A cDNA from Schizosaccharomyces pombe encoding a putative enolase

Biological functions of Arabidopsis thaliana MBP-1-like protein encoded by ENO2 in the response to drought and salt stresses

Arabidopsis thaliana ENO2 (AtENO2) plays an important role in plant growth and development. It encodes two proteins, a full-length AtENO2 and a truncated version, AtMBP-1, alternatively translated from the second start codon of the mRNA. The AtENO2 mutant (eno2^- ) exhibited reduced leaf size, shortened siliques, a dwarf phenotype and higher sensitivity to abiotic stress. The objectives of this study were to analyze the regulatory network of the ENO2 gene in plant growth development and understand the function of AtENO2/AtMBP-1 to abiotic stresses. An eno2^- /35S:AtENO2-GFP line and an eno2^- /35S:AtMBP-1-GFP line of Arabidopsis were obtained. Results of sequencing by 454 GS FLX identified 578 upregulated and 720 downregulated differential expressed genes (DEGs) in a pairwise comparison (WT-VS-eno2^- ). All the high-quality reads were annotated using the Gene Ontology (GO) terms. The DEGs with KEGG pathway annotations occurred in 110 pathways. The metabolic pathways and biosynthesis of secondary metabolites contained more DEGs. Moreover, the eno2^- /35S:AtENO2-GFP line returned to the wild-type (WT) phenotype and was tolerant to drought and salt stresses. However, the eno2^- /35S:AtMBP-1-GFP line was not able to recover the WT phenotype but it has a higher tolerance to drought and salt stresses. Results from this study demonstrate that AtENO2 is critical for the growth and development, and the AtMBP-1 coded by AtENO2 is important in tolerance of Arabidopsis to abiotic stresses.

cDNA cloning and characterization of enolase from Chinese cabbage, Brassica campestris ssp. Pekinensis

An enolase-encoding cDNA clone from Chinese cabbage, Brassica campestris ssp. Pekinensis, was isolated. This gene (Accession number: AY307448) had a total length of 1580bp with an open reading frame of 1335bp, and encoded a predicted polypeptide of 444 amino acids with a molecular weight of 47.38 kDa. The deduced amino acid (aa) sequence shared identity with a number of enolases ranging from Bacillus subtilis to human beings and had much higher identity with other plant enolases than with enolases from Bacillus, yeast and human beings. Comparison of its primary structure with those of other enolases revealed the presence of an insertion of 5 amino acids in enolase of Chinese cabbage. Expression of the cloned enolase gene decreased under salt stress, but increased in response to low temperature. Southern blot analysis of genomic DNA indicated that low-copies of enolase gene were present in the genome of Chinese cabbage.

Glucose-inducible expression of rrg1+ in Schizosaccharomyces pombe: post-transcriptional regulation of mRNA stability mediated by the downstream region of the poly(A) site

rrg1+(rapid response to glucose) has been isolated previously as a UV-inducible gene in Schizosaccharomyces pombe, designated as uvi22+. However, it was revealed that the transcript level of this gene was regulated by glucose, not by DNA-damaging agents. Glucose depletion led to a rapid decrease in the level of rrg1+ mRNA, by approximately 50% within 30 min. This effect was readily reversed upon re-introduction of glucose within 1 h. High concentrations (4 and 8%) of glucose showed similar effects on increasing the rrg1+ mRNA level compared with 2% glucose, while a low concentration (0.1%) was not effective in raising the rrg1+ mRNA level. In addition, sucrose and fructose could increase rrg1+ mRNA level. Interestingly, the rapid decline in mRNA level seen upon glucose deprivation resulted from precipitous reduction of mRNA half-life. Serial and internal deletions within the 3'-flanking region of rrg1+ revealed that a 210-nt region downstream of the distal poly(A) site was critical for glucose-regulated expression. Moreover, this downstream region participated in 3'-end formation of mRNA. Taken together, this is the first report on glucose-inducible expression regulated post-transcriptionally by control of mRNA stability in S.pombe.

Plasminogen-binding activity of enolase in the opportunistic pathogen Pneumocystis carinii

The glycolytic enzyme enolase is one of the most abundant proteins expressed in fungi and has been shown to be an immunodominant cell-wall-associated antigen of the pathogenic fungus, Candida albicans. Enolase has also been found on the surface of some mammalian cells where it functions as a plasminogen-binding motif and facilitator of plasminogen activation to plasmin. To investigate the immunogenicity of enolase in the opportunistic pathogen, Pneumocystis carinii, the genomic and complementary DNA (cDNA) enolase were cloned and characterized. The predicted protein comprises 433 amino-acid residues and shows extensive homology to other fungal enolases, including those of C. albicans (76%), Aspergillus oryzae (79%) and Saccharomyces cerevisiae (77%). The purified recombinant P. carinii enolase was immunogenic, and may be an important antigen and indicator of P. carinii infection. The active site and conformation metal ion-binding site residues necessary for dimerization and enzyme function are conserved in the predicted P. carinii enolase protein. Enolase of P. carinii is unique among the fungal enolases in that it possesses a catalytic carboxyl-terminal lysyl residue that was necessary and sufficient for the plasminogen-binding activity of the enolase of P. carinii. The activity of the plasminogen binding suggests its involvement in the local regulation of fibrinolysis within the alveolar space.

Carbohydrate and energy-yielding metabolism in non-conventional yeasts

Sugars are excellent carbon sources for all yeasts. Since a vast amount of information is available on the components of the pathways of sugar utilization in Saccharomyces cerevisiae it has been tacitly assumed that other yeasts use sugars in the same way. However, although the pathways of sugar utilization follow the same theme in all yeasts, important biochemical and genetic variations on it exist. Basically, in most non-conventional yeasts, in contrast to S. cerevisiae, respiration in the presence of oxygen is prominent for the use of sugars. This review provides comparative information on the different steps of the fundamental pathways of sugar utilization in non-conventional yeasts: glycolysis, fermentation, tricarboxylic acid cycle, pentose phosphate pathway and respiration. We consider also gluconeogenesis and, briefly, catabolite repression. We have centered our attention in the genera Kluyveromyces, Candida, Pichia, Yarrowia and Schizosaccharomyces, although occasional reference to other genera is made. The review shows that basic knowledge is missing on many components of these pathways and also that studies on regulation of critical steps are scarce. Information on these points would be important to generate genetically engineered yeast strains for certain industrial uses.

Cloning of the gene encoding the mitochondrial adenine nucleotide carrier of Schizosaccharomyces pombe by functional complementation in Saccharomyces cerevisiae

We describe the isolation and sequencing of both cDNA and genomic clones encoding the mitochondrial ADP/ATP carrier (Anc) of Schizosaccharomyces pombe (Sp). The cDNA clone was isolated from a cDNA library of this fission yeast by complementation of a Saccharomyces cerevisiae (Sc) strain defective in adenine nucleotide carrier. The predicted amino acid (aa) sequence (322 aa) shared similarity with the known Anc sequences. It is more closely related to Neurospora crassa (Nc) Anc than to ScAnc1, 2, or 3 or Kluyveromyces lactis (Kl) Anc. Hybridization experiments with ordered libraries of Sp genomic DNA led to the physical mapping (chromosome II, NotI-B region) and the isolation of the Sp ANC1 gene. We also conclude that a single-copy gene encodes the Sp Anc.

Cloning and sequencing of a gene encoding pyruvate kinase from Schizosaccharomyces pombe; implications for quaternary structure and regulation of the enzyme

A cDNA encoding pyruvate kinase from Schizosaccharomyces pombe has been isolated from a lambda ZAPII library. This cDNA was sequenced and found to contain an open reading frame of 1524 nucleotides, giving a predicted protein subunit M, of 55470. The sequence shows a high degree of identity with other pyruvate kinase sequences, with residues implicated in the binding of substrate and metal ion co-factors conserved. However, there are significant differences in the putative subunit interface and effector binding regions which may account for the unusual quaternary structure and regulatory properties of the S. pombe enzyme.