Overexpression of a heat shock protein (ThHSP18.3) from <Emphasis Type="Italic">Tamarix hispida</Emphasis> confers stress tolerance to yeast

It is well known that plant heat shock proteins (HSPs) play important roles both in response to adverse environmental conditions and in various developmental processes. However, among plant HSPs, the functions of tree plant HSPs are poorly characterized. To improve our understanding of tree HSPs, we cloned and characterized an HSP gene (ThHSP18.3) from Tamarix hispida. Sequence alignment reveals that ThHSP18.3 belongs to the class I small heat shock protein family. A transient expression assay showed that ThHSP18.3 protein was targeted to the cell nucleus. Treatment of Tamarix hispida with cold and heat shock highly induced ThHSP18.3 expression in all studied leaves, roots and stems, whereas, treatment of T. hispida with NaCl, NaHCO₃, and PEG induced ThHSP18.3 expression in leaves and decreased its expression in roots and stems. Further, to study the role of ThHSP18.3 in stress tolerance under different stress conditions, we cloned ThHSP18.3 into the pYES2 vector, transformed and expressed the vector in yeast Saccharomyces cerevisiae. Yeast cells transformed with an empty pYES2 vector were employed as a control. Compared to the control, yeast cells expressing ThHSP18.3 showed greater tolerance to salt, drought, heavy metals, and both low and high temperatures, indicating that ThHSP18.3 confers tolerance to these stress conditions. These results suggested that ThHSP18.3 is involved in tolerance to a variety of stress conditions in T. hispida.     

Structure of two melon regions reveals high microsynteny with sequenced plant species

In this study, two melon bacterial artificial chromosome (BAC) clones have been sequenced and annotated. BAC 1-21-10 spans 92 kb and contains the nsv locus conferring resistance to the Melon Necrotic Spot Virus (MNSV) in melon linkage group 11. BAC 13J4 spans 98 kb and belongs to a BAC contig containing resistance gene homologues, extending a previous sequenced region of 117 kb in linkage group 4. Both regions have microsyntenic relationships to the model plant species Arabidopsis thaliana, and to Medicago truncatula and Populus trichocarpa. The network of synteny found between melon and each of the sequenced genomes reflects the polyploid structure of Arabidopsis, Populus, and Medicago genomes due to whole genome duplications (WGD). A detailed analysis revealed that both melon regions have a lower relative syntenic quality with Arabidopsis (eurosid II) than when compared to Populus and Medicago (eurosid I). Although phylogenetically Cucurbitales seem to be closer to Fabales than to Malphigiales, synteny was higher between both melon regions and Populus. Presented data imply that the recently completed Populus genome sequence could preferentially be used to obtain positional information in melon, based on microsynteny. Wim Deleu and Víctor González contributed equally to this work. The nucleotide sequences of BACs 1-21-10 and 13J4 are available in the DDBJ/EMBL/GenBank databases under the accession numbers EF188258 and EF657230, respectively.     

Expression of the Major Heat Shock Proteins DnaK and GroEL in Streptococcus pyogenes: A Comparison to Enterococcus faecalis and Staphylococcus aureus

One of the outstanding problems in the field of heat shock response has been to elucidate the mechanism underlying the induction of heat shock proteins (HSPs). In this work, we initiate an analysis of the expression of heat shock groEL and dnaK genes and their promoters in S. pyogenes. The synthesis of total cellular proteins was studied upon transfer of a log-phase culture from 37°C to 42°C by performing 5-min pulse-labeling experiments with ³⁵S-Met. The heat shock responses in the pathogenic Gram-positive cocci, Enterococcus faecalis and Staphylococcus aureus, were also analyzed. Received: 12 July 2000 / Accepted: 27 August 2000     

热休克因子生理功能研究进展

热休克因子是调控真核细胞热休克基因转录的关键因子,在应激和正常生理条件下发挥重要作用,使其成为近年来的研究热点。该文简要综述热休克因子在抗炎反应、肿瘤发生与维持、生长发育、衰老等生理病理过程中的重要生理功能。