In vitro secretion of ecdysteroid-dependent proteins and of a 70 kDa subunit reactive to anti-prophenoloxidase serum by Apis mellifera integument

Abstract

A tissue culture approach was used to monitor changes in protein secretion by integuments from Apis mellifera along the pupal stage. A dramatic change in epidermal protein secretion was correlated with the variation in endogenous ecdysteroid from a low level at the beginning of the pupal stage to a maximum level in the middle of this stage. Only a fraction of these proteins, however, turned out to be directly regulated by ecdysteroids when we exposed cultured integument to 20-hydroxyecdysone. An antiserum raised against a honey bee activated prophenoloxidase (proPO) found in hemolymph recognized a 70 kDa subunit in pupal integument incubations, strongly suggesting that honey bee epidermis synthesizes a genuine proPO. The 70 kDa subunit is not developmentally regulated by the ecdysteroid titer. Its constitutive expression throughout the pupal stage makes it difficult to reconcile the function of this protein with progressive cuticle pigmentation in late honey bee pupae. Apis mellifera / integument / epidermis / cuticle / cuticular protein / prophenoloxidase