wzc is rendered inoperative by self-phosphorylation. The presence of EPS promotes the phosphorylation of a glycosyltransferase in the pathway, thus producing EPS. Wzc-mediated self-regulation is an attribute for the control of exopolysaccharide biosynthesis in G. diazotrophicus.

Highlights

The use of microbial inoculants with biofertiliser and biostimulant properties has emerged as an alternative to replace or complement the use of synthetic fertilisers to promote plant growth and development
Wzc protein from strain to other bacterial species with a An protein found in Genbank showed that itPal5 had compared
The attachment of plant growth-promoting bacteria (PGPB) to the plant root surface is the first step in enabling endophytic establishment

Summary

Introduction

The use of microbial inoculants with biofertiliser and biostimulant properties has emerged as an alternative to replace or complement the use of synthetic fertilisers to promote plant growth and development. Gluconacetobacter diazotrophicus is a plant growth-promoting bacteria (PGPB) that can be found colonising the internal tissues of many plants of agricultural importance, such as sugarcane (Saccharum officinarum) [1], rice (Oryza sativa) [2] and the C4 - energy crop, and elephant grass (Pennisetum purpureum) [3], in high numbers. In addition to fixing nitrogen in association with sugarcane plants, it has been demonstrated that this bacterium has other interesting physiological abilities, such as the production of indole acetic acid [4] and siderophores [5] and the solubilisation of inorganic phosphate and zinc oxide [6]. G. diazotrophicus strains tolerate high concentrations of sucrose (10%) and low pH, suggesting the existence of highly efficient mechanisms for protection against acidity and osmotolerance [8]. Nitrogenase activity is inhibited by high concentrations (20 mM) of ammonium sulphate, ammonium chloride, and glutamate [9], whereas amino acids (asparagine, aspartic acid and glutamic acid) partially inhibit this activity [10]

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