Stimulatory and inhibitory G-protein signaling relays drive cAMP accumulation for timely metamorphosis in the chordate Ciona

Abstract Larvae of the ascidian Ciona initiate metamorphosis tens of minutes after adhesion to a substratum via their adhesive organ. The gap between adhesion and metamorphosis initiation is suggested to ensure the rigidity of adhesion, allowing Ciona to maintain settlement after losing locomotive activity through metamorphosis. The mechanism producing the gap is unknown. Here, by combining gene functional analyses, pharmacological analyses, and live imaging, we propose that the gap represents the time required for sufficient cAMP accumulation to trigger metamorphosis. Not only the Gs pathway but also the Gi and Gq pathways are involved in the initiation of metamorphosis in the downstream signaling cascade of the neurotransmitter GABA, the known initiator of Ciona metamorphosis. The mutual crosstalk of stimulatory and inhibitory G-proteins functions as the accelerator and brake for cAMP production, ensuring the faithful initiation of metamorphosis at an appropriate time and in the right situation. Competing Interest Statement The authors have declared no competing interest. Footnotes ↵7 Lead contact We added the following modifications to the text: On page 8, line 12, "not strong" was changed to "milder". On page 14, line 3, "perfectly" was changed to "completely". On page 22, line 3, "rigidity" was changed to "robustness". On page 23, line 13, "PNs" was changed to "papilla neurons (PNs)". On page 24, lines 22-23, "papilla neurons (PNs)" was changed to "PNs".