Dean Kim
Faculty Advisor: Georg Jander
Year: 2017

Project Summary

Plants are constantly exposed to pathogen attack, yet they manage to thrive and fight off these threats.  Our food supply is dependent on crops’ ability to fend off these pathogens, making their biochemical defense systems a point of research interest.  From a previous comparative metabolomics study, we identified two feruloyl acetylsucroses in maize seedling roots that could be strongly induced upon infection by Fusarium graminearum, a common fungal pathogen.  We hypothesized these metabolites could play a role in maize biochemical defense against this fungal pathogen. Further genetic study on this metabolite led us to hypothesize that ethylene signaling is a positive regulator of these metabolites.  Taking an integrated genetic and physiological approach, we treated seedlings of B73 wildtype and aminocyclopropane-1-carboxylic acid synthase (ACS) 2/6 double mutant, a maize genotype which lacks an enzyme in the ethylene biosynthetic pathway and therefore produce less ethylene, with aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene.  We then used mass spectrometry to analyze harvested root extract to measure the concentration of the two feruloyl acetylsucroses.  In results, we found that the ACS 2/6 double mutant seedlings had constitutive lower content of these two metabolites, and that the ACC treatment induced accumulation of these two metabolites in both B73 wildtype and the ACS 2/6 mutant seedling roots. Interestingly, exogenous ACC treatment rescued the ACS 2/6 mutant seedlings from their metabolite deficiency. These results strongly support our hypothesis that ethylene signaling is a positive regulator of the two feruloyl acetylsucroses. In the future, we hope to see if other maize phytohormones induce these metabolites by studying other known signaling pathways involved in maize biochemical defense.

My Experience

This summer PGRP intern experience has been extremely rewarding.  I take away from this internship not only research experience in a professional lab environment, but also lifelong problem-solving skills I gained and great memories working on my project and with my mentor.  This summer I refined basic lab techniques from running PCR to creating different stock solutions we use in lab daily.   These are incredibly useful skills for whatever lab I find myself in in my future endeavors.  I learned to think like a scientist; when I encounter a problem, I can find ways to fix the issue myself as opposed to relying on my mentor to search for an answer.  Learning to become a more independent thinker and worker has allowed me to better understand what I am doing in lab with the bigger picture, as opposed to solely focusing on day-to-day tasks.  This has in turn made me more confident in my abilities as a scientist.  I would like to thank all the PGRP staff and all those in the Jander Lab for making my summer experience so positive and rewarding.