Induced responses to pathogen infection in Norway spruce phloem: changes in polyphenolic parenchyma cells, XXXX synthase transcript levels and peroxidase activity.

@entity75 @entity3978 @entity6398 @entity25368
Polyphenolic parenchyma cells (PP cells) in Norway spruce (Picea abies (L.) Karst.) stem phloem play important roles in constitutive and inducible defenses. To determine whether anatomical and molecular changes in PP cells are correlated with tree resistance, we infected two Norway spruce clones with the pathogenic fungus Ceratocystis polonica (Siem.) C. Moreau. The fungus induced significantly different lesion lengths in the two clones, indicating that one clone was more resistant to the fungus ( @entity75 ) than the other (long lesions). After infection, the cross-sectional area of PP cells and their vacuolar @entity3978 bodies increased in the three most recent annual rings of PP cells in both clones. The more resistant clone had larger PP cells with denser @entity3978 bodies than the less resistant clone, whereas the less resistant clone accumulated relatively more @entity6398 after infection. Compared with the less resistant clone, the more resistant clone contained higher starch concentrations before infection that were reduced more quickly after infection before returning to original values. Low transcript levels of @entity25368 synthase were detected in uninfected tissues of both clones, but the levels increased dramatically after infection. Transcript levels were higher and peaked 6 days earlier in the more resistant clone than in the less resistant clone. The activity of at least one highly basic peroxidase isoform was greatly enhanced after infection, and this increase occurred earlier in the more resistant clone.
