PubMed Health⌕ Search

Biomedical subjects

H G Zheng

Publications and source records attributed to H G Zheng.

10 recordsLinked to original sources
PubMed2001

Cloning of new members of heat shock protein HSP101 gene family in wheat (Triticum aestivum (L.) Moench) inducible by heat, dehydration, and ABA(1).

We have cloned two cDNAs, TaHSP101B and TaHSP101C, encoding two heat stress-inducible members of HSP101/ClpB family in bread wheat (Triticum aestivum (L.) Moench.). Proteins encoded by these cDNAs are highly similar at the primary sequence level and diverged from the previously reported TaHSP101 (designated TaHSP101A) both in the consensus ATP/GTP-binding region II and in the carboxy terminal region. The HSP101 gene was determined to be a single copy gene or a member of a small gene family in hexaploid wheat. Messages encoding HSP101 proteins were inducible by heat stress treatments in both wheat leaves and roots. Accumulation of the TaHSP101C mRNA was less abundant than that of TaHSP101B mRNA. We are showing for the first time that in addition to heat stress, expression of HSP101 mRNAs in wheat leaves was induced by a 2-h dehydration and a treatment with 5x10(-5)M ABA, but not affected by chilling or wounding, indicating that HSP101 proteins may be involved in both heat and drought responses in wheat.

Abscisic Acid↗
PubMed2000

Quantitative trait loci for root-penetration ability and root thickness in rice: comparison of genetic backgrounds.

Drought is the major abiotic stress limiting rice (Oryza sativa) production and yield stability in rainfed lowland and upland ecosystems. Root systems play an important role in drought resistance. Incorporation of root selection criteria in drought resistance improvement is difficult due to lack of reliable and efficient screening techniques. Using a wax-petrolatum layer system simulated to compacted soil layers, root traits were evaluated in a doubled haploid (DH) population derived from the cross between 'IR64' and 'Azucena'. Twelve putative QTLs (quantitative trait loci) were detected by interval mapping comprising four QTLs for root-penetration ability, four QTLs for root thickness, two QTLs for penetrated root number, and two QTLs for total root number. These QTLs individually explained 8.4% to 16.4% of the phenotypic variation. No QTL was detected for maximum penetrated root length by interval mapping. One QTL located between RG104 and RG348 was found to influence both root-penetration ability and root thickness. QTLs for root-penetration ability and root thickness were compared across two populations, 'IR64'-'Azucena' and 'CO39'-'Moroberekan', and different testing conditions. The identified consistent QTLs could be used for marker-assisted selection for deep and thick roots with high root-penetration ability in rice.

Oryza↗
PubMed2000

[AFLP analysis of photoperiod-sensitive genic male sterile(PGMS) rice mutant lines].

The reaction conditions for rice AFLP assay were optimized. The relative efficiencies for polymorphism detection of RFLP, RAPD and AFLP were compared through the analysis between a pair of PGMS allelic mutant lines(NK58S and NK58F). Results indicated that the efficiency for polymorphism detection in rice is in the order of AFLP > RAPD > RFLP, and also indicated that AFLP is a powerful DNA molecular marker technique for polymorphism detection, especially in the cases of extremely low polymorphism, such as isogeneic lines and allelic mutant lines. The advantages and disadvantages of these three molecular marker systems were discussed. Using AFLP in conjunction with bulked segregating analysis, 5106 AFLP loci were screened and 9 of them showed polymorphism between NK58S and NK58F, 4 of the polymorphic AFLP products were cloned, Southern bloting analysis showed that two of them were single copy sequences while the other two were low copy sequences in rice genome.

Mutation↗
PubMed1993

[The establishment of genomic DNA libraries for the human malaria parasite Plasmodium falciparum].

The DNA of Plasmodium falciparum has been purified and fragmented with restriction endonuclease BamHI. The fragments have been incorporated in vitro into derivatives of bacteriophage lambda EMBL4 digested with BamHI and Sal I. The recombinant mixture has been ligated and packaged in vitro. The recombinant phages have been identified in E. coli L95 host cell and the libraries have been established in which most of the parasite DNA is represented. The ligation proportion of vector to insert is 3:1. The recombinant phages of 4 x 10(5) have been obtained. By plaque hybridization, we have been able to recover from these libraries specific clones containing repetitive DNA sequences.

Animals↗
PubMed1991

Immunoregulatory activity of the T-cell receptor alpha chain demonstrated by retroviral gene transfer.

We have previously described an antigen-specific I-Ad-restricted T-cell hybridoma, A1.1, that constitutively releases an antigen-specific immunoregulatory activity into supernatants. Using retrovirally mediated gene transfer, we have found that transfer of the T-cell receptor alpha chain (TCR alpha) gene from A1.1 to a number of other T-cell hybridomas effectively transferred the ability to produce the activity. Gene transfer of the TCR beta chain (TCR beta), however, did not transfer this ability. The regulatory activity from cells expressing the A1.1 TCR alpha bound to and was eluted from an anti-TCR alpha monoclonal antibody and displayed fine antigenic specificity identical to that of supernatants from A1.1. The possibility that this activity represents a secreted form of the TCR alpha (as opposed to shed cell-surface TCR) was examined in BW1100 cells, lacking TCR alpha and TCR beta, which produced the antigen-specific activity after gene transfer of the A1.1 TCR alpha gene. The expression of the immunoregulatory activity in supernatants correlated with a direct antigen-binding activity as detected by ELISA, thus raising the possibility that antigen binding is relevant to the mechanism of action of the soluble TCR alpha. We discuss these observations and our earlier studies suggesting an immunoregulatory role for soluble TCR alpha.

Amino Acid Sequence↗
PubMed1991

A T helper cell hybridoma produces an antigen-specific regulatory activity. Relationship to the T cell receptor by serology and antigenic fine specificity.

We have previously shown that a T cell hybridoma, A1.1, constitutively produces an Ag-specific regulatory factor with specificity for poly-18, a synthetic polypeptide. This cell also responds to poly-18 plus I-Ad by producing lymphokines. The antigenic specificity of the factor and the T cell appeared to be the same. This suggested the possibility that some part of the TCR, responsible for antigenic specificity of the cell, also imparts specificity to the A1.1-derived factor. This was supported by the observation that the factor was bound and eluted from a monospecific anti-TCR antiserum. Further, we demonstrated that antisense oligodeoxynucleotides corresponding to the TCR V alpha of A1.1 (but not TCR V beta) block production of the Ag-specific factor. Herein, we report recent findings that strengthen the proposed relationship between the TCR and the A1.1-derived factor. The factor was bound and eluted from a monoclonal anti-TCR C alpha antibody, but not from anti-TCR beta, anti-V beta 6, nor anti-CD3 epsilon. The anti-TCR C alpha antibody bound a Mr 46-kDa protein from A1.1 supernatants, which is the same apparent size at which activity could be eluted from an SDS-PAGE gel separation of concentrated factor. Antigenic fine-specificity analysis revealed that two amino acids in poly-18 are critical for the recognition of the antigen by the Ag-specific factor. These two amino acids appear to be those recognized by the TCR. The factor that was bound and eluted from the monoclonal anti-TCR C alpha showed this fine-specificity as well. This, combined with our earlier studies, supports the view that the A1.1-derived factor is encoded, at least in part, by TCR-alpha.

Amino Acid Sequence↗
PubMed1987

A helper T cell clone produces an antigen-specific molecule (T-ABM) which functions in the induction of suppression.

Among Ly-1+,2-T cells there appears to be two independent modes of antigen recognition. Helper and cytotoxic Ly-1 T cells recognize antigen only in the context of I region products whereas regulatory T cells, such as T suppressor inducer cells, produce antigen-specific, antigen-binding molecules (T-ABM). These T-ABM often have been found to form a part of biologically active, antigen-specific regulatory factors. A number of environmental conditions effect whether a foreign antigen will produce a positive response leading to immunity or a negative one leading to tolerance. Many of the conditions which favor the induction of suppressor T cells simultaneously preclude the proper interaction of antigen presenting cells with helper T cells. This parallel led us to ask whether helper T cells perform at least two, apparently opposite functions: a) under conditions favoring immunity helper T cells produce lymphokines to activate immune effector cells, and b) under conditions favoring suppression they produce molecules which function in suppressor cell induction. Therefore, this question relates to the mechanisms by which an immune response is switched into either a positive (help) or negative (suppressive) track. In addition, it begins to address the relationship between the different modes of antigen recognition exhibited by helper T cells vs. T suppressor inducer cells (see above). To explore this problem we employed an antigen-specific, I-Ak restricted helper T cell clone as the purest available source of helper T cells. We presented antigen to the cloned T cells under conditions which favor suppression rather than help (for example, by ultraviolet irradiation of the antigen-presenting cells) and collected supernatants 48 hrs later. The supernatants were then examined for activity in a functional assay for antigen-specific suppressor factors. Our results indicate that under conditions favoring suppression, a T-ABM was produced which functioned in the antigen-specific induction of suppression in vitro. The T-ABM had the same antigen specificity as that exhibited by the helper T cell and was therefore probably derived from the clone. This observation introduces the possibility that the interaction between antigen-presenting cells and helper T cells is a crucial decision point in the immune response which can lead to either immunity or suppression. The latter would be achieved through the production, by helper T cells, of an antigen-specific component of T suppressor inducer factor (i.e., the T-ABM). The possible relationship between T-ABMs and the T cell receptor is discussed.

Animals↗