Nutrient resorption responses to water and nitrogen amendment in semi-arid grassland of Inner Mongolia, China

Litterfall and fine root production is a major pathway for carbon and nutrient cycling in forest ecosystems. We investigated leaf litterfall, fine-root mass, production and turnover rate in the upper soil (0–30 cm) under four major tree species (Leucaena leucocephala, Acacia nilotica, Azadirachta indica, Prosopis juliflora) of the semi-arid region of India. All the four tree species showed an unimodal peak of leaf litterfall with distinct seasonality. Leucaena leucocephala and Acacia nilotica had maximum leaf litterfall between September and December while Azadirachta indica and Prosopis juliflora shed most of their leaves between February and May. Annual leaf litterfall of the four species ranged from 3.3 Mg ha^?1 (Leucaena leucocephala) to 8.1 Mg ha^?1 (Prosopis juliflora). Marked seasonal variations in amount of fine root biomass were observed in all the four tree species. Fine root production was maximum in Prosopis juliflora (171 g m^?2 y^?1) followed by Azadirachta indica (169 g m^?2 y^?1), Acacia nilotica (106 g m^?2 y^?1) and Leucaena leucocephala (79 g m^?2 y^?1). Fine root biomass showed a seasonal peak after the rainy season but fell to its lowest value during the winter and dry summer season. Fine root turnover rate ranged from 0.56 to 0.97 y^?1 and followed the order Azadirachta indica > Leucaena leucocephala > Prosopis juliflora > Acacia nilotica. The results of this study demonstrated that Prosopis juliflora and Azadirachta indica had greater capability for maintaining site productivity as evidenced from greater leaf litterfall and fine root production.     

萘胁迫下秋茄MnSOD基因和C4H基因的实时定量表达分析

研究首次探讨了萘胁迫下红树植物秋茄不同组织C₄H基因和MnSOD基因的表达特征.研究结果表明,两个基因在叶茎根中的表达量有明显的差异,C₄H基因在叶茎中的表达量明显大于根,MnSOD基因的表达量为叶最大,茎次之,根最小.在5个不同浓度的萘胁迫下,C₄H基因和MnSOD基因的表达普遍被诱导,转录水平都随着处理浓度的升高而增强,而且在叶组织中的表达量和萘处理浓度表现出明显的相关关系,相关系数分别达到0.846和0.902(p<0.05),而在根和茎中并不具有显著的相关关系.在萘胁迫下秋茄叶子是最敏感的部位,而C₄H基因和MnSOD基因在叶子中的表达量则为指示萘胁迫强度的良好生物学指标.     

Abiotic stress induces change in Cinnamoyl CoA Reductase (CCR) protein abundance and lignin deposition in developing seedlings of Leucaena leucocephala

Aboitic stress such as drought and salinity are class of major threats, which plants undergo through their lifetime. Lignin deposition is one of the responses to such abiotic stresses. The gene encoding Cinnamoyl CoA Reductase (CCR) is a key gene for lignin biosynthesis, which has been shown to be over-expressed under stress conditions. In the present study, developing seedlings of Leucaena leucocephala (Vernacular name: Subabul, White popinac) were treated with 1 % mannitol and 200 mM NaCl to mimic drought and salinity stress conditions, respectively. Enzyme linked immunosorbant assay (ELISA) based expression pattern of CCR protein was monitored coupled with Phlorogucinol/HCl activity staining of lignin in transverse sections of developing L. leucocephala seedlings under stress. Our result suggests a differential lignification pattern in developing root and stem under stress conditions. Increase in lignification was observed in mannitol treated stems and corresponding CCR protein accumulation was also higher than control and salt stress treated samples. On the contrary CCR protein was lower in NaCl treated stems and corresponding lignin deposition was also low. Developing root tissue showed a high level of CCR content and lignin deposition than stem samples under all conditions tested. Overall result suggested that lignin accumulation was not affected much in case of developing root however developing stems were significantly affected under drought and salinity stress condition.Keyword: Abiotic stress, Cinnamoyl CoA reductase, Developing seedlings, Leucaena leucocephala     

Virus induced gene silencing of three putative prolyl 4-hydroxylases enhances plant growth in tomato (Solanum lycopersicum)

Proline hydroxylation is a major posttranslational modification of hydroxyproline-rich glycoproteins (HRGPs) that is catalyzed by prolyl 4-hydroxylases (P4Hs). HRGPs such as arabinogalactan proteins (AGPs) and extensios play significant roles on cell wall structure and function and their implication in cell division and expansion has been reported. We used tobacco rattle virus (TRV)-based virus induced gene silencing to investigate the role of three tomato P4Hs, out of ten present in the tomato genome, in growth and development. Eight-days old tomato seedlings were infected with the appropriate TRV vectors and plants were allowed to grow under standard conditions for 6 weeks. Lower P4H mRNA levels were associated with lower hydroxyproline content in root and shoot tissues indicating successful gene silencing. P4H-silenced plants had longer roots and shoots and larger leaves. The increased leaf area can be attributed to increased cell division as indicated by the higher leaf epidermal cell number in SlP4H1- and SlP4H9-silenced plants. In contrast, SlP4H7-silenced plants had larger leaves due to enhanced cell expansion. Western blot analysis revealed that silencing of SlP4H7 and SlP4H9 was associated with reduced levels of JIM8-bound AGP and JIM11-bound extensin epitopes, while silencing of SlP4H1 reduced only the levels of AGP proteins. Collectively these results show that P4Hs have significant and distinct roles in cell division and expansion of tomato leaves.     

Effect of salinity on antioxidant responses of chickpea seedlings

The changes in the activity of antioxidant enzymes, like superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase, and growth parameters such as length, fresh and dry weight, proline and H₂O₂ contents, chlorophyll fluorescence (Fv/Fm), quantum yield of PSII and the rate of lipid peroxidation in terms of malondialdehyde in leaf and root tissues of a chickpea cultivar (Cicer arietinum L. cv. Gökçe) under salt treatment were investigated. Plants were subjected to 0.1, 0.2 and 0.5 M NaCl treatments for 2 and 4 days. Compared to controls, salinity resulted in the reduction of length and of the fresh and dry weights of shoot and root tissues. Salinity caused significant (P < 0.05) changes in proline and MDA levels in leaf tissue. In general, a dose-dependent decrease was observed in H₂O₂ content, Fv/Fm and quantum yield of photosynthesis under salt stress. Leaf tissue extracts exhibited three activity bands, of which the higher band was identified as MnSOD and the others as FeSOD and Cu/ZnSOD. A significant enhancement was detected in the activities of Cu/ZnSOD and MnSOD isozymes in both tissues. APX and GR activities exhibited significant increases (P < 0.05) in leaf tissue under all stress treatments, whereas no significant change was observed in root tissue. The activity of CAT was significantly increased under 0.5 M NaCl stress in root tissue, while its activity was decreased in leaf tissue under 0.5 M NaCl stress for 4 days. These results suggest that CAT and SOD activities play an essential protective role against salt stress in chickpea seedlings.     

LNA mediated in situ hybridization of miR171 and miR397a in leaf and ambient root tissues revealed expressional homogeneity in response to shoot heat shock in Arabidopsis thaliana

MicroRNAs (miRNAs) are endogenous non-protein coding RNA molecules of approximately 21 nucleotides in length capable of modulating gene expression in animals and plants. The role of miRNA based gene regulation has been proved in several pathways including in plant growth, development and stress response. In this study miR171 and miR397a were tested for their expression pattern under different heat shock regimes in shoot and root tissues of Arabidopsis thaliana using Locked Nucleic Acid (LNA) mediated in situ hybridization. With an increase in temperature across 35 °C, 40 °C and 45 °C there was a corresponding increased up-regulation of miR171 in leaf tissues compared to ambient temperature. Similarly, an unambiguous elevated expression of miR171 within increase in duration of exposure at each temperature regime across 1 h, 2 h and 3 h was noticed in comparison to ambient control leaf tissue. On the other hand, miR397a, which expressed at ambient control conditions, got down-regulated both with increase in heat and exposure regime in leaf tissues. Both miRNAs expressed in control ambient root tissues. Maintaining the root zone temperature at ambient conditions, upon imposing heat shock regime to shoot system, miR171 recorded corresponding increased up-regulation as indicated by the intensity of in situ hybridization, while miR397a got down-regulated. Given the differential homogeneity in expression pattern of both miRNA in leaf and root tissues experiencing heat shock regimes, possibilities of movement of heat shock induced signals to root tissues seem to be obvious.     

Expression of Human BMP-2 Gene in Different Tissues of Tobacco Plants

The bone morphogenetic proteins (BMPs) are a family of growth factors that regulate the development of bone. BMP-2 is the most effective in the induction of bone tissue. A large amount of BMP-2 is needed for both bone tissue engineering research and clinical application. Thus, an effective way is necessary to produce sufficient BMP-2 protein. With the advance in plant biotechnology, transgenic plants have been targeted as a bioreactor to produce desired recombinant proteins. Here, the expression of recombinant human bmp-2 gene (rhbmp-2) was studied in tobacco plants using gus as a reporter gene. The difference of expression levels in root, stem and leaf tissues was analyzed by GUS activity assay, semi-quantitive RT-PCR and western blotting. The results indicated that the expression levels of fusion protein in root and stem tissues were significantly higher than those in leaf tissue. For the protein compositions in root and stem tissues were simpler than those in leaf tissue, this suggested that the purification process with root and stem tissues would potentially be easier.     

<Emphasis Type="Italic">FAT4</Emphasis> hypermethylation and grade dependent downregulation in gastric adenocarcinoma

Gastric cancer is one of the major causes of death due to cancer in the world. It is a multi-factorial disease with epigenetic factors being also involved in its development. FAT4 is a tumor suppressor gene exerting an important role in cell adhesion. This study aimed at analyzing FAT4 expression and promoter methylation in gastric cancer. FAT4 expression was studied in 30 tumoral tissues and their non-tumoral counterparts using Taqman real time PCR method. Promoter methylation was assessed using bisulfite conversion method followed by sequencing. Tumor tissues showed reduced FAT4 expression (P = 0.04). FAT4 downregulation was associated with tumor grade, with higher repression at advanced grades. Significant increase of promoter methylation was observed in tumoral tissues. Reduced expression of FAT4 and increased methylation of its promoter may be one of the effective processes in turning a healthy stomach tissue into a tumor tissue.     

European corn borer injury effects on lignin, carbon and nitrogen in corn tissues

Plant herbivores often stimulate lignin deposition in injured plant tissue, but it is not known whether corn (Zea mays L.) reacts to European corn borer (ECB, Ostrinia nubilalis Hubner) injury in this manner. Bt (Bacillus thuringiensis) genetic modification is also reported to affect lignin in corn. This study evaluated the effects of ECB injury and the Bt gene on the chemical composition and decomposition of corn tissues. Eight near isolines (Bt and NBt) were grown in pots and half were infested with ECB. The experiment was repeated in 2 years. ECB injury increased the lignin concentration in corn leaves in one of 2 years and lowered the C:N ratio in injured stems. Lignin concentration in leaves was greater in Bt than NBt corn in 1 year and Bt stems had greater N concentration than NBt stems in 1 year of the 2 year study. ECB injury affected the composition of lignin-derived phenols, however ECB infested and non-infested stems lost the same amount of mass after 5 months in buried field litterbags. In conclusion ECB injury and the Bt gene had subtle effects on the chemical composition of corn tissue, which did not alter the short-term decomposition of corn residues.     

Allele-specific marker development and selection efficiencies for both flavonoid 3′-hydroxylase and flavonoid 3′,5′-hydroxylase genes in soybean subgenus soja

Color is one of the phenotypic markers mostly used to study soybean (Glycine max L. Merr.) genetic, molecular and biochemical processes. Two P450-dependent mono-oxygenases, flavonoid 3′-hydroxylase (F3′H; EC1.14.3.21) and flavonoid 3′,5′-hydroxylase (F3′5′H, EC1.14.13.88), both catalyzing the hydroxylation of the B-ring in flavonoids, play an important role in coloration. Previous studies showed that the T locus was a gene encoding F3′H and the W1 locus co-segregated with a gene encoding F3′5′H in soybean. These two genetic loci have identified to control seed coat, flower and pubescence colors. However, the allelic distributions of both F3′H and F3′5′H genes in soybean were unknown. In this study, three novel alleles were identified (two of four alleles for GmF3′H and one of three alleles for GmF3′5′H). A set of gene-tagged markers was developed and verified based on the sequence diversity of all seven alleles. Furthermore, the markers were used to analyze soybean accessions including 170 cultivated soybeans (G. max) from a mini core collection and 102 wild soybeans (G. soja). For both F3′H and F3′5′H, the marker selection efficiencies for pubescence color and flower color were determined. The results showed that one GmF3′H allele explained 92.2 % of the variation in tawny and two gmf3′h alleles explained 63.8 % of the variation in gray pubescence colors. In addition, two GmF3′5′H alleles and one gmF3′5′h allele explained 94.0 % of the variation in purple and 75.3 % in white flowers, respectively. By the combination of the two loci, seed coat color was determined. In total, 90.9 % of accessions possessing both the gmf3′h-b and gmf3′5′h alleles had yellow seed coats. Therefore, seed coat colors are controlled by more than two loci.     

Compartmentalization and ultrastructural alterations induced by chromium in aquatic macrophytes

The aim of the present study was to identify the sites of accumulation of Cr in the species of macrophytes that are abundant in the Cachoeira river, namely, Alternanthera philoxeroides, Borreria scabiosoides, Polygonum ferrugineum and Eichhornia crassipes. Plants were grown in nutritive solution supplemented with 0.25 and 50 mg l^?1 of CrCl₃·6H₂O. Samples of plant tissues were digested with HNO₃/HCl in a closed-vessel microwave system and the concentrations of Cr determined using inductively-coupled plasma mass spectrometry (ICP-MS). The ultrastructure of root, stem and leaf tissue was examined using transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) in order to determine the sites of accumulation of Cr and to detect possible alterations in cell organelles induced by the presence of the metal. Chromium accumulated principally in the roots of the four macrophytes (8.6?C30 mg kg^?1 dw), with much lower concentrations present in the stems and leaves (3.8?C8.6 and 0.01?C9.0 mg kg^?1 dw, respectively). Within root tissue, Cr was present mainly in the vacuoles of parenchyma cells and cell walls of xylem and parenchyma. Alterations in the shape of the chloroplasts and nuclei were detected in A. philoxeroides and B. scabiosoides, suggesting a possible application of these aquatic plants as biomarkers from Cr contamination.     

Characteristics of Lignin Extracted from Different Lignocellulosic Materials via Organosolv Fractionation

Among biomass-derived compounds, lignin is an underused component with potential for conversion to industrial-needed products in biorefinery. In this study, organosolv fractionation of four lignocellulosic materials including bagasse (BG), pararubber wood sawdust (PS), palm fiber (PF), and cassava fiber (CF) was studied using a ternary solvent mixture comprising methyl isobutyl ketone (MIBK), ethanol, and water in the presence of H₂SO₄ to separate high-purity lignin. The fractionation reaction was performed at 160 °C for 40 min with MIBK/ethanol/water proportion of 0.25/0.42/0.33 and 0.025 M of H₂SO₄, which led to the highest lignin removal efficiency of 88.2, 70.6, 67.3, and 71.7% (w/w) from BG, PS, PF, and CF, respectively. Physicochemical characteristics of the fractionated lignin were determined for Klason lignin and by X-ray fluorescence spectroscopy, organic elemental analysis, ¹H nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The lignin samples were thermally depolymerized in MIBK to determine the content of specific lignin-derived chemicals. The main phenolic derivatives from BG-lignin were 4-ethylphenol and 4-vinylguaiacol, whereas those from PS-lignin were syringaldehyde and cis-isoeugenol. Phenol and bis(2-ethylhexyl) phthalate were mainly produced from depolymerization of PF-lignin while trans-isoeugenol and hexadecanoic acid were the major products from CF-lignin. This work demonstrates the potential of the fractionated lignin for production of valuable chemicals in biorefineries.