Discipline: Biological Sciences
Subcategory: Plant Research
Room: Exhibit Hall
Ebenezer Abban Faidoo - Virginia State University
Co-Author(s): Samantha Cordingley, University of California, Riverside, CA; Emily Blair, University of California, Riverside, CA; Sarah Melissa Witiak, Virginia State University, Petersburg, VA; Dawn Nagel, University of California, Riverside, CA; Paul Nabity, University of California, Riverside, CA
The circadian clock is an intrinsic timekeeping mechanism that controls the physiological activities of many organisms including plants and animals over a 24-hour cycle. The clock helps organisms align their metabolism with environmental changes, allowing them to perform biological processes at relevant times of the day. Clock components control a variety of plant responses such as defense, leaf and flower development, stomata opening through transcriptional regulation. The circadian system comprises an input signal from the environment (which tends to reset the clock), a central oscillator (which maintains a 24- hour rhythm in the absence of a signal) and an output signal (that is responsible for daily rhythms in physiology). The central oscillator components include the evening expressed transcription factors LUX and ELF4 and dawn expressed gene, RVE6.Daktulosphaira vitifoliae induced galls on Vitis vinifera are the most important insect threat to viticulture. Clock-regulated processes such as defense, leaf and flowering developmental programs, and metabolism are also involved in gall development. In addition, components of the clock are differentially expressed during development over several weeks, but have not been characterized at different times during the day. We hypothesized that components of the clock such as LUX and ELF4 would increase in the morning compared to control and expression levels of RVE6 would decrease in the morning compared to the control in response to insect exposure.To test these hypotheses, individual grapevines (Vitis vinifera, n=8) were exposed to crawlers and eggs of D. vitifoliae. Four plants were left uninfected. After 3 days, 4 to 5 leaves of each plant were collected at 6:30 am and 1:30 pm. We extracted mRNA, synthesized cDNA and performed RT-qPCR to quantify expression of LUX, ELF4, RVE6 and TUA (reference gene). Three replicates of each reaction were performed. Significant differences were determined using Student’s t-test. Our results show some insect effects. While a comparison of infected tissues harvested in the morning with control tissues harvested at the same time showed no significant expression differences in LUX, ELF4 or RVE6 (P>0.05), LUX expression in infected tissue harvested in the afternoon increased compared to control tissue (p=0.019). To see clock components continue to cycle in infested tissues, we compared expression levels in galled tissue harvested in the morning and afternoon. Insects induced greater LUX accumulation in the afternoon (p=0.014) whereas uninfested leaves showed an opposite pattern. The master regulator of RVE6 tended to increase upon feeding in the morning but did not differ in the afternoon. This suggests insect control of the circadian rhythms may lead to changes in defense, sugar regulation, and/or organ development to sustain gall development and nutritional quality.
Funder Acknowledgement(s): Funding was provided by a grant to Paul Nabity from University of California Office of the President.
Faculty Advisor: Sarah Melissa Witiak, email@example.com
Role: I infested and harvested the tissue. I also performed RNA extraction, cDNA synthesis, RT-qPCR, and analyzed data. I also helped to design the primers used in RT-qPCR.