Ultrastructural Studies on the Pheromone-Producing Cells in The Silkmoth, Bombyx mori: Formation of Cytoplasmic Lipid Droplets Before Adult Eclosion


In Bombyx mori, pheromone-producing cells accumulate a. number of lipid droplets in the cytoplasm pre-ceding the production of the sex pheromone, bombykol. The process of lipid droplet formation in the pheromone-producing cells was investigated by using light and electron microscopy. Light microscopy revealed that the lipid droplets appeared from 2 days before adult eclosion and dramatic accumulation took place between 2 days and 1 day before eclosion. Electron microscopical studies revealed that smooth endoplasmic reticulum and numerous vesicles, their sizes being less than 1 μm, were detectable 2 days before eclosion, and some vesicles were fused with mitochondria at this stage. These characteristic changes in the pheromone-producing cells suggest that fatty acyl-CoA synthesis following de novo fatty acid synthesis takes place at this time. Involutions in the basal plasma membrane of the cells occurred throughout the observed period, which were extensive on the day before adult eclosion. Besides extensive basal involutions, immature lipid droplets appeared and then mature fully electron-dense lipid droplets were observed on the day of adult eclosion. These ultrastructural observations, combined with recent physiological studies suggest, that the basal involutions presumably reflect the uptake of lipidic components required for the construction of lipid droplets, the function of which is to store the bombykol precursor and to provide it for bombykol biosynthesis in response to pheromonotropic stimuli by pheromone biosynthesis activating neuropeptide (PBAN).


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We thank Mr. Shinji Atsusawa and Mr. Masaaki Kurihara for excellent technical assistance. This work was supported by the Bioarchitect Research Program from RIKEN, the Scientific Research Program from the Naito Foundation, Grants-in-Aid for Scientific Research (A) (no. 12306003) and Exploratory Research (no. 14656022) from the Ministry of Education, Science, Sports and Culture of Japan. Dr. Adrien Fónagy gratefully acknowledges the receipt of a JSPS Short-term Invitation Research Fellowship (1999), RIKEN Co-operation Research Fellowship (2000) and OTKA (T 032229) Research Grant, and is a holder of Bolyai János Scholarship.

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Yokoyama, N., Fónagy, A., Tatsuki, S. et al. Ultrastructural Studies on the Pheromone-Producing Cells in The Silkmoth, Bombyx mori: Formation of Cytoplasmic Lipid Droplets Before Adult Eclosion. BIOLOGIA FUTURA 54, 299–311 (2003). https://doi.org/10.1556/ABiol.54.2003.3-4.8

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  • Bombyx mori
  • pheromone biosynthesis
  • lipid droplets
  • basal involution
  • PBAN