Poster: Plant-pathogen interactions

Abs # 555: Maize produce compouds that modulate bacterial quorum sensing communication

Presenter:	Savka, Michael A, massbi@rit.edu
Authors	Le, Phuong T (A)   Klemann, Nicole T (A)   Scott, Russell A (A)   von Bodman, Susanne  (B)   Savka, Michael A (A)
Affiliations:	(A): Rochester Institute of Technology (B): University of Connecticut

Pantoea stewartii ssp. stewartii (Pss) is the bacterial pathogen of Stewart’s wilt and leaf blight diseases on sweet corn and maize. Disease exhibit symptoms of wilting followed by death as a result of xylem vessel blockage by Pss extracellular polysaccharide (EPS) capsule. EPS capsule synthesis occurs at high Pss cell densities and is controlled by diffusible signals called N-acyl-homoserine lactones (acyl-HSLs) in a mechanism called quorum sensing (QS). Improved sweet, flour and dent corn exhibit tolerance to Pss, but mechanism(s) of Pss resistance remains elusive. Perhaps maize genotypes produce QS antagonists and / or agonists, which contribute to useful Pss field tolerance. We have evaluated maize accessions for mimics of QS signals through the use of bacterial acyl-HSL sensors. Leaf and stem cell extracts of certain genotypes of sweet, white food grade and dent corn exhibited antagonistic activity with acyl-HSL sensor CV026. Cell extracts of the genotypes failed to exhibit agonist activity in CV026 indicating extract components do not substitute for authentic Pss QS signal. A second acyl-HSL sensor, JM109 (pSB401), failed to induce a QS regulated phenotype in presence of cell extracts, confirming maize varieties do not contain QS agonists. However, extracts antagonized activation by authentic acyl-HSL signal in sensor JM109 (pSB401) up to eighty seven percent in comparison to activation in assays containing only purified Pss QS signal. These results suggest that certain genotypes produce substances that antagonize QS regulated activity in Pss. Our findings could suggest that Pss tolerant genotypes evade disease progression by producing substances that interfere with QS-regulated processes.