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FRIMEDBIO-Fri prosj.st. med.,helse,biol

Peroxisome-Mediated Mechanisms of Plant Innate Immunity

Awarded: NOK 4.2 mill.

Report period 1, 20120301 - 20130930 Not only humans but also plants possess an innate immune system that allows them to defend themselves against viral and bacterial pathogens, fungi, insects and nematodes. If we understand how this immune system works at the cellular in a model plant, we can possibly strengthen the health and fitness of crop plants by applying “biological” and environmentally friendly strategies in agriculture, avoid spraying of fungicides and bactericides and reduce annual crop losses caused by various plant diseases world-wide. Most researchers worldwide presently focus in their molecular research activities on the small plant Arabidopsis - thus so did we to merge forces. We identified a new group of proteins (the so-called NHL proteins) that is located in an important cell organelle, the peroxisomes, where toxic molecules are synthesized and mediate plant defense against pathogens. In this first report period, we started with carrying out a literature survey and wrote a review article to summarize which research had been carried out worldwide previously in our field of interest. We used computational tools to predict which genes are co-expressed together and likely function altogether in a molecular network with our NHL proteins of interest. Most excitingly, we obtained indications that our proteins are directed to peroxisomes by a novel, yet unknown and undescribed pathway. Report period 2, 20131001 - 20140930 At the cellular level, the innate immune system of plants is surprisingly similar to that of humans, and both research fields can learn from each other. In this second report period, we focused on the novel pathway by which the interesting the so-called NHL proteins are directed to peroxisomes. We shortened the protein sequence and analyzed how this affected where the protein was localized in the cell. We also investigated experimentally under which conditions the genes are expressed and found out that they are expressed (and hence most likely needed) when plants are attacked by bacterial pathogens. In addition, we isolated so-called single “knock-out mutants” of the genes of interest. These are plants that are no longer able to make a specific protein. If such a mutant has a weaker immune system, the deleted protein most likely has an important function in plant innate immunity. Report period 3, 20141001 - 20151201 In this third report period, we continued the interesting and completely novel pathway analyses by constructing and analyzing additional deletion constructs and using other expression systems. We performed so-called “pathogen assays” with the isolated “knock-out mutants” but could not find any changes, likely because the three proteins have similar functions. To overcome this limitation, we prepared double mutants, where two genes are deleted. The mutants showed an interesting phenotype and the level of small metabolites. These exciting results were supplemented by proteome analyses of peroxisomes, investigating differences in the entity of approx. 200 peroxisomal proteins.

The devastating impacts of crop pathogens are well-known and significantly reduce agricultural productivity. However, most plants are resistant to pathogens due to complex mechanisms of innate immunity. New knowledge of defense mechanisms is needed to inc rease pathogen resistance of crop plants. Here, we will identify and characterize new pathogen resistance pathways in Arabidopsis. Peroxisomes have well-known metabolic functions, but are not normally associated with defense responses. Our data show that many unknown defense-related proteins are located in peroxisomes. We will determine the new emerging function of peroxisomes in plant innate immunity. For one of two major families of peroxisome-targeted defense proteins, we will determine protein functio ns, identify protein networks and defense pathways, and will describe the molecular mechanisms underlying pathogen resistance. The knowledge will be translatable to biotechnological applications to increase pathogen resistance of crop plants. The goals wi ll be achieved by a strong inter-disciplinary and internationally unique research consortium. The trinational team involves three Norwegian groups, three FUGE nodes, one German and two US partners. The central expertise of the project manager in peroxisom e biology and applied bioinformatics is complemented by top-level competence in plant pathology, hard-core bioinformatics, and systems biology. The basic research project will act as a springboard for applied agronomic projects, open up industrial funding streams, and may lead to patentable knowledge. The plant project might even have pioneering character for medical research and lead to the discovery of conserved immunity-related functions of human peroxisomes. Internationally seen, no other peroxisome r esearch group is known to focus on pathogen resistance mechanisms in plants, fungi, or mammals.

Funding scheme:

FRIMEDBIO-Fri prosj.st. med.,helse,biol