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Biomedical subjects

Y L Meng

Publications and source records attributed to Y L Meng.

6 recordsLinked to original sources
PubMed2001

Molecular cloning and functional characterization of two kinds of betaine-aldehyde dehydrogenase in betaine-accumulating mangrove Avicennia marina (Forsk.) Vierh.

Glycinebetaine is an important osmoprotectant in bacteria, plants, and animals, but only little information is available on the synthesis of glycinebetaine in tree plants. Among four mangrove species, glycinebetaine could be detected only in Avicennia marina. Pinitol was the main osmoprotectant in the other three species. The level of glycinebetaine in A. marina increased under high salinity. Betaine-aldehyde dehydrogenase (BADH) was detected in all four species, but choline monooxygenase could not be detected. A cDNA library was constructed from the leaves of A. marina. Two kinds of BADH cDNAs were isolated, one homologous to the spinach chloroplast BADH, and the other with unique residues SKL at the end of C-terminus. The BADH transcription levels of the former were higher than those of the latter. The levels of the former BADH increased at high salinity whereas those of the latter were independent of salinity. BADHs were expressed in Escherichia coli and purified. Two kinds of A. marina BADHs exhibited similar kinetic and stability properties, but were significantly different from those of spinach BADH. A. marina BADHs efficiently catalyzed the oxidation of betainealdehyde, but not the oxidation of omega-aminoaldehydes and were more stable at high temperature than the spinach BADH.

Aldehyde Oxidoreductases↗
PubMed2001

Isolation of a choline monooxygenase cDNA clone from Amaranthus tricolor and its expressions under stress conditions.

Plants synthesize the osmoprotectant glycine betaine (GB) via choline-->betaine aldehyde-->glycine betaine[1]. Two enzymes are involved in the pathway, choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH). A full length CMO cDNA (1,643bp) was cloned from Amaranthus tricolor. The open reading frame encoded a 442-amino acid polypeptide, which showed 69% identity with CMOs in Spinacia oleracea L. and Beta vulgaris L. DNA gel blot analysis indicated the presence of one copy of CMO gene in the A. tricolor genome. The expressions of CMO and BADH proteins in A.tricolor leaves significantly increased under salinization, drought and heat stress (42 degrees C), as determined by immunoblot analysis, but did not respond to cold stress (4 degrees C), or exogenous ABA application. The increase of GB content in leaves was parallel to CMO and BADH contents.

Aldehyde Oxidoreductases↗
PubMed2000

Overproduction of spinach betaine aldehyde dehydrogenase in Escherichia coli. Structural and functional properties of wild-type, mutants and E. coli enzymes.

Betaine aldehyde dehydrogenase (BADH) catalyzes the last step in the synthesis of the osmoprotectant glycine betaine from choline. Although betaine aldehyde has been thought to be a specific substrate for BADH, recent studies have shown that human and sugar beet BADHs also catalyze the oxidation of omega-aminoaldehydes. To characterize the kinetic and stability properties of spinach BADH, five kinds of expression vectors encoding full length, mature, E103Q, E103K, and chimera BADHs were constructed. These enzymes together with Escherichia coli BADH were expressed in E. coli and purified. The affinities for betaine aldehyde were similar in the spinach and E. coli BADHs, whereas those for omega-aminoaldehydes were higher in spinach BADH than in E. coli BADH. A chimera BADH in which part of the Rossmann type fold in the spinach BADH was replaced with that of E. coli BADH, showed properties which resembled spinach BADH more than E. coli BADH. The spinach E103K mutant was almost inactive, whereas the E103Q mutant showed a similar activity for the oxidation of betaine aldehyde to that of wild type BADH, but a lower affinity for omega-aminoaldehydes. All spinach BADHs were dimers whereas E. coli BADH was a tetramer. E. coli BADH was more stable at high temperature than spinach BADHs. The E103Q mutant was most labile to high temperature. These properties are discussed in relation to the structure of spinach BADH.

Aldehyde Oxidoreductases↗
PubMed1999

Coordinated accumulation of (+)-delta-cadinene synthase mRNAs and gossypol in developing seeds of Gossypium hirsutum and a new member of the cad1 family from G. arboreum.

A new member of the (+)-delta-cadinene synthase (CAD1) family was isolated from a Gossypium arboreum cDNA library. This cDNA encodes a protein that showed 97.3%, 96.9%, and 79.2% sequence identities with the proteins encoded by previously isolated cDNAs of cad1-C1, cad1-C14, and cad1-A, respectively. It may be grouped into the cad1-C subfamily as cad1-C2. Seeds of a glanded cotton cultivar, G. hirsutum cv. Sumian-6, were collected at different intervals during maturation, and the cad1 mRNA levels were analyzed by quantitative RT-PCR. The transcripts could be detected in seeds of 27 DPA (days postanthesis) and increased dramatically along with the seed maturation, which coordinated with an increase in sesquiterpene cyclase activities and subsequently the accumulation of gossypol. The transcription level detected with primers specific to cad1-C (including at least C1, C14, and cdn1) was higher than that detected with primers specific to cad1-A, and mRNA was detected also with cad1-C2-specific primers. This investigation indicates that, in developing seeds of the glanded cotton cultivar, genes of both the CAD1-C and CAD1-A subfamilies are expressed and there is an active biosynthesis of cadinene-type sesquiterpenes.

Amino Acid Sequence↗
PubMed1988

Tumorigenicity of simian virus 40-hepatocyte cell lines: effect of in vitro and in vivo passage on expression of liver-specific genes and oncogenes.

Five simian virus 40 (SV40)-hepatocyte cell lines were examined for tumorigenicity and the effect of in vitro passage on the expression of four liver-specific genes (albumin, transferrin, alpha 1-antitrypsin, and phosphoenolpyruvate carboxykinase), two oncogenes (c-Ha-ras and c-raf), and two genes associated with hepatocarcinogenesis (alpha-fetoprotein and placental-type glutathione-S-transferase). At low passage (12 to 22), all five cell lines expressed the four liver-specific genes at levels similar to those in the liver and were not tumorigenic or were weakly tumorigenic. At high passage (33 to 61), the cell lines formed carcinomas, and four out of five cell lines produced primary tumors that metastasized. At least two cell lines produced well-differentiated hepatocellular carcinomas that expressed liver-specific RNAs. Levels of expression of liver-specific genes changed with time in culture. Some of the changes in liver-specific gene expression in the tumor tissue (such as for the phosphoenolpyruvate carboxykinase gene) paralleled those that occurred with in vitro passage, while other changes (such as for the albumin gene) did not parallel those that occurred with in vitro passage. Correlations between enhanced expression of c-Ha-ras and tumorigenic potential and between the process of SV40 immortalization and induced expression of c-raf and glutathione-S-transferase-P were observed. Induction of alpha-fetoprotein was detected with in vitro and in vivo passage only in the CWSV14 cell line and was paralleled by diminished albumin expression. In conclusion, we developed a model system with five SV40-hepatocyte cell lines, tumors induced by them, and tumor cell lines to examine changes in gene expression that accompany the progression from a normal cell to a hepatocellular carcinoma. Because the SV40-hepatocyte cell lines and tumor cell lines remain highly differentiated and vary in the magnitude of expression of specific genes, they can be used to study the molecular mechanisms regulating gene expression, in particular those regulating specific genes associated with differentiation.

Animals↗