Jasmonate-independent regulation of digestive enzyme activity in the carnivorous butterwort Pinguicula x Tina.

The carnivorous plants within the order Caryophyllales use jasmonates, a class of phytohormone, in the regulation of digestive enzyme activities. We used the carnivorous butterwort Pinguicula x Tina from the order Lamiales to investigate if jasmonate signaling is a universal and ubiquitous signaling pathway also outside the order Caryophyllales. We measured the electrical signals, enzyme activities and phytohormone tissue level in response to prey capture. Mass spectrometry was used for the identification of proteins in the secretion. We identified eight enzymes in the digestive fluid, many of them were found before in other genera of carnivorous plants. Among them, the alpha-amylase is unique among carnivorous plants. The enzymatic activities increased in response to prey capture, however the tissue content of jasmonic acid (JA) and its isoleucine conjugate (JA-Ile) remained rather low in contrast to wounding. The enzyme activities did not increase in response to the exogenous application of JA or coronatine. Whereas similar digestive enzymes were co-opted from plant defense mechanisms among carnivorous plants, the mode of their regulation differs. The butterwort has not co-opted jasmonate signaling for induction of enzyme activities in response to prey capture. Moreover, the presence of alpha-amylase in digestive fluid of P. x Tina, which has not been found in other genera of carnivorous plants, might indicate that non-defense-related genes have also been co-opted for the carnivorous syndrome.