Volvox germline-specific genes that are putative targets of RegA repression encode chloroplast proteins

Abstract

In Volvox carteri, regA acts as a master gene to suppress all germ cell functions in somatic cells. Its product, RegA, has features of a transcriptional repressor. Here we report cDNA sequences representing 15 nuclear genes with properties expected of RegA targets: they are expressed strongly in germ cells and in regA ⁻, but not regA ⁺, somatic cells. Two of them encode polypeptides with no recognizable features, but ten (like three previously sequenced ones) encode chloroplast proteins of known function, and the remaining three encode putative chloroplast proteins of unknown function. This suggests that RegA blocks reproductive development in somatic cells by preventing chloroplast biogenesis, thereby making it impossible for the cells to grow enough to reproduce.