Chlorophyll-Based Optogenetics to Control Membraneless Organelles

Membraneless organelles (MLOs) formed via protein phase separation have garnered significant attention recently due to their relevance to cellular physiology and pathology. However, there is a lack of tools available to study their behavior and control their bioactivity in complex biological systems. This chapter describes a new optogenetic tool based on water-soluble chlorophyll protein (WSCP), a red light-induced singlet oxygen-generating protein, to control synthetic MLOs. Upon exposure to red light, WSCP generates singlet oxygen, which triggers the crosslinking of the proteins in the MLOs, resulting in their liquid-to-solid phase transition. The effective delivery of chlorophylls enables the successful reconstitution of WSCP in living cells, thus offering a potential approach to biological regulation at the subcellular level.