Rab proteins are low-molecular weight (20-25 kDa) monomeric GTPases that are central to the control and regulation of vesicle trafficking. RabX6 is an insect-specific Rab protein that has no close homolog in vertebrates. However, little information about insect-specific Rab proteins is available. In this study, RabX6 was expressed in Escherichia coli and subsequently purified. Antibodies against Bombyx mori RabX6 were produced in rabbits and rats for western immunoblotting and immunohistochemistry. Western blotting of testis tissues revealed two bands, at positions corresponding to a molecular weight of approximately 26 kDa. RabX6-like immunohistochemical reactivity (RabX6-ir) was identified at the face of the testis, not in the spermatogonia, and was specifically detected at a pair of tritocerebral cells of the male brain. Furthermore, RNA interference of RabX6 was shown to decrease testicular growth. These findings suggest that RabX6 is involved in the regulation of testicular growth and male-specific neuropeptide secretion in the brain of B. mori.

The aldo-keto reductase AKR2E4 reduces 3-dehydroecdysone to ecdysone in the silkworm Bombyx mori L. In this study, a quantitative polymerase chain reaction analysis revealed that the level of AKR2E4 mRNA was higher in the testes than in other tissues, and a western immunoblot analysis revealed that the AKR2E4 content in the testes was stage-specific from the fifth larval instar to the pupal stage. Immunohistochemical analysis showed that the AKR2E4 protein was present in cyst cells associated with sperm cells and spermatocytes. These results indicate that AKR2E4 plays an important role in 3-dehydroecdysone conversion to ecdysone and spermatogenesis in silkworm testes.

http://www.eje.cz 2014). In insects, Rab proteins participate in important cellular processes, such as the immune response, autophagy, neurotransmitter release, phagocytosis, development, fertility and oogenesis (