Báo cáo lâm nghiệp: Carbon partitioning: fructose 2,6-bisphosphate content as an indicator of specific changes in carbohydrate metabolism in needles from class II spruce trees

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Báo cáo lâm nghiệp: "Carbon partitioning: fructose 2,6-bisphosphate content as an indicator of specific changes in carbohydrate metabolism in needles from class II spruce trees"Carbon partitioning: fructose 2,6-bisphosphate contentas an indicator of specific changes in carbohydratemetabolism in needles from class II spruce treesW. Einig R. Hampp F.R.G. D-7400 Tobingen, Tubingen, Biochemie der Pflanzen, Auf der Morgenstelle 1,Universitit available about metabolic acclimation ofIntroduction tissues to pollutants. It has thus been our aim to screen for biochemical indicationsIt has been shown that very low doses of of altered patterns of carbon allocation inairborne pollutants (ozone, sulfite) can needles of Norway spruce (Picea abies).significantly change source-sink relation-ships. These shifts in allocation or trans-portation out of leaves can occur prior toreductions in photosynthesis (ozone;Mcl_aughlin and McConathy, 1983) and Materials and Methodscan take place within minutes (Minchinand Gould, 1986). In spite of intense research in this area, The materials used for our investigations were needles from spruce trees from 2 locations inthere is, however, only little information well as metatrolite analysesthe southern part of the Black Forest (Kalbele- descri- were as as bed elsewhere (Einig andscheuer and Haldenhof, near Freiburg, F.R.G.). Hampp, 1988;Collection and freeze-drying of needle samples Hampp etaL, 1989). control trees have optimum starch levelsResults and Discussion in early summer (Fig. 2a). Independent of needle age, there is a continuous declineSeason- and age-dependent variations in towards October. Sucrose, in contrast, ispool sizes much more constant in its seasonal pool sizes (Fig. 2b).There is considerable evidence that the There are, however, specific differences,rate of starch synthesis is controlled by when pool sizes of phosphorylated inter-the rates of sucrose formation and trans- mediates are compared. An intimate cor-port. relation between pool sizes of TP, F6P and F26BP is observed when the average Metabolites involved in the regulation of contents of all needles (1980-1985) arecarbon partitioning between starch and plotted versus the sampling date (Fig. 3).sucrose are triose phosphates (TP; dihy-droxyacetone phosphate, glyceraldehyde Under the assumption that the changes3-phosphate), glyceric acid 3-phosphate in pool sizes observed for F6P and TP(PGA), fructose 6-phosphate (F6P), ortho- also occur in the cytosol of our needlephosphate (P and pyrophosphate (PP ). i ) i mesophyll cells, all these observationsLevels of these metabolites control syn- can easily be explained by the schemethesis and degradation of the most impor- shown in Fig. 1. In June samples, e.g.,tant regulator, fructose 2,6-bisphosphate starch, F6P and F26BP are high, while TP(F26BP). This compound affects cytosolic are low; high levels of F6P, possibly indi-sucrose synthesis by inhibiting the fruc- cative of limited sucrose export (rates oftose bisphosphatase (FBPase) reaction synthesis exceed rates of export), activate(gluconeogenesis) and activating a PP- i F26BP synthesis. Increased levels ofdependent phosphofructokinase (PFP; ac- F26BP, however, favor glycolysis over glu-tive in both directions, glycolysis and glu- coneogenesis and thus TP are divertedconeogenesis (for a review see Stitt, into starch synthesis. In July, in contrast,1987; compare also Fig. 1 ). opposite situation emerges with an decreased amounts of F6P and F26BP Sucrose and starch as ’endpoints’ of and high levels of TP. This metabolicthis regulatory system show distinct dif- situation should thus be indicative offerences in their pool sizes. Needles from tween starch and sucrose will partitioning of carbon into precede anyincreased visible signs of damage. The determina- (starch decreases) and this situa-sucrose ...