Locations of Rab, Allatotropin, Prothoracicotropic hormone and Period in the larval brain, corpus allatum and frontal ganglion of Bombyx mori

Abstract

Rab, a low molecular weight GTP-binding protein, regulates the transmission of intracellular proteins. Insect neuropeptides that are directly involved in growth, development, reproduction, homeostasis, courtship, feeding, circadian rhythm and many other physiological processes are synthesized in neurons and ganglia in the brain and secreted by specific neurosecretory cells in tissues such as the corpus allatum and frontal ganglion. To clarify the relationship between Rabs, two neuropeptides, Allatotropin (AT) and Prothoracicotropic hormone (PTTH) and the circadian clock protein, Period (PER), were used to determine the locations of nine Rabs (Rab1, Rab3, Rab6, Rab7, Rab11, Rab14, Rab19, Rab21 and RabX4). Rab6-, Rab11-, Rab14- and Rab21-immunohistochemical reactivities (IRs) partially overlapped AT-IR in the brain in B. mori. Rab3-, Rab6-, Rab11-, Rab14-, and Rab21-IRs overlapped AT-IR in the frontal ganglion. Of the seven Rabs, only Rab11-IR overlapped PTTH-IR in the brain. Rab1-, Rab3-, Rab11-, Rab14-, Rab19-, Rab21-, RabX4- and NUF (nuclear fallout, an effector of Rab11)-IRs, overlapped PER-IR in the brain. Therefore, Rab may regulate the exocytosis of PTTH, AT and a protein associated with the circadian rhythm.

Keywords

• lepidoptera
• bombycidae
• immunohistochemistry
• silkworm
• frontal ganglion
• insect neurohormone
• ptth