Speaker: Pradeep Kachroo, University of Kentucky professor in the Department of Plant Pathology

Title: "Signaling pathways in plant-pathogen interactions"

Abstract: Systemic acquired resistance (SAR) is a form of broad-spectrum resistance induced in response to local infection that protects uninfected parts against subsequent secondary infections. Several diverse chemical signals contributing to SAR have been isolated and characterized, including glycerol-3-phosphate (G3P) and pipecolic acid (Pip), both of which play an important role in human and plant disease physiologies. In addition to these, salicylic acid (SA) also regulates SAR and normal transport of SA and G3P is required for de novo biosynthesis of Pip in the distal leaves. Pip is catabolized via multiple pathways, and this in turn regulates vitamin homeostasis. A normal SAR also requires a normal cuticle, which in turn regulates water potential and thereby apoplastic transport of SA. Interestingly, cellular pH also plays an important role in SA transport and this was established using pH sensor lines as well as analysis of mutants affected in pH homeostasis. Both SA and G3P regulate the stability of trans-acting small interfering RNA (tasi-RNA), which function as an early mobile signal in SAR. Conversely, knock-out mutations in tasi-RNA or RNA silencing components required for tasi-RNA biogenesis compromise SAR without altering levels of SA or G3P. Together, these results highlight a novel relationship between plant cuticle, SA, G3P, Pip and RNA-mediated signaling in SAR.

Host: Joe Aung, genetics, development and cell biology assistant professor