A MATE Transporter is Involved in Pathogenicity and IAA Homeostasis in the Hyperplastic Plant Pathogen Pseudomonas savastanoi pv. nerii.

Stefania Tegli,Matteo Cerboneschi,Carola Biancalani,Lorenzo Bini,Silvia Calamai

doi:10.3390/microorganisms8020156

Stefania Tegli, Matteo Cerboneschi + Show 3 more

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https://doi.org/10.3390/microorganisms8020156

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Journal: Microorganisms	Publication Date: Jan 22, 2020
Citations: 10	License type: CC BY 4.0

Affiliation: University of Florence

Abstract

During the last years, many evidences have been accumulating about the phytohormone indole-3-acetic acid (IAA) as a multifaceted compound in the microbial world, with IAA playing a role as a bacterial intra and intercellular signaling molecule or as an effector during pathogenic or beneficial plant–bacteria interactions. However, pretty much nothing is known on the mechanisms that bacteria use to modulate IAA homeostasis, in particular on IAA active transport systems. Here, by an approach combining in silico three-dimensional (3D) structural modeling and docking, mutagenesis, quantitative gene expression analysis, and HPLC FLD auxin quantitative detection, for the first time a bacterial multidrug and toxic compound extrusion (MATE) transporter was demonstrated to be involved in the efflux of IAA, as well as of its conjugate IAA–Lysine, in the plant pathogenic hyperplastic bacterium Pseudomonas savastanoi pv. nerii strain Psn23. Furthermore, according to the role proved to be played by Psn23 MatE in the development of plant disease, and to the presence of Psn23 MatE homologs in all the genomospecies of the P. syringae complex, this membrane transporter could likely represent a promising target for the design of novel and selective anti-infective molecules for plant disease control.

Highlights

Auxin are plant hormones whose correct homeostasis is pivotal for proper plant growth and development, as well as for plant defense [1]
By an approach combining in silico three-dimensional (3D) structural modeling and docking, mutagenesis, quantitative gene expression analysis, and HPLC FLD auxin quantitative detection, for the first time a bacterial multidrug and toxic compound extrusion (MATE) transporter was demonstrated to be involved in the efflux of indole-3-acetic acid (IAA), as well as of its conjugate IAA–Lysine, in the plant pathogenic hyperplastic bacterium Pseudomonas savastanoi pv. nerii strain Psn23
A pivotal role is played by the auxin IAA, whose levels in planta can be modulated by phytopathogens to promote susceptibility in their potential hosts

Summary

Introduction

Auxin are plant hormones whose correct homeostasis is pivotal for proper plant growth and development, as well as for plant defense [1]. Indole-3-acetic acid (IAA) is the main and most abundant naturally occurring auxin in plants, as well as the best studied, whose de novo biosynthesis is mainly through four interlinked pathways having L-tryptophan (Trp) as a precursor. The Trp-dependent pathways are two-step reactions, named to their specific key intermediate molecule, indole-3-pyruvic acid (IPyA), indole-3-acetamide (IAM), tryptamine (TAM), or indole-3-acetaldoxime (IAOX). Less information is definitely available for Trp-independent IAA biosynthesis, where indole-3-glycerol phosphate or indole are considered the main precursors. The IPyA and IAM pathways are considered the most conserved and used routes for IAA biosynthesis in plants. Many other important aspects still remain to be fully elucidated, such as which pathways are used in the different plant species and if they are likely to play alternative roles [2,3]

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