Originally published as Genetics Published Articles Ahead of Print on October 14, 2008.

Genetics, Vol. 180, 2111-2122, December 2008, Copyright © 2008
doi:10.1534/genetics.108.093773

Regulation of Caenorhabditis elegans Male Mate Searching Behavior by the Nuclear Receptor DAF-12

Gunnar Kleemann1, Lingyun Jia2 and Scott W. Emmons3

Department of Genetics, Albert Einstein College of Medicine, Bronx, New York 10461

3 Corresponding author: Department of Genetics, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461.
E-mail: emmons{at}aecom.yu.edu

Coordination of animal behavior with reproductive status is often achieved through elaboration of hormones by the gonad. In the nematode Caenorhabditis elegans, adult males explore their environment to locate mates. Mate searching is regulated by presence of mates, nutritional status, and a signal from the gonad. Here we show that the gonadal signal acts via the nuclear receptor DAF-12, a protein known to regulate several C. elegans life-history traits. DAF-12 has both activational and organizational functions to stimulate exploratory behavior and acts downstream of the gonadal signal, outside of the gonad. DAF-12 acts upstream of sensory input from mating partners and physiological signals indicating nutritional status. Mate searching was rescued in germ-line ablated animals, but not if both germ line and somatic gonad were ablated, by a precursor of the DAF-12 ligand, dafachronic acid (DA). The results are interpreted to suggest that the germ line produces a DA precursor that is converted to DA outside of the germ line, possibly in the somatic gonad. As it does in other pathways in which it functions, in regulation of male mate searching behavior DAF-12 acts at a choice point between alternatives favoring reproduction (mate searching) vs. survival (remaining on food).