Red-shifted optogenetic excitation: a tool for fast neural control derived from Volvox carteri

The introduction of two microbial opsin–based tools, channelrhodopsin-2 (ChR2) and halorhodopsin (NpHR), to neuroscience has generated interest in fast, multimodal, cell type–specific neural circuit control. Here we describe a cation-conducting channelrhodopsin (VChR1) from Volvox carteri that can drive spiking at 589 nm, with excitation maximum red-shifted ∼70 nm compared with ChR2. These results demonstrate fast photostimulation with yellow light, thereby defining a functionally distinct third category of microbial rhodopsin proteins.