The relationships of annulate lamellae, fibrogranular bodies, nucleolus, and polyribosomes during spermatogenesis in Drosophila melanogaster

Irregularly shaped masses of electron-dense material that are located in the perinuclear cytoplasm of Drosophila spermatocytes contain small granular and fibrillar subunits. These fibrogranular bodies can be observed to extend toward and into the nuclear pores where the material is also continuous with nucleolar material. These observations further substantiate a nucleolar origin for the fibrogranular bodies. As pores of annulate lamellae differentiate within the fibrogranular bodies, structural configurations resembling polyribosomes are noted. Microtubules can also be observed in the fibrogranular material and in some cases they are close to differentiated pores of annulate lamellae. These morphological observations tend to confirm and extend previous suggestions that the fibrogranular bodies may represent stored gene products, and that the differentiation of pores is associated with the dispersal, processing, and assembly of the material perhaps in the form of special functioning polyribosomes. The studies also raise the question of whether or not tubulin may be one of the proteins synthesized by these newly formed polyribosomes.