Conifer cell cultures as a tool for studying the induction of terpenoid defense compounds

Conifer trees often increase their production of terpene resins after attack by herbivores or pathogens, a defense response that may be critical in their survival. Yet it has proved difficult to study such terpene induction under laboratory conditions because of the need for mature trees and specific organs and cells at the proper stage of development. Here we explore the potential of Norway spruce (Picea abies) cell cultures to be a convenient system for studying terpene induction in this species. We demonstrated that P. abies cell suspension cultures accumulated a mixture of monoterpenes (but not of sesquiterpenes or diterpenes), similar to that found in intact trees, but at level of only 0.5–2.5% those in intact trees. However, treatment with the hormone methyl jasmonate and the fungal elicitor chitosan increased monoterpene accumulation 2–4-fold. Based on in vitro assays of terpene synthase activity, this increase was driven by an increased rate of biosynthesis, and was likely not due to pH changes caused by hormone or fungal elicitor treatment. Since these defense responses of P. abies cell cultures are typical of the response of intact spruce needles and bark, such cultures may have promise as a laboratory system for studying the induction of terpene resin defenses.