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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #322120
Title: Genes expressed by the biological control bacterium Pseudomonas protegens Pf-5 on seed surfaces

Author
item Kidarsa, Teresa
item Loper, Joyce

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/10/2015
Publication Date: 6/16/2015
Citation: Kidarsa, T.A., Loper, J.E. 2015. Genes expressed by the biological control bacterium Pseudomonas protegens Pf-5 on seed surfaces [abstract]. 10th International PGPR Workshop.

Interpretive Summary:

Technical Abstract: Propagules of many fungal and oomycete plant pathogens can remain dormant in the soil for months or years but germinate quickly in response to seed exudates, producing germ tubes or mycelia that infect seeds. Consequently, the spermosphere is often the initial point of interaction between seed-infecting pathogens and biocontrol bacteria and represents a rich and dynamic habitat for microbial interactions. Our studies focus on Pseudomonas protegens strain Pf-5, which produces a suite of antibiotics toxic to seed-infecting fungi and oomycetes. During the past decade, genomic sequences have become available for Pf-5 and hundreds of other rhizosphere bacteria. An important contribution of the genomics era has been in providing the opportunity to formulate our hypotheses regarding mechanisms of biological control on intrinsic characteristics of an antagonist or its activity on plant surfaces rather than its activity in culture. The primary focus of this work was to identify genes expressed under the control of the global regulators GacA and RpoS by Pf-5 inhabiting seed surfaces. Because both GacA and RpoS influence biological control by Pseudomonas spp., the GacA and RpoS transcriptomes of Pf-5 inhabiting the spermosphere are expected to include genes contributing to biological control. This study provides evidence for the expression of hundreds of genes by Pf-5 inhabiting seed surfaces and highlights GacA- and RpoS-regulated genes that could contribute to biological control of seed-infecting pathogens. While many genes were regulated by GacA and RpoS both in culture and on seed surfaces, the majority of genes were regulated significantly under only one condition. The limited overlap between the regulons defined in culture versus the spermosphere highlights the importance of formulating hypotheses regarding mechanisms of biological control based on the activity of an antagonist in the habitat where it interacts with a target pathogen to suppress disease.