Evolution of nitric oxide regulation of gut function

Significance In vertebrate digestive tracts, pyloric sphincters play an important role in controlling the passage of food from stomach to intestine. A major regulator of sphincter relaxation is nitric oxide (NO). However, it is unknown when and how this important means of control was acquired, in part because we lack information on how nonvertebrate deuterostome sphincters are regulated. Here, we show that a NO-dependent regulatory system is present in the pyloric sphincters of sea urchin larvae. Our data suggest that NO-dependent regulation of the pyloric sphincter was present in deuterostome stem groups, and the common deuterostome ancestor had endodermally derived cells that regulated gut function.