Repression of Rx gene on the left side of the sensory vesicle by Nodal signaling is crucial for right-sided formation of the ocellus photoreceptor in the development of Ciona intestinalis

► Right-sided ocellus formation is perturbed upon Nodal signaling inhibition. ► Nodal signaling inhibition causes bilateral formation of photoreceptor cells. ► Nodal signaling inhibition causes bilateral expression of Ci-Rx. ► Repression of Ci-Rx by Ci-Nodal is crucial for the right-sided ocellus formation.