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Spring 2008 Seminar (back to list)

Feb. 29

Gerry Berkowitz, National Science Foundation

"The Grateful Dead: Calcium and innate immunity in plants"

Abstract:

Ca influx into plant cells is a critical early signal in many information response transduction cascades, including plant innate immune responses leading to nitric oxide (NO) generation and programmed cell death or hypersensitive response (HR) to avirulent pathogens. However, not much has been clarified about two key outstanding questions in plant biology related to this issue; what are the proteins that facilitate cytosolic Ca elevations during these signaling cascades, and how is recognition of a ‘nonself' invader transduced to altered regulation of Ca transport.  In the case of pathogen perception signaling events, recent work has identified leucine-rich-repeat receptor like kinases (LRR-RLKs) as initial sentry receptors allowing for perception of pathogens through physical interaction with Pathogen-Associated Molecular Pattern (PAMP) molecules which, upon recognition, initiate the signaling cascade. We have recently demonstrated involvement of cyclic nucleotide (cAMP or cGMP) gated (i.e. activated) cation channels (CNGCs) as contributing to the Ca flux upstream from the HR cascade. Here, we used biochemical and genetic approaches to identify cyclic nucleotides (cNMPs) as involved in translating pathogen recognition and PAMP perception into a cytosolic signal leading to Ca influx (through CNGCs) and downstream innate immunity and HR signaling. Results of patch clamp experiments, and monitoring of cytosolic Ca levels in aequorin-expressing plants, HR in plants, and NO generation in response to PAMPs and pathogens all link cNMPs with this signal cascade. Bioinformatic approaches intriguingly identify a nucleotide cyclase (cNMP-generating) functional domain in a LRR-RLK (AtPepR1) involved in pathogen signaling; our preliminary results suggest recombinant AtPepR1 displays such cyclase activity, and cNMP elevations occur in plant cells upon pathogen perception. Thus, we can present a new model linking several molecular events as involved in plant innate immunity signal perception and transduction.

This seminar will be held at 12:00 noon in Rm. 1103 Biosciences Research Building

Past seminars: Fall 2004 Spring 2005 Fall 2005 Spring 2006 Fall 2006 Spring 2007 Fall 2007