Induction of isoprenyl diphosphate synthases, plant hormones and defense signalling genes correlates with traumatic resin duct formation in Norway spruce (Picea abies)

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

Elevated thiol levels affect virus infection in Cucurbita pepo plants regenerated via somatic embryogenesis

Thiols are known to play crucial roles in plant defense responses, e.g. against pathogens. In the present study, the efficiency of these molecules was evaluated in regenerated Cucurbita pepo L. subsp. pepo var. styriaca Greb. plants in response to compatible Zucchini yellow mosaic virus infection. Thiol contents were modulated by applying the cysteine precursor L-2-oxothiazolidine-4-carboxylic acid (OTC) to callus cells. Cytological and biochemical methods were used for determination of glutathione within callus cells and leaves of plants regenerated via somatic embryogenesis. Reduced glutathione levels (GSH) significantly increased in callus cells one week after 1.0 mM OTC treatment by about 56% and resulted in enhanced GSH levels throughout the investigation period of 13 weeks. Three weeks after ZYMV infection untreated plants regenerated from callus culture exhibited stunted growth forms, yellowing, mosaic and blistering on the leaves whereas 68% of 1.0 mM OTC pretreated regenerated plants were characterized by a complete absence of symptoms. Treatment with OTC stimulated the synthesis, conversion and translocation of thiols during advanced ZYMV infection. Compared to untreated infected leaves, a graduate increase in cysteine (cys) and γ-glutamyl-cysteine (γ-glucys) contents was measured in 0.5 mM and 1.0 mM OTC treated older leaves, whereas total glutathione (tGSH) decreased significantly after infection. In OTC treated younger leaves cys and tGSH concentrations remained at control levels and were unaffected by ZYMV. In contrast, OTC treatment caused a dramatic induction of γ-glucys, up to 191% in younger infected leaves. The results show that altered levels of thiols by OTC were accompanied by enhanced tolerance against ZYMV, suppression of ZYMV induced symptoms as well as delayed symptom development

Development and distribution of quality related compounds in apples during growth

Colour and taste are important attributes of apple fruit quality and have therefore been widely studied. Nevertheless, because of the destructive sampling methods commonly used to obtain the data, and of the subsequent traditional analyses, ignoring the effects of biological variation, the knowledge on the kinetic mechanisms of synthesis and degradation of individual quality components during fruit development and growth is still lacking. Spatio-temporal changes of taste components (sugars: fructose, sucrose, glucose, organic acids: malic, citric, shikimic and fumaric acid) and colour aspects (a) in individual apple fruits were monitored to assess the dynamics and mechanisms of change during development and ripening with respect to location within fruit as a factor and the variation between individual apples. Data were analysed with non-linear indexed regression based on either a logistic or an exponential process oriented model assessing the technical variation simultaneously. The rate constants for colour or taste component were roughly similar between cultivars, suggesting a similar mechanism of development and confirming the generic nature of the model. There was a very large biological variation in individual quality components observed in the raw data (the biological variation), which can be almost exclusively explained by the difference in the maturity stage between individual fruit. The explained parts (R2 adj) were, with one exception, higher than 0.90. The major contribution of this study is the fact that all the herein monitored taste defining components can be analysed and described with the same process-oriented model.</p