Research in the Sharkey lab focuses on three main areas centered on the biochemistry and biophysics of gas exchange reactions between plants and the atmosphere. Photosynthetic carbon fixation from carbon dioxide uptake through to synthesis of sucrose and starch is one major area of research. Recent progress includes the genetic engineering of plants to accumulate up to 50% of their dry weight as starch in their leaves. These plants have potential use in the biofuel and agricultural industries.
A second major research focus area is biochemical analysis of isoprene emission from plants. Isoprene is made by the methyl erythritol 4-phosphate (MEP) pathway that is unique to bacteria and plastids of plants. Plants make isoprene to help them cope with rapid increases in temperature that can occur in sunlight (see the figure). Recently we have found that the first enzyme in the MEP pathway, DXS, is inhibited by the end product metabolites of the MEP pathway DMADP and IDP.
Since isoprene emission appears related to heat tolerance, we initiated a third focus area, studies of heat tolerance mechanisms of photosynthesis. We found that the energy gradient for making ATP dissipates faster after turning off the light when leaves are at high temperature. This could indicate that heat causes thylakoid membranes to become leaky. In a series of in vitro experiments we found that isoprene increases the thickness of membranes. Further, the addition of isoprene prevented heat induced membrane leakage.