PhD Candidate Purdue University Lafayette, Indiana
Body of Abstract: Significant gaps remain in our understanding of drought signaling and the molecular mechanisms of drought responses in plants. The bypass1 (bps1) mutant of Arabidopsis thaliana has shoot and root defects and overproduces a root-derived graft-transmissible signal of unknown chemical identity that is sufficient to arrest development of wildtype plants. Transcriptional response to this signal include genes induced by water limitation. We hypothesize that the bps1 mutant is hyperactive in drought signaling where the bypass signal is used to communicate drought perception from the roots to the shoots. The goal of this project is to identify the bypass signal and identify bypass signal response and synthesis genes. Arabidopsis encodes four paralogs of bps1, and BYPASS2 encodes a dosage-sensitive suppressor of bps1. Through suppressor screens, multiple lines with restored growth were identified indicating that either bypass signal production and transmission or signal response can be disrupted. We have made significant steps in the identification of the bypass signal. Using different chromatography separation methods, we determined the signal is a polar uncharged molecule. Using liquid chromatography mass spectrometry (LC-MS) we identified 46 candidates in both positive (31) and negative (15) ionization modes. We analyzed these candidates using tandem mass spectrometry (MS/MS) to obtain fragmentation patterns to help identify our candidates. The MS/MS revealed many candidates to be fragments of other candidates, thus we were able to reduce our candidate list even further to 13 candidates in both positive (8) and negative (5) ionization modes. Currently we are working on identifying our candidates.