Effect of propagators and inhibitors on the ultraweak luminescence from maize roots

This study has investigated the kinetics and mechanism of ultraweak luminescence in maize roots. Mannitol induced the second maximum and enhanced the main maximum of the relative intensity of luminescence from the roots. Hydroquinone and quinone enhanced the relative intensity of the luminescence. Catalase enhanced the maximum of the luminescence and changed the kinetics of the light emission. The effect of catalase on the kinetics was abolished by superoxide dismutase. Ascorbate in the presence of catalase reduced the luminescence maximum, but did not alter the kinetics. In the presence of catalase only, or in the combination with superoxide dismutase, or ascorbate, the luminescence intensity in the stationary phase was significantly lower compared to the control. The results support the participation of superoxide-radical, singlet oxygen, electron transfer and the role of peroxidase in the reactions generating ultraweak luminescence in the roots. Ascorbate, catalase and superoxide dismutase have a protective role in the luminescent reactions.     

Immunocytochemical localization of phenylalanine ammonia-lyase in tissues of Populus kitakamiensis

The polypeptide encoded by the partial fragment of cDNA of phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), PALcDNAl (Osakabe et al., 1995, Plant Sci. 105: 217–226), isolated from Populus kitakamiensis (P. sieboldii x P. grandidentata), was expressed in Escherichia coli cells. The polypeptide was purified and an antiserum raised against it. The antiserum recognized a protein of 77 kDa on nitrocellulose blots after sodium dodecyl sulfate-poly-acrylamide gel electrophoresis of total protein and the partially purified PAL protein from P. kitakamiensis. Moreover,the antiserum recognized a protein on the blot after non-denaturing polyacrylamide gel electrophoresis of P. kitakamiensis proteins and this protein had PAL activity. Furthermore, the antibody inhibited PAL activity of extracts from stem tissues. These results showed that the antiserum against the partial PAL peptide recognized only the PAL subunits in extracts of P. kitakamiensis. Immunolocalization studies of P. kitakamiensis tissues revealed that the PAL protein was specifically localized in the xylem and the phloem fibers and no immunogold signal was found in the epidermis, the cortex, the pith, or the cambium of either stems or leaves.Abbreviations IgG immunoglobulin G - IPTG isopropylthio--d-galactoside - PAL phenylalanine ammonia-lyase The authors thank Dr. Kunio Hata of Nippon Paper Industries Co., Ltd. (Japan) for supplying P. kitakamiensis. This work was supported in part by a grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan (No. 07406008).     

Effect of snow removal on leaf water potential,soil moisture,leaf and soil nutrient status and leaf peroxidase activity of sugar maple

Effect of removal of snow cover in winter was investigated in an 80-year-old sugar maple (Acer saccharum Marsh.) stand in southern Quebec. We hypothesized that winter soil frost would induce some of the decline symptoms observed in sugar maple stands in southern Quebec in the early 1980's. Snow was continuously removed from around trees for a one week (partial removal) or for a four-month period (complete removal) during the 1990–1991 winter. Foliage and soils were sampled periodically during the summer of 1991. The complete snow removal treated trees showed decreased leaf water potential and increased peroxidase activity over most of the growing season. Foliar Ca was reduced in both snow removal treatments early in the growing season while foliar N was reduced in the complete snow removal trees late in the growing season. Soil NO ₃ ^– and K⁺ were elevated in both snow removal treatments at various times throughout the growing season. Prolonged soil frost in a sugar maple stand can induce lower leaf water potential, higher leaf peroxidase activity and early leaf senescence during the following growing season. Soil frost may have reduced nutrient uptake without affecting significantly the leaf nutrient status.     

Tissue and subcellular immunolocalisation of enzymes of lignin synthesis in differentiating and wounded hypocotyl tissue of French bean (Phaseolus vulgaris L.)

Antisera raised againstl-phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and a cationic cell-wall peroxidase, which had all been purified from suspension-cultured cells of French bean, have been used to carry out immunogold localisations in the growing plant. Immunoglobulin-G fractions were prepared from each antiserum and used to study the distribution of the enzymes in differentiating and wounded hypocotyls by immunogold techniques and visualisation by both light and electron microscopy. Following silver enhancement to amplify the signal, proteins were detected by confocal microscopy in both developing (pre-xylem/ phloem) and later metaxylem stelar tissue.l-Phenylalanine ammonia-lyase and C4H also accumulated in cells adjacent to metaxylem, presumably involved in maintaining a supply of phenylpropanoid precursors to the enucleated xylem for further lignin synthesis. In these cells, PAL subunits were cytosolic although some were associated with endomembrane. Cinnamate-4-hydroxylase was wholly associated with membrane and particularly high concentrations were found in the Golgi bodies. The cationic peroxidase accumulated in xylem at sites of secondary thickening and in the middle lamella. The three proteins are also involved in defensive lignification. Thus when visualised by light microscopy, PAL and C4H were seen to accumulate to high levels throughout the cell types in wound sites and especially in the epidermal cells. An even more intense general distribution was found upon hyperinduction of wounded cells with-aminooxy--phenylpropionic acid. At the subcellular level, PAL was found to be localised in the cytosol in the wounded cells; however, because of the loss of membrane through mechanical damage, association with membrane structures, particularly endoplasmic reticulum, in unwounded cells is not entirely ruled out. Cinnamate-4-hydroxylase was associated with membranes when these were preserved. In wounded tissue, the peroxidase was found at the growing edges of tylose-like structures in the vascular xylem.Abbreviations AOPP -aminooxy--phenylpropionic acid - C4H cinnamic acid-4-hydroxylase - CHS chalcone synthase - GRP glycine-rich glycoprotein - HRGP hydroxyproline-rich glycoprotein - Ig immunoglobulin - PAL phenylalanine ammonia-lyase G.P.B. thanks the Agicultural and Food Research Council for support.     

Effect of lignin-related phenols and their methylated derivatives on the growth of eight white-rot fungi

When various lignin-related para-phenolic benzoic acids, para-phenolic cinnamic acids, para-phenolic phenylpropionic acids, the corresponding unsubstituted and 4-O-methylated derivatives, and 4-hydroxyl substituted benzaldehydes were tested on the growth of eight white-rot fungi, methylation of the 4-hydroxy substituent resulted, in most cases, in increased inhibition of fungal growth. This effect was most notable with monomethoxylated compounds. When the aromatic ring contained additional methoxyl substituents, the toxicity of the 4-O-methylated derivative was less pronounced. Marked inhibition of fungal growth was also observed with aromatic compounds lacking a para-substituent. Higher concentrations of aromatic aldehydes were manifestly more toxic than the corresponding carboxylic acid.J.A. Buswell is with the Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong. K.-E.L. Eriksson is with the Department of Biochemistry, The University of Georgia, Athens, Georgia, 30602, USA.     

Homology models of two isozymes of manganese peroxidase: Prediction of a Mn(II) binding site

The three-dimensional structures of two isozymes of manganese peroxidase (MnP) have been predicted from homology modeling using lignin peroxidase as a template. Although highly homologous, MnP differs from LiP by the requirement of Mn(II) as an intermediate in its oxidation of substrates. The Mn(II) site is absent in LiP and unique to the MnP family of peroxidases. The model structures were used to identify the unique Mn(II) binding sites, to determine to what extent they were conserved in the two isozymes, and to provide insight into why this site is absent in LiP. For each isozyme of MnP, three candidate Mn(II) binding sites were identified. Energy optimizations of the three possible Mn(II) enzyme complexes allowed the selection of the most favorable Mn(II) binding site as one with the most anionic oxygen moieties best configured to act as ligands for the Mn(II). At the preferred site, the Mn(II) is coordinated to the carboxyl oxygens of Glu-35, Glu-39, and Asp-179, and a propionate group of the heme. The predicted Mn(II) binding site is conserved in both isozymes. Comparison between the residues at this site in MnP and the corresponding residues in LiP shows that two of the three anionic residues in MnP are replaced by neutral residues in LiP, explaining why LiP does not bind Mn(II). © 1994 Wiley-Liss, Inc.     

Energy requirement for foliage construction depends on tree size inyoung Picea abies trees

 The relationship between stand biomass production, and tree age and size is generally a curve with a maximum. To understand why wood production decreases in the final stages of stand development, the influence of increasing tree size on foliage chemical composition and substrate requirement for foliage construction in terms of glucose [CC, g glucose (g dry mass)^{–  1}] was investigated in the evergreen conifer Picea abies (L.) Karst. Because it was already known that irradiance affects both foliage morphology and chemistry in this species, and it was expected that the foliage in large overstory trees would intercept on average more light than that in saplings in understory, irradiance was measured in the sampling locations and included in the statistical models. CC of needles increased with increasing total tree height (TH) and was independent of relative irradiance. A major reason for increasing CC with increasing TH was a greater proportion of carbon-rich lignin in the needles in large trees. However, lignin did not fully account for the observed changes in CC, and it was necessary to assume that certain other carbon-rich secondary metabolites such as terpenes also accumulate in the foliage of large trees. Enhanced requirements for needle mechanical strength as evidenced by greater lignin concentrations in large trees were attributed to increased water limitations with increasing tree height. Because water relations may also control the sink capacities for assimilate usage, apart from the mechanical requirements, they may provide an explanation for the accumulation of other energetically expensive compounds in the needles as well. Biomass partitioning within the shoot was another foliar parameter modified in response to increasing tree size. The proportion of shoot axes, which serve to provide needles with mechanical support and to supply them with water, decreased with increasing TH. This may limit water availability in the needles, and/or manifest a lower water requirement of the needles containing proportionally more supporting and storage substances, and consequently, less physiologically active compounds such as proteins. Probably the same factors which caused CC of the needles to depend on TH, were also responsible for greater CC of the shoot axes in larger trees. These results collectively suggest that increasingly more adverse water relations with increasing tree size may provide a mechanistic explanation for the decline in foliar biomass and its functional activity during stand ageing. Received: 9 April 1996 / Accepted: 14 January 1997     

Microbial cultures in the utilization of cellulosic materials

This review elaborates on the most recent microbial development in saccharification of cellulose and cellulase formation. A particular highlight is a new genetic-immunochemical approach investigating the mechanism of adhesion of bacterial cellulase to cellulose during cellulose conversion. New developments and recent reviews in hemicellulose and lignin degradation are also covered.     

Biodegradation of rice stumps by soil mycoflora

Summary Cellulose and lignin contents in left-overs of rice stump decreased due to decay caused by soil mycoflora. The loss of cellulose and lignin was considerable in presence of Curvularia and Fusarium respectively. Other tested mycoflora could also destroy cellulose and lignin to some extent. The amount of loss of cellulose and lignin increased with time of incubation of the tested mycoflora.     

Ligninolytic activity of Phanerochaete chrysosporium: Physiology of suppression by NH 4 + and l-glutamate

Previous research showed that addition of nutrient nitrogen to ligninolytic (stationary, nitrogen-starved) cultures of the wood-decomposing basidiomycete Phanerochaete chrysosporium causes a suppression of lignin degradation. The present study examined early effects on nitrogen metabolism that followed addition of NH ₄ ⁺ and l-glutamate at concentrations that yield similar patterns of suppression. Both nitrogenous compounds were rapidly assimilated (>80% in 6 h). Both caused an initial 80% or greater increase in the intracellular glutamate pool and had similar effects in increasing the specific activities of NADP- and NAD-glutamate dehydrogenases and glutamine synthetase. Differences between the effects of added NH ₄ ⁺ and glutamate showed that suppression was not correlated with intracellular pools of arginine or glutamine, nor was the maintenance of an elevated glutamate pool required to maintain the suppressed state. While a portion of the initial glutamate suppression could be attributed to an effect on central carbon metabolism through glutamate catabolism by NAD-glutamate dehydrogenase, the long term suppression by glutamate and the suppression by NH ₄ ⁺ were more specific. Suppression by NH ₄ ⁺ or glutamate in the presence or absence of protein synthesis (cycloheximide) followed essentially identical kinetics during 12 h. These results indicate that nitrogen additions cause a biochemical repression of enzymes associated with lignin degradation. Results are consistent with the hypothesis that nitrogen metabolism via glutamate plays a role in initiation of repression.Non-Standard Abbreviations DMS 2,2-dimethylsuccinate - TCA trichloroacetic acid