Plants have a sophisticated immune system that is very different in molecular terms from that of humans, but serves the same general purpose: recognize and respond to pathogen infection. Plant pathogens cause diseases that result in the loss of up to 30% of crops annually, and this is often after the required fresh water has been added to the crops, and despite the use of chemicals to control infections. Thus, learning about how the plant immune system works, in order to 'help plants help themselves' will result in saving lots of fresh water and lead to environmentally sustainable agronomic practices.
This project fits the 2009 call for the NSF Arabidopsis 2010 Programs heading (2) Adaptation to the environment. The research will "determine the function of Arabidopsis genes and gene networks involved in plant responses to the environment and in adaptation to biotic or abiotic conditions." The project concerns the control of intracellular receptors of the plant immune system. A multi-disciplinary approach combining genetics (forward and reverse), biochemistry and cell biology will be used to understand how these receptors, called NB-LRR proteins, are assembled into a pre-activation, signal competent state and to define how they are specifically activated after infection.
Broader impacts: An increasingly detailed view of how the plant immune system functions to mitigate losses is emerging from a community focus on the application of Arabidopsis to important problems in plant pathology. The reference plant species, Arabidopsis thaliana, is useful for studies of nearly all classes of pathogens that are agronomically relevant. Hence, a broader impact of this project is that the results will significantly inform translation to crop species. This has already begun with the cloning and utilization of genes from crops originally identified in Arabidopsis. The use of genetics, molecular biology, biochemistry, and cell biology makes this project an excellent training ground for scientists from undergraduate to post-doctoral levels. Topics investigated are incorporated into a course taught by the PI on 'Strategies of Host-Microbe Interactions'. The PI's lab actively seeks to engage undergraduates in research projects and the PI is involved in public policy and public debates directly related to the topics of this proposal.
Learn more about this project at:
www.bio.unc.edu/dangl/lab/projects/index.htm
Plants are critical for human health and well being. We eat plants, or animals that ate plants before we ate them; we use plant fibers for our clothes and our homes; we rely on plants to provide ecosystems conducive to environmental well being. Plants provide us with oxygen. Without plants, human life would be impossible. Hence, research to understand plant growth, health and productivity is explicitly relevant to human health and well being, as was stressed in the 2009 National Research Council report: ‘A New Biology for the 21st Century: Ensuring the United States Leads the Coming Biology Revolution.’ Plants turn sunlight into sugar. Thus, plants are rich nutrient and water sources that are unsurprisingly host to diverse microbial communities both above and below the ground. Microbes are likely to have accompanied the first plants that emigrated from water to land 400-500 hundred million years ago. Many of their descendant contemporary microbes are adapted to take advantage of the nutrient niches afforded to them by the huge diversity of plants all over the earth. Plants are protected from infection by a ‘skin’: a waxy cuticular layer atop the cell wall. Potential pathogens breaching this barrier encounter an active plant immune system that specifically recognizes pathogen and altered-self molecules generated during infection. Consequent regulation of a network of inducible defenses can halt pathogen proliferation and signal distal plant organs to become non-specifically primed against further infection Plants deploy a two layered immune system. The first layer consists of cell surface receptors that monitor the 'outside of the cell' for pathogens. The second layer consists of special protein receptors 'inside the cell' that are activated by pathogen molecules that get into the plant cell to suppress defense mediated by the first layer of recognition. We focus on the 'inside the cell' receptors, called NLR proteins, which are critical for pathogen detection in the innate immune systems of both plants and animals. NLRs typically contain one of several N-terminal signaling domains, a central nucleotide-binding domain with ATPase and/or GTPase function, and C-terminal leucine-rich repeats (LRRs). Originally discovered in plants in the mid-1990s, NLRs are the basis for disease resistance in plants and have been manipulated, unknowingly at first, by crop breeders as ‘disease resistance genes’ for over a century. NLRs were subsequently discovered in animals, where they play a major role in regulating innate immune signaling in infectious and autoimmune disease. Once activated, NLRs direct a complex output response that ultimately restricts pathogen growth. We have discovered important aspects of NLR function that will enhance plant breeding for disease resistance.
