Defence responses induced in embryogenic cultures of Norway spruce by two fractions of Gremmeniella abietina mycelia

Abstract

SummaryWe have examined defence responses in embryogenic cell suspension cultures of Norway spruce (Picea abies L.) elicited by intracellular protein and wall fractions (PF and WF, respectively) prepared from mycelia of the fungus Gremmeniella abietina (Lagerberg), focusing on changes in levels of phenolics (soluble and cell wall‐bound), polyamines (free and soluble conjugates) and activities of enzymes that catalyse important steps in their metabolism: phenylalanine ammonia‐lyase (PAL, EC 4.3.1.5) and diamine oxidase (DAO, EC 1.4.3.6), respectively. Treatment with both preparations induced increases in the spruce cells total contents of phenolic acids and polyamines but they responded more rapidly to WF than to PF. The contents of soluble (especially benzoic acid derivatives) and cell wall‐bound (especially ferulic acid) phenolic acids and soluble conjugates of putrescine (mainly amides of hydroxycinnamic acids), started to increase relative to controls (C) within 4 h of the addition of the WF preparation and, more weakly, within 8 h of exposure to the PF preparation. These changes correlated with the induction of PAL activity in spruce cells at 4 and 8 h following the addition of WF and PF preparations, respectively. Increases in the spruce cell’s DAO activity were also detected after just 4 h exposure to WF, and after 24 h exposure to PF. These results demonstrate that both intracellular protein and cell wall fractions prepared from A. abietina mycelium elicit changes in the metabolism of phenylpropanoids and polyamines, substances that are known to be heavily involved in the defence responses of plants to pathogens.