| Abstract: | In asexual individuals of the green alga Volvox carteri, more than 99% of the cells are somatic cells which undergo synchronous programmed senescence and cell death every generation. Only a small number of reproductive cells survive to produce the next generation. The specific activity of pulse-labelled somatic cell protein preparations declines sharply during senescence, but no decline is seen in the nonageing reproductive cells. Two-dimensional polyacrylamide gel electrophoresis reveals that somatic and reproductive cells synthesize very different patterns of polypeptides. During the period when observable senescent changes are first evident in somatic cells, there is a change in the pattern of polypeptides being synthesized. Our results suggest that senescence in Volvox somatic cells is triggered by a change in the pattern of gene expression and are consistent with theories of programmed cell senescence. |
