Identification of Aspergillus resistance factors present in Arabidopsis thaliana

A plant seed coat is essential to the survival of the embryo. Protection from mechanical destruction, UV shielding and microbial defense are among the safeguards afforded by the seed coat. Aspergillus is a genus of fungus known to attack seed crops such as corn and peanuts. When these crops become infected and are subsequently consumed it easily can lead to sickness and death. However, Arabidopsis thaliana has resistance to this genus of fungus. It is hypothesized that many of the compounds that give the seed coat its protective abilities are produced by the phenylalanine-ammonia-lyase (PAL) pathway in A. thaliana. Through genetic dissection of the PAL pathway, this study aims to isolate where and when changes in the seed coat enable resistance to infection by the species of Aspergillus examined in this study, A. nidulans. We use wild-type A. thaliana seeds as a standard due to their natural resistance to infection by A. nidulans. There are also knockout mutants available for every enzymatic step along the PAL pathway, which have their respective enzymatic function removed. Through the systematic infection of these various mutants with A. nidulans we have identified a portion of the pathway for initial biochemical analysis. Preliminary data show that the inhibitory compound(s) in wild-type seed coats are water soluble. We are developing protocols to isolate and identify these bioactive compounds. We are also investigating the development of pathogen resistance during post-harvest seed maturation. The identification of the factors conferring pathogen resistance in A. thaliana may influence future directions in agriculture.