Understanding the fundamental processes of photosynthesis and its regulation has become more and more important with growing energy and agricultural demands and the need to enhance feedstock performance and yields. Until recently, research on photosynthesis has been focused largely on cyanobacteria, green algae and land plants. However, heterokont microalgae, such as Nannochloropsis, are emerging as potential feedstocks for biofuels due to their high photoautotrophic biomass and lipid accumulation rates. The photosynthetic properties of Nannochloropsis are similar to, but also significantly different, from green algae, e.g. in terms of light harvesting or dissipation of excess light energy (Non-Photochemical Quenching, NPQ). We want to understand these mechanisms and their regulation in Nannochloropsis and therefore designed molecular tools for the genetic modification of this non-model organism. Using a non-lethal, easy-to-screen mutant phenotype, we have established protocols for targeted gene knockout by homologous recombination and by the CRISPR/Cas9 system for the Nannochloropsis oceanica strain CCMP1779. Furthermore, we have created a library of random insertional mutants with altered NPQ capacities and/ or kinetics and identified disrupted genes using PCR-based methods. Combining the forward and reverse genetics approaches with biochemical and spectroscopic analyses, we are now able to address the significance of the xanthophyll cycle-dependent vs. the LHCX(LHCSR)-dependent component of NPQ and the molecular basis of light harvesting in Nannochloropsis.
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