Aquaporin water channel in the salivary glands of the Formosan subterranean termite Coptotermes formosanus is predominant in workers and absent in soldiers

Authors

  • Kohei Kambara,

    1. Laboratory of Insect Physiology, The United Graduate School of Agricultural Sciences, Tottori University, Tottori, Japan
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  • Tomone Nagae,

    1. Laboratory of Insect Physiology, The United Graduate School of Agricultural Sciences, Tottori University, Tottori, Japan
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  • Wakako Ohmura,

    1. Wood Protection Laboratory, Department of Wood Improvement, Forestry and Forest Products Research Institute, Tsukuba, Japan
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  • Masaaki Azuma

    Corresponding author
    1. Laboratory of Insect Physiology, The United Graduate School of Agricultural Sciences, Tottori University, Tottori, Japan
    • Correspondence: Masaaki Azuma, Laboratory of Insect Physiology, The United Graduate School of Agricultural Sciences, Tottori University, Koyama-cho, Minami 4-101, Tottori 680-8553, Japan. Tel.: +81 857 31 5358; e-mail: azuma@muses.tottori-u.ac.jp

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Abstract

Termite society is unique because the worker caste fetches and carries free water, utilizing it as a solvent for nest construction and gallery building and to maintain wetness for their nestmates. Such water management in a social organization relies largely upon the function of the workers in the colony, as well as on the individuals controlling the location and movement of water inside their bodies. The movement of water via aquaporins (AQPs; water channels) into and out of cells is a key feature of the numerous physiological functions related to whole-insect water balance. In the present study, the homologue of the water-specific Drosophila AQP [Drosophila integral protein (DRIP)] is characterized in workers of the Formosan subterranean termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), a highly active wood decomposer. Immunoblot analysis of DRIP-type AQP using an antibody from the silkworm Bombyx mori reveals that the Coptotermes DRIP (formerly cloned as ‘CfAQP1’) with a molecular mass of approximately 25.7 kDa is expressed predominantly in the salivary (labial) gland of the workers. The Coptotermes DRIP is present at the basal plasma membrane of the parietal cells, as demonstrated by immunocytochemistry. By contrast, there is no DRIP detected within the salivary glands of soldier termites, and neither caste expresses DRIP in their labial gland reservoir (water sac), a tissue that is suggested to have a function as a water sink. The AQP present in the salivary glands is of physiological importance with respect to salivation, aiding in the secretion of cellulolytic enzymes for wood ingestion by the workers of the subterranean termite.

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