Two distinct cinnamoyl-CoA reductases in Selaginella moellendorffii offer insight into the divergence of CCRs in plants.

MAIN CONCLUSION: Two distinct cinnamoyl-coenzyme A reductases (CCRs) from Selaginella moellendorffii were evaluated, and of these, SmCCR2-1, which has both distinct sequence motifs and catalytic properties, was clustered into a new CCR subgroup. Cinnamoyl-coenzyme A reductases (CCRs) have been reported in many land plants to have critical functions in monolignol biosynthesis. In this study, we performed a genome-wide screen and obtained two distinct SmCCRs from S. moellendorffii. Phylogenetic analysis indicated that SmCCR2 (both SmCCR2-1 and 2-2) and SmCCR3 together with PpaCCR belong to a distinct subgroup of genuine CCRs with variations in the NAD(P)H-binding motif. Enzymatic assays showed detectable activity by both SmCCR1 and SmCCR2-1 toward four hydroxycinnamoyl-CoA esters. SmCCR1, which clustered with reported CCRs from angiosperms and gymnosperms, exhibited specificity toward feruloyl-CoA, while SmCCR2-1 showed a preference for sinapoyl-CoA. Interestingly, the reaction temperature profiles for SmCCR1 and SmCCR2-1 are complementary. Homology models and molecular simulations suggest that the variations in NADPH-binding motifs, especially R(X)6K instead of R(X)5K, affect the NADP+ conformation. Notably, the signature motif NWYCY was replaced with NGYCL in SmCCR1 and with EWYCL in SmCCR2-1, while the signature residues H202 and R253, reported in a previous study, were conserved in SmCCR1 and SmCCR2-1 but varied in SmCCR-like genes. It is likely that NWYCY is not a reliable signature for CCRs in plants. The detectable activity of site-direct mutant S123T of SmCCR1 suggested that S123 which consists of catalytic triad is changeable. Possible evolution process for the emergence of two subgroups of genuine CCRs was also revealed. Altogether, these findings revise our understanding of CCRs with regard to divergence and active sites.

Characterization of the cinnamoyl-CoA reductase (CCR) gene family in Populus tomentosa reveals the enzymatic active sites and evolution of CCR.

MAIN CONCLUSION: Two distinct cinnamoyl-coenzyme A reductases (CCRs) from Populus tomentosa were cloned and studied and active sites in CCRs were further identified based on sequence divergence, molecular simulation, and site-directed mutants. Cinnamoyl-coenzyme A (CoA) reductase (CCR) is the first committed gene in the lignin-specific pathway and plays a role in the lignin biosynthesis pathway. In this study, we cloned 11 genes encoding CCR or CCR-like proteins in Populus tomentosa. An enzymatic assay of the purified recombinant P. tomentosa (Pto) CCR and PtoCCR-like proteins indicated that only PtoCCR1 and PtoCCR7 had detectable activities toward hydroxycinnamoyl-CoA esters. PtoCCR1 exhibited specificity for feruloyl-CoA, with no detectable activity for any other hydroxycinnamoyl-CoA esters. However, PtoCCR7 catalyzed p-coumaroyl-CoA, caffeoyl-CoA, feruloyl-CoA, and sinapoyl-CoA with a preference for feruloyl-CoA. Site-directed mutations of selected amino acids divergent between PtoCCR1 and 7, combined with modeling and docking, showed that A132 in CCR7 combined with the catalytic triad might comprise the catalytic center. In CCR7, L192, F155, and H208 were identified as the substrate-binding sites, and site-directed mutations of these amino acids showed obvious changes in catalytic efficiency with respect to both feruloyl-CoA and sinapoyl-CoA. Mutant F155Y exhibited greater catalytic efficiency for sinapoyl-CoA compared with that of wild-type PtoCCR7. Finally, recent genome duplication events provided the foundation for CCR divergence. This study further identified the active sites in CCRs and the evolutionary process of CCRs in terrestrial plants.

Molecular cloning and functional analysis of nine cinnamyl alcohol dehydrogenase family members in Populus tomentosa.

MAIN CONCLUSION: Nine CAD/CAD-like genes in P. tomentosa were classified into four classes based on expression patterns, phylogenetic analysis and biochemical properties with modification for the previous claim of SAD. Cinnamyl alcohol dehydrogenase (CAD) functions in monolignol biosynthesis and plays a critical role in wood development and defense. In this study, we isolated and cloned nine CAD/CAD-like genes in the Populus tomentosa genome. We investigated differential expression using microarray chips and found that PtoCAD1 was highly expressed in bud, root and vascular tissues (xylem and phloem) with the greatest expression in the root. Differential expression in tissues was demonstrated for PtoCAD3, PtoCAD6 and PtoCAD9. Biochemical analysis of purified PtoCADs in vitro indicated PtoCAD1, PtoCAD2 and PtoCAD8 had detectable activity against both coniferaldehyde and sinapaldehyde. PtoCAD1 used both substrates with high efficiency. PtoCAD2 showed no specific requirement for sinapaldehyde in spite of its high identity with so-called PtrSAD (sinapyl alcohol dehydrogenase). In addition, the enzymatic activity of PtoCAD1 and PtoCAD2 was affected by temperature. We classified these nine CAD/CAD-like genes into four classes: class I included PtoCAD1, which was a bone fide CAD with the highest activity; class II included PtoCAD2, -5, -7, -8, which might function in monolignol biosynthesis and defense; class III genes included PtoCAD3, -6, -9, which have a distinct expression pattern; class IV included PtoCAD12, which has a distinct structure. These data suggest divergence of the PtoCADs and its homologs, related to their functions. We propose genes in class II are a subset of CAD genes that evolved before angiosperms appeared. These results suggest CAD/CAD-like genes in classes I and II play a role in monolignol biosynthesis and contribute to our knowledge of lignin biosynthesis in P. tomentosa.

Crystal structures of a Populus tomentosa 4-coumarate:CoA ligase shed light on its enzymatic mechanisms.

4-Coumaric acid:CoA ligase (4CL) is the central enzyme of the plant-specific phenylpropanoid pathway. It catalyzes the synthesis of hydroxycinnamate-CoA thioesters, the precursors of lignin and other important phenylpropanoids, in two-step reactions involving the formation of hydroxycinnamate-AMP anhydride and then the nucleophilic substitution of AMP by CoA. In this study, we determined the crystal structures of Populus tomentosa 4CL1 in the unmodified (apo) form and in forms complexed with AMP and adenosine 5'-(3-(4-hydroxyphenyl)propyl)phosphate (APP), an intermediate analog, at 2.4, 2.5, and 1.9 Å resolution, respectively. 4CL1 consists of two globular domains connected by a flexible linker region. The larger N-domain contains a substrate binding pocket, while the C-domain contains catalytic residues. Upon binding of APP, the C-domain rotates 81° relative to the N-domain. The crystal structure of 4CL1-APP reveals its substrate binding pocket. We identified residues essential for catalytic activities (Lys-438, Gln-443, and Lys-523) and substrate binding (Tyr-236, Gly-306, Gly-331, Pro-337, and Val-338) based on their crystal structures and by means of mutagenesis and enzymatic activity studies. We also demonstrated that the size of the binding pocket is the most important factor in determining the substrate specificities of 4CL1. These findings shed light on the enzymatic mechanisms of 4CLs and provide a solid foundation for the bioengineering of these enzymes.

Profiles of organochlorine pesticides in earthworms from urban leisure areas of Beijing, China.

In this study, organochlorine pesticides (HCHs and DDTs) in earthworm and soil contacted closely with it were determined for the purpose of the risk assessment of chemicals in the urban leisure environment. The level of total hexachlorocyclohexanes and (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in earthworms was 0.6500-44.78 ng g(-1) and 18.97-1.112 x 104 ng g(-1), respectively. Absolutely high levels of DDT and its metabolites in earthworm and correlative soils samples, and the bioaccumulation factor (BAF) of DDTs probably presents certain risk to the higher trophic organisms through its food chain, especially birds.

[Value of Serum Free Light Chain Kappa/Lambda Ratio Detection Combined with Immunofixation Electrophoresis in the Prognosis Evaluation of Patients with Multiple Myeloma].

OBJECTIVE: To analyzed the prognostic value of serum free light chain kappa/lambda ratio detection combined with immunofixation electrophoresis in multiple myeloma (MM) patients. METHODS: 72 patients with MM treated in our hospital from January 2017 to December 2018 were selected. Serum free light chain kappa/lambda ratio (sFLCR) and immune typing were detected respectively. The clinical characteristics and survival time were compared among patients. COX regression was used to analyze the factors influencing prognosis. RESULTS: 38 patients showed high sFLCR, and 34 showed low sFLCR. Compared with the low sFLCR group, the DS stage of patients in high sFLCR group elevated, the levels of ß2-MG and Scrwere increased, and Hb decreased, all the differences were statistically significant (P＜0.05). Among 72 patients, there were 40 cases of IgG type (55.56%), 27 cases of IgA type (37.50%) and 5 cases of IgM type (6.94%). Compared with IgG and IgA patients, the serum calcium and creatinine in IgM patients were increased significantly, while Hb decreased significantly (P＜0.05). The median survival time was 19.2 months in 21 patients with IgG type and high sFLCR; 24.0 months in 19 patients with IgG type and low sFLCR; 15.0 months in 12 patients with IgA type and high sFLCR; 16.7 months in 15 patients with IgA type and low sFLCR; 6.0 months in 5 patients with IgM type and high sFLCR,respectively. DS stage, M protein typing and sFLCR correlated with prognosis of patients (P＜0.05). CONCLUSION: The serum free light chain kappa/lambda ratio combined with immunofixation electrophoresis is valuable for the prognostic evaluation of patients with multiple myeloma.

Levels and chiral signatures of organochlorine pesticides in urban soils of Yinchuan, China.

In this study, residual level and enantiomeric composition of typical organochlorine pesticides (OCPs) were surveyed in urban soils of Yinchuan, China. The median levels of summation Sigma HCHs and summation Sigma DDTs were 0.852 and 2.24 ng/g, respectively, which suggested little risk for ecological environment and human health in the study area. Both chiral alpha-HCH and o,p'-DDT displayed the non-racemic signatures in all samples. The isomer ratios of summation Sigma HCHs and summation Sigma DDTs combined with enantiomer fractions (EFs) of alpha-HCH and o,p'-DDT, suggested that contamination source of HCHs derived from historical HCHs (including technical HCHs and Lindane) and that of DDTs originated from old source with the usage of mixed technical DDTs and dicofol.

Novel motif is capable of determining CCR and CCR-like proteins based on the divergence of CCRs in plants.

Cinnamoyl-coenzyme A reductases (CCRs) have been reported as key enzymes involved in monolignol biosynthesis. In this study, a motif-aware workflow based on a new signature motif effectively distinguished CCRs from CCR-like proteins. The divergence of CCRs and CCR-like sequences in Populus tomentosa Carr, Panicum virgatum L, Oryza sativa L and Selaginella moellendorffii Hieron suggests that NWYCY is not efficient for CCR recognition. The novel motif H202(X)2K205 (CCR-SBM or CCR substrate binding motif) was introduced to distinguish between CCRs and CCR-like proteins. The site-directed mutant R205K in Os(I)CCR-like and H202 in PtoCCR7 resulted in the rescue and loss of activity, respectively, further validating the fact that CCR-SBM is critical for maintaining CCR activity. The molecular docking using feruloyl-cinnamoyl-coenzyme A (CoA) as the ligand and binary PhCCR-NADP structures as receptors indicated an interaction between H202 and K205 with CoA moiety. The genuine CCRs and CCR-like proteins from several angiosperms and gymnosperms were screened using a motif-aware workflow and were validated using a biochemical assay. Our results suggest that the motif-aware workflow is efficient and effective for the identification of CCRs and CCR-like proteins in land plants and can be used as a more accurate way of identifying genuine CCRs among land plants.

Unraveling the impact of Pto4CL1 regulation on the cell wall components and wood properties of perennial transgenic Populus tomentosa.

Cell wall components and structure impact the physical and mechanical properties of plants, thereby affecting wood applications. Lignin is the most abundant biopolymer after cellulose in the wood cell wall and can be modified by certain lignin biosynthesis enzymes. 4-Coumarate: coenzyme A ligase(4CL) is an important lignin biosynthesis enzyme. To demonstrate the impact of the regulation of Pto4CL1 from poplar on wood properties, we analyzed the composition and anatomy of 5-year-old Pto4CL1-modified poplar cell walls, assessing the density, strength, volume shrinkage, and impact toughness of the transgenic trees. These results showed that the up-regulation of Pto4CL1 increased the lignin content to 46.65% from 33.11% in the control plants, while hydrophilic polysaccharides such as cellulose, hemi-cellulose, and pectin decreased. In contrast, the down-regulation of Pto4CL1 resulted in a reduction in lignin content to 27.39%, and the content of cellulose and hemi-cellulose showed compensatory variation. Raman spectroscopy showed that the change in lignin in the transgenic events was embodied in the deposition and concentration of lignin in the secondary cell wall. Moreover, the increased lignin content caused significantly increased wood strength and slightly increased wood density. In contrast, a reduction in lignin content resulted in a significant decrease in wood strength and a slight decrease in wood density. However, the Pto4CL1-modified trees had similar stiffness to the control group. We also found a significant decrease in volume shrinkage and increase in impact toughness in the low-lignin events. These results indicate that Pto4CL1 regulation alters the chemical composition of plant cell walls and these changes affect the physical and mechanical properties of the wood.

Contamination of soils with organochlorine pesticides in urban parks in Beijing, China.

Urban parks are an integral component of healthy urban living. Since they are frequently visited, an understanding of the environmental quality of these urban facilities is crucial. Here, a study was conducted on the contamination of soils in the parks of Beijing. Organochlorine pesticides (OCPs), which have the potential to cause endocrine disturbances, were considered study objectives. Hexachlorocyclohexanes (HCHs) were found at concentrations of 0.2490-197.0 ng g(-1) and dichlorodiphenyltrichloroethanes (DDTs) were found at concentrations of 5.942-1039 ng g(-1) in the soils investigated. The preliminary pollution assessment indicated that DDTs have caused high pollution levels in the soils of some parks. Analysis of the sources of contamination showed that HCHs in the soils were derived from an old mixed source of technical HCHs and lindane and that DDTs, which were suspected to have recent application to the soils at some sites, were derived mainly from a mixture of technical DDTs and dicofol containing DDT impurities. An independent sample t-test proved that pesticides containing DDTs had been used in large amounts in the soils of parks before 1983 (p<0.05) and that the levels of DDTs in the soils of parks administered by the Beijing municipal government were significantly higher than the levels in those administered by the district government (p<0.05). However, the main difference in this situation needs to be further studied. This study suggested that open spaces like urban parks were not as sound as was expected and that there was potential for exposure of visitors/workers in the parks to organochlorine pesticides.

Cloning, expression, crystallization and crystallographic analysis of CouR from Rhodopseudomonas palustris.

CouR from Rhodopseudomonas palustris is a member of the MarR transcriptional regulator family. It regulates the expression of CouA and CouB, enzymes that are involved in the degradation of p-coumarate. In vivo, CouR binds to a DNA fragment containing the couAB promoter and suppresses the expression of CouA and CouB, while binding of p-coumaroyl-CoA attenuates its affinity towards DNA and activates the expression of CouA and CouB. Here, the crystallization and X-ray diffraction analyses of CouR alone and in complex with p-coumaroyl-CoA are reported. Apo and ligand-complexed CouR crystals diffracted to 2.5 and 3.3 Å resolution, respectively. The crystals of apo CouR belonged to space group P22121, with unit-cell parameters a = 62.78, b = 76.15, c = 87.38 Å, whereas the crystals of the CouR-ligand complex belonged to space group P212121, with unit-cell parameters a = 61.37, b = 69.82, c = 70.32 Å. The crystals were predicted to contain two CouR molecules or CouR-ligand complexes per asymmetric unit.

[Review on plant gene promoters].

Promoters are the important regulation factors/elements in gene expression. In this paper, the structure and function of promoters are analyzed and reviewed. Plant gene promoters are classified into constitutive promoters, inducible promoters, tissue (spatial) and developmental (temporary) specific promoters. The bi-directional promoters existed in nature and reconstructed artificially by some strategies are introduced and their applications in plant genetic engineering are prospected.

[Expression and clinical significance of HBsAg and HBcAg in hepatocytes in chronic hepatitis B].

OBJECTIVE: To study the expression of HBsAg and HBcAg in hepatocytes in CHB patients, and analyze the correlation among the expression of HBsAg and HBcAg, the quantity of HBV DNA in serum, the pathology of liver tissue and the clinical manifestation. METHODS: Quantitative polymerase chain reaction was used to assay the quantity of HBV DNA in serum in 351 CHB patients. Furthermore pathological diagnosis was performed using liver biopsy to assay the expression of HBsAg and HBcAg in hepatocytes by an immunohistochemical staining technique. RESULTS: The positive expression rate of HBsAg and HBcAg in hepatocytes was 92.3% and 76.9% respectively. Cytoplasm-membrane HBcAg expression type (75.6%) was observed in the CHB with more active inflammation, while Nucleus HBcAg expression type (24.4%) was observed in the CHB with more sedative one (P < 0.0001). The expression of HBsAg was correlated with the quantity of HBV DNA in serum (rp = 0.24, P = 0.0129), while inversely correlated with the inflammation and the fibrillation of liver tissue (rp = -0.22, P = 0.0279; rp = -0.23, P = 0.0186). The expression of HBcAg was correlated with the quantity of HBV DNA in serum (rp = 0.52, P < 0.0001), while was inversely correlated with the inflammation and the fibrosis of liver (rp = -0.33, P < 0.0001; rp = -0.34, P < 0.0001). CONCLUSION: Cytoplasm-membrane HBcAg expression type was observed in the CHB with more active inflammation, while Nucleus HBcAg expression type was observed in the CHB with mild change. In the immunopathogenesis of the liver damage in CHB, HBcAg might be a main target antigen. HBsAg might be a sensitive index to screen HBV infection; HBcAg might probably be a reliable index to evaluate the replication of HBV

Peroxidation due to cryoprotectant treatment is a vital factor for cell survival in Arabidopsis cryopreservation.

Cryopreservation can be a safe and cost-effective tool for the long-term storage of plant germplasm. In Arabidopsis, the ability to recover from cryogenic treatment was lost as growth progressed. Growth could be restored in 48-h seedlings, whereas 72-h seedlings died after cryogenic treatment. Why seedling age and survival are negatively correlated is an interesting issue. A comparative transcriptomics was performed to screen differentially expressed genes between 48- and 72-h seedlings after exposure to cryoprotectant. Among differentially expressed genes, oxidative stress response genes played important roles in cryoprotectant treatment, and peroxidation was a key factor related to cell survival. Seedlings underwent more peroxidation at 72-h than at 48-h. A comprehensive analysis indicated that peroxidation injured membrane systems leading to photophosphorylation and oxidative phosphorylation damage. Furthermore, the apoptosis-like events were found in cryogenic treatment of Arabidopsis seedlings. 48- and 72-h seedlings underwent different degrees of membrane lipid peroxidation during cryoprotectant treatment, and reducing the injury of oxidative stress was an important factor to successful cryopreservation. This study provided a novel insight of genetic regulatory mechanisms in cryopreservation, and established an excellent model to test and evaluate the effect of exogenous antioxidants and conventional cryoprotectants in plant cryopreservation.

Effects of Panax notoginseng saponins on proliferation and differentiation of rat hippocampal neural stem cells.

We aimed to investigate the effects of Panax notoginseng saponins (PNS) on proliferation, differentiation and self-renewal of rat hippocampal neural stem cells (NSCs) in vitro. Rat hippocampal NSCs were isolated from post-natal day 1 (P1) rats and cultured in a serum-free medium. The neurospheres were identified by the expressions of nestin, class III ß-tublin (Tuj-1) and glial fibrillary acid protein (GFAP). The cells were given PNS and subjected to oxygen glucose deprivation (OGD) as an in vitro model of brain ischemia reperfusion. The proliferation of NSCs was determined by MTT colorimetry, nestin/BrdU immunofluorescent double-labeling and RT-PCR. Differentiation of NSCs was assessed by immunofluorescent double-labeling of nestin/BrdU, nestin/vimentin, and nestin/Tuj-1. The primary cells and the first two passages of cells formed certain amount of neurospheres, the cells derived from a single cell clone also formed neurospheres. Nestin, BrdU, GFAP and Tuj-1-positive cells appeared in those neurospheres. Compared to the control group, PNS significantly promoted NSC proliferation and the expression of nestin/BrdU, and also enhanced Tuj-1, vimentin, and nestin mRNA expressions in hippocampal NSCs. PNS significantly increased area density, optical density and numbers of nestin/BrdU, nestin/vimentin, and nestin/Tuj-1 positive cells following OGD. These results indicate that PNS can promote proliferation and differentiation of hippocampus NCSs in vitro after OGD, suggesting its potential benefits on neurogenesis and neuroregeneration in brain ischemic injury.

Heterologous expression and characterization of a proxidomal ascorbate peroxidase from Populus tomentosa.

The present study reported for the first time, cloning, expression and characteristics of a Proxidomal APX gene (PpAPX) from Populus tomentosa. The PpAPX gene encodes a protein of 287 amino acid residues with a calculated molecular mass of 31.58 kDa. The over-expressed recombinant PpAPX protein showed high activity towards the substrates ascorbate aicd (ASA) and H(2)O(2). At fixed ASA concentrations, the K (m) and V (max) values were 0.12 +/- 0.01 mM and 23.4 +/- 4.2 mmol/min mg for H(2)O(2). And at fixed H(2)O(2) concentrations, the K (m) and V (max) values were 0.53 +/- 0.04 mM and 20.0 +/- 2.3 mmol/min mg for ASA.

[Effects of Dendrolimus punctatus feeding and methyl jasmonate (MeJA)--or terpenes fumigation on abscisic acid and jasmonic acid contents in Pinus massoniana seedling needles].

Abscisic acid (ABA) and Jasmonic acid (JA) play an important role in inducing the stress-resistance of plants. In this study, parts of the needles on a ring of Pinus massoniana seedling shoots were subjected to 4 hours Dendrolimus punctatus feeding or 4 hours fumigation with 10 micromol x L(-1) of methyl jasmonate (MeJA) or terpenes, and the ABA and JA contents in treated needles, untreated neighboring sister needles, and untreated needles above and below the ring were determined by GC/MS. An obvious increase of ABA and JA contents was observed in all of the needles, whether they were treated or not, illustrating that ABA and JA were the vital signaling molecules in the wound signal transduction pathway, and participated in the formation of systematic resistance of P. massoniana seedlings.

[Prokaryotic expression of DNA recombinase FLP and its purification with enzymatic activity].

DNA recombinase FLP gene exists on the 2 micro plasmid of Saccharomyces cerevisiae. Recombinase FLP could recognize an FRT site composed of 34bp and function the sequences for exchange, recombination, deletion and reversion between the two orientated FRT sites. These functions are highly recognized by molecular biologists and biotechnology engineers for theoretic and applicable technology studies. This work constructed a prokaryotic over-expressed vector harboring FLP gene nominated as pQE30-flpe and established its over-expression culture system in which recombinase FLP could be efficiently expressed in E. coli strain M15. Purification procedures for high purity and active FLP are established through combination of ammonium sulfate precipitation with a 0.5-1.0 mL micro-column technique of Ni affinity chromatography with gradient elution. To verify the recombinase activity of purified FLP, substrate vectors, sequence donor vector (pUC18-FRT-gfp-FRT) and sequence accepting vector (pET30a-FRT) are constructed with various number, orientation of FRTs harboring the GFP gene for the expression of visible assay of the functions of recombination, exchange and deletion. Results showed that the system not only over expressed recombinase FLP in prokaryotic E. coli, but also efficiently purified the enzyme with a higher activity of the function of recombination, exchange and deletion. The system and the method are easily implemented and feasibly manipulated for theoretic study and biotechnology application.

Stable and specific expression of 4-coumarate:coenzyme A ligase gene (4CL1) driven by the xylem-specific Pto4CL1 promoter in the transgenic tobacco.

The ability of 4-coumarate:coenzyme A ligase promoter from Populus tomentosa (Pto4CL1p) to drive expression of the GUS reporter gene and 4-coumarate:coenzyme A ligase gene in tobacco has been studied using transgenic plants produced by Agrobacterium-mediated transformation. Intense GUS histochemical staining was detected in the xylem of stem in transgenic tobacco plants carrying the 1140 bp Pto4CL1p promoter. To further investigate the regulation function of the tissue-specific expression promoter, Pto4CL1p, a binary vector containing Pto4CL1p promoter fused with 4CL1 gene was transferred into tobacco. The activity of the 4CL1 enzyme doubled in the stems of transgenic tobacco but did not increase in the leaves. The content of lignin was increased 25% in the stem but there was no increase in the leaves of transgenic tobacco.