Mechanosensory Systems and Sensory Integration Mediate C. elegans Negative Gravitaxis

SummaryThe ability to sense Earth’s gravitational pull is essential for orientation, navigation, and proprioception in most organisms. We report here that C. elegans dauer larvae and adults exhibit pronounced negative gravitaxis. This behavior is antagonized by light and electromagnetic fields, suggesting that it is integrated with other sensory inputs. We found that the MEC-7 and MEC-12 microtubule components of the mechanosensory transduction system involved in gentle touch sensation are essential for negative gravitaxis. Further, TRPA-1, a channel protein associated with cold and mechanosensation in both mammals and invertebrates, is required for this behavior. However, the MEC-4/10 DEG/ENaC channels and other components that transduce gentle touch sensation are not required, suggesting that the sensory system for detecting and responding to gravity is separable from the touch sensation system. We found that the PVD neurons, which use TRPA-1 to detect harsh cold, but neither their quaternary processes nor the touch receptor neurons (TRNs), are essential for negative gravitaxis. These findings implicate an interconnected mechanism for gravity sensation involving an ion channel that is also present in the mammalian vestibular system, suggesting possible homology in gravity sensing across animal phylogeny.