Effects of the plant growth-promoting bacterium Burkholderia phytofirmans PsJN throughout the life cycle of Arabidopsis thaliana

PLoS One. 2013 Jul 15;8(7):e69435. doi: 10.1371/journal.pone.0069435. Print 2013.

Abstract

Plant growth-promoting rhizobacteria (PGPR) induce positive effects in plants, such as increased growth or reduced stress susceptibility. The mechanisms behind PGPR/plant interaction are poorly understood, as most studies have described short-term responses on plants and only a few studies have analyzed plant molecular responses under PGPR colonization. Here, we studied the effects of the PGPR bacterial model Burkholderiaphytofirmans PsJN on the whole life cycle of Arabidopsis thaliana plants. We reported that at different plant developmental points, strain PsJN can be found in the rhizosphere and also colonizing their internal tissues. In early ontogeny, strain PsJN increased several growth parameters and accelerated growth rate of the plants. Also, an Arabidopsis transcriptome analysis revealed that 408 genes showed differential expression in PsJN-inoculated plants; some of these genes are involved in stress response and hormone pathways. Specifically, genes implicated in auxin and gibberellin pathways were induced. Quantitative transcriptional analyses of selected genes in different developmental stages revealed that the beginning of these changes could be evidenced early in development, especially among the down-regulated genes. The inoculation with heat-killed bacteria provoked a more severe transcriptional response in plants, but was not able to induce plant growth-promotion. Later in ontogeny, the growth rates of inoculated plants decreased with respect to the non-inoculated group and, interestingly, the inoculation accelerated the flowering time and the appearance of senescence signs in plants; these modifications correlate with the early up-regulation of flowering control genes. Then, we show that a single inoculation with a PGPR could affect the whole life cycle of a plant, accelerating its growth rate and shortening its vegetative period, both effects relevant for most crops. Thus, these findings provide novel and interesting aspects of these relevant biological interactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / microbiology*
  • Burkholderia / physiology*
  • Flowers / growth & development
  • Flowers / microbiology
  • Gene Expression Regulation, Plant
  • Germination
  • Plant Development / genetics
  • Rhizosphere
  • Seeds / growth & development
  • Seeds / microbiology

Grant support

This research was funded by grants FONDECYT 3100040 (www.fondecyt.cl), CONICYT PAI/IAC 9090016 (www.conicyt.cl), and Millennium nucleus on Plant Functional Genomics P10-062-F. AV is supported by FONDECYT 11110095 and is part of ceCIBUC. AZ is a CONICYT PhD Fellow. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.