The role of light receptors during asexual and sexual development of Volvox carteri

• Applicant: Dr. Arash Kianianmomeni
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2013 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 229971462

With only two different cell types (somatic and reproductive cells), the green alga Volvox carteri provides the simplest model system for the study of cellular differentiation. Two fundamental cellular processes that lead to produce these cell types; i.e., embryonic cleavage division and cellular differentiation are both light dependent. The molecular background of light reception and signal transduction of these processes in Volvox is poorly understood. The genome of V. carteri possesses at least 11 light receptors: three cryptochromes (VcCRYp, VcCRYa and VcCRYd), one phototropin (VcPhot1) and seven members of rhodopsin family (VR1, VChR1, VChR2, VR5, VR6, VR7 and VR8). To understand the potential involvement of light receptors in specific developmental processes such as light dependent embryonic cleavage and cellular differentiation, the expression pattern of light receptors will be investigated during asexual and sexual development. Furthermore, cell type specific function will be studied by gene expression analysis in both cell types at different developmental stages. Heterologous expression of somatic cell specific light receptor in gonidia and vice versa will disclose valuable insight into the in vivo function of light receptors. Moreover, since the environmental stimuli trigger the light dependent sexual development in Volvox, their effect on the expression of light receptors will be analyzed. In this connection, the role of enzymerhodopsins which can potentially change the cAMP/cGAMP concentration in a light dependent manner is of high interest, especially during sexual differentiation. In addition, the asexual and sexual development of living alga will be investigated under different wavelengths of light; helps to classify the light receptors into associated developmental stages. Finally, the function of the most promising light receptor with focus on Volvox development will be studied in transgenic RNAi-mediated strains. The results will reveal new insights into the fundamental biological processes which are light dependent or induced. In the long run, this information could be used to control cellular and physiological pathways in living organisms using external light stimuli.

• DFG Programme: Research Grants