Investigation of cell- type specific gene expression pattern in Volvox carteri alga under light stress conditions

UV-B radiation can penetrate into water deeper than each light wavelength. Complex eukaryotic organisms evolved in response to developmental and environmental signs such as UV-B radiation through the selective expression of a specific section of the same genome in different cell types. The foundation of multicellular organisms needs genetically predefined signaling pathways in diverse cell types. Cell types should be enabled to modulate appropriate adaptive reactions in ever-changing comprehensive environment. The multicellular green alga Volvox carteri consists of only two types with a distinct division of function. Here, the RNA-seq technique was employed to investigate transcriptome profiling of two separated cell types of V. carteri under 1h UV-B treatment. Our results revealed that almost one-third of the V. carteri genes (8392 genes out of 23778 genes) were significantly differentially expressed between the two cell types. The results showed that in somatic cells, potassium ion transmembrane transport and RNA phosphodiester bond hydrolysis were activated. However, in reproductive cells, mismatch repair (MMR), nucleosome assembly and chromosome assembly occurred after UV-B radiation. RNA-dependent DNA biosynthetic process was a common response of both cells to UV-B radiation. The cell type-specific genes were examined to determine cell function in response to UV-B radiation. Overall, two cell-types have initiated defense mechanisms and decreased the sensitivity of alga to UV-B radiation.