UC Riverside

Providing food for human beings is one of the major challenges for the future. Plant diseases cause massive losses in crop production all over the world. Pesticides have been used as a major strategy of crop disease control, however conventional pesticides typically rely on toxic activity leading to environmental problems. Synthetic elicitors can protect plants from diseases by activating host immune responses. The identification and characterization of synthetic elicitors can result in valuable tools for the dissection of the plant defense network as well as leads for the development of environmentally-safe pesticide alternatives.

Synthetic elicitors have been classified and the vast majority of known them belong to the large group of functional SA analogs. Additionally imprimatins, sulfonamides, adipic acid derivatives and jasmonic acid analogs were found to have synthetic elicitor activity.

By high-throughput screening we identified over 100 synthetic elicitors. By using model pathosystems Arabidopsis/Hpa, I functionally characterized two novel synthetic elicitors, BHTC and DPMP and their effects on plant defense pathways. BHTC can induce disease resistance quickly and transiently, has a distinct mode-of- action from already characterized synthetic elicitors. BHTC can enhance root elongation on Arabidopsis when applied at low doses, while induces defense reactions at high doses. This phenomenon is known as hormesis. Transcriptional patterns associated with BHTC-mediated hormesis were different from those associated BHTC-mediated defense. Furthermore, the WRKY70 transcription factor is required for both BHTC-mediated immunity and hormetic root elongation and links plant defense signaling to hormetic developmental responses.

DPMP is one of the strongest synthetic elicitors that were identified by our screening. It also exhibited hormesis effect at low doses and induces disease resistance at high doses. Its activity is fully dependent on NPR1 and partially dependent on WRKY70. Interestingly, two separate moieties of DPMP can independently induce immune responses. While their direct targets in plant defense are still yet to be defined, it is clear that they are powerful tools to dissect plant defense networks as well as develop novel pesticide alternatives