The biocontrol agent Pseudomonas chlororaphis PA23 primes Brassica napus defenses through distinct gene networks

Pseudomonas chlororaphis PA23 is a biocontrol agent that protects against the fungal pathogen Sclerotinia sclerotiorum. Employing transposon mutagenesis, we isolated a gacS mutant that no longer exhibited antifungal activity. Pseudomonas chlororaphis PA23 was previously reported to produce the nonvolatile antibiotics phenazine 1-carboxylic acid and 2-hydroxyphenazine. We report here that PA23 produces additional compounds, including protease, lipase, hydrogen cyanide, and siderophores, that may contribute to its biocontrol ability. In the gacS mutant background, generation of these products was markedly reduced or delayed with the exception of siderophores, which were elevated. Not surprisingly, this mutant was unable to protect canola from disease incited by S. sclerotiorum. The gacS mutant was able to sustain itself in the canola phyllosphere, therefore, the loss of biocontrol activity can be attributed to a reduced production of antifungal compounds and not a declining population size. Competition assays between the mutant and wild type revealed equivalent fitness in aged batch culture; consequently, the gacS mutation did not impart a growth advantage in the stationary phase phenotype. Under minimal nutrient conditions, the gacS-deficient strain produced a tenfold less biofilm than the wild type. However, no difference was observed in the ability of the mutant biofilm to protect cells from lethal antibiotic challenge.Key words: Pseudomonas, biocontrol, gacS, fitness, biofilms.

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Obesity Drives Delayed Infarct Expansion, Inflammation, and Distinct Gene Networks in a Mouse Stroke Model

Translational Stroke Research ◽

10.1007/s12975-020-00826-9 ◽

2020 ◽

Author(s):

Todd C. Peterson ◽

Kendra J. Lechtenberg ◽

Brian D. Piening ◽

Tawaun A. Lucas ◽

Eric Wei ◽

...

Keyword(s):

Gene Networks ◽

Stroke Model ◽

Distinct Gene ◽

Infarct Expansion

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CBP and P300 regulate distinct gene networks required for human primary myoblast differentiation and muscle integrity

Scientific Reports ◽

10.1038/s41598-018-31102-4 ◽

2018 ◽

Vol 8 (1) ◽

Cited By ~ 11

Author(s):

Lucas Fauquier ◽

Karim Azzag ◽

Marco Antonio Mendoza Parra ◽

Aurélie Quillien ◽

Manon Boulet ◽

...

Keyword(s):

Gene Networks ◽

Myoblast Differentiation ◽

Distinct Gene ◽

Primary Myoblast

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Pseudomonas chlororaphis PA23 metabolites protect against protozoan grazing by the predator Acanthamoeba castellanii

PeerJ ◽

10.7717/peerj.10756 ◽

2021 ◽

Vol 9 ◽

pp. e10756

Author(s):

Akrm Ghergab ◽

Carrie Selin ◽

Jennifer Tanner ◽

Ann Karen Brassinga ◽

Teresa Dekievit

Keyword(s):

Gene Expression ◽

Biocontrol Agent ◽

Pathogenic Fungus ◽

Acanthamoeba Castellanii ◽

Cyst Formation ◽

Phenotypic Characterization ◽

Pseudomonas Chlororaphis ◽

Bacterial Gene ◽

Metabolite Production ◽

Protozoan Grazing

Background Pseudomonas chlororaphis strain PA23 is a biocontrol agent that is able to protect canola against the pathogenic fungus Sclerotinia sclerotiorum. This bacterium secretes a number of metabolites that contribute to fungal antagonism, including pyrrolnitrin (PRN), phenazine (PHZ), hydrogen cyanide (HCN) and degradative enzymes. In order to be successful, a biocontrol agent must be able to persist in the environment and avoid the threat of grazing predators. The focus of the current study was to investigate whether PA23 is able to resist grazing by the protozoan predator Acanthamoeba castellanii (Ac) and to define the role of bacterial metabolites in the PA23-Ac interaction. Methods Ac was co-cultured with PA23 WT and a panel of derivative strains for a period of 15 days, and bacteria and amoebae were enumerated on days 1, 5, 10 and 15. Ac was subsequently incubated in the presence of purified PRN, PHZ, and KCN and viability was assessed at 24, 48 and 72 h. Chemotactic assays were conducted to assess whether PA23 compounds exhibit repellent or attractant properties towards Ac. Finally, PA23 grown in the presence and absence of amoebae was subject to phenotypic characterization and gene expression analyses. Results PRN, PHZ and HCN were found to contribute to PA23 toxicity towards Ac trophozoites, either by killing or inducing cyst formation. This is the first report of PHZ-mediated toxicity towards amoebae. In chemotaxis assays, amoebae preferentially migrated towards regulatory mutants devoid of extracellular metabolite production as well as a PRN mutant, indicating this antibiotic has repellent properties. Co-culturing of bacteria with amoebae led to elevated expression of the PA23 phzI/phzR quorum-sensing (QS) genes and phzA and prnA, which are under QS control. PHZ and PRN levels were similarly increased in Ac co-cultures, suggesting that PA23 can respond to predator cues and upregulate expression of toxins accordingly. Conclusions PA23 compounds including PRN, PHZ and HCN exhibited both toxic and repellent effects on Ac. Co-culturing of bacteria and amoebae lead to changes in bacterial gene expression and secondary metabolite production, suggesting that PA23 can sense the presence of these would-be predators and adjust its physiology in response.

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LEC1 sequentially regulates the transcription of genes involved in diverse developmental processes during seed development

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1707957114 ◽

2017 ◽

Vol 114 (32) ◽

pp. E6710-E6719 ◽

Cited By ~ 53

Author(s):

Julie M. Pelletier ◽

Raymond W. Kwong ◽

Soomin Park ◽

Brandon H. Le ◽

Russell Baden ◽

...

Keyword(s):

Transcription Factor ◽

Seed Development ◽

Gene Networks ◽

Target Genes ◽

Regulatory Elements ◽

Sequence Motifs ◽

In Planta ◽

Developmental Processes ◽

Distinct Gene ◽

Gene Sets

LEAFY COTYLEDON1 (LEC1), an atypical subunit of the nuclear transcription factor Y (NF-Y) CCAAT-binding transcription factor, is a central regulator that controls many aspects of seed development including the maturation phase during which seeds accumulate storage macromolecules and embryos acquire the ability to withstand desiccation. To define the gene networks and developmental processes controlled by LEC1, genes regulated directly by and downstream of LEC1 were identified. We compared the mRNA profiles of wild-type and lec1-null mutant seeds at several stages of development to define genes that are down-regulated or up-regulated by the lec1 mutation. We used ChIP and differential gene-expression analyses in Arabidopsis seedlings overexpressing LEC1 and in developing Arabidopsis and soybean seeds to identify globally the target genes that are transcriptionally regulated by LEC1 in planta. Collectively, our results show that LEC1 controls distinct gene sets at different developmental stages, including those that mediate the temporal transition between photosynthesis and chloroplast biogenesis early in seed development and seed maturation late in development. Analyses of enriched DNA sequence motifs that may act as cis-regulatory elements in the promoters of LEC1 target genes suggest that LEC1 may interact with other transcription factors to regulate distinct gene sets at different stages of seed development. Moreover, our results demonstrate strong conservation in the developmental processes and gene networks regulated by LEC1 in two dicotyledonous plants that diverged ∼92 Mya.

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