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H Kende

Publications and source records attributed to H Kende.

At least 37 records · Page 2Linked to original sources
PubMed1997

Expression of expansin genes is correlated with growth in deepwater rice.

Expansins are a family of proteins that catalyze long-term extension of isolated cell walls. Previously, two expansin proteins have been isolated from internodes of deepwater rice, and three rice expansin genes, Os-EXP1, Os-EXP2, and Os-EXP3, have been identified. We report here on the identification of a fourth rice expansin gene, Os-EXP4, and on the expression pattern of the rice expansin gene family in deepwater rice. Rice expansin genes show organ-specific differential expression in the coleoptile, root, leaf, and internode. In these organs, there is increased expression of Os-EXP1, Os-EXP3, and Os-EXP4 in developmental regions where elongation occurs. This pattern of gene expression is also correlated with acid-induced in vitro cell wall extensibility. Submergence and treatment with gibberellin, both of which promote rapid internodal elongation, induced accumulation of Os-EXP4 mRNA before the rate of growth started to increase. Our results indicate that the expression of expansin genes in deepwater rice is differentially regulated by developmental, hormonal, and environmental signals and is correlated with cell elongation.

Amino Acid Sequence↗
PubMed1996

Submergence enhances expression of a gene encoding 1-aminocyclopropane-1-carboxylate oxidase in deepwater rice.

Partial submergence greatly stimulates internodal growth in deep water rice (Oryza sativa L.). Previous work has shown that the effect of submergence is, at least in part, mediated by ethylene, which accumulates in the air spaces of submerged internodes. To investigate the expression of the genes encoding ethylene biosynthetic enzymes during accelerated growth of deep water rice, we cloned a 1-aminocyclopropane-1-carboxylate (ACC) oxidase cDNA (OS-ACO1) from internodes of submerged plants and measured the activity of the enzyme in tissue extracts with an improved assay. We found an increase in ACC oxidase mRNA levels and enzyme activity after 4 to 24 h of submergence. Thus, it is likely that ethylene biosynthesis in internodes of deep water rice is controlled, at least in part, at the level of ACC oxidase.

Amino Acid Oxidoreductases↗
PubMed1995

Analysis of Arabidopsis cDNA that shows homology to the tomato E8 cDNA.

The negative regulatory protein of ethylene synthesis in ripening tomato fruit, E8, is structurally related to the enzyme that catalyzes the last step in ethylene synthesis, 1-aminocyclopropane-1-carboxylate (ACC) oxidase, and to a large family of 2-oxoglutarate-dependent dioxygenases (2-ODD). A cDNA with structural homology to the tomato E8 was isolated from a cDNA library of Arabidopsis thaliana. Sequence analysis showed that this cDNA, 2A6, encodes a protein of 361 amino acids. Southern blot analysis indicated that the corresponding gene is unique in the Arabidopsis genome. The level of the 2A6 transcript was not increased by ethylene in siliques of Arabidopsis, as was E8 in tomato fruits, and was also expressed in etiolated seedlings, leaves, stems and flowers. The 2A6 protein shows three domains that are highly conserved among E8, ACC oxidases, and 2-ODDs.

Amino Acid Sequence↗
PubMed1995

Sequential induction of the ethylene biosynthetic enzymes by indole-3-acetic acid in etiolated peas.

Ethylene induced an increase in the accumulation of 1-aminocyclopropane-1-carboxylate (ACC) oxidase transcript level and enzyme activity in the first internode of 5- to 6-day-old etiolated pea (Pisum sativum L.) seedlings. Indole-3-acetic acid (IAA), which stimulates ethylene production by enhancing ACC synthase activity, also caused an increase in ACC oxidase transcript and activity levels. The IAA-induced increase in ACC oxidase mRNA level and enzyme activity was blocked by 2,5-norbornadiene (NBD), a competitive inhibitor of ethylene action. This indicates that IAA induced ACC oxidase through the action of ethylene. The level of ACC synthase mRNA and enzyme activity started to increase less than 1 h after the start of IAA treatment, whereas ACC oxidase activity and transcript levels began to rise after 2 h of IAA treatment. These results indicate that the enzymes of ethylene biosynthesis are sequentially induced after treatment of intact pea seedlings with IAA. The increase in ACC synthase activity leads to the production of ACC, which is converted by the low constitutive level of ACC oxidase activity to ethylene. Through a positive feedback loop, ethylene promotes the accumulation of ACC oxidase mRNA and the increase in ACC oxidase activity.

Amino Acid Oxidoreductases↗
PubMed1995

Identification of a gibberellin-induced gene in deepwater rice using differential display of mRNA.

Differential display of mRNA was employed to identify gibberellin (GA)-regulated genes in deepwater rice. One of the first differentially displayed products identified was shown to be ten-fold induced after start of GA treatment. The sequence of the clone shows complete amino acid identity with histone H3, and its increased mRNA level correlates with the onset of DNA synthesis. We also identified a gene whose expression pattern did not change over the course of treatment with GA and can be used as standard to correct for loading differences on northern blots.

Amino Acid Sequence↗
PubMed1995

Gibberellin promotes histone H1 kinase activity and the expression of cdc2 and cyclin genes during the induction of rapid growth in deepwater rice internodes.

Partial submergence or treatment with either ethylene or gibberellin (GA) promotes rapid internodal growth in deepwater rice (Oryza sativa L.). Earlier work has shown that GA is the immediate hormonal signal for this growth response, which involves induction of the cell cycle at the G2/M phase transition and subsequent enhancement in the rate of DNA synthesis. In all eukaryotes, onset of mitosis is regulated by the p34cdc2/CDC28 protein kinase, whose activity is assayed by in vitro phosphorylation of histone H1. It was found that GA enhanced the activity of p34cdc2/CDC28-like histone H1 kinase in the intercalary meristem of rice internodes. The enzyme activity showed a sharp peak that correlated with a decrease in the population of cells in the G2 phase during the first 4 h of GA treatment but not with changes in DNA synthesis. The level of histone H1 kinase activity increased again when cell division activity in the intercalary meristem is known to be high. The expression of two cdc2 homologs was examined. The mRNA level of one of these, cdc2Os-2, was increased after 1 h of GA treatment, whereas the mRNA level of the other, cdc2Os-1, was not affected. Two cDNAs, cycOs1 and cycOs2, which show high homology to cyclin cDNAs, were cloned from rice. They share 75.1% sequence identity at the amino acid level, and both of them are encoded by mRNAs of 1.6 kb. Expression of the two corresponding cyclin genes was enhanced by GA, and the time course of the induction was compatible with a role for both cyclins in regulating the G2/M phase transition. The cyclins were expressed in the intercalary meristem and the elongation zone of the internode, but the GA-induced increase in transcript levels was restricted to the meristem only. The results support the hypothesis that induction of mitosis by GA is brought about by increased p34cdc2/CDC28 protein kinase activity, which may be the result of transcriptional activation of the cdc2Os-2, cycOs1 and cycOs2 genes.

Amino Acid Sequence↗
PubMed1994

Genes galore: a summary of methods for accessing results from large-scale partial sequencing of anonymous Arabidopsis cDNA clones.

High-throughput automated partial sequencing of anonymous cDNA clones provides a method to survey the repertoire of expressed genes from an organism. Comparison of the coding capacity of these expressed sequence tags (ESTs) with the sequences in the public data bases results in assignment of putative function to a significant proportion of the ESTs. Thus, the more than 13,400 plant ESTs that are currently available provide a new resource that will facilitate progress in many areas of plant biology. These opportunities are illustrated by a description of the results obtained from analysis of 1500 Arabidopsis ESTs from a cDNA library prepared from equal portions of poly(A+) mRNA from etiolated seedlings, roots, leaves, and flowering inflorescences. More than 900 different sequences were represented, 32% of which showed significant nucleotide or deduced amino acid sequences similarity to previously characterized genes or proteins from a wide range of organisms. At least 165 of the clones had significant deduced amino acid sequence homology to proteins or gene products that have not been previously characterized from higher plants. A summary of methods for accessing the information and materials generated by the Arabidopsis cDNA sequencing project is provided.

Amino Acid Sequence↗
PubMed1992

On the role of abscisic Acid and gibberellin in the regulation of growth in rice.

Submergence induces rapid elongation of rice coleoptiles (Oryza sativa L.) and of deepwater rice internodes. This adaptive feature helps rice to grow out of the water and to survive flooding. Earlier, we found that the growth response of submerged deepwater rice plants is mediated by ethylene and gibberellin (GA). Ethylene promotes growth, at least in part, by increasing the responsiveness of the internodal tissue to GA. In the present work, we examined the possibility that increased responsiveness to GA was based on a reduction in endogenous abscisic acid (ABA) levels. Submergence and treatment with ethylene led, within 3 hours, to a 75% reduction in the level of ABA in the intercalary meristem and the growing zone of deepwater rice internodes. The level of GA(1) increased fourfold during the same time period. An interaction between GA and ABA could also be shown by application of the hormones. ABA inhibited growth of submerged internodes, and GA counteracted this inhibition. Our results indicate that the growth rate of deepwater rice internodes is determined by the ratio of an endogenous growth promoter (GA) and a growth inhibitor (ABA). We also investigated whether ABA is involved in regulating the growth of rice coleoptiles. Rice seedlings were grown on solutions containing fluridone, an inhibitor of carotenoid and, indirectly, of ABA biosynthesis. Treatment with fluridone reduced the level of ABA in coleoptiles and first leaves by more than 75% and promoted coleoptile growth by more than 60%. Little or no enhancement of growth by fluridone was observed in barley, oat, or wheat. The involvement of ABA in determining the growth rate of rice coleoptiles and deepwater rice internodes may be related to the semiaquatic growth habit of this plant.

Journal Article↗
PubMed1991

Differential expression of two genes for 1-aminocyclopropane-1-carboxylate synthase in tomato fruits.

1-Aminocyclopropane-1-carboxylate synthase (ACC synthase; S-adenosyl-L-methionine methylthioadenosine-lyase, EC 4.4.1.14) is the regulated enzyme in the biosynthetic pathway of the plant hormone ethylene. A full-length cDNA encoding this enzyme has been cloned from tomato fruits [Van Der Straeten, D., Van Wiemeersch, L., Goodman, H. M. & Van Montagu, M. Proc. Natl. Acad. Sci. USA (1990) 87, 4859-4863]. We report here the complete nucleotide and derived amino acid sequences of a cDNA encoding a second isoform of ACC synthase from tomato fruits. The cDNAs coding for both isoforms contain highly conserved regions that are surrounded by regions of low homology, especially at the 5' and 3' ends. Gene-specific probes were constructed to examine the expression of transcripts encoding the two ACC synthase isoforms under two conditions of enhanced ethylene formation--namely, during fruit ripening and in response to mechanical stress (wounding). The level of mRNA encoding both isoforms, ACC synthase 1 and 2, increased during ripening. In contrast, wounding caused an increase in only the level of mRNA coding for ACC synthase 1. Blot analysis of genomic DNA digested with restriction enzymes confirmed that ACC synthase 1 and 2 are encoded by different genes.

Amino Acid Sequence↗
PubMed1989

Enzymes of ethylene biosynthesis.

The properties of enzymes involved in ethylene biosynthesis are reviewed and progress toward the purification of these enzymes is described. The enzyme whose activity usually limits ethylene biosynthesis is 1-aminocyclopropane-1-carboxylate (ACC) synthase. Even though its level in plants is extremely low, it has now been purified from several sources. The enzyme that converts ACC to ethylene does not survive homogenization, apparently because it is membrane-bound and because its activity requires membrane integrity. Properties of this enzyme have been elucidated in vivo and in vacuolar preparations which possess the capacity to convert ACC to ethylene.

Journal Article↗
PubMed1988

The biophysical basis of elongation growth in internodes of deepwater rice.

Partial submergence induces rapid internodal elongation in deepwater rice (Oryza sativa L., cv Habiganj Aman II). We measured in vivo extensibility, tissue tension, hydraulic conductance and osmotic potential in the region of cell elongation in the uppermost internode. The in vivo extensibility of the internode, measured by stretching of living tissue with a custom-made constant stress extensiometer, rose rapidly following submergence of the plant. Both the elastic (E(el)) and plastic (E(pl)) extensibility increased when growth of the internode was induced. The submerged internode displayed tissue tension (elastic outward bending of longitudinally split internode sections); in air-grown control internodes, no such bending occurred. The hydraulic conductance, estimated from the kinetics of tissue shrinkage in 0.5 molar mannitol and subsequent swelling in distilled water, was not changed by submergence. The osmotic potential, measured with a dew-point hygrometer using frozen-thawed tissue, was only 18% less negative in the submerged internode than in the air-grown control. This indicates that osmoregulation takes place in rapidly elongating rice internodes. We suggest that the rapid expansion of the newly formed internodal cells of submerged plants is controlled by the yielding properties (E(pl)) of the cell walls. Experiments with excised stem sections indicate that gibberellin is involved in increasing the E(pl) of the elongating cell walls.

Journal Article↗
PubMed1987

In vivo 1-aminocyclopropane-1-carboxylate synthase activity in internodes of deepwater rice : enhancement by submergence and low oxygen levels.

Inasmuch as the activity of 1-aminocyclopropane-1-carboxylate (ACC) synthase cannot be measured in homogenates of deepwater rice internodes (Oryza sativa L.), we have employed an in vivo assay to determine the activity of this enzyme. This assay is based on the accumulation of ACC in tissue kept under N(2). Submergence of whole plants or stem sections containing the uppermost, developing internode enhances the in vivo activity of ACC synthase in the stem. This stimulation of in vivo ACC-synthase activity is especially pronounced in the region of the internode containing the intercalary meristem and the elongation zone above it. Enhancement of in vivo ACC-synthase activity is evident after 2 hours of submergence and shows a peak after 4 hours. Reduced levels of atmospheric O(2), which promote ethylene synthesis and growth in internodes of deepwater rice, also enhance the in vivo activity of ACC synthase. Our results are consistent with the hypothesis that induction of ACC-synthase activity at low partial O(2) pressures is among the first biochemical events leading to internodal growth in deepwater rice.

Journal Article↗
PubMed1987

An evaluation of 2,5-norbornadiene as a reversible inhibitor of ethylene action in deepwater rice.

Partial submergence of deepwater rice (Oryza sativa L. cv Habiganj Aman II) elicits three responses: enhancement of internodal elongation, inhibition of leaf growth, and promotion of adventitious root formation. All three responses can be induced in isolated stem sections by treatment with ethylene. Dose-response curves indicate that the responses are linearly related to the logarithm of the ethylene concentration over two orders of magnitude. Application of the cyclic olefin 2,5-norbornadiene (NBD) to ethylene-treated sections results in a parallel shift in dose-response curves to higher ethylene concentrations, indicating that NBD behaves as a competitive inhibitor of ethylene action. Internodal elongation of stem sections is promoted by gibberellic acid (GA(3)) in the absence of exogenous ethylene. Endogenous ethylene levels do not increase in GA(3)-treated sections, and application of NBD does not prevent GA(3)-promoted elongation. To the contrary, NBD treatment results in increased growth at intermediate GA(3) concentrations. These results support the idea that ethylene acts through endogenous GA in promoting growth in deepwater rice. NBD applied to GA(3)-treated stem sections results in increased ethylene production. This enhancement of ethylene formation is reversed by application of either ethylene or propylene, indicating that ethylene biosynthesis in rice internodes is under negative feedback control.

Journal Article↗
PubMed1986

Use of monoclonal antibodies in the purification and characterization of 1-aminocyclopropane-1-carboxylate synthase, an enzyme in ethylene biosynthesis.

1-Aminocyclopropane-1-carboxylate (ACC) synthase (EC 4.4.1.14), extracted from tomato pericarp tissue, was purified 6500-fold by conventional and high-performance liquid chromatography. Two-dimensional gel electrophoresis of this preparation indicated that ACC synthase activity was associated with a protein band at 50 kDa, a value consistent with size determinations by gel filtration. Monoclonal antibodies against ACC synthase were obtained from murine hybridoma cell lines. These antibodies recognized the native enzyme, as shown with an immunoprecipitation assay. A monoclonal IgG immunoaffinity gel was used to isolate, from a relatively crude enzyme preparation, a single protein, which migrated at 50 kDa in a NaDodSO(4)/polyacrylamide gel. In vivo labeling of wounded tomato pericarp tissue with [(35)S]methionine followed by immunoaffinity purification of ACC synthase yielded a radioactive protein of 50 kDa. We conclude that the 50-kDa protein represents ACC synthase in extracts of wounded tomato pericarp tissue.

Journal Article↗
PubMed1986

A comparison of the submergence response of deepwater and non-deepwater rice.

Twelve cultivars of rice (Oryza sativa L.), representing deepwater, short-statured, and semidwarf types, were tested for their response to submergence. The magnitude of the response varied between cultivars; however, all cultivars responded to submergence by rapid growth once internodal elongation had started. Three of these cultivars were tested for elongation capacity at four ages. The deepwater rice was capable of rapid internodal elongation in response to submergence at 4 weeks of age. Growth of the short-statured and semidwarf cultivars was not stimulated by submergence until about 10 weeks of age. In air, the internodes of deepwater rice grew slower than did those of the short-statured and semidwarf cultivars. We also investigated the elongation response of stem sections of all 12 cultivars to an atmosphere containing 3% O(2), 6% CO(2), 91% N(2) (all by volume), and 1 microliter per liter ethylene. We found that the response of each of the non-deepwater cultivars was qualitatively and quantitatively similar to that of the deepwater rice.

Journal Article↗
PubMed1985

Stereochemical course of the reaction catalyzed by the pyridoxal phosphate-dependent enzyme 1-aminocyclopropane-1-carboxylate synthase.

(+/-)-S-adenosyl-DL-(3R*,4S*)-[3,4-2H2]-methionine [a 1:1 mixture of (3R,4S) and (3S,4R)] and (+/-)-S-adenosyl-DL-(3R*,4R*)-[3,4-2H2]methionine [a 1:1 mixture of (3R,4R) and (3S,4S)] were synthesized from (Z)- and (E)-[1,2-2H2]ethene, respectively. Key steps in the synthesis were the antiperiplanar addition of methanesulfenyl chloride to (Z)-[1,2-2H2]ethene, to give a 1:1 mixture of (R,R)- and (S,S)-1-chloro-2-(methylthio)[1,2-2H2)ethane, followed by alkylation with sodium acetamidomalonate and hydrolysis to give an equal mixture of four stereoisomers of [3,4-2H2]methionine [(2R,3R,4S), (2R,3S,4R), (2S,3R,4S), and (2S,3S,4R)]. The other four stereoisomers of [3,4-2H2]methionine were prepared from (E)-(1,2-2H2]ethene. The two sets of stereoisomers of [3,4-2H2]methionine were chemically converted to S-adenosylhomocysteine, methylated to give the corresponding (+/-)-S-adenosyl-DL-methionines, and then incubated with 1-aminocyclopropane-1-carboxylate synthase partially purified from tomato (Lycopersicon esculentum, L.) pericarp tissue. The stereochemistry of the resulting samples of 1-aminocyclopropane-1-carboxylic acid was determined by comparison with the 1H NMR of the chemically synthesized and regio- and stereo-specifically deuterated compound. The results indicate that the hydrogens at the beta carbon of the methionine portion of S-adenosylmethionine do not participate in the reaction and that the ring closure occurs with inversion of configuration at the gamma carbon of the methionine portion of S-adenosyl-methionine, probably through a direct SN2-type displacement of the 5'-methylthio-5'-deoxyadenosine moiety by a carbanion equivalent formed at the alpha carbon of the methionine portion of S-adenosylmethionine.

Amino Acids↗