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TECHNICAL SESSION: Elucidation of plant immune responses to bacterial plant pathogens

Exploring Apoplastic Sulfate Restriction as a Component of Pattern Triggered Immunity in Arabidopsis thaliana
Amelia Lovelace - University of Georgia. Brian Kvitko- University of Georgia

Transcriptome analysis of the pathogen Pseudomonas syringae pv. tomato DC3000 (DC3K) during early infection and exposure to Pattern Triggered Immunity (PTI) in Arabidopsis thaliana provided insights into the earliest transcriptional events corresponding with immune exposure. We observed that the induction of sulfur starvation response genes such as alternative sulfur importers in DC3K is a rapid and specific response to PTI exposure. We confirmed observations that A. thaliana SULTR1;2, a high affinity sulfate transporter gene, is induced in leaves during PTI. The objective of our study is to determine if the apoplast becomes sulfate depleted during PTI and thus restricts pathogen access to sulfur. To test our hypothesis, we optimized a method for extracting high purity apoplastic wash fluid from A. thaliana free of cytoplasmic contamination. We used ion chromatography analysis to determine that apoplastic fluid from naïve A. thaliana contains approximately 2mM sulfate. We also found that DC3K growth in vitro is inhibited at sulfate concentrations below 10 µM. In addition, we are conducting mutagenesis of five sulfate transporters in DC3K, to determine whether sulfate uptake is important for growth in planta. Taken together, our research suggests that apoplastic sulfate limitation could be a mechanism for PTI. Our findings bridge the gap of plant immunity and nutrient metabolism in the context of plant-microbe interactions.