Distribution of gustatory receptors and their co-expression with FMRFamide-related peptides in enteroendocrine cells and neurosecretory cells of larvae of the silkworm bombyx mori (original) (raw)

Insects taste nonvolatile chemicals through gustatory receptors (Grs) and make choices for feeding, mating, and oviposition. To date, genome projects have identified 69 Gr genes in the silkworm, Bombyx mori. However, the expression sites of these Grs remain to be explored. In the Chapter 1, I explored expression cells of BmGr6. I used reverse transcription-polymerase chain reaction (RT-PCR) to investigate expression of the B. mori Gr-6 (BmGr6) gene, a member of the putative sugar clade gene family in various tissues. BmGr6 was expressed in the midgut, central nervous system, and oral sensory organs. Immunohistochemistry using an anti-BmGr6 antiserum demonstrated that BmGr6 is expressed in cells of the antenna, labrum, maxillary galea, maxillary palps, and labium of the oral sensory organs. Furthermore, immunohistochemistry showed that BmGr6 is expressed in putative midgut enteroendocrine cells and in cells of the central nervous system including putative neurosecretory cells of the brain and ganglia. These results demonstrated that BmGr6 is widely expressed in both gustatory and non-gustatory organs. In the Chapter 2, I clarified whether BmGr6-expressing cells are midgut enteroendocrine cells and CNS neurosecretory cells. Double-immunohistochemistry indicated that BmGr6 is expressed in midgut enteroendocrine cells, also in CNS neurosecretory cells. In particular, a portion of BmGr6-expressing cells, in both midgut and CNS, secreting FMRFamide-related peptides (FaRPs). These results 7 showed that BmGr53 is expressed in cells of the brain, suggesting that BmGr53 may play roles in modulating feeding behavior or physiological homeostasis.