Location: Emerging Pests and Pathogens ResearchTitle: Identification of IAA-regulated genes in Pseudomonas syringae pv. tomato strain DC3000
|DJAMI-TCHATCHOU, ARNAUD-THIERRY - Washington University
|LI, ZHIPENG - Washington University
|KUNKEL, BARBARA - Washington University
Submitted to: Journal of Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2021
Publication Date: 10/18/2021
Citation: Djami-Tchatchou, A., Li, Z., Stodghill, P., Filiatrault, M.J., Kunkel, B. 2021. Identification of IAA-regulated genes in Pseudomonas syringae pv. tomato strain DC3000. Journal of Bacteriology. https://doi.org/10.1128/JB.00380-21.
Interpretive Summary: Indole 3 acetic acid (IAA), a common form of the plant hormone auxin, is used by many plant-associated bacteria, including plant pathogens, as an environmental cue to sense the plant environment. In previous work we showed that IAA can promote disease in interactions between the plant pathogen Pseudomonas syringae strain PtoDC000 and one of its hosts, Arabidopsis thaliana. However, the mechanisms by which IAA impacts the biology of PtoDC3000 and promotes disease is not well understood. Here we demonstrate that IAA is a signal molecule that regulates gene expression in PtoDC3000. The presence of IAA affects expression of over 700 genes in the bacteria, including genes involved in Type III secretion, a key component in virulence, and genes involved in stress response. This work offers insight into the roles of auxin promoting pathogenesis.
Technical Abstract: The auxin indole-3-acetic-acid (IAA) is a plant hormone that not only regulates plant growth and development but also plays important roles in plant-microbe interactions. We previously reported that IAA alters expression of several virulence-related genes in the plant pathogen Pseudomonas syringae pv. tomato strain DC3000 (PtoDC3000). To learn more about the impact of IAA on regulation of PtoDC3000 gene expression we performed a global transcriptomic analysis of bacteria grown in culture, in the presence or absence of exogenous IAA. We observed that IAA repressed expression of genes involved in the Type III secretion (T3S) system and motility and promoted expression of several known and putative transcriptional regulators. Several of these regulators are orthologs of factors known to regulate stress responses and accordingly expression of several stress response-related genes were also upregulated by IAA. The expression profiles of several of these differentially regulated genes were verified by RT-qPCR. Using an Arabidopsis auxin receptor mutant that accumulates elevated auxin, we found that many of the P. syringae genes regulated by IAA in vitro were also regulated by auxin in planta. Collectively the data indicate that IAA modulates many aspects of PtoDC3000 biology, presumably to promote both virulence and survival under stressful conditions, including those encountered in or on plant leaves.