XVI International Botanical Congess

The multicellular alga Volvox carteri - with just two types of cells, somatic and germline - is an ideal model for studies of the molecular genetics and evolution of cytodifferentiation. We have developed three crucial techniques in Volvox to facilitate such studies, namely, transposon tagging, nuclear transformation, and antisense silencing. Using these tools, we have isolated and analyzed a central controlling gene, regA (somatic regenerator), of V.carteri essential for maintaining the differentiated state of the somatic cells, including senescence and death. RegA has features of a novel transcription factor that acts as repressor of reproductive functions, notably of nuclear-encoded chloroplast proteins, in soma cells. The regA gene itself is under control of an enhancer with a prominent (TG)15 repeat located downstream of the polyA signal. The pattern of gene controls exerted by regA as elucidated in the simple alga Volvox may well be a paradigm for algae and higher plants.