Study on the gene expression of photoreceptors and target genes of UV-B response pathway to UV-B radiation in alga Volvox carteri

Light is an important source of energy for the photosynthetic organisms. Photoreceptor proteins are able to perception of the specific wavelengths of light and initiate a signal transduction pathway. Volvox carteri is a simple multicellular green alga with many features that is recommended as a lower eukaryote model organism for studying the development of photoreception. In this research, the effect of UV-B radiation (0.056 mw.cm-2) was studied on gene expression of 13 photoreceptors using RNA-seq data. These photoreceptors are required for light-monitoring and adaptation of physiological activities to environmental changes. According to our results, under low intensity of UV-B radiation, the photoreceptors were differentially expressed neither in reproductive cells nor in somatic cells as compared to their corresponding control groups. However, comparing the transcriptome of somatic cells with reproductive cells revealed that Phot, CRYp, and ChR1-2, HKR1-4 and Vop (VR1) photoreceptors exhibited a cell-type specific expression pattern while photoreceptors such as UVR8, CRYd1-2 and CRYa were differentially expressed. However, it seems that due to dominantly transcript accumulations of target genes of UV-B response pathway in somatic cells, likely UV-B may indirectly affect gene transcription in this organism. The transcriptional profile pattern between two cell-types, both for photoreceptors and for target genes of UV-B response pathway, shows a different nature and differentiation between reproductive and somatic cells.