Studies on the Control Mechanisms of Body Color Polymorphism and Prophenoloxidase Cascade in Insect

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To clear the molecular mechanisms and its control of larval color polymorphism in insect, the factors participating in body color expression in Agrius convolvuli and Bombyx mori were studied.1) The pigments of green and black larvae of A. convoluvli were analyzed. The green larvae have insecticyanin, AcINS (blue) and epidermal carotenoid-binding protein, eCBP (yellow) in epidermal cells. On the other hand, the black larvae have ommochrome in epidermis and melanin in cuticle.2) The precursors of melanin and its transports were examined. Tyrosine, L-dopa, dopamine were precursors of melanin of B. mori and A. convolvuli. However, beta-alanine was only incorporated in brown melanin.3) AcINS-a and -b were purified and characterized. The cDNA sequence of AcINS gene has high similarities with Manduca INSs. AcINS in the epidermis of the black larva was about 1/30 in the green larva.4) The eCBP were purified from the green larva of A. convolvuli. The apo-protein of eCBP was about 27,500 Da, and only lutein was detected in eCBP. The cDNA and N-terminal amino acids sequences of eCBPs showed high similarity with JP29, a 29 k Da nuclear protein of Manduca sexta.5) The granular phenoloxidase (gPO) of B. mori was purified and characterized. The pPOs were synthesized as proenzymes. The molecular mass of pro-gPO was about 78,000 Da. The Km values of gPO were 1.67 mM for L-dopa and 0.313 mM for dopamine. The purified pro-gPO was not activated by prophenoloxidase activating enzyme.6) The dopa decarboxylase (DDC) gene was isolated from Antherea pernyi, A. yamamai, and Samia cynthiaricini. The sequences of these DDC genes showed high similarity with each other.7) The pattern-recognition protein was purified and characterized from hemolymph of B. mori.8) The mechanisms of trans-epithelial transport of the prophenoloxidase from hemolymph to cuticle were investigated.