Effect of RIM21 gene disruption on flocculation of lager yeast / 生物工程学报

Lager yeast is the most popular yeast strain used for beer production in China. The flocculation of yeast plays an important role in cell separation at the end of fermentation. Therefore, appropriately enhancing the flocculation capability of the lager yeast without affecting its fermentation performance would be desirable for beer industry. Our previous study showed that the defect of gene RIM21 might contribute to the enhanced flocculation capability of a lager yeast G03. To further investigate the role of the RIM21 gene in flocculation of strain G03, this study constructed a RIM21-deleted mutant strain G03-RIM21Δ through homologous recombination. Deletion of RIM21 improved the flocculation capability of strain G03 during wort fermentation at 11 °C without changing its fermentation performance significantly. The expression of FLO5, Lg-FLO1 and some other genes involved in cell wall integrity pathway were up-regulated in strain G03-RIM21Δ. In addition, the disruption of RIM21 enhanced resistance of yeast cells to cell wall inhibitors. These results provide a basis for elucidating the flocculation mechanism of lager yeast under low-temperature fermentation conditions.

New insights of growth hormone (GH) actions from tissue-specific GH receptor knockouts in mice

ABSTRACT In order to provide new insights into the various activities of GH in specific tissues, recent advances have allowed for the generation of tissue-specific GHR knockout mice. To date, 21 distinct tissue-specific mouse lines have been created and reported in 28 publications. Targeted tissues include liver, muscle, fat, brain, bone, heart, intestine, macrophage, pancreatic beta cells, hematopoietic stem cells, and multi-tissue "global". In this review, we provide a brief history and description of the 21 tissue-specific GHR knockout mouse lines. Arch Endocrinol Metab. 2019;63(6):557-67

Isolation and expression of two polyketide synthase genes from Trichoderma harzianum 88 during mycoparasitism

Abstract Metabolites of mycoparasitic fungal species such as Trichoderma harzianum 88 have important biological roles. In this study, two new ketoacyl synthase (KS) fragments were isolated from cultured Trichoderma harzianum 88 mycelia using degenerate primers and analysed using a phylogenetic tree. The gene fragments were determined to be present as single copies in Trichoderma harzianum 88 through southern blot analysis using digoxigenin-labelled KS gene fragments as probes. The complete sequence analysis in formation of pksT-1 (5669 bp) and pksT-2 (7901 bp) suggests that pksT-1 exhibited features of a non-reducing type I fungal PKS, whereas pksT-2 exhibited features of a highly reducing type I fungal PKS. Reverse transcription polymerase chain reaction indicated that the isolated genes are differentially regulated in Trichoderma harzianum 88 during challenge with three fungal plant pathogens, which suggests that they participate in the response of Trichoderma harzianum 88 to fungal plant pathogens. Furthermore, disruption of the pksT-2 encoding ketosynthase–acyltransferase domains through Agrobacterium -mediated gene transformation indicated that pksT-2 is a key factor for conidial pigmentation in Trichoderma harzianum 88.

Disruption and Compensation of dnmV Gene from Daunorubicin-producing Strain Streptomyces coeruleorubidus SIPI-1482 / 中国生物工程杂志

TDP-4-ketohexulose reductase, encoded by dnmV, is important in daunorubicin biosynthesis. To obtain a daunorubicin block mutant, double cross-over plasmid pYG817 was constructed by inserting apramycin resistant gene and amplified dnmV together with upstream dnmU into vector pUC18. dnmV was successfully disrupted after transformation of daunorubicin-producing strain SIPI-1482 by pYG817. Daunorubicin was absent from metabolites of the resulting transformant, and its biosynthesis can be reconstituted by introducing dnmV expression plasmid into the disruptant, although the yield is lower than wild-type SIPI-1482, according to HPLC analysis. This mutant can be a good candidate for production of anthracycline such as epi-daunorubicin by introducing exogenous gene into the host.

Gene Disruption in Yeast / 生物化学与生物物理进展

Gene disruption by homologous recombination is a powerfu l tool for investigating gene function in yeast. Since 1980’s, it has been deve loped a lot. PCR-mediated gene disruption technique makes the manipulation easi er and it can be used to precisely delete genes in yeast. Multi-gene disruption technique can delete several genes successively in the same yeast strain. After the completion of the yeast Saccharomyces cerevisiae genome sequencing, the gene disruption technique for systematic analysis meets the need of the functio nal genomics in yeast. It also enlighten the study on human functional genomics.

Construction of Saccharomyces cerevisiae Mutant Deficient in adh2 and ald6 Genes / 微生物学通报

The purpose of this investigation is to improve ethanol production and decrease acetate formation in Saccharomyces cerevisiae strain YS2-?adh2.The strain YS2-?adh2 with deleted alcohol dehydrogenase Ⅱ(adh2) gene was isolated in our lab with higher ethanol production than that of the strain YS2.The ace-taldehyde dehydrogenase Ⅵ(ald6) gene encoded a cytosolic acetaldehyde dehydrogenase,a key enzyme of the pyruvate dehydrogenase(PDH) bypass,transfers acetaldehyde to acetate.To disrupt ald6 gene of the strain YS2-?adh2,ald6 gene targeting cassettes were synthesized by long flanking homology PCR(LFH-PCR) and then were transformed into YS2-?adh2 mutants by LiAc/SS Carrier DNA/PEG method.Positive transformants were selected with G418 and further confirmed by PCR.Once correctly integrated into the genome,the selective marker was rescued by transforming the plasmid pSH65 into the positive transformants and inducing the Cre expression with a Cre/loxP-mediated marker removal procedure.We named the ald6 gene knocked-out strain as YS2-?adh2-?ald6 which has a 12.5% higher ethanol production and a 18% lower acetate formation compared to the strain YS2.

Progress in the Studies of Fungal Chitin Synthases / 微生物学通报

Chitin is one of the most important component in fungal cell wall.Biosynthesis of chitin is a complex processes and needs several chitin synthase isoenzymes.The knowledge of structure,function and regulation of chitin synthases is mainly derived from the study of Saccharomyces cerevisiae.In contrast with the 3 chitin synthases in S.cerevisiae,7 were found in most filamentous fungi.In this review the classification and function of chitin synthases are summerized,and progress in the studies on chitin synthases of filamentous fungi which are of theoretical or medical or agricultural importance,including Aspergillus nidulans,Aspergillus fumigatus and Ustilago maydis are emphasized.Recent ad-vance of research on chitin synthase as antifungal target is also discussed.

Disrupting sfa1 Gene to Enhance Biosynthesis of Ethanol in Saccharomyces cerevisiae / 微生物学通报

The sfa1 gene encoded a bifunctional enzyme with the activities of both alcohol dehydrogenase and glutathione-dependent formaldehyde dehydrogenase in Saccharomyces cerevisiae.The gene disruption cassette produced by PCR using the same long oligonucleotides which comprise 19 or 22 nucleotides complementary to sequences in the templates(pUG6 and pUG66 marker plasmid)at 3' end and 45 nucleotides at 5' end that annealed to sites upstream or downstream of the genomic target sequence to be deleted.After two linear disruption cassettes with a Cre/loxP mediated marker were transformed into the cells of Saccharomyces cerevisiae YS-1,the positive transformants were checked by PCR to correct the integration of the cassette and concurrent deletion of the chromosomal target sequence.Once correctly integrated into the genome,the select marker can be efficiently rescued by transformating the plasmid pSH47 into YS-1 and inducing the Cre expression with a Cre/loxP-mediated marker removal procedure.The expression of the Cre recombinase finally resulted in the removal of the marker gene,leaving behind a single loxP site at the chromosomal locus.The diploid mutant YS-1-sfa1 was generated,which could enhance the output of ethanol with 8.0% by shaking culture in flask compared with the original strain YS-1.