Metla Project 3388
Polyamines in conifers
Keywords: Polyamines, ectomycorrhiza, embryogenesis, gene expression, hardening, needles, ozone, potassium deficiency, stress, trees
Research project group: Distinct projects 1 - Structure and function of forest ecosystems
Objectives The objective of the present work is to use molecular, microscopical and biochemical methods to study polyamine metabolism starting at early embryogenesis until mycorrhiza formation in young seedlings of Scots pine (Pinus sylvestris L.). The genes encoding polyamine synthesis and degradation arginine decarboxylase (ADC), ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (SAMDC), diamino oxidase (DAO) and polyamine oxidase (PAO) will be characterised to study regulatory mechanisms controlling polyamine content and quality in young Scots pine material. Analyses of free and conjugated fractions of polyamines combined with gene expression studies and microscopical studies will be done to get the overall view of polyamine synthesis and degradation at different developmental stages. Polyamine metabolism during symbiotic mycorrhiza formation on Scots pine roots will be studied.
|Figure 1. Pathways of biosynthesis and degradation of the major plant polyamines (putrescine, spermidine and spermine). Enzymes in the pathways: 1 = arginase (ARG), 2 = arginine decarboxylase (ADC), 3 = agmatine imidohydrolase (AIH), 4 = N-carbamoylputrescine amidohydrolase (NCPAH), 5 = ornithine decarboxylase (ODC), 6 = spermidine synthase (SpdSyn), 7 = spermine synthase (SpmSyn), 8 = diamine oxidase (DAO), 9 = polyamine oxidase (PAO) and 10 = SAM decarboxylase (SAMDC).|
Results Zygotic embryos were collected and induction of somatic embryogenesis have been repeated three times. Soluble and conjugated polyamine fractions covering different developmental stages of zygotic embryos, two elite Scots pine clones, and two years have been analyzed. RNA and DNA isolation methods based on the use of magnetic beads and applicable for limited amount of material have been developed (Vuosku et al. 2004). In situ hybridization of ADC mRNA, realtime RT-PCR and protein activity analyses have been made from zygotic embryos in different developmental stages (Vuosku et al 2006). We have created a regression model for polyamine fluctuation during zygotic embryo development and localized ADC activity in mitotic cells of embryos (Vuosku et al. 2006). We have cloned partial cDNAs of ADC and ODC from Suillus variegatus and in situ hybridization studies have been made from mycorrhizal root tips. We have found out that inoculation with Suillus variegatus caused an increase in the growth of Scots pine seedlings in vitro and in the concentrations of specific free and soluble conjugated polyamines in needles, stems and roots. Increase in both growth and polyamine concentration was observed already after the first week in co-culture. Simultaneously, spermidine concentration in the mycelium decreased dramatically (Niemi et al. 2006). Significant changes in polyamine concentrations were also observed in four months old Scots pine seedlings after inoculation with S. variegatus (Sarjala and Taulavuori 2004).
The Finnish Forest Research Institute,
Kaironiementie 15, FI-39700 PARKANO, FINLAND
Phone: +358 29 532 4064
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