Fig. 6.

RpDuox mediates symbiosis and tracheal network stability. Tracheal network in the M4 before symbiont infection (Top Right). Development of the tracheal network is stimulated to supply oxygen to the M4 when colonized by the symbiont, which consumes high levels of oxygen (Middle Left and Right; red, newly ramified tracheoles; green, gut symbiont; gray, epithelial cells experiencing reduced oxygen levels and attracting growing tracheoles). The branched tracheoles are stabilized by RpDuox (Bottom Right). RpDuox stabilizes the DTN of the tracheal cuticle layer, which is critical for structurally maintaining trachea (Bottom Left). The developmental order is in the direction of the arrows.