A maturing understanding of the composition of the insect gene repertoire

• Insect genome sequencing has built a comprehensive catalogue of the insect gene repertoire.
• Cross-species comparisons and new sources of evidence refine the catalogue of insect genes.
• Orthology helps generate functional hypotheses for many genes from newly-sequenced genomes.
• Taxonomically-restricted genes likely represent the source of many novel insect adaptations.

Recent insect genome sequencing initiatives have dramatically accelerated the accumulation of genomics data resources sampling species from different lineages to explore the incredible diversity of insect biology. These efforts have built a comprehensive catalogue of the insect gene repertoire, which is expanded with each newly-sequenced genome and continually refined using knowledge from cross-species comparisons and new sources of evidence. Since the sequencing of the very first insect genomes, comparative analyses have identified shared (homologous) and equivalent (orthologous) genes, as well as subsets of genes that appear to be unique. With the number of available insect genomes fast approaching one hundred, a maturing understanding of the composition of the insect gene repertoire broadly partitions it into an expected core of universally-present orthologues and a diverse array of lineage-specific and species-specific genes. While homology and orthology help to build evolutionarily-informed functional hypotheses for many genes from these newly-sequenced genomes, experimental interrogations are required to test such hypotheses and to probe the functions of genes for which homology offers no clues. Such taxonomically-restricted genes may represent the current contents of an evolutionary melting pot, out of which novel adaptations have emerged to make insects the most successful group of animals on Earth.