Biomedical subjects

Zheng-Jun Xu

Publications and source records attributed to Zheng-Jun Xu.

5 recordsLinked to original sources

PubMed2006

[Progress in the study on DREB transcription factor].

DREB transcription factor is a dehydration responsive element (DRE) binding protein. It can specifically interact with the dehydration-responsive element/C-repeat (DRE/CRT) cis-acting element contained in the promoter region of many stress-inducible genes, and can therefore control the expression of many stress-inducible genes in plant and increase strong tolerance to drought, low temperature and high salt. In this paper we described the relation between DREB transcription factor and DRE/CRT cis-acting element, the functional and structural character, and expression and regulation of DREB. We also briefly introduced the progress of research on DREB gene cloning and identification. DREB transcription factor plays an important role in the expression of many stress-inducible genes in plant, so it thus shows a very broad application future in aspect of increasing strong tolerance to stress. At the same time, we described the DREB complexity in signal transduction and the mechanism for action and expression of gene.

Gene Expression Regulation, Plant↗

PubMed2005

Gibberellin 2-oxidases from seedlings of adzuki bean (Vigna angularis) show high gibberellin-binding activity in the presence of 2-oxoglutarate and Co2+.

Five full-length cDNA encoding gibberellin 2-oxidases, VaGA2oxA1, VaGA2oxA2, VaGA2oxB1, VaGA2oxB2, and VaGA2oxB3, were cloned from etiolated adzuki bean (Vigna angularis cv. Dainagon) seedlings, and their enzymatic characteristics were examined using recombinant enzymes fused with glutathione S-transferase (GST). Recombinant VaGA2oxA1 (rVaGA2oxA1) and rVaGA2oxA2 showed 2beta-hydroxylation activity by converting GA1, GA4, GA9, GA20, GA4-methyl ester, and 16,17-dihydro-GA4 to the corresponding 2beta-hydroxylated gibberellins, which were identified by GC/MS. rVaGA2oxB1, rVaGA2oxB2, and rVaGA2oxB3 showed similar activity by converting [3H4]-16,17-dihydro-GA4 to a metabolite showing an Rf value of 16,17-dihydro-GA34. RNA-blot analysis showed that VaGA2oxA1 and VaGA2oxA2 were the major ones expressed in etiolated hypocotyls. The addition of Co2+ instead of Fe2+ to the assay medium apparently reduced the enzymatic activity, but increased the binding of [3H4]-16,17-dihydro-GA4 to rVaGA2oxA1, indicating the possibility that VaGA2oxs can be detected as gibberellin-binding proteins under certain conditions.

Amino Acid Sequence↗

PubMed2004

Gibberellin induces alpha-amylase gene in seed coat of Ipomoea nil immature seeds.

Two full-length cDNAs encoding gibberellin 3-oxidases, InGA3ox1 and InGA3ox2, were cloned from developing seeds of morning glory (Ipomoea nil (Pharbitis nil) Choisy cv. Violet) with degenerate-PCR and RACEs. The RNA-blot analysis for these clones revealed that the InGA3ox2 gene was organ-specifically expressed in the developing seeds at 6-18 days after anthesis. In situ hybridization showed the signals of InGA3ox2 mRNA in the seed coat, suggesting that active gibberellins (GAs) were synthesized in the tissue, although no active GA was detected there by immunohistochemistry. In situ hybridization analysis for InAmy1 (former PnAmy1) mRNA showed that InAmy1 was also synthesized in the seed coat. Both InGA3ox2 and InAmy1 genes were expressed spatially overlapped without a clear time lag, suggesting that both active GAs and InAmy1 were synthesized almost simultaneously in seed coat and secreted to the integument. These observations support the idea that GAs play an important role in seed development by inducing alpha-amylase.

Amino Acid Sequence↗

PubMed2002

Molecular characterization of a novel protein disulfide isomerase in carrot.

A protein disulfide isomerase (PDI) coding sequence was cloned from a cDNA library derived from carrot (Daucus carota L.) somatic embryos. The cDNA is 2060 bp in length and encodes for a protein of 581 amino acids and molecular weight of 64.4 kDa. Primary structure analysis of the deduced protein revealed two thioredoxin-like active sites and an endoplasmic reticulum-retention signal at its C-terminus, which is also found in PDIs in plants and animals. Although between the carrot protein and other plant PDIs there is only about 30% identity, the active site regions are almost identical. The corresponding mRNA was found in varying amounts, in all tissues investigated. A recombinant protein expressed from the carrot cDNA clone effectively catalyzed both glutathione-insulin transhydrogenation and the oxidative renaturation of denatured RNase A. These results suggest that the protein coded for by the carrot gene is a novel member of the PDI family in plants. We therefore designated this novel carrot gene PDIL1. The protein expressed by the PDIL1 cDNA sequence had a highly acidic stretch at its N-terminal region (no such domain exists in known plant PDIs), and was located far from known plant PDIs on a maximum likelihood tree. The PDIL1 gene, together with closely-related genes identified in Arabidopsis and tomato, was suggested to belong to a novel subfamily of PDIs.

Amino Acid Sequence↗

PubMed2002

Cloning and characterization of the abscisic acid-specific glucosyltransferase gene from adzuki bean seedlings.

The glycosylated forms of abscisic acid (ABA) have been identified from many plant species and are known to be the forms of ABA-catabolism, although their (physiological) roles have not yet been elucidated. ABA-glucosyltransferase (-GTase) is thought to play a key role in the glycosylation of ABA. We isolated an ABA-inducible GTase gene from UDP-GTase homologs obtained from adzuki bean (Vigna angularis) seedlings. The deduced amino acid sequence (accession no. AB065190) showed 30% to 44% identity with the known UDP-GTase homologs. The recombinant protein with a glutathione S-transferase-tag was expressed in Escherichia coli and showed enzymatic activity in an ABA-specific manner. The enzymatic activity was detected over a wide pH range from 5.0 to 9.0, the optimum range being between pH 6.0 and 7.3, in a citrate and Tris-HCl buffer. The product from racemic ABA and UDP-D-glucose was identified to be ABA-GE by gas chromatography/mass spectrometry. The recombinant GTase (rAOG) converted 2-trans-(+)-ABA better than (+)-S-ABA and (-)-R-ABA. Although trans-cinnamic acid was slightly converted to its conjugate by the GTase, (-)-PA was not at all. The mRNA level was increased by ABA application or by water stress and wounding. We suggest that the gene encodes an ABA-specific GTase and that its expression is regulated by environmental stress.

Abscisic Acid↗