Pseudomonas fluorescensInduces Strain-Dependent and Strain-Independent Host Plant Responses in Defense Networks, Primary Metabolism, Photosynthesis, and Fitness

Abstract

Colonization of plants by nonpathogenic Pseudomonas fluorescens strains can confer enhanced defense capacity against a broad spectrum of pathogens. Few studies, however, have linked defense pathway regulation to primary metabolism and physiology. In this study, physiological data, metabolites, and transcript profiles are integrated to elucidate how molecular networks initiated at the root-microbe interface influence shoot metabolism and whole-plant performance. Experiments with Arabidopsis thaliana were performed using the newly identified P. fluorescens GM30 or P. fluorescens Pf-5 strains. Co-expression networks indicated that Pf-5 and GM30 induced a subnetwork specific to roots enriched for genes participating in RNA regulation, protein degradation, and hormonal metabolism. In contrast, only GM30 induced a subnetwork enriched for calcium signaling, sugar and nutrient signaling, and auxin metabolism, suggesting strain dependence in network architecture. In addition, one subnetwork present in shoots was enriched for genes in secondary metabolism, photosynthetic light reactions, and hormone metabolism. Metabolite analysis indicated that this network initiated changes in carbohydrate and amino acid metabolism. Consistent with this, we observed strain-specific responses in tryptophan and phenylalanine abundance. Both strains reduced host plant carbon gain and fitness, yet provided a clear fitness benefit when plants were challenged with the pathogen P. syringae DC3000.

Leaf endophytes and Populus genotype affect severity of damage from the necrotrophic leaf pathogen, Drepanopeziza populi

“…Total RNA was isolated, DNase treated and checked for quality using an Experion RNA StdSens analysis kit and chip (BioRad) as described in (Weston et al 2012). cDNA was synthesized using a SuperScript III First-Strand Synthesis SuperMix for qRT-PCR (Invitrogen) according to provided protocols.…”

“…One hypothesis is that leaf endophytes reduce disease severity by priming plant resistance to pathogens, as has been shown for rhizobacteria and mycorrhizal fungi (Wang et al 2005, Weston et al 2012. The idea of plant symbionts as ''vaccines'' was first suggested long ago (Beauv- v www.esajournals.org erie 1901), and is now referred to as systemic acquired resistance (SAR) or induced systemic resistance (ISR; Van Wees et al 2008).…”

Metabolic and Transcriptomic Changes Induced in Arabidopsis by the Rhizobacterium Pseudomonas fluorescens SS101

“…To date, there is little information available on metabolic changes induced in plants by PGPR that enhance resistance against pathogens or insect pests (Walker et al, 2011;Weston et al, 2012). Furthermore, for only few rhizobacterial strains, transcriptomic analyses have been conducted to unravel the molecular changes in plants associated with induced systemic resistance (Cartieaux et al, 2003(Cartieaux et al, , 2008Verhagen et al, 2004;Wang et al, 2005;Weston et al, 2012).…”

“…Furthermore, for only few rhizobacterial strains, transcriptomic analyses have been conducted to unravel the molecular changes in plants associated with induced systemic resistance (Cartieaux et al, 2003(Cartieaux et al, , 2008Verhagen et al, 2004;Wang et al, 2005;Weston et al, 2012). Almost all of these microarray studies revealed relatively few transcriptional changes: for instance, plant-growth promoting Pseudomonas thivervalensis strain MLG45 induced transcriptional changes in 63 genes in the shoots and in nine genes in the roots of Arabidopsis (Arabidopsis thaliana), with an increase in defense-related transcripts and a repression of photosynthesis-related genes (Cartieaux et al, 2003).…”

Rhizobacteria Pseudomonas fluorescens and Azospirillum sp. association enhances growth of Lactuca sativa L. under tropical conditions

“…For instance, P. fluorescens bacteria are able to use a broad range of nutritional sources, producing high-affinity Fe +3 binding siderophores, thus restricting the growth of other rhizosphere bacteria under conditions of low iron concentrations. They can also remain viable for long periods of time under very adverse conditions, making them suitable as biofertilizers (Weston et al, 2012).…”