Ecological process of leaf litter decomposition in tropical rainforest in Xishuangbanna, southwest China. III. Enzyme dynamics

We tested the dynamics of nine enzymes during leaf litter decomposition in Xishuangbanna tropical rain-forest both in the field and laboratory to explore the response of enzyme dynamics to decomposition under different food-web structures. We used coarse and fine (1 mm and 100 μm mesh size, respectively) litterbags in the field to create different food-web structures during litter decomposition. Most soil macrofauna such as nematodes could access only the coarse mesh litterbags, leaving only microbiota, such as mites, in the fine mesh litterbags. In the laboratory, sterilization and inoculation were adopted to investigate different enzyme dynamics with nematodes or only microbiota participating in litter decomposition. Invertase and amylase increased more for shorter food webs at the early stages of decomposition, while activities of endocellulase, β-glucosidase, xylanase and polyphenoloxydase increased to their maxima at the later stages, but greater increase occurred with extended food webs. Invertase and amylase had negative relationships and endocellulase, β-glucosidase, xylanase and polyphenoloxydase had positive relationships with litter decomposition (mass loss). The activities of enzymes responded to the process of litter decomposition. Invertase and amylase played key roles for microbiota utilizing the substrates at early stages of decomposition, while endocellulase, β-glucosidase, xylanase and polyphenoloxydase worked on the further decay of recalcitrant compounds at later stages. All enzymes related to carbon decay acted as effective indicators of litter decomposition. The decomposition of plant organic matter was essentially an enzymatic process. __________ Translated from Journal of Plant Ecology (Chinese Version), 2008, 32(3): 622–631 [译自: 植物生态学报]     

Soil quality indicator responses to row crop,grazed pasture,and agroforestry buffer management

Soil enzyme activities and water stable aggregates have been identified as sensitive soil quality indicators, but few studies exist comparing those parameters within buffers, grazed pastures and row-crop systems. Our objective was to examine the effects of these land uses on the activities of selected enzymes (β-glucosidase, β-glucosaminidase, fluorescein diacetate (FDA) hydrolase, and dehydrogenase), proportion of water stable aggregates (WSA), soil organic carbon and total nitrogen content. Four management treatments [grazed pasture (GP), agroforestry buffer (AgB), grass buffer (GB) and row crop (RC)] were sampled in 2009 and 2010 at two depths (0 to 10- and 10 to 20-cm) and analyzed. Most of the soil quality indicators were significantly greater under perennial vegetation when compared to row crop treatments. Although there were numerical variations, soil quality response trends were consistent between years. The β-glucosaminidase activity increased slightly from 156 to 177 μg PNP g⁻¹ dry soil while β-glucosidase activity slightly decreased from 248 to 237 μg PNP g⁻¹ dry soil in GB treatment during 2 years. The surface (0–10 cm depth) had greater enzyme activities and WSA than sub-surface (10–20 cm) samples. WSA increased from 178 to 314 g kg⁻¹ in row crop areas while all other treatments had similar values during the 2 year study. The treatment by depth interaction was significant (P < 0.05) for β-glucosidase and β-glucosaminidase enzymes in 2009 and for dehydrogenase and β-glucosaminidase in 2010. Soil enzyme activities were significantly correlated with soil organic carbon content (r ≥ 0.94, P < 0.0001). This is important because soil enzyme activities and microbial biomass can be enhanced by perennial vegetation and thus improve several other soil quality parameters. These results also support the hypothesis that positive interactions among management practices, soil biota and subsequent environmental quality effects are of great agricultural and ecological importance.     

Pyrolysis reactions of various lignin model dimers

Primary pyrolysis reactions and relative reactivities for depolymerization and condensation/carbonization were evaluated for various lignin model dimers with α-O-4, β-O-4, β-1, and biphenyl substructures by characterizing the tetrahydrofuran (THF)-soluble and THF-insoluble fractions obtained after pyrolysis at 400°C. Reactivity was quite different depending on the model structure: depolymerization: α-O-4 [phenolic (ph), nonphenolic (nonph)], β-O-4 (ph) > β-O-4 (nonph), β-1 (ph, nonph) > biphenyl (ph, nonph); condensation/carbonization: β-1 (ph) > β-O-4 (ph) > α-O-4 (ph) > β-O-4 (nonph), biphenyl (ph, nonph), α-O-4 (nonph), β-1 (nonph). Major degradation pathways were also identified for β-O-4 and β-1 model dimers: β-O-4 types: C_β-O cleavage to form cinnamyl alcohols and phenols and C_γ-elimination yielding vinyl ethers; β-1 types: C_α-C_β cleavage yielding benzaldehydes and styrenes and C_γ-elimination yielding stilbenes. Relative reactivities of these pathways were also quite different between phenolic and nonphenolic forms even in the same types; C_β-O cleavage (β-O-4) and C_γ-elimination (β-1) were substantially enhanced in phenolic forms.     

Characterization and application of recombinant β-glucosidase (BglH) from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> KCTC 1918

β-Glucosidase (β-1,4-D-glucoside glucohydrolase: EC.3.2.1.21) catalyzes the hydrolysis of β-glucosidic bonds between saccharides and aryl or alkyl groups. A gene encoding β-glucosidase from Bacillus licheniformis KCTC 1918, an anaerobic spore-forming soil bacterium, was cloned and characterized. The structural gene for the β-glucosidase consists of 1410 bp encoding 469 amino acid residues, and has a molecular weight of 53.4 kDa as estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis with 12% separating gel. The enzyme activity was determined against pNPG as a substrate. The enzyme was optimally active at pH 6.0 (citrate-phosphate buffer) and 47°C. β-Glucosidase retained 100% of its original activity for 24 h. The activity of the enzyme was stimulated by glycerol and urea and was decreased by Ca²⁺, Cu²⁺, Hg²⁺, Mg²⁺, and Mn²⁺. In particular, Cu²⁺ had the strongest negative effect on β-glucosidase activity. The purified β-glucosidase was active against pNPG and cellobiose. When the β-glucosidase was tested for cellulose hydrolysis, the supplement of β-glucosidase with cellulose increased the glucose yield from pine wood powder by 139.8%.     

Effect of host plant alternation on some adaptive enzymes of the bird cherry–oat aphid, <Emphasis Type="Italic">Rhopalosiphum padi</Emphasis> (L.)

Changes in the activity of some adaptive enzymes of the bird cherry–oat aphid R. padi after transfer from primary (bird cherry) to secondary (triticales) host plants were assessed. The following groups of enzymes were studied: (1) transferases—glutathione S-transferase (GST) and UDP-glucosyltransferase (UDPGT); (2) antioxidant enzymes—superoxide dismutase (SOD) and catalase (CAT); (3) oxidoreductases—polyphenol oxidase (PPO) and peroxidase (PX); and (4) glucoside hydrolases—α- and β-glucosidase. The activity of the transferases and the antioxidant enzymes increased after transfer to the secondary host, but the level of activity was closely associated with feeding duration on the secondary host. The strongest induction was noted for SOD, the activity of which was more than three times greater on the secondary than on the primary host. In contrast, transfer of the bird cherry–oat aphid was accompanied by a decline in activity of PPO, PX, and β-glucosidase; PPO and PX activity was 50% less in aphids fed on the secondary host rather than on the primary host. Activity of α-glucosidase increased after prolonged feeding on the secondary host. The results indicated that the adaptive enzymes of the bird cherry–oat aphid enable it to feed on distantly related host plants.     

Purification of the toxin protein PC from Arthrinium phaeospermum and its effect on the defence enzymes of Bambusa pervariabilis × Dendrocalamopsis grandis varieties

Bamboo blight in hybrid Bambusa pervariabilis × Dendrocalamopsis grandis is caused by the fungus Arthrinium phaeospermum. One component designated as P_C with pathogenic activity and a molecular weight of about 27 kDa was obtained from this fungus by ammonium sulphate precipitation, polyethylene glycol concentration, Sephadex G‐100 gel chromatography and Q‐Sepharose Fast Flow anion exchange resin. The toxin P_C was shown to cause the same typical symptoms caused by the pathogen itself, although the reaction of the toxin was quicker than the pathogen in all four hybrid bamboo varieties. A threshold toxic dose of 10–20 μg/ml was observed for two resistant varieties, while only 5–10 μg/ml was observed for two susceptible varieties. Moreover, effects of the purified toxic protein on the activities of superoxide dismutase, peroxidase, phenylalanine amonnialyase, polyphenol oxidase, chitinase and β‐1,3 glucanase in the different bamboo varieties were analysed using the impregnation and leaf disc methods. The results showed a positive correlation between the resistance of bamboo and the activities of all six enzymes. The activities of all enzymes except β‐1,3 glucanase decreased over the time course of investigation. These results proved the important role played by toxic proteins in the pathogenicity of A. phaeospermum and their potential for selecting resistant varieties or identify the resistance of this bamboo.     

Transition state leading to β-O′ quinonemethide intermediate of p-coumaryl alcohol analyzed by semi-empirical molecular orbital calculation

The radical coupling reaction leading to the β-0′ quinonemethide intermediate of p-coumaryl alcohol was analyzed by semi-empirical molecular orbital calculation with MOPAC2002. By analyzing the radical monomer in a one-electron oxidation, the spin density of the unpaired electron at the 4-oxygen was less than half of the values at the C₁, C₃, C₅, and C_β positions. By analyzing the transition state during the radical coupling reaction, the activation enthalpy was evaluated as 9.76 kcal/mol, which corresponds to the activation energies for the propagation of common vinyl polymers. From the analysis of atomic interactions in the transition state, it was found that the activation enthalpy was largely composed of a high coulombic repulsion between C_β of the first monomer and the phenolic oxygen of the second monomer. After passing the transition state, the two radical monomers formed a metastable quinone-methide intermediate. The optimum conformation of the quinonemethide intermediate was formed from the meta-stable conformation through a second transition state with a small energy barrier. Part of this article was presented at the 46th Lignin Symposium, held in Fukuoka, October 31-November 1, 2002     

Influences of nitrogen and phosphorus addition on polyphenol oxidase activity in a forested Andisol

Increased atmospheric N deposition could suppress plant litter decomposition, due to the P limitation for soil microorganisms in Japanese forested Andisols with a high P sorption capacity. To explore this possibility, we used a laboratory incubation experiment to study the influence of N addition on β-d-glucosidase and polyphenol oxidase activities, which are important for cellulose and lignin degradation, respectively, in an Andisol with larch (Larix kaempferi) leaf litter. The addition of N increased the β-d-glucosidase activity, whereas it decreased the polyphenol oxidase activity in the soil. However, the addition of both N and P increased the polyphenol oxidase activity in the soil, suggesting the possibility of; (1) an inferior competitive ability of polyphenol oxidase-producing microorganisms under nutrient-rich conditions and; of (2) their P limitation through competition in the Andisol.     

Effects of side-chain hydroxyl groups on pyrolytic <Emphasis Type="Italic">β</Emphasis>-ether cleavage of phenolic lignin model dimer

Effects of side chain hydroxyl groups on pyrolytic β-ether cleavage of phenolic model dimers were studied with various deoxygenated dimers under pyrolysis conditions of N₂/400°C/1 min. Although phenolic dimer with hydroxyl groups at the C _α ⁻ and C _γ ⁻positions was much more reactive than the corresponding nonphenolic type, deoxygenation at the C _γ -position substantially reduced the reactivity up to the level of the nonphenolic type. These results are discussed with the cleavage mechanism via quinone methide intermediate formation, which is activated through intramolecular hydrogen bonds between C _α ⁻ and C _γ ⁻ hydroxyl groups.     

Investigation on hydrogen abstraction from methyl glucoside by active oxygen species under oxygen delignification conditions III: effects of the origin of active oxygen species

Carbohydrate model compounds methyl β-d-glucopyranoside (MGPβ), methyl α-d-glucopyranoside (MGPα), and methyl β-d-mannopyranoside (MMPβ) and the deuterium compounds of MGPβ labeled at the anomeric or C-2 positions (MGPβ-1D, MGPβ-2D) were reacted with active oxygen species (AOS) generated in situ by reactions between O₂ and a co-treated phenolic lignin model compound, 4-hydroxy-3-methoxybenzyl alcohol (VAlc), under conditions simulating oxygen delignification (0.5 mol/l NaOH, 0.36 mmol/l Fe³⁺, 1.1 MPa O₂, 95°C). MGPβ was degraded more than MGPα but less than MMPβ when the pairs MGPβ/MGPα and MGPβ/MMPβ, respectively, were treated, which indicates that the configurational differences at the anomeric and C-2 positions influence the reactivity of AOS toward these compounds. When the pairs MGPβ/MGPβ-1D and MGPβ/MGPβ-2D were treated, no clear kinetic isotope effects were observed in either case. These results contrasted with those obtained when another phenolic compound, 2,4,6-trimethylphenol (TMPh), was used as the AOS generator instead of VAlc under exactly the same conditions. Clear kinetic isotope effects were observed when using TMPh. Because it is not easily accepted that the anomeric and C-2 hydrogen abstractions are minor reaction modes only for AOS generated in the VAlc system, it is suspected that the AOS do not show any clear kinetic isotope effect even though the AOS abstract an objective hydrogen.     

Revisiting the mechanism of <Emphasis Type="Italic">β-O</Emphasis>-4 bond cleavage during acidolysis of lignin IV: dependence of acidolysis reaction on the type of acid

The dependence of the acidolysis reaction of a C₆-C₃ dimeric nonphenolic β-O-4 type lignin model compound, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl) propane-1,3-diol (veratrylglycerol-β-guaiacyl ether, VG), on the type of acid applied was examined using three different acids [0.2 mol/l HCl, 0.2 mol/l HBr, and 0.1 mol/l (0.2 N) H₂SO₄ in 82% aqueous 1,4-dioxane at 85°C]. In the HCl system, the major reaction modes of the corresponding benzyl cation-type intermediate (BC), which is produced by protonation of the α-hydroxyl group of VG and successive release of the water molecule, are the abstraction of the β-proton and hydride transfer from the β-to the α-position. The liberation of formaldehyde from the γ-hydroxymethyl group of BC is the predominant reaction mode in the H₂SO₄ system. Apparently, an unknown reaction mode or modes is operative in the early stage of the HBr system that causes rapid disappearance of VG accompanied by the quantitative formation of 2-methoxyphenol without affording the common counterpart of a Hibbert’s ketone, 1-hydroxy-3-(3,4-dimethoxyphenyl) propan-2-one. The reaction mode in the HBr system changes with the progress of the reaction and is the same as that in the HCl system after the early stage.     

New diagrams to evaluate soil pore radius distribution and saturated hydraulic conductivity of forest soil

Based on the widely used soil pore classification systems, soil pore ratios α, β and γ were derived. α, β, and γ represent ratios of the fine capillary porosity, coarse capillary porosity, and non-capillary porosity to the effective porosity, respectively. The parametersψ _m and σ of the soil water retention model developed by Kosugi were related to these pore ratios, and a simple method was suggested to estimateψ _m and σ from measured soil pore ratios. By analyzing the observed retention data sets of forest soils, it was shown that the soil pore ratios are effectively used to evaluate the soil pore radius distribution. A coordinate system with log(−ψ _m ) on the abscissa and σ on the ordinate, which represents the constant α, β, and γ lines, was developed as a new diagram to evaluate the soil pore radius distribution in connection with the soil water retention characteristic. Then, the saturated hydraulic conductivityK _s of forest soils was correlated with the parametersψ _m and σ, and with the ratios α, β, and γ using the coordinate system and the triangle diagram. Results showed thatK _s is higher for the soil with a greater median and with a greater width of the pore radius distribution.K _s increases as the non-capillary pore ratio γ becomes greater and the coarse capillary pore ratio β becomes smaller. Functional relationships betweenK _s and the water retention parameters, and betweenK _s and the soil pore ratios were derived based on Mualem's model. The title is tentative translation from the original Japanese title by the author of this paper.     

Apple cultivars acceptance by Dysaphis plantaginea Passerini (Homoptera: Aphididae)

The development time, longevity, and fecundity of Dysaphis plantaginea were measured on six apple cultivars (Golden delicious, Red delicious, Renetta canada, Florina querina, Golden lasa, and Golden orange) under controlled conditions, in order to establish the life tables of D. plantaginea on the different cultivars and to evaluate the tolerance of the cultivars against this pest. The intrinsic rates of increase (r _m) were 0.07 and 0.11 day⁻¹ on F. querina and G. orange, respectively. On the other four cultivars, rates ranged between 0.22 and 0.26 day⁻¹, with the maximum value registered on G. lasa. All the biological and demographic parameters evaluated, i.e. survival of larvae (M = 5.8–72.2%), mean generation time (T = 14.94–20.62 days), and net reproduction rate (R ₀ = 4.23–47.37), show that G. orange and F. querina are tolerant cultivars while R. delicious, R. canada, G. lasa, and G. delicious are susceptible hosts.     

Cellulase in <Emphasis Type="Italic">Anoplophora glabripennis</Emphasis> adults fed on original host tree species and non-original host trees

Cellulase activities of Anoplophora glabripennis (Motsch.) adults from two host plants (Populus simonii × P.pyramidliscr cv.Opera Hsu.and Salix matsudana Koidz) fed on three different host tree species (Acer negundo Linn.,S.matsudana Koidz and P.simonii × P.pyramidliscr cv.Opera Hsu.) were investigated.Enzyme activities of endoglucanase and β-glucosidase in the intestines of the insects were measured.The results show that there are no statistically significant differences in the enzyme activities of endoglu...     

Tangential and radial shrinkage variation within trees in sugi (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) cultivars

The transverse shrinkage variation within trees was examined for five sugi cultivars. The within-tree trends of tangential shrinkage (α _T) were different by cultivar, whereas radial shrinkage (α _R) increased from pith to bark in most cultivars. The tangential/radial shrinkage ratio (α _T/α _R) decreased from pith to bark in most cultivars, because the radial variation of α _R was larger than that of α _T. The cultivars showed significant differences among cultivars in α _T, α _R, and α _T/α _R, but the difference among cultivars for α _T/α _R was smaller. The relationships between transverse shrinkage and microfi bril angle (MFA), basic density (BD), tree ring parameters, and modulus of elasticity were examined. The α _T and α _R showed positive relationships with BD, latewood percentage, latewood density, and modulus of elasticity, and negative relationships with MFA and ring width. The relationships with earlywood density were weak. Sugi exhibited variation in transverse shrinkage within stem and among cultivars, with the variation affected by MFA, density, and tree ring parameters. Part of this article was presented at the 56th Annual Meeting of the Japan Wood Research Society, Akita, Japan, August 2006, and the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, Japan, August 2007     

STRUCTURAL ANALYSIS OF TETRACETRON SINENSE MWL

The Structural nature of Tctracctron sinense MWL is characterized by means of Chemical analysis.GC,IR,’H NMR and ~C(13) NMR spectra.The researches indicated that the MWL is of guaiacyl—syringyl type.The main connective form between structural units is β—O—4aryl ether bonds.The quantity of β—O—4 and 5—5 substructures is 0.53/C_9 and 0.06/C_9,respectively.The alipatic and phenolic hydroxy contents are respectively.The OCH_3 content is estimated by ~C(13)NMR is spectrum (1.14/C_9),which is con-sistent with chemical method(1.11/C_9) The degree of condensetion of the MWL is 0.51/C_9(from 'HNMR),which is consistent with the result from ~C(13)NMR.     

Allomorphs of native crystalline cellulose I evaluated by two equatoriald-spacings

The aim of this study was to develop a facile method for categorizing native celluloses as the algal-bacterial type or the cotton-ramie type and for estimating the I_α/I_β (triclinic/monoclinic) ratio of the cellulose samples. We investigated various native celluloses by X-ray diffractometry; and discriminant analysis was carried out using two equatoriald-spacings: 0.59–0.62 nm (d ₁) and 0.52–0.55 nm (d ₂). All of the samples were classified into the two groups without error. The function used to discriminate between the two groups is represented as:Z=1693d₁ — 902d ₂ — 549, whereZ>0 indicates the algal-bacterial (I_α-rich) type andZ<0 indicates the cotton-ramie (I_β-dominant) type. Another X-ray diffraction study of hydrothermally treatedCladophora cellulose revealed the relation between thed-spacings (d ₁,d ₂) and the I_α/I_β ratio. A calibrating equation by which the I_α/I_β ratio was estimated from the two parameters,d ₁ andd ₂, was then prepared. In the case of relatively highly crystalline native celluloses, it was found that the I_α/I_β ratio is easily determined by applying the two parameters in the equation.     

Effect of major inorganic nutrients on <Emphasis Type="Italic">β</Emphasis>-thujaplicin production in a suspension culture of <Emphasis Type="Italic">Cupressus lusitanica</Emphasis> cells

 The optimum conditions for β-thujaplicin production in a Cupressus lusitanica cell suspension culture were investigated. The conditions required for β-thujaplicin production were clearly different from the conditions for cell growth. The initial phosphate concentration and pH did not affect β-thujaplicin production. A total nitrogen source concentration higher than 3.2 mM suppressed production due to the presence of the ammonium ion. β-Thujaplicin production was observed at 95 mg/l without adding the ammonium ion to the medium. Strict control of major inorganic nutrients was not necessary to produce β-thujaplicin. This finding seems to be favorable for future automated production of β-thujaplicin in commercial cell culture plants.     

Cell growth and nutrient uptake by cell suspensions of <Emphasis Type="Italic">Cupressus lusitanica</Emphasis>

 Conditions for cell growth of suspension cultures of Cupressus lusitanica, which has high β-thujaplicin productivity, were studied. The medium that provided the highest growth rate was IS-1 medium (pH 5.5), modified from Gamborg B5 medium containing 32 mM of total nitrogen. Its NO₃-N/NH₄-N ratio was 30 : 2. The maximum growth represented a 25-fold increase over the initial biomass on a fresh weight basis after 30 days of culture in this medium. The highest cell growth was obtained with an initial pH of 3.5–5.5, but the pH of the medium settled to about pH 4.0 from any of the initial pH values in this report. The cells cultured under this condition were able to produce a high level of β-thujaplicin. Received: September 7, 2001 / Accepted: May 7, 2002 Present address: Teijin Ltd., Ehime 791-8530, Japan Present address: Q'SAI Co. Ltd., Fukuoka 811-3422, Japan Part of this report was presented at the 10th international symposium on wood and pulp chemistry, Yokohama, Japan, June 1999 Correspondence to:K. Fujita     

Enzymatic saccharification of water-soluble portion after hot-compressed water treatment of Japanese beech with xylanase and <Emphasis Type="Italic">β</Emphasis>-xylosidase

Enzymatic saccharifications of the hydrolysate collected as the water-soluble (WS) portion after hot-compressed water (HCW) treatment of Japanese beech with xylanase and β-xylosidase were performed to investigate the hydrolytic properties of these enzymes. The WS portions with different molecular weight distributions and initial concentrations of xylooligosaccharides were prepared as substrates, one of which contained mainly smaller xylooligosaccharides [degree of polymerization (DP) = 2 or 3], while the other contained larger xylooligosaccharides (DP ≥ 4). The highest xylose recovery was obtained from both of the WS portions treated with β-xylosidase rather than with xylanase. This suggests that β-xylosidase could have a higher activity than xylanase toward larger xylooligosaccharides (DP ≥ 4) as well as smaller xylooligosaccharides (DP = 2 or 3) recovered from HCW treatment. As a result, the use of β-xylosidase was found to be effective for saccharifi cation of the WS portion, even with a short reaction time for the HCW treatment.