小麦抗赤霉病外源种质的创制和育种利用

小麦赤霉病是危害小麦安全生产的重要病害之一,种植抗病品种是防治赤霉病最经济有效的手段。目前在生产上应用的抗源很少,越来越多的研究者将目光转移到小麦的近缘属种,寻找新的抗源以及寻求新的育种突破。携带抗性基因的外源染色体可以通过染色体工程手段以附加系、代换系和易位系等形式导入小麦。综述了将大赖草等多个小麦近缘种的抗赤霉病基因导入普通小麦、创制抗病外源种质和育种利用的最新研究进展,以期为小麦抗赤霉病育种提供参考信息。     

The high expression of Aspergillus pseudoglaucus protease in Escherichia coli for hydrolysis of soy protein and milk protein

Abstract

The hydrolysates of soy protein and milk protein are nutritional and functional food ingredients. Aspergillus pseudoglaucus aspergillopepsin I (App) is an acidic protease, including signal peptide, propeptide, and catalytic domain. Here, we cloned the catalytic domain App with or without propeptide in Escherichia coli. The results showed that the App without propeptide was not expressed or did not exhibit activity and App with propeptide (proApp) was highly expressed with a specific activity of 903?U/mg. Moreover, the denaturation temperature of proApp was 4.1?°C higher than App’s. The proApp showed 104?U/mg and 252?U/mg hydrolysis activities towards soy protein and milk protein under acidic conditions. By RP-HPLC analysis, the peptides obtained from the hydrolysates of soy protein and milk protein were hydrophilic peptides. This work first demonstrates efficient proteolysis of soy protein and milk protein through the functional expression of full-length proApp, which will likely have valuable industrial applications.     

piRNA-Triggered MIWI Ubiquitination and Removal by APC/C in Late Spermatogenesis

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Highlights? MIWI is a substrate of APC/C, and piRNA loading is essential for MIWI ubiquitination ? piRNA loading promotes MIWI binding to the APC/C substrate-binding subunit ? MIWI and piRNAs are coordinately eliminated in late spermatids ? Inhibition of MIWI destruction in late spermatids prevents sperm maturation     

Crp‐dependent cytochrome bd oxidase confers nitrite resistance to Shewanella oneidensis

Shewanella oneidensis is able to respire on a variety of organic and inorganic substrates, including nitrate and nitrite. Conversion of nitrate to nitrite and nitrite to ammonium is catalysed by periplasmic nitrate and nitrite reductases (NAP and NRF) respectively. Global regulator Crp (c yclic AMP r eceptor p rotein) is essential for growth of S. oneidensis on both nitrate and nitrite. In this study, we discovered that crp mutants are not only severely deficient in nitrate or nitrite respiration, but are also hypersensitive to nitrite. This hypersusceptibility phenotype is independent of nitrite respiration. Using random transposon mutagenesis, we obtained 73 Δcrp suppressor strains resistant to nitrite. Transposon insertion sites in 24 suppressor strains were exclusively mapped in the region upstream of the cyd operon encoding a cytochrome bd oxidase, resulting in expression of the operon now driven by a Crp‐independent promoter. Further investigation indicated that the promoter in suppressor strains comes from the transposon. Mutational analysis of the cydB gene (encoding the essential subunit II of the bd oxidase) confirmed that the cytochrome bd oxidase confers nitrite resistance to S. oneidensis.     

A Quality Control Mechanism Linking Meiotic Success to Release of Ascospores

Eukaryotic organisms employ a variety of mechanisms during meiosis to assess and ensure the quality of their gametes. Defects or delays in successful meiotic recombination activate conserved mechanisms to delay the meiotic divisions, but many multicellular eukaryotes also induce cell death programs to eliminate gametes deemed to have failed during meiosis. It is generally thought that yeasts lack such mechanisms. Here, we show that in the fission yeast Schizosaccharomyces pombe, defects in meiotic recombination lead to the activation of a checkpoint that is linked to ascus wall endolysis – the process by which spores are released in response to nutritional cues for subsequent germination. Defects in meiotic recombination are sensed as unrepaired DNA damage through the canonical ATM and ATR DNA damage response kinases, and this information is communicated to the machinery that stimulates ascus wall breakdown. Viability of spores that undergo endolysis spontaneously is significantly higher than that seen upon chemical endolysis, demonstrating that this checkpoint contributes to a selective mechanism for the germination of high quality progeny. These results provide the first evidence for the existence of a checkpoint linking germination to meiosis and suggest that analysis solely based on artificial, enzymatic endolysis bypasses an important quality control mechanism in this organism and potentially other ascomycota, which are models widely used to study meiosis.     

Isolation of Novel Afipia septicemium and Identification of Previously Unknown Bacteria Bradyrhizobium sp. OHSU_III from Blood of Patients with Poorly Defined Illnesses

Cultures previously set up for isolation of mycoplasmal agents from blood of patients with poorly-defined illnesses, although not yielding positive results, were cryopreserved because of suspicion of having low numbers of unknown microbes living in an inactive state in the broth. We re-initiated a set of 3 cultures for analysis of the "uncultivable" or poorly-grown microbes using NGS technology. Broth of cultures from 3 blood samples, submitted from OHSU between 2000 and 2004, were inoculated into culture flasks containing fresh modified SP4 medium and kept at room temperature (RT), 30°C and 35°C. The cultures showing evidence of microbial growth were expanded and subjected to DNA analysis by genomic sequencing using Illumina MiSeq. Two of the 3 re-initiated blood cultures kept at RT after 7–8 weeks showed evidence of microbial growth that gradually reached into a cell density with detectable turbidity. The microbes in the broth when streaked on SP4 agar plates produced microscopic colonies in ∼ 2 weeks. Genomic studies revealed that the microbes isolated from the 2 blood cultures were a novel Afipia species, tentatively named Afipia septicemium. Microbes in the 3^rd culture (OHSU_III) kept at RT had a limited level of growth and could not reach a plateau with high cell density. Genomic sequencing identified the microbe in the culture as a previously unknown species of Bradyrhizobium bacteria. This study reports on the isolation of novel Afipia and Bradyrhizobium species. Isolation of Bradyrhizobium species bacteria has never been reported in humans. The study also reveals a previously unrecognized nature of hematogenous infections by the 2 unique groups of Bradyrhizobiaceae. Our studies show that improvement of culture system plus effective use of NGS technology can facilitate findings of infections by unusual microbes in patients having poorly-defined, sometimes mysterious illnesses.