ECDYSTEROID-DEPENDENT PROTEIN-SYNTHESIS IN CASTE-SPECIFIC DEVELOPMENTOF THE LARVAL HONEY-BEE OVARY

In the honey bee, Apis mellifera, the fifth larval instar is a critica l period for caste differentiation. During this premetamorphic phase t he hormonal milieu shows pronounced caste differences and several orga ns, particularly the ovaries, enter different developmental pathways l eading to highly fertile queens and nearly sterile workers. Developmen tal profiles of total protein synthesis in larval ovaries showed marke d caste differences starting with the early fifth instar, By two-dimen sional electrophoresis, caste-specific patterns could be detected in t he synthesis of a 29 kDa/pI 4.6 and two 24 kDa/pI 5.2-5.5. proteins (p I=isoelectric point). A marked decrease in the expression of these pro teins was found to coincide with caste-specific differences in the hae molymph ecdysteroid titer. In vitro exposure of larval worker ovaries to physiological (10(-7)M) concentrations of synthetic makisterone A e licited an identical response. Juvenile hormone did not affect protein synthesis patterns in larval ovaries, and also did not inhibit or rev erse the ecdysteroid-induced effects. Heat shock experiments revealed that the 29 kDa/pI 4.6 ecdysteroid-regulated protein belongs to the cl ass of small heat shock proteins.