Pelton Award Lecture - Hawes
Hawes, Martha .
Extracellular DNA-based trapping by border cells in defense of the root tip.
'Early recognition of the sloughing away of certain root tissues as a normal process during root growth led to little more than mere speculation as to what the role of such a process might be in the nutrition of the plant. The process was assigned, quite summarily it seems, the function of lubricating the advancing root tip as it forced its way into the soil.' HT Rogers et al. (1942) Soil Sci 54:353-365
The rhizosphere (Hiltner 1904) is defined as a 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 delivered by the root cap of cereals and legumes. Yet 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. Histone-linked extracellular DNA (exDNA) and antimicrobial proteins operate as neutrophil extracellular traps ('NETs') which attract and immobilize pathogens. Group A Streptococcus can escape NETs by the activity of extracellular DNase (exDNase). 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. Knockout mutations of Ralstonia solanacaerum and Cochliobolus heterostrophus result in reduced virulence on their hosts. Our progress in defining the dynamics of extracellular trapping, and its implications for plant and environmental health will be presented.
Martha Hawes, Gilberto Curlango Rivera, Zhongguo Xiong
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1 - University of Arizona, Tuscon, AZ, USA
Presentation Type: Special Presentation
Location: Hall A/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 4:00 PM
Candidate for Awards:None