Rhodopsins convert light into signals and energy in animals and microbes. Heliorhodopsins (HeRs), a recently discovered new rhodopsin family, are widely present in archaea, bacteria, unicellular eukaryotes, and giant viruses, however their function remains unknown. Here we report that a viral HeR from marine giant virus (V2HeR3) is a light-activated proton transporter. Three environmental viral HeRs from the same group, as well as a more distantly related HeR exhibited similar ion transport activity. We here propose a proton transporting mechanism and physiological role of HeRs.
Being sessile, plants adapt to fluctuating environments and survive in their habitats; to accomplish this, plant cells have evolved their own physical properties by developing “cell wall” and “large vacuole”, the former of which provides the physical strength and protection, while the latter generates turgor pressure from within the cell, thereby acting as the driving force for cell expansion. In such unique physical environments within plant cells, material circulation is facilitated through the fast flow of the cytoplasm, namely “cytoplasmic streaming”. This review summarizes how these plant-specific facets are organized in plant cells with the aid of cytoskeletal elements.