Genome Evolution

Recent de novo origin of human protein-coding genes Knowles, D. G. & McLysaght, A. Genome Res. 19, 1752–1759 (2009)

Emergence of a new gene from an intergenic region Heinen, T. J. A. J., Staubach, F., Häming, D. & Tautz, D. Curr. Biol. 19, 1527–1531 (2009)

It is generally assumed that new genes arise through duplication or recombination. Two studies have now identified genes that have arisen from non-coding DNA. By comparing the human genome with syntenic regions of other primates, Knowles and McLysaght detected three protein-coding genes that are present only in humans but are non-coding in all ancestral sequences. Heinen and colleagues identified a sequence that is present only in mice and has arisen in a large intergenic region owing to 5′ indel mutations. The sequence is expressed in post-meiotic cells of the testis: a functional role was suggested by a recent selective sweep in the region and by the sperm-related defects of knockout mice.

Epigenetics

Epigenetic resetting of a gene imprinted in plant embryos Jahnke, S. & Scholten, S. Curr. Biol. 24 Sep 2009 (doi:10.1016/j.cub.2009.08.053)

Imprinting of the Polycomb group gene MEDEA serves as a ploidy sensor in Arabidopsis Erilova, A. et al. PLoS Genet. 5, e1000663 (2009)

These papers provide new insights into the functions and mechanisms of plant genomic imprinting. Jahnke and Scholten report that the imprinting of the maize maternally expressed in embryo gene occurs in the embryo in addition to extra-embryonic tissues and is reset across generations. Both findings show that there is greater similarity between plant and mammalian imprinting than previously thought. Erilova and colleagues give experimental support for a previously proposed function of imprinted genes as 'ploidy sensors' by showing that perturbation of the correct parent of origin-specific expression of the Polycomb gene MEDEA is responsible for aborted seeds in crosses between Arabidopsis thaliana plants of different ploidy.

Evolution

A role for a neo-sex chromosome in stickleback speciation Kitano, J. et al. Nature 27 Sep 2009 (doi:10.1038/nature08441)

Sexual conflict resolved by invasion of a novel sex determiner in Lake Malawi cichlid fishes Roberts, R. B., Ser, J. R. & Kocher, T. D. Science 1 Oct 2009 (doi:10.1126/science.1174705)

Sexual antagonism is predicted to drive sex chromosome evolution, but does sex-chromosome divergence driven by sexual conflict promote speciation? Two papers suggest that it might: Kitano and colleagues found a neo-sex chromosome in Japanese sticklebacks that contains loci for male behavioural traits that have contributed to isolation from an ancestral population; and Roberts et al. found an allele for a colour pattern in cichlid fish that is beneficial to females and is tightly linked to a sex-determination locus, and suggest that such linkage might contribute to diversification and speciation.