Identification and characterization of a novel Channelrhodopsin gene HpChR1 in Haematococcus pluvialis

Exposure to light with certain wavelengths was demonstrated to enhance the biosynthesis of astaxanthin in Haematococcus pluvialis for industrial purposes. Photo-responsive biosynthetic process is likely to be mediated by photoreceptor proteins. Therefore, the study of photoreceptors particularly responsible for algal growth and metabolite synthesis is in urgent demand. A novel channelrhodopsin gene HpChR1 was cloned. We examined the subcellular localization and cellular functions of HpChR1 in HeLa cells by living cell imaging. HpChR1 was shown to mainly be localized to the endoplasmic reticulum and the nucleus and mediate endoplasmic reticulum calcium release in HeLa cells. HpChR1 protein comprises seven transmembrane domains at N-terminus and a putative MED15 (mediator complex subunit 15) domain at C-terminus. By using Yeast Two-Hybrid, we showed the binding partners of HpChR1 and they further assisting to interpret the functional roles of HpChR1.These results showed HpChR1 may involve in the reception and transformation of photon energy and signal as channelrhodopsin, and this may shed light on understanding photo-responsive biosynthetic mechanisms in H. pluvialis.