Genetics, Vol. 167, 645-661, June 2004, Copyright © 2004
doi:10.1534/genetics.103.023093

The PGL Family Proteins Associate With Germ Granules and Function Redundantly in Caenorhabditis elegans Germline Development

Ichiro Kawasaki^*,,,1, Anahita Amiri^,2, Yuan Fan, Nicole Meyer, Steve Dunkelbarger, Tomoko Motohashi, Takeshi Karashima, Olaf Bossinger^,3 and Susan Strome

^* PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan
Genome Biology Laboratory, Center for Genetic Resource Information, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan
Department of Biology, Indiana University, Bloomington, Indiana 47405
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

¹ Corresponding author: Molecular Genetics Research Laboratory, University of Tokyo, Science Bldg. No. 7, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
E-mail: ikawasak{at}gen.s.u-tokyo.ac.jp

PGL-1 is a constitutive protein component of C. elegans germ granules, also known as P granules. Maternally supplied PGL-1 is essential for germline development but only at elevated temperature, raising the possibility that redundant factors provide sufficient function at lower temperatures. We have identified two PGL-1-related proteins, PGL-2 and PGL-3, by sequence analysis of the C. elegans genome and by a yeast two-hybrid screen for proteins that interact with PGL-1. PGL-3 is associated with P granules at all stages of development, while PGL-2 is associated with P granules only during postembryonic development. All three PGL proteins interact with each other in vitro. Furthermore, PGL-1 and PGL-3 are co-immunoprecipitated from embryo extracts, indicating that they are indeed in the same protein complex in vivo. Nevertheless, each PGL protein localizes to P granules independently of the other two. pgl-2 or pgl-3 single-mutant worms do not show obvious defects in germline development. However, pgl-1; pgl-3 (but not pgl-2; pgl-1) double-mutant hermaphrodites and males show significantly enhanced sterility at all temperatures, compared to pgl-1 alone. Mutant hermaphrodites show defects in germline proliferation and in production of healthy gametes and viable embryos. Our findings demonstrate that both PGL-2 and PGL-3 are components of P granules, both interact with PGL-1, and at least PGL-3 functions redundantly with PGL-1 to ensure fertility in both sexes of C. elegans.

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