Atp and Related Purines Stimulate Motility, Spatial Congregation, and Coalescence in Red Algal Spores

Adenosine 5?-triphosphate (ATP) is a versatile extracellular signal along the tree of life, whereas cAMP plays a major role in vertebrates as an intracellular messenger for hormones, transmitters, tastants, and odorants. Since red algal spore coalescence may be considered analogous to the congregation process of social amoeba, which is stimulated by cAMP, we ascertained whether exogenous applications of ATP, cAMP, adenine, or adenosine modified spore survival and motility, spore settlement and coalescence. Concentration-response studies were performed with carpospores of Mazzaella laminarioides (Gigartinales), incubated with and without added purines. Stirring of algal blades released ADP/ATP to the cell media in a time-dependent manner. 10-300 ?M ATP significantly increased spore survival; however, 1,500 ?M ATP, cAMP or adenine induced 100% mortality within less than 24 h; the exception was adenosine, which up to 3,000 ?M, did not alter spore survival. ATP exposure elicited spore movement with speeds of 2.2-2.5 ?m · s-1. 14 d after 1,000 ?M ATP addition, spore abundance in the central zone of the plaques was increased 2.7-fold as compared with parallel controls. Likewise, 1-10 ?M cAMP or 30-100 ?M adenine also increased central zone spore abundance, albeit these purines were less efficacious than ATP; adenosine up to 3,000 ?M did not influence settlement. Moreover, 1,000 ?M ATP markedly accelerated coalescence, the other purines caused a variable effect. We conclude that exogenous cAMP, adenine, but particularly ATP, markedly influence red algal spore physiology; effects are compatible with the expression of one or more membrane purinoceptor(s), discarding adenosine receptor participation. © 2015 Phycological Society of America.