Originally published as Genetics Published Articles Ahead of Print on December 18, 2006.

Genetics, Vol. 175, 709-724, February 2007, Copyright © 2007
doi:10.1534/genetics.106.066035

Genes Required for Osmoregulation and Apical Secretion in Caenorhabditis elegans

Samuel Liégeois1, Alexandre Benedetto, Grégoire Michaux2, Guillaume Belliard and Michel Labouesse3

Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique Institut National de la Santé et de la Recherche Médicale Université Louis Pasteur BP.10142, 67400 Illkirch, France

3 Corresponding author: IGBMC, 1 rue Laurent Fries, BP.10142, 67400 Illkirch, France.
E-mail: lmichel{at}igbmc.u-strasbg.fr

Few studies have investigated whether or not there is an interdependence between osmoregulation and vesicular trafficking. We previously showed that in Caenorhabditis elegans che-14 mutations affect osmoregulation, cuticle secretion, and sensory organ development. We report the identification of seven lethal mutations displaying che-14-like phenotypes, which define four new genes, rdy-1–rdy-4 (rod-like larval lethality and dye-filling defective). rdy-1, rdy-2, and rdy-4 mutations affect excretory canal function and cuticle formation. Moreover, rdy-1 and rdy-2 mutations reduce the amount of matrix material normally secreted by sheath cells in the amphid channel. In contrast, rdy-3 mutants have short cystic excretory canals, suggesting that it acts in a different process. rdy-1 encodes the vacuolar H+-ATPase a-subunit VHA-5, whereas rdy-2 encodes a new tetraspan protein. We suggest that RDY-1/VHA-5 acts upstream of RDY-2 and CHE-14 in some tissues, since it is required for their delivery to the epidermal, but not the amphid sheath, apical plasma membrane. Hence, the RDY-1/VHA-5 trafficking function appears essential in some cells and its proton pump function essential in others. Finally, we show that RDY-1/VHA-5 distribution changes prior to molting in parallel with that of actin microfilaments and propose a model for molting whereby actin provides a spatial cue for secretion.




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