New Genes in Drosophila Quickly Become Essential

Essential and New Genes can be broadly grouped into two sets on the basis of their contribution to fitness: those that are essential to the life of an organism and those that can be dispensed with. However, the degree of essentiality in evolutionarily “new” genes—genes that have originated in the recent past—is unknown. Chen et al. (p. 1682) investigated the origination and evolution of new genes within 12 Drosophila species and found, surprisingly, that over one-third of genes that have originated within the last 3.5 million years show essential function and that these functions are overrepresented during larval development. Approximately the same proportion of older genes was essential, although many of these genes also appear to show enrichment at later developmental stages. These findings challenge conventional wisdom that would claim that essential genes are ancient and conserved among animal taxa. One-third of evolutionary young genes is essential to fruit flies. To investigate the origin and evolution of essential genes, we identified and phenotyped 195 young protein-coding genes, which originated 3 to 35 million years ago in Drosophila. Knocking down expression with RNA interference showed that 30% of newly arisen genes are essential for viability. The proportion of genes that are essential is similar in every evolutionary age group that we examined. Under constitutive silencing of these young essential genes, lethality was high in the pupal stage and also found in the larval stages. Lethality was attributed to diverse cellular and developmental defects, such as organ formation and patterning defects. These data suggest that new genes frequently and rapidly evolve essential functions and participate in development.

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