A carotenoid‐binding protein (CBP) plays a crucial role in cocoon pigmentation of silkworm (Bombyx mori) larvae

We examined the role of carotenoid‐binding protein (CBP) in yellow cocoon pigmentation. First, using yellow or white cocoon races, we investigated the linkage between the yellow pigmentation and CBP expression. CBP was expressed only in the silk gland of the yellow cocoon races, which utilize carotenoids for cocoon pigmentation. Furthermore, CBP expression in the silk glands of day 1–7 fifth instar larvae matched the period of carotenoid uptake into the silk gland. Finally, we gave double‐stranded CBP RNA to Bombyx mori ( B. mori ) larvae to induce RNA interference. The significantly reduced expression of CBP in the silk gland of fifth instar larva was confirmed on day 4 and a decrease in yellow pigmentation was observed in the cocoon. We showed that CBP plays a key role in the yellow cocoon pigmentation caused by carotenoids.