Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2011
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Gene expression levels (PAL, CCR1, HCT1, and CAD for the phenylpropanoid pathway, PX3 peroxidase, and CHI4 class IV chitinase), lignin, and soluble and cell wall bound phenolic compounds in bark and sapwood of Picea sitchensis clones inoculated with Heterobasidion annosum s.s. were compared before and 3 days after wounding and artificial inoculation, at site of inoculation and 1 cm above the inoculation site. In bark all genes were up-regulated at the site of inoculation but, except for CAD, not in the distal zone. In sapwood all genes were down-regulated, except for PX3 and CHI4; PAL, CCR1, HCT1 and CAD were present at lower levels around the inoculation site than in the distal zone. Compared to wounding only, inoculation with H. annosum triggered different CAD, PX3, and CHI4 levels in bark but not in sapwood. Different concentrations of cell wall bound phenolic compounds (unknown2, unknown3, coniferin, astringin, taxifolin, piceid, and isorhapontin) were found in bark after wounding and inoculation compared to constitutive material (i.e. untreated samples), whereas in sapwood concentrations did not differ following treatment. These results indicate that bark of Sitka spruce has a stronger and earlier response to wounding and pathogen inoculation than sapwood.
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We treated Norway spruce (Picea abies) stems with methyl jasmonate (MeJA) to determine possible quantitative and qualitative eVects of induced tree defenses on pheromone emission by the spruce bark beetle Ips typographus. We measured the amounts of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two main components of the beetle’s aggregation pheromone, released from beetle entrance holes, along with phloem terpene content and beetle performance in MeJA-treated and untreated Norway spruce logs. As expected, phloem terpene levels were higher and beetle tunnel length was shorter (an indication of poor performance) in MeJA-treated logs relative to untreated logs. Parallel to the higher phloem terpene content and poorer beetle performance, beetles in MeJA-treated logs released signiWcantly less 2-methyl-3-buten-2-ol and (S)-cis-verbenol, and the ratio between the two pheromone components was signiWcantly altered. These results suggest that host resistance elicited by MeJA application reduces pheromone emission by I. typographus and alters the critical ratio between the two main pheromone components needed to elicit aggregation. The results also provide a mechanistic explanation for the reduced performance and attractivity observed in earlier studies when bark beetles colonize trees with elicited host defenses, and extend our understanding of the ecological functions of conifer resistance against bark beetles.
Authors
Axel Schmidt Raimund Nagel Trygve Krekling Erik Christiansen Jonathan Gershenzon Paal KrokeneAbstract
Norway spruce (Picea abies) defends itself against herbivores and pathogens by formation of traumatic resin ducts filled with terpenoid-based oleoresin. An important group of enzymes in terpenoid biosynthesis are the short-chain isoprenyl diphosphate synthases which produce geranyl diphosphate (C10), farnesyl diphosphate (C15), and geranylgeranyl diphosphate (C20) as precursors of monoterpenes, sesquiterpenes, and diterpene resin acids, respectively. After treatment with methyl jasmonate (MJ) we investigated the expression of all isoprenyl diphosphate synthase genes characterized to date from Norway spruce and correlated this with formation of traumatic resin ducts and terpene accumulation. Formation of traumatic resin ducts correlated with higher amounts of monoterpenes, sesquiterpenes and diterpene resin acids and an upregulation of isoprenyl diphosphate synthase genes producing geranyl diphosphate or geranylgeranyl diphosphate. Among defense hormones, jasmonate and jasmonate-isoleucine conjugate accumulated to higher levels in trees with extensive traumatic resin duct formation, whereas salicylate did not. Jasmonate and ethylene are likely to both be involved in formation of traumatic resin ducts based on elevated transcripts of genes encoding lipoxygenase and 1-aminocyclopropane-1-carboxylic acid oxidase associated with resin duct formation. Other genes involved in defense signalling in other systems, mitogen-activated protein kinase3 and nonexpressor of pathogenesis-related gene1, were also associated with traumatic resin duct formation. These responses were detected not only at the site of MJ treatment, but also systemically up to 60 cm above the site of treatment on the trunk.
Authors
Abdelhameed Elameen Arild Larsen Sonja Klemsdal Siri Fjellheim Leif Sundheim Susan Msolla Esther Masumba Odd Arne RognliAbstract
No abstract has been registered
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