Jasmonate and ethylene signalling and their interaction are integral parts of the elicitor signalling pathway leading to β-thujaplicin biosynthesis in Cupressus lusitanica cell cultures

Roles of jasmonate and ethylene signalling and their interaction in yeast elicitor-induced biosynthesis of a phytoalexin, β-thujaplicin, were investigated in Cupressus lusitanica cell cultures. Yeast elicitor, methyl jasmonate, and ethylene all induce the production of β-thujaplicin. Elicitor also stimulates the biosynthesis of jasmonate and ethylene before the induction of β-thujapllcln accumulation. The elicitor-induced β-thujaplicin accumulation can be partly blocked by inhibitors of jasmonate and ethylene biosynthesis or signal transduction. These results indicate that the jasmonate and ethylene signalling pathways are integral parts of the elicitor signal transduction leading to β-thujaplicin accumulation. Methyl jasmonate treatment can induce ethylene production, whereas ethylene does not induce jasmonate biosynthesis; methyl jasmonate-induced β-thujaplicin accumulation can be partly blocked by inhibitors of ethylene biosynthesis and signalling, while blocking jasmonate biosynthesis inhibits almost all ethylene-induced β-thujaplicin accumulation. These results indicate that the ethylene and jasmonate pathways interact in mediating β-thujaplicin production, with the jasmonate pathway working as a main control and the ethylene pathway as a fine modulator for β-thujaplicin accumulation. Both the ethylene and jasmonate signalling pathways can be regulated upstream by Ca²⁺. Ca²⁺ influx negatively regulates ethylene production, and differentially regulates elicitor- or methyl jasmonate-stimulated ethylene production.