Studies of the molecular bases of plant responses to enemies have focused more on microbes than on insects, despite the great ecological, evolutionary, and economic impacts of herbivores. Research on plant responses to insects has been limited mainly to phenotypic (chemical) defenses. Little attempt has been made to link molecular and chemical responses to either type of pest to understand the mechanisms underlying plant defense.
This project will employ microarrays of approximately 2500 stress-responsive genes (developed by a previous NSF Plant Genome project) plus critical genes in the glucosinolate biosynthetic pathway. Gene expression and glucosinolate profiles will be developed for plants responding to insect species and pathogens representing chewing and sucking feeding types and a range of specialization on Brassicaceae. The major goal of this limited proof-of-concept project is to demonstrate that gene function can be inferred by using multivariate statistical treatments to link array results to defense metabolite response profiles and to ecological outcomes. "Gene function" in terms of defense will be inferred in terms of expression pattern in relation to known functions (e.g., in signaling pathways, metabolite synthesis) and in the context of the ecological outcome (e.g., impact on insect, resistance to herbivory) using standard multivariate clustering techniques, concordance analysis, and Mantel covariate statistics. Identities and functions of critical components of plant defense responses identified statistically will eventually be confirmed using mutants and knockouts in bioassays with specific insects and microbes under varying environmental conditions. Images of expression patterns, metabolite profile data, integrative results, protocol updates, and instructions for obtaining material will be posted monthly at the following TAIR-linked URL: http://schultzlab.cas.psu.edu/ . Metabolomics data will be archived at the Genomic Arabidopsis Resource Network (www.york.ac.uk/res/garnet/beale.htm) and functional genomics data at TAIR (www.arabidopsis.org/info/2010_projects/ ).
Arabidopsis 2010 objectives addressed by this project include determining the functions of genes in the context of plant defense, producing a stress microarray and chemical analytical protocols as tools useful to a wide range of investigators, and developing statistical protocols molecular ecologists can use to link genotypic and phenotypic responses. In addition, the project will be coordinated with 2 existing Arabidopsis 2010 programs (Wurtele et al. "Visual informatics tools" and Lewis et al. "Phenylpropanoid metabolite networks") and establishes an international collaboration with the Max Planck Institute for Chemical Ecology (Jena, Germany).
Broader impacts of the limited project will include training 3 graduate students, exploiting existing K-12, teacher, and undergraduate research experience links that already exist in the PSU College of Agricultural Sciences and Chemistry Department, and developing platforms for using Arabidopsis responses as a teaching tool in the K-8 environment.
