The Bacterial Soft Rot Pathogens, Pectobacterium carotovorum and P. atrosepticum, Respond to Different Classes of Virulence-Inducing Host Chemical Signals

Paul A Agyemang,C Korsi Dumenyo,Caleb M Kersey,Md Niamul Kabir

doi:10.3390/horticulturae6010013

Paul A Agyemang, C Korsi Dumenyo + Show 2 more

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https://doi.org/10.3390/horticulturae6010013

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Abstract

Soft rot bacteria of the Pectobacterium and Dickeya genera are Gram-negative phytopathogens that produce and secrete plant cell wall-degrading enzymes (PCWDE), the actions of which lead to rotting and decay of their hosts in the field and in storage. Host chemical signals are among the factors that induce the bacteria into extracellular enzyme production and virulence. A class of compounds (Class I) made up of intermediate products of cell wall (pectin) degradation induce exoenzyme synthesis through KdgR, a global negative regulator of exoenzyme production. While the KdgR− mutant of P. carotovorum is no longer inducible by Class I inducers, we demonstrated that exoenzyme production is induced in this strain in the presence of extracts from hosts including celery, potato, carrot, and tomato, suggesting that host plants contain another class of compounds (Class II inducers) different from the plant cell wall-degradative products that work through KdgR. The Class II inducers are thermostable, water-soluble, diffusible, and dialysable through 1 kDa molecular weight cut off pore size membranes, and could be a target for soft rot disease management strategies.

Highlights

Pectobacterium species are Gram-negative plant pathogenic bacteria belonging to the familyPectobacteriaceae
To determine how widely distributed the inducer(s) might be among different host plant species with filtered extracts (FE) from ten hosts of Pectobacterium, the levels of extracellular pectate lyase (Pel) produced by bacteria growing in MM were compared to that of the same bacterial strains growing in the same medium supplemented with cut and autoclaved (CA) extract from celery, potato, carrot, and tomato
We present evidence that a second class of signal molecules (Class II) in plant host extracts induces pectate lyase and protease activities in Pectobacterium, and that these Class II inducers are different from pectin degradation products or Class I inducers

Summary

Introduction

Pectobacterium species are Gram-negative plant pathogenic bacteria belonging to the familyPectobacteriaceae. Pectobacterium species are Gram-negative plant pathogenic bacteria belonging to the family. Exoenzyme production and pathogenicity in soft rot Enterobacteriaceae are coordinately regulated by transcriptional and posttranscriptional mechanisms involving a complex network of positive and negative regulatory proteins. This regulation, in turn, is influenced by physiological and environmental factors including chemical signals produced by both the pathogen and the host [6,7,8,9,10,11,12,13,14,15].

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