Evolutionary insights from bladderwort genome

The humped bladderwort (Utricularia gibba) is a carnivorous plant with a small nuclear genome, despite having undergone at least two whole-genome duplications since the plant diverged from an ancestor shared with grapes and tomatoes. To uncover the basis of U. gibba’s insect-trapping traits, Tianying Lan et al. (pp. E4435–E4441) generated a highly contiguous nuclear genome assembly of U. gibba. The authors categorized encoded genes as having been derived from small-scale or whole-genome duplication events and reconstructed two ancestral genomes of U. gibba that existed prior to its ancient genome doubling events. Analyses of duplicate gene pairs from the most recent whole-genome duplication indicate that the duplication involved hybridization of two species accompanied by genome doubling. The duplicate gene pairs retained after the wholegenome duplication were enriched in gene regulatory functions. In contrast, duplicate gene pairs from ongoing tandem duplication events, which represent small-scale duplication, were enriched in metabolic functions tied to carnivory. Such functions include trap-specific expression of cysteine protease enzymes for prey digestion, intercellular transport of digested prey proteins, enzyme-mediated control of bladdertrap acidification, and nutrient transport. According to the authors, tandem gene duplication was essential to the bladderwort’s adaptation to carnivory. - Read at PNAS