© 2004 Heron Publishing—Victoria, Canada
Induced responses to pathogen infection in Norway spruce phloem: changes in polyphenolic parenchyma cells, chalcone synthase
transcript levels and peroxidase activity
Nina Elisabeth Nagy (1, 2), Carl Gunnar Fossdal (1), Paal Krokene (1), Trygve Krekling (3), Anders Lönneborg (1, 4) and Halvor Solheim (1)
1. Norwegian Forest Research Institute, Høgskoleveien 12, N-1432 Ås, Norway / 2. Corresponding author (nina.nagy@skogforsk.no) / 3. Institute of Chemistry and Biotechnology, Agricultural University of Norway, Ås, Norway / 4. DiaGenic A.S., Oslo, Norway / Received October 2, 2002; accepted September 21, 2003; published online March 1, 2004
Summary
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 (short lesions) than the other (long lesions). After infection, the cross-sectional area
of PP cells and their vacuolar polyphenol 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 polyphenol bodies than the less resistant clone, whereas the less
resistant clone accumulated relatively more polyphenols 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 chalcone 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.
Keywords:
Ceratocystis polonica, defense responses, phenol synthesizing enzymes, phenolic content, phloem parenchyma cells, Picea abies, starch concentration.
