Research Associate MSU-DOE Plant Research Laboratory East lansing, Michigan
Body of Abstract: We applied high-throughput, yet detailed, field-deployable instruments to explore the photoprotective nonphotochemical quenching (NPQ) responses of photosynthesis to real-world, dynamic environmental conditions, focusing on the interplay between rapid light fluctuations and temperature changes (Kanazawa et al 2021). These results suggested that NPQ can be induced very rapidly (in a few seconds) to high levels, but that these rapid responses were also highly sensitive to temperature. To understand the underlying mechanisms and limitations of rapid NPQ, we replicated these effects in the laboratory and applied more extensive spectroscopic measurements on a series of Arabidopsis mutants (including npq1, npq2, npq4). Deconvolution of absorbance measurements and chlorophyll fluorescence yields indicated that the rapid NPQ can be attributed to the qE mechanism. Detailed analyses allowed us to assess the rate-limiting steps for qE formation and recovery. At higher temperatures (25-35oC) the qE kinetics are likely controlled by antenna conformational changes and formation/decay of the pH-gradient component of proton motive force (pmf). Pre-existed content of zeaxanthin appears to modulate these responses, showing faster induction and slower decay in superfast qE in npq2. However, the kinetics of accumulation and decay of zeaxanthin (Zx) during the experiment did not directly control the qE response. Further, even moderate decreases in temperature (below about 20oC) strongly suppressed rapid qE for all mutants, despite the accumulation of Zx. The talk will discuss the importance of these findings in efforts to improve the efficiency of photochemistry while avoiding photodamage, especially under real-world conditions.