Cyclic AMP as an intraspheroidal differentiation signal in Volvox carteri

The action of the macromolecular inducer glycoprotein on sexual reproduction in the green alga Volvox carteri can be modified by altering the external (intraspheroidal) cAMP concentration. Direct proof for the presence of cAMP in the spheroids is given. Protein binding assay and HPLC-fluorimetric analysis independently demonstrate the existence of cAMP in the matrix, cells, and culture medium. Its concentration is higher in sexual cultures, pointing to a transmitting function in sex induction. The presence in the matrix of other members of a protein phosphorylation system suggests an induction-specific signal cascade in this plant.