Abstract
Roles of jasmonate and ethylene signalling and their interaction in yeast elicitor-induced biosynthesis of a phytoalexin, beta-thujaplicin, were investigated in Cupressus lusitanica cell cultures. Yeast elicitor, methyl jasmonate, and ethylene all induce the production of beta-thujaplicin. Elicitor also stimulates the biosynthesis of jasmonate and ethylene before the induction of beta-thujaplicin accumulation. The elicitor-induced beta-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 beta-thujaplicin accumulation. Methyl jasmonate treatment can induce ethylene production, whereas ethylene does not induce jasmonate biosynthesis; methyl jasmonate-induced beta-thujaplicin accumulation can be partly blocked by inhibitors of ethylene biosynthesis and signalling, while blocking jasmonate biosynthesis inhibits almost all ethylene-induced beta-thujaplicin accumulation. These results indicate that the ethylene and jasmonate pathways interact in mediating beta-thujaplicin production, with the jasmonate pathway working as a main control and the ethylene pathway as a fine modulator for beta-thujaplicin accumulation. Both the ethylene and jasmonate signalling pathways can be regulated upstream by Ca(2+). Ca(2+) influx negatively regulates ethylene production, and differentially regulates elicitor- or methyl jasmonate-stimulated ethylene production.
Highlights
Jasmonate (JA) is widely distributed in the plant kingdom with multiple physiological functions during plant development, growth, and defence responses
These results indicate that the jasmonate and ethylene signalling pathways are integral parts of the elicitor signal transduction leading to b-thujaplicin accumulation
This paper presents solid evidence for the JA signalling pathway acting as an integral signal and elicitor signal transducer for b-thujaplicin accumulation
Summary
Jasmonate (JA) is widely distributed in the plant kingdom with multiple physiological functions during plant development, growth, and defence responses. It is accumulated in plants in response to wounding, pathogen and herbivore attack, as well as other biotic or abiotic stresses (Creelman and Mullet, 1997). Methyl jasmonate (MeJA), a methyl ester of JA with the same physiological activity, has been reported to stimulate ET production in many plants such as tomato, Arabidopsis, and tobacco (Xu et al, 1994; O'Donnell et al, 1996; Penninckx et al, 1998). While JA and ET acting antagonistically in nicotine biosynthesis in tobacco, no signi®cant interaction can be observed for insect-induced sesquiterpene emission, even though both JA and ET pathways are required (Shoji et al, 2000; Kahl et al, 2000)
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