Originally published as Genetics Published Articles Ahead of Print on January 31, 2005.

Genetics, Vol. 169, 1997-2011, April 2005, Copyright © 2005
doi:10.1534/genetics.104.040121

Autosomal Genes of Autosomal/X-Linked Duplicated Gene Pairs and Germ-Line Proliferation in Caenorhabditis elegans

John Maciejowski^*, James Hyungsoo Ahn^*, Patricia Giselle Cipriani^*, Darrell J. Killian^*, Aisha L. Chaudhary^*, Ji Inn Lee^*, Roumen Voutev^*, Robert C. Johnsen, David L. Baillie, Kristin C. Gunsalus^*,, David H. A. Fitch^* and E. Jane Albert Hubbard^*,1

^* Department of Biology, New York University, New York, New York 10003
Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
Center for Comparative Functional Genomics, New York University, New York, New York 10003

¹ Corresponding author: Department of Biology, New York University, 100 Washington Square East, 1009 Silver Center, New York, NY 10003.
E-mail: jane.hubbard{at}nyu.edu

We report molecular genetic studies of three genes involved in early germ-line proliferation in Caenorhabditis elegans that lend unexpected insight into a germ-line/soma functional separation of autosomal/X-linked duplicated gene pairs. In a genetic screen for germ-line proliferation-defective mutants, we identified mutations in rpl-11.1 (L11 protein of the large ribosomal subunit), pab-1 [a poly(A)-binding protein], and glp-3/eft-3 (an elongation factor 1- homolog). All three are members of autosome/X gene pairs. Consistent with a germ-line-restricted function of rpl-11.1 and pab-1, mutations in these genes extend life span and cause gigantism. We further examined the RNAi phenotypes of the three sets of rpl genes (rpl-11, rpl-24, and rpl-25) and found that for the two rpl genes with autosomal/X-linked pairs (rpl-11 and rpl-25), zygotic germ-line function is carried by the autosomal copy. Available RNAi results for highly conserved autosomal/X-linked gene pairs suggest that other duplicated genes may follow a similar trend. The three rpl and the pab-1/2 duplications predate the divergence between C. elegans and C. briggsae, while the eft-3/4 duplication appears to have occurred in the lineage to C. elegans after it diverged from C. briggsae. The duplicated C. briggsae orthologs of the three C. elegans autosomal/X-linked gene pairs also display functional differences between paralogs. We present hypotheses for evolutionary mechanisms that may underlie germ-line/soma subfunctionalization of duplicated genes, taking into account the role of X chromosome silencing in the germ line and analogous mammalian phenomena.

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