PubMed Health⌕ Search

Biomedical subjects

Z H Ye

Publications and source records attributed to Z H Ye.

At least 19 recordsLinked to original sources
PubMed2000

Ectopic deposition of lignin in the pith of stems of two Arabidopsis mutants.

The biosynthesis of lignin in vascular plants is regulated both developmentally and environmentally. In the inflorescence stems of Arabidopsis, lignin is mainly deposited in the walls of xylem cells and interfascicular fiber cells during normal plant growth and development. The mechanisms controlling the spatial deposition of lignin remain unknown. By screening ethyl methanesulfonate-mutagenized populations of Arabidopsis, we have isolated two allelic elp1 (ectopic deposition of lignin in pith) mutants with altered lignin deposition patterns. In elp1 stems, lignin was ectopically deposited in the walls of pith parenchyma cells in addition to its normal deposition in the walls of xylem and fiber cells. Lignin appeared to be deposited in patches of parenchyma cells in the pith of both young and mature elp1 stems. The ectopic deposition of lignin in the pith of elp1 stems was accompanied by an increase in the activities of enzymes in the lignin biosynthetic pathway and with the ectopic expression of caffeoyl coenzyme A O-methyltransferase in pith cells. These results indicate that the ELP1 locus is involved in the repression of the lignin biosynthetic pathway in the pith. Isolation of the elp1 mutants provides a novel means with which to study the molecular mechanisms underlying the spatial control of lignification.

Arabidopsis↗
PubMed2000

Essential role of caffeoyl coenzyme A O-methyltransferase in lignin biosynthesis in woody poplar plants.

Caffeoyl coenzyme A O-methyltransferase (CCoAOMT) has recently been shown to participate in lignin biosynthesis in herbacious tobacco plants. Here, we demonstrate that CCoAOMT is essential in lignin biosynthesis in woody poplar (Populus tremula x Populus alba) plants. In poplar stems, CCoAOMT was found to be expressed in all lignifying cells including vessel elements and fibers as well as in xylem ray parenchyma cells. Repression of CCoAOMT expression by the antisense approach in transgenic poplar plants caused a significant decrease in total lignin content as detected by both Klason lignin assay and Fourier-transform infrared spectroscopy. The reduction in lignin content was the result of a decrease in both guaiacyl and syringyl lignins as determined by in-source pyrolysis mass spectrometry. Fourier-transform infrared spectroscopy indicated that the reduction in lignin content resulted in a less condensed and less cross-linked lignin structure in wood. Repression of CCoAOMT expression also led to coloration of wood and an elevation of wall-bound p-hydroxybenzoic acid. Taken together, these results indicate that CCoAOMT plays a dominant role in the methylation of the 3-hydroxyl group of caffeoyl CoA, and the CCoAOMT-mediated methylation reaction is essential to channel substrates for 5-methoxylation of hydroxycinnamates. They also suggest that antisense repression of CCoAOMT is an efficient means for genetic engineering of trees with low lignin content.

Base Sequence↗
PubMed2000

[Genetic analysis on flowering and boll setting in upland cotton (Gossypium hirsutum L.). III. Genetic behavior at different developing stages].

An additive-dominant genetic model with genotype by environment interaction was employed to analyze the genetic behavior of flowering and fruiting at different development stages, with 2-year data from 4 x 4 diallel crosses. The results of variance analysis indicated that flowering and fruiting behaviors were mainly controlled by dominant effects at early period, but by additive effects later on. Compared with genetic main effects, GE interaction effects playeda minor role on the flowering and fruiting behavior. The analysis of covariance between average flower number, boll number at different development stages and total number of bolls showed that there were significant positive dominant correlation and negative or zero additive correlation before August 1st, but having the opposite results afterward. Interaction correlation existed during the whole period. It was found, by further analysis of conditional variances, that different development stages have diverse gene action intensity. The last ten days of July and the first-middle ten days of August had the highest gene action level. Time interval of investigation played a great role on exploring the law of gene action during the flowering and fruiting period; when selecting the time interval of investigation, it is necessary to contemplate the purpose of the experiment, environmental condition, investigating traits and developing period simultaneously.

Gossypium↗
PubMed1999

Transformation of the collateral vascular bundles into amphivasal vascular bundles in an Arabidopsis mutant.

Arabidopsis inflorescence stems develop a vascular pattern similar to that found in most dicots. The arrangement of vascular tissues within the bundle is collateral, and vascular bundles in the stele are arranged in a ring. Although auxin has been shown to be an inducer of vascular differentiation, little is known about the molecular mechanisms controlling vascular pattern formation. By screening ethyl methanesufonate-mutagenized populations of Arabidopsis, we have isolated an avb1 (amphivasal vascular bundle) mutant with a novel vascular pattern. Unlike the collateral vascular bundles seen in the wild-type stems, the vascular bundles in the avb1 stems were similar to amphivasal bundles, i.e. the xylem completely surrounded the phloem. Furthermore, branching vascular bundles in the avb1 stems abnormally penetrated into the pith, which resulted in a disruption in the ring-like arrangement of vascular bundles in the stele. The avb1 mutation did not affect leaf venation pattern and root vascular organization. Auxin polar transport assay indicated that the avb1 mutation did not disrupt the auxin polar transport activity in inflorescence stems. The avb1 mutation also exhibited pleiotropic phenotypes, including curled stems and extra cauline branches. Genetic analysis indicated that the avb1 mutation was monogenic and partially dominant. The avb1 locus was mapped to a region between markers mi69 and ASB2, which is covered by a yeast artificial chromosome clone, CIC9E2, on chromosome 5. Isolation of the avb1 mutant provides a novel means to study the evolutionary mechanisms controlling the arrangement of vascular tissues within the bundle, as well as the mechanisms controlling the arrangement of vascular bundles in the stele.

Arabidopsis↗
PubMed1999

IFL1, a gene regulating interfascicular fiber differentiation in Arabidopsis, encodes a homeodomain-leucine zipper protein.

Arabidopsis inflorescence stems develop extraxylary fibers at specific sites in interfascicular regions. The spatial specification of interfascicular fiber differentiation is regulated by the INTERFASCICULAR FIBERLESS1 (IFL1) gene because mutation of that gene abolishes the formation of normal interfascicular fibers in Arabidopsis stems. To understand further the role of IFL1 in the specification of fiber differentiation, we cloned the IFL1 gene by using a positional cloning strategy. Sequence analysis showed that the IFL1 gene encodes a transcription factor that has the same features as a family of homeodomain-leucine zipper (HD-ZIP) proteins found only in plants. The predicted IFL1 protein is composed of three distinct domains, including a 60-amino acid HD at the N terminus followed by a 28-amino acid ZIP motif and a 724-amino acid C-terminal region. A nuclear targeting assay showed that IFL1 is able to direct a beta-glucuronidase fusion protein into the nucleus, which is consistent with IFL1's presumed function as a transcription factor. Gene expression analysis demonstrated that the IFL1 gene is expressed in the interfascicular regions in which fibers differentiate, which is consistent with its role in the control of interfascicular fiber differentiation. Furthermore, the IFL1 gene was shown to be expressed in the vascular regions, indicating its possible role in the regulation of vascular tissue formation. This possibility is supported by the observation that differentiation of both xylary fibers and vessel elements is altered in the vascular bundles of ifl1 mutants. Our results provide direct evidence that an HD-ZIP protein plays a role in the spatial control of fiber differentiation.

Amino Acid Sequence↗
PubMed1997

Association of caffeoyl coenzyme A 3-O-methyltransferase expression with lignifying tissues in several dicot plants.

Caffeoyl coenzyme A 3-O-methyltransferase (CCoAOMT) was previously shown to be associated with lignification in both in vitro tracheary elements (TEs) and organs of zinnia (Zinnia elegans). However, it is not known whether this is a general pattern in dicot plants. To address this question, polyclonal antibodies against zinnia recombinant CCoAOMT fusion protein were raiseed and used for immunolocalization in several dicot plants. The antibodies predominantly recognized a protein band with a molecular mass of 28 kD on western analysis of tissue extracts from zinnia, forsythia (Forsythia suspensa), tobacco (Nicotiana tabacum), alfalfa (Medicago sativa), and soybean (Glycine max). Western analyses showed that the accumulation of CCoAOMT protein was closely correlated with lignification in in vitro TEs of zinnia. Immunolocalization results showed that CCoAOMT was localized in developing TEs of young zinnia stems and in TEs, xylem fibers, and phloem fibers of old stems. CCoAOMT was also found to be specifically associated with all lignifying tissues, including TEs, xylem fibers, and phloem fibers in stems of forsythia, tobacco, alfalfa, soybean, and tomato (Lycopersicon esculentum). The presence of CCoAOMT was evident in xylem ray parenchyma cells of forsythia, tobacco, and tomato. In forsythia and alfalfa, pith parenchyma cells next to the vascular cylinder were lignified. Accordingly, marked accumulation of CCoAOMT in these cells was observed. Taken together, these results showed a close association of CCoAOMT expression with lignification in dicot plants. This supports the hypothesis that the CCoAOMT-mediated methylation branch is a general one in lignin biosynthesis during normal growth and development in dicot plants.

Blotting, Western↗
PubMed1997

Disruption of interfascicular fiber differentiation in an Arabidopsis mutant.

Arabidopsis develops interfascicular fibers in stems for needed support of shoots. To study the molecular mechanisms controlling fiber differentiation, we isolated an interfascicular fiber mutant (ifl1) by screening ethyl methanesulfonate-mutagenized Arabidopsis populations. This mutant lacks normal interfascicular fibers in stems. Interestingly, some interfascicular cells were sclerified in the upper parts but not in the basal parts of the ifl1 stems. These sclerified cells were differentiated at a position different from that of interfascicular fibers in the wild type. Lack of interfascicular fibers correlated with a dramatic change of stem strength. Stems of the mutant could not stand erect and were easily broken by bending. Quantitative measurement showed that it took approximately six times less force to break basal stems of the mutant than of the wild type. In addition, noticeable morphological changes were associated with the mutant, including long stems, dark green leaves with delayed senescence, and reduced numbers of cauline leaves and branches. Genetic analysis showed that the ifl1 mutation was monogenic and recessive. The ifl1 locus was mapped to a region between the 17C2 and 7H9L markers on chromosome 5. Isolation of the ifl1 mutant provides a novel means to study the genetic control of fiber differentiation.

Arabidopsis↗
PubMed1996

Isolation and characterization of cDNAs encoding xylogenesis-associated and wounding-induced ribonucleases in Zinnia elegans.

The study of plant ribonuclease (RNase) functions is complicated by a complex profile of RNase activities detected in tissues. Thus, isolation of individual RNase genes will be desirable for the further understanding of function of each RNase. Here, we describe the isolation of cDNAs encoding two RNases, ZRNaseI and ZRNaseII, in differentiating tracheary elements (TEs) induced from isolated mesophyll cells of Zinnia elegans. Both the ZRNaseI and ZRNaseII exhibit putative secretion signal sequences at the amino-terminal ends with predicted molecular masses of 24 247 Da and 22 448 Da as mature proteins, respectively. DNA gel blot analysis showed that both RNases in Zinnia appear to be encoded by a small gene family. RNA gel blot analysis showed that the expression of the ZRNaseI gene was associated with the late stage of in vitro TE differentiation, whereas the ZRNaseII gene was mainly induced in response to stress. Neither RNase gene was induced in response to phosphate starvation, or to H2O2 challenge in the cultured mesophyll cells, or to senescence in the leaves. In young leaves, the ZRNaseI gene was not induced in response to wounding. But the ZRNaseII gene was markedly induced by 6 h after wounding. Tissue print hybridization showed that the expression of the ZRNaseI gene was preferentially associated with the differentiation TEs in Zinnia stems, while the ZRNaseII mRNA was not detected in unwounded Zinnia organs. Taken together, the results indicated that the ZRNaseI gene is expressed during the process of xylogenesis both in vitro and in the plant, whereas the ZRNaseII gene is predominantly induced in response to wounding. The identification of these RNase genes provides molecular tools for the dissection of the process of autolysis during xylogenesis, and for the dissection of the role of RNase in wounding response.

Amino Acid Sequence↗
PubMed1996

Induction of cysteine and serine proteases during xylogenesis in Zinnia elegans.

The terminal process of xylogenesis, autolysis, is essential for the formulation of a tubular system for conduction of water and solutes throughout the whole plant. Several hydrolase types are implicated in autolysis responsible for the breakdown of cytoplasm. Here, we characterize p48h-17 cDNA from in vitro tracheary elements (TEs) of Zinnia elegans which encodes a preproprotein similar to papain. The putative mature protein, a cysteine protease, has a molecular mass of 22,699 Da with a pI of 5.7. DNA gel blot analysis indicated that p48h-17 is likely encoded by one or two genes. The p48h-17 mRNA accumulated markedly in in vitro differentiating TEs, whereas it appeared not to be induced in response to senescence and wounding in the leaves or H2O2 challenge in the cultured mesophyll cells. In stems, the expression of the p48h-17 gene was preferentially associated with differentiating xylem. Activity gel assays demonstrated that a cysteine and a serine protease, which had apparent molecular masses of 20 kDa and 60 kDa, respectively, were markedly induced during in vitro TE differentiation. The cysteine protease activity was also preferentially present in the xylem of Zinnia stems. Transient expression of the p48h-17 cDNA in tobacco protoplasts resulted in the production of a 20 kDa cysteine protease. Taken together, the results indicate that the p48h-17 gene appears to be preferentially associated with xylogenesis, and both the cysteine and serine proteases might be involved in autolysis during xylogenesis.

Amino Acid Sequence↗
PubMed1995

Differential expression of two O-methyltransferases in lignin biosynthesis in Zinnia elegans.

Caffeic acid 3-O-methyltransferase (CAOMT) and caffeoyl-coenzyme A 3-O-methyltransferase (CCoAOMT) are involved in different methylation pathways in lignin biosynthesis. We previously showed that only the CCoAOMT was markedly induced during lignification in in vitro differentiating tracheary elements (TEs) of Zinnia elegans. To further examine the expression patterns of CAOMT in lignification, we isolated a cDNA clone for Zinnia CAOMT. RNA gel blot analysis showed that the expression of the CAOMT gene did not correlate well with lignification during in vitro TE differentiation from Zinnia-isolated mesophyll cells. Tissue-print hybridization showed that, in the young internodes, the CAOMT mRNA signal was much more evident in phloem fibers than in xylem, whereas the CCoAOMT mRNA signal was predominantly present in differentiating xylem regions. In the older internode, both the CAOMT and CCoAOMT mRNAs markedly accumulated in phloem fibers and differentiating xylem regions. Immunocytochemical localization showed that the CAOMT protein staining was much more evident in phloem fibers and xylem fibers than in xylem TEs. These results indicate that the expression of these two O-methyltransferases is differentially regulated during lignification in different cell types in Zinnia. We suggest that all the intermediates in the CAOMT-mediated methylation pathway might become substrates for the CCoAOMT-mediated methylation pathway after coenzyme A ligation when these two pathways occur in the same lignifying cell types.

Cells, Cultured↗
PubMed1994

An alternative methylation pathway in lignin biosynthesis in Zinnia.

S-Adenosyl-L-methionine:trans-caffeoyl-coenzyme A 3-O-methyltransferase (CCoAOMT) is implicated in disease resistant response, but whether it is involved in lignin biosynthesis is not known. We isolated a cDNA clone for CCoAOMT in differentiating tracheary elements (TEs) induced from Zinnia-isolated mesophyll cells. RNA gel blot analysis showed that the expression of the CCoAOMT gene was markedly induced during TE differentiation from the isolated mesophyll cells. Tissue print hybridization showed that the expression of the CCoAOMT gene is temporally and spatially regulated and that it is associated with lignification in xylem and in phloem fibers in Zinnia organs. Both CCoAOMT and caffeic acid O-methyltransferase (COMT) activities increased when the isolated Zinnia mesophyll cells were cultured, whereas only CCoAOMT activity was markedly enhanced during lignification in the in vitro-differentiating TEs. The induction pattern of the OMT activity using 5-hydroxyferuloyl CoA as substrate during lignification was the same as that using caffeoyl CoA. Taken together, the results indicate that CCoAOMT is associated with lignification during xylogenesis both in vitro and in the plant, whereas COMT is only involved in a stress response in vitro. We propose that CCoAOMT is involved in an alternative methylation pathway in lignin biosynthesis. In Zinnia in vitro-differentiating TEs, the CCoAOMT mediated methylation pathway is dominant.

Acyl Coenzyme A↗
PubMed1994

ralGDS family members interact with the effector loop of ras p21.

Using a yeast two-hybrid system, we identified a novel protein which interacts with ras p21. This protein shares 69% amino acid homology with ral guanine nucleotide dissociation stimulator (ralGDS), a GDP/GTP exchange protein for ral p24. We designated this protein RGL, for ralGDS-like. Using the yeast two-hybrid system, we found that an effector loop mutant of ras p21 was defective in interacting with the ras p21-interacting domain of RGL, suggesting that this domain binds to ras p21 through the effector loop of ras p21. Since ralGDS contained a region highly homologous with the ras p21-interacting domain of RGL, we examined whether ralGDS could interact with ras p21. In the yeast two-hybrid system, ralGDS failed to interact with an effector loop mutant of ras p21. In insect cells, ralGDS made a complex with v-ras p21 but not with a dominant negative mutant of ras p21. ralGDS interacted with the GTP-bound form of ras p21 but not with the GDP-bound form in vitro. ralGDS inhibited both the GTPase-activating activity of the neurofibromatosis gene product (NF1) for ras p21 and the interaction of Raf with ras p21 in vitro. These results demonstrate that ralGDS specifically interacts with the active form of ras p21 and that ralGDS can compete with NF1 and Raf for binding to the effector loop of ras p21. Therefore, ralGDS family members may be effector proteins of ras p21 or may inhibit interactions between ras p21 and its effectors.

Amino Acid Sequence↗
PubMed1993

Physical and functional characterization of the cloned lys1+ gene of Schizosaccharomyces pombe.

The alpha-aminoadipate pathway for the biosynthesis of lysine is present in yeast and other higher fungi. The lys2 and lys5 mutants of Saccharomyces cerevisiae as well as the lys1- and lys7-mutants of Schizosacharomyces pombe are blocked at the alpha-aminoadipate reductase step of this pathway. The cloned lys1+ gene in the plasmid pLYS1 isolated from a S. pombe genomic library complemented lys1-mutant of S. pombe. The cloned LYS2 gene in the plasmid YEp620 and the LYS5 gene in the plasmid pSC5 of S. cerevisiae exhibited heterologous complementation of lys1- and lys7-mutants, respectively, of S. pombe. The homologous lys1+ transformed cells exhibited five fold higher alpha-aminoadipate reductase activity while the heterologous lys1+ and lys7+ transformed cells exhibited much less activity than the wild type cells. The DNA insert of the plasmid pLYS1 was determined to be 16.7 kb long and the lys1+ gene has been subcloned within a 9.1 kb Clal-Clal DNA insert of the recombinant plasmids pLYS1B and pLYS1C. The restriction pattern for 12 enzymes of the 9.1 kb DNA insert, (Apal, Aval, BamHI, Clal, EcoRI, EcoRV, HindIII, Hpal, Pstl, Pvull, Sphl, and Xbal), exhibited no obvious similarity to that of the LYS2 gene of S. cerevisiae. A 1.7 kb EcoRI-HindIII DNA fragment of pLYS1B and pLYS1C complemented the lys1-131 mutation in an integrative transformation. Although the lys1+ gene of S. pombe is isofunctional to the LYS2 gene of S. cerevisiae, the restriction sites, and expression of these two genes exhibited considerable divergence.

Aldehyde Oxidoreductases↗
PubMed1993

Pharmacokinetic study of RU 486 and its metabolites after oral administration of single doses to pregnant and non-pregnant women.

RU 486 and three of its metabolites (RU 42633-monodemethyl, RU 42848-didemethyl, and RU 42698-hydroxymetabolite) were determined by HPLC in plasma from nine non-pregnant and 36 pregnant women. Each non-pregnant subject took an oral dose of RU 486 (25, 100, 400 and 600 mg consecutively) once per menstrual cycle. Six of the nine women also received a dose of 200 mg. The 36 pregnant women were randomized into four groups which were given a single dose of 25, 100, 400 or 600 mg RU 486. Blood samples were taken up to 120 h after dosing. Peak concentrations of RU 486 occurred on most occasions within 2 h. Plasma concentrations at 1 h and at 24 h increased in proportion to log dose. There was a wide variability (up to ten-fold) in the pharmacokinetic parameters within each dose group. Plasma concentrations of RU 42633 were similar to those of RU 486 but concentrations of RU 42848 and RU 42698 were much lower. As with RU 486, the plasma concentrations of the metabolites were maintained at high levels for up to 48-72 h after dosing. The findings were consistent with a rapid metabolism of RU 486 to RU 42633; removal of the second methyl group leading to RU 42698 occurred much more slowly and to a much less extent than removal of the first. There appeared to be no significant differences between the non-pregnant and pregnant women in either the plasma concentrations or pharmacokinetic parameters of RU 486 and its metabolites.

Administration, Oral↗
PubMed1993

Gene expression patterns associated with in vitro tracheary element formation in isolated single mesophyll cells of Zinnia elegans.

Tracheary element formation from isolated Zinnia leaf mesophyll cells is an excellent system for the dissection of patterned secondary cell wall thickening and lignification. We used mRNAs from cells cultured for 48 h in the induction medium to isolate differentially regulated genes. Thirteen unique cDNA clones were isolated using a subtractive hybridization method. These clones can be divided into three distinct groups according to their characteristic gene expression in different media. The first group includes those genes whose expression is induced in the basal medium without 1-naphthaleneacetic acid (NAA) and benzyladenine; this indicates that the expression of these genes is regulated by chemical and physical factors other than these hormones. Three of these clones, p48h-229, p48h-114, and p48h-102, show significant homology to a pathogenesis-related protein II, a serine proteinase inhibitor, and a sunflower anther-specific proline-rich protein, respectively. The second group includes those genes whose expression is mainly NAA induced. One of these clones, p48h-10, shows high protein sequence homology to a barley aleurone-specific cDNA, B11E. The p48h-10-encoded protein shares some common characteristics of plant nonspecific lipid transfer proteins (low molecular weight, the secretion signal peptide, eight conserved cysteine residues, and a basic protein), although no significant protein sequence homology is found between p48-10 and other plant nonspecific lipid transfer proteins. The third group includes those genes whose expression is induced primarily in the induction medium; this indicates that the expression of these genes is closely associated with the process of tracheary element formation. Two of these clones, p48h-107 and p48h-17, show high homology to adenylate kinase and papaya proteinase I, respectively. The possible roles of these differentiation-specific genes during tracheary element formation are discussed.

Adenine↗
PubMed1993

Cloning, sequencing, and genetic characterization of regulatory genes, rinA and rinB, required for the activation of staphylococcal phage phi 11 int expression.

The int gene of staphylococcal bacteriophage phi 11 is the only viral gene responsible for the integrative recombination of phi 11. To study the regulation of int gene expression, we determined the 5' end of the transcript by S1 mapping. The presumed promoter is located just 22 nucleotides upstream of the int open reading frame in a region which is conserved between phi 11 and a closely related staphylococcal phage, L54a. To clone the possible regulatory gene, a vector which contained the reporter gene, xylE, of Pseudomonas putida under the control of the phi 11 int promoter was constructed. Subsequently, a 2-kb DNA fragment from the phi 11 genome, which mapped distal to the int gene, was shown to increase the XylE activity from the int promoter. Sequencing and subsequent deletion analysis of the 2-kb fragment revealed that two phi 11 regulatory genes, rinA and rinB, were both required to activate expression of the int gene. Northern (RNA) analysis suggested that the activation was, at least partly, at the transcriptional level. In addition, one of these regulatory genes, rinA, was capable of activating L54a int gene transcription.

Amino Acid Sequence↗