UC San Diego

In agriculture, plants are constantly attacked by pests and disease, thus threatening food security, and increasing the chemical input of pesticides and fungicides meant to maximize crop yields. Analyses of the effects phosphorylation has on asparaginase enzymatic activity have suggested that phosphorylation promotes asparaginase activity (Ahmadian, N., 2020), increasing catabolism of asparagine to release nitrogen in support of the resource-intense immune response. To elucidate whether there is a correlation between asparaginase phosphorylation and enhanced plant immune response, we developed stable transgenic lines expressing phosphomimetic and phosphoabolishing variants of asparaginase. When these plants were inoculated with the fungal pathogen Botrytis cinerea, a decrease in disease resistance was observed in the phosphoabolishing line. This decreased resistance indicates that asparaginase phosphorylation is needed to facilitate plant immune response. As a future testable hypothesis, we speculate that amino acid levels of ammonium and aspartate are affected by asparaginase phosphorylation and subsequently its enzymatic activity. Together this work created and initiated characterization of genetic resources to better develop our understanding of how primary metabolism and nitrogen availability affect plant immunity.