RIG: The Molecular Effects of Pathogen-derived Auxin on the Plant Immune System

California State University San Marcos Corporation, San Marcos CA

Investigators

Abstract

Plants possess a complex and multi-layered immune system. Though the general operation of this immune system is now reasonably well understood, the specific molecular mechanisms that underlie plant defense against pathogens remain largely mysterious. Recent studies have suggested that the plant hormone auxin, which is also produced by a variety of plant pathogens, may act as a critical negative regulator of plant immune response. The broad objective of this project is to characterize how auxin alters a plant's ability to perceive and respond to pathogen infection at the molecular level. In order to study the relationship between auxin and the plant immune system, the studies will make use of two isogenic strains of the plant pathogenic bacterium Agrobacterium tumefaciens: A348 (wild-type) and A328 (auxin-deficient mutant). The relative activation and timing of plant defense responses induced by A348 and A328 will be examined by introducing the strains into the leaves of the model plant Arabidopsis thaliana though pressure infiltration. During the week following infiltration, measurements of reactive oxygen species production, bacterial growth, and cell death-based plant defense responses in Arabidopsis leaves will be done. In this way, the effect of pathogen-produced auxin on specific Arabidopsis immune responses may be quantitatively assessed. In addition, these studies will identify the differences in the plant's global transcriptional response to infection with strains A348 and A328 using microarray technology. The microarray data will then be used to identify the specific cellular regulatory networks that are manipulated by auxin-producing plant pathogens. Overall, this project will substantially increase an understanding of the effects of pathogen-produced auxin on the plant immune system, and may ultimately inform the future development of chemical agents and plant cultivars that minimize pathogen-associated losses in crop productivity. California State University San Marcos undergraduates, supervised by the PI and a salaried technician, will play a major role in carrying out the research. Because approximately one-third of CSUSM undergraduates are members of minority groups that are underrepresented in the sciences, this also promises to broaden the participation of these students in plant biology research. This intensive research experience at the undergraduate level will greatly benefit these minority scientists as they move on to graduate school and industry, where they can serve as role models for future minority scholars. In addition, the results of the research will be disseminated widely in peer-reviewed scientific journals, at scientific meetings, and on the internet (microarray data will be deposited in NCBIs Gene Expression Omnibus). Finally, as discussed above, the basic research described here has the potential to substantially inform the applied field of crop protection, thus providing broad benefits to the U.S. agricultural industry, and society as a whole.