LAUSR

A fundamental question in biology is how multicellular organisms regulate cellular and physiological processes in response to environmental signals in a tissue/cell type-specific manner. Light is one such cue but little is known about its effect on molecular mechanisms underlying cell-type specific signaling. The Volvox genus presents a Germ-Soma differentiation that can be used to understand the genetic mechanisms of evolutionary transition from single-cell to multicellular organisms. Here we report the transcriptional analysis throughout both asexual and sexual life cycles of Volvox carteri in two different cell types under UV-B light irradiation. Our data show that VcUVR8-V1, the main splice variant of the VcUVR8 transcript, accumulates during initiation of cleavage division. Moreover, the transcript level of VcUVR8-V1 increases in response to the sex inducer. VcUVR8 expression seems to remain the same in both cell types, while VcCOP1, the interacting partner of VcUVR8, is expressed in a cell-type specific manner. Interestingly, illumination with low doses of UV-B leads to an increase of VcCOP1 transcript levels only in the somatic cells. Our results indicate that UV-B signaling pathway is differentially regulated between two cell types and environmental UV-B could be involved in cell-type specific regulation of developmental and physiological processes.