Abstract
Visual acuity in Drosophila requires precise photoreceptor alignment along the optical axis, maintained by longitudinal tension between a rigid cornea and a contractile retinal base. Here, we identify the rhabdomere caps-an extracellular matrix (ECM) structure that links rhabdomere tips to the integrin-decorated basal surfaces of overlying, lens-forming cone cells. Rhabdomere caps form perlecan-filled peaks shaped by a trapezoidal LanB1 (laminin) grid, which mirrors the inter-rhabdomeral space (IRS) contour. Our study revealed that Eys (eyes shut), a photoreceptor-secreted proteoglycan essential for IRS formation, guides LanB1 and perlecan deposition by cone cells during pupal development. Disruption of LanB1 results in rhabdomere tip detachment, IRS collapse, and impaired tension transmission. These findings reveal that cone cells and photoreceptors collaboratively sculpt a rigid LanB1 grid that caps and reinforces the distal IRS lumen. This composite ECM structure preserves rhabdomere organization and evenly distributes mechanical forces, ensuring photoreceptor alignment and optical fidelity.
