How the diversity in digestion in carnivorous plants may have evolved.

Carnivorous plants secrete digestive enzymes for prey degradation. Although carnivorous plants have a polyphyletic origin and evolved several times independently, they surprisingly co-opted similar digestive enzymes during convergent evolution. However, despite having similar digestive enzymes, the mode of their regulation strongly differs across different phylogenetic lineages. But what factors are responsible for such diversity in their digestion? By combining phylogenetic relationships of digestive fluid proteins and biochemical data, the analyses showed that phylogeny seems to be a significant factor determining the regulation of digestion, but environment (water vs terrestrial) and type of trap do not affect regulation. The oldest carnivorous plant lineage, Caryophyllales, co-opted phytohormone jasmonic acid (JA) for regulation of digestive enzyme activity. However, the remaining orders of carnivorous plants do not accumulate JA in response to prey capture, and their digestive enzyme activity is not responsive to exogenous JA application. Instead, they use different modes of regulation, for example, development/senescence, osmotically induced and constitutive. These different modes of regulation can be explained by co-option, albeit of similar genes but different paralogs with different cis regulatory elements that have been fine-tuned during evolution.