iLight2: A near‐infrared optogenetic tool for gene transcription with low background activation

Optogenetic tools (OTs) operating in the far‐red and near‐infrared (NIR) region offer advantages for light‐controlling biological processes in deep tissues and spectral multiplexing with fluorescent probes and OTs acting in the visible range. However, many NIR OTs suffer from background activation in darkness. Through shortening linkers, we engineered a novel NIR OT, iLight2, which exhibits a significantly reduced background activity in darkness, thereby increasing the light‐to‐dark activation contrast. The resultant optimal configuration of iLight2 components suggests a molecular mechanism of iLight2 action. Using a biliverdin reductase knock‐out mouse model, we show that iLight2 exhibits advanced performance in mouse primary cells and deep tissues in vivo. Efficient light‐controlled cell migration in wound healing cellular model demonstrates the possibility of using iLight2 in therapy and, overall, positions it as a valuable addition to the NIR OT toolkit for gene transcription applications.