Postdoctoral Research Associate Michigan State University East Lansing, Michigan
Body of Abstract: Isoprene is the most abundant hydrocarbon emitted by some plants, especially trees. Multiple studies have elucidated the role of isoprene in protecting plants from stresses like high temperature, ozone, and herbivory. However, isoprene emission adversely affects atmospheric chemistry by contributing to ozone and aerosol production. Therefore, it is important to study changes in isoprene emission with varying environmental conditions, such as increasing CO2 levels, in order to understand how plants will respond to climate change. Isoprene emission decreases with increasing CO2 concentration; however, the underlying mechanism of this response is unknown. We demonstrated that high-CO2-mediated inhibition of isoprene is independent of light intensity but it intensifies with increasing temperature. We have also shown that high CO2 inhibition of isoprene emission is unrelated to photosynthesis, TPU limitation, and PSII, PSI, or ATP synthase energetics. Additionally, we also showed that this phenomenon is unrelated to ABA-dependent pathways of stomatal regulation by testing the effect of abscisic acid on suppression of isoprene in the presence of high CO2. Furthermore, we measured MEP pathway metabolites by LC-MS/MS in Poplar leaves harvested at ambient and high CO2 and found that among the MEP pathway metabolites, hydroxymethylbutenyl diphosphate (HMBDP) accumulates and dimethylallyl diphosphate (DMADP) decreases at high CO2.This indicates that high CO2 results in modifications of the HDR enzyme such that the conversion of HMBDP to DMADP is inhibited, resulting in lower isoprene emission at high CO2. We will look further into the modifications of HDR enzyme at high CO2 to gain a better understanding of the MEP pathway regulation.