UC Berkeley

Photosynthesis necessitates photoprotection. In land plants, Photosystem II Subunit S (PsbS) is necessary for a vast majority of non-photochemical quenching (NPQ) capacity in planta. But in the 20+ years since its characterization, our understanding of the mechanisms in which PsbS induces NPQ, the structural differences that define its success and efficiency in quenching, and the potential of engineering NPQ as a trait for photosynthetic efficiency remain poorly understood. This work seeks to narrow knowledge gaps in our understanding and application of PsbS-dependent NPQ. In Chapter 1, I introduce light harvesting and briefly discuss persistent questions and contrasting dogmas in the field. In Chapter 2, I describe new Nicotiana benthamiana CRISPR/Cas9 NPQ mutants and discuss their potential in interrogating the ultrafast biophysical mechanisms that underlie quenching. In Chapter 3, I show how CRISPR/Cas9 can also be used to alter expression of PsbS and drive beneficial agronomic traits. Finally in Chapter 4, I showcase the potential behind our current era of transcriptomics—mining the Viridiplantae for diverse LHCSR and PsbS orthologs and applying a high-throughput transient expression pipeline to assess their relative ability to induce NPQ in planta. In sum, the confluence of phenotypes described here expands our functional knowledge of PsbS-dependent NPQ and provides exciting ways to interrogate the biophysical mechanisms and structural differences that modulate NPQ efficiency in vivo.