Pelton Award Lecture - Martha Hawes
Hawes, Martha .
The role of the extracellular matrix in defense: New insights into plant and animal immune responses.
The rhizosphere (Hiltner 1904) is defined as that region where microbial growth is stimulated by the release of nutrient-rich exudates from roots, and plant health in turn is influenced by associated microflora. The root apex is the primary site of exudation in healthy young seedlings of diverse species, with >90% of the total carbon delivered by the root cap of cereals and legumes. Yet despite this apparent abundance of nutrients released by the root cap, the root cap repeatedly has been shown to remain free of microbial infection and colonization. Insight into the function of root border cells, a population of specialized cells programmed to detach from the root cap into the soil environment, may shed light on this longstanding mystery: Border cells operate by a newly defined mechanism analogous to that of mammalian cells functioning in innate defense. In animal systems, histone-linked extracellular DNA (exDNA) and antimicrobial proteins released by neutrophils operate as extracellular traps ('NETs') which attract and immobilize pathogens. Group A Streptococcus can escape NETs by the activity of extracellular DNase (exDNase), and loss of this exDNase activity in the bacteria results in reduced virulence. exDNA also is a component of plant defense. DNA synthesized and exported by cells at the root cap periphery is a component of the surrounding mucilage which attracts, traps and immobilizes pathogens in a host-microbe specific manner. When exDNA is degraded concurrently with inoculation by root-rotting fungal pathogens, resistance of the root tip to infection is abolished, and pathogens with reduced exDNase activity exhibit reduced virulence. Our progress in defining the dynamics of extracellular trapping, and its implications for plant and environmental health will be presented.
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1 - University of Arizona, Soil, Water and Environmental Sciences, Shantz Building, Tucson, AZ, 85721, USA
Presentation Type: Special Presentation
Session: S8, Pelton Award Lecture - Hawes
Location: Oglethrope Auditorium/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 3:00 PM
Candidate for Awards:None