Gene Identification for Phototropin-dependent Photoprotection in Chlamydomonas Reinhardtii

Photosynthetic organisms convert solar energy into chemical energy through photosynthesis, generating carbohydrates and lipids that are valuable for biofuels. Algae, renowned for their rapid growth and efficiency, have developed mechanisms to adapt to varying light conditions, ensuring their survival and prosperity. Among these mechanisms, photoprotection strategies such as Non-Photochemical Quenching (NPQ) enhance their tolerance to high light intensities. Excessive light intensity can cause detrimental overexcitation of the photosystems. In Chlamydomonas, one of the proteins, LHCSR3, provides a quick protective response known as energy-dependent quenching (qE), the fastest and most important component of NPQ. Deletion of LHCSR3 leads to cell death under high light conditions. Recent research has shown that blue light, perceived by phototropin (PHOT), mediates the photoprotection of the photosynthetic machinery under high light conditions in Chlamydomonas reinhardtii. Deletion of PHOT leads to compromised expression of LHCSR3 under high light conditions, therefore leading to cell death. However, the downstream signaling components of the PHOT-LHCSR3 pathway remain largely undiscovered. The objective of this project was to identify and characterize new actors involved in PHOT-dependent photoprotection in Chlamydomonas. Using forward genetics and omics analysis, we built a mutant library that could survive under high light intensity in a phot background. We also identified 8 putative PHOT-dependent photoprotection downstream signaling components. Overall, this project brings new insights into the acclimation of photosynthesis to high light. The mutant library could be further used for additional research. Furthermore, understanding photoprotection will not only help increase microalgae biofuel production productivity but could also provide new insights into the genetic engineering of crops for high light resistance.