A B-lectin receptor kinase gene conferring rice blast resistance

Rice blast, caused by the fungal pathogen Magnaporthe grisea, is one of the most devastating diseases in rice worldwide. The dominant resistance gene, Pi-d2 [previously named Pi-d(t)2], present in the rice variety Digu, confers gene-for-gene resistance to the Chinese blast strain, ZB15. Pi-d2 was previously mapped close to the centromere of chromosome 6. In this study, the Pi-d2 gene was isolated by a map-based cloning strategy. Pi-d2 encodes a receptor-like kinase protein with a predicted extracellular domain of a bulb-type mannose specific binding lectin (B-lectin) and an intracellular serine-threonine kinase domain. Pi-d2 is a single-copy gene that is constitutively expressed in the rice variety Digu. Transgenic plants carrying the Pi-d2 transgene confer race-specific resistance to the M. grisea strain, ZB15. The Pi-d2 protein is plasma membrane localized. A single amino acid difference at position 441 of Pi-d2 distinguishes resistant and susceptible alleles of rice blast resistance gene Pi-d2. Because of its novel extracellular domain, Pi-d2 represents a new class of plant resistance genes.     

Impacts of fertilizer practices on environmental risk of nitrate in semiarid farmlands in the Loess Plateau of China

The lack of understanding of nitrate dynamics in soil profiles of semiarid regions hampers the assessment of the environmental risks associated with nitrate. A long-term field experiment established in the Loess Plateau of Northwest China in 1984 was used to investigate the seasonal dynamics of water and nitrate contents in the soil profile (0–300 cm) under bare fallow and continuous winter wheat (Triticum aestivum L.) with various fertilizer treatments. For treatments without mineral N input (i.e., no fertilizer, farmyard manure alone, and with P fertilizer), the amount of nitrate accumulated in the soil profile (52–120 kg N ha^?1, the average for June, August, February and April) was significantly lower than that (292 kg N ha^?1) accumulated in the bare fallow treatment. A large amount of nitrate (1,065 kg N ha^?1) was found accumulated in the soil profile with the treatment applied with mineral N at a rate of 120 kg N ha^?1 year^?1 for 17 years (1984–2001) and this nitrate moved downward during the wet season (from August to February). Clearly, the amount of nitrate accumulated in the soil profiles, and its tendency of downward movement, appears to potentially be an environmental risk as it may reach groundwater. Fertilization as mineral N fertilizers coupled with FYM or P resulted in 50–70% less nitrate accumulation in the soil profiles than that using mineral N fertilizer alone, and therefore the environmental risk was reduced. It is proposed that a “break point” of nitrate distribution existed in the soil profiles, providing an indication of soil depth to which nitrate can transfer.     

Analysis and location of a rice BAG clone containing telomeric DNA sequences

BAC2, a rice BAC clone containing (TTTAGGG)n homologous sequences, was analyzed by Southern hybridization and DNA sequencing of its subclones. It was disclosed that there were many tandem repeated satellite DNA sequences, called TA352, as well as simple tandem repeats consisting of TTTAGGG or its variant within the BAC2 insert. A 0. 8 kb (TTTAGGG) n-containing fragment in BAC2 was mapped in the telomere regions of at least 5 pairs of rice chromosomes by using fluorescence in situ hybridization (FISH). By RFLP analysis of low copy sequences the BAC2 clone was localized in one terminal region of chromosome 6. All the results strongly suggest that the telomeric DNA sequences of rice are TTTAGGG or its variant, and the linked satellite DNA TA352 sequences belong to telomere-associated sequences.     

Analysis and location of a rice BAG clone containing telomeric DNA sequences

BAC2, a rice BAC clone containing (TTTAGGG)_n homologous sequences, was analyzed by Southern hybridization and DNA sequencing of its subclones. It was disclosed that there were many tandem repeated satellite DNA sequences, called TA352, as well as simple tandem repeats consisting of TTTAGGG or its variant within the BAC2 insert. A 0. 8 kb (TTTAGGG)_n-containing fragment in BAC2 was mapped in the telomere regions of at least 5 pairs of rice chromosomes by using fluorescencein situ hybridization (FISH). By RFLP analysis of low copy sequences the BAC2 clone was localized in one terminal region of chromosome 6. All the results strongly suggest that the telomeric DNA sequences of rice are TTTAGGG or its variant, and the linked satellite DNA TA352 sequences belong to telomere-associated sequences.     

Antiapoptotic property of human alpha-synuclein in neuronal cell lines is associated with the inhibition of caspase-3 but not caspase-9 activity

Abnormalities of alpha-synuclein (alpha-Syn) are mechanistically linked to Parkinson's disease (PD) and other alpha-synucleinopathies. To gain additional insights into the relationships between alpha-Syn expression and cell death, we examined the effects of expressing human alpha-Syn (Hualpha-Syn) variants on the cellular vulnerability to apoptotic stimuli. We show that the expression of wild-type (WT) and A30P mutant, but not A53T mutant, Hualpha-Syn leads to the protection of neuronal cell lines from apoptosis but not necrosis. Significantly, Hualpha-Syn did not protect non-neuronal cell lines from apoptosis. We also show that A53T mutant is a loss of function in regards to the antiapoptotic property since the expression of WT Hualpha-Syn with an excess of A53T mutant Hualpha-Syn leads to protection of the cells from apoptosis. The antiapoptotic property is specific to human alpha-Syn as neither beta-Syn nor mouse alpha-Syn protected cells from apoptosis, and the carboxy-terminal 20 amino acids are required for the antiapoptotic property. Analyses of capase-3 and caspase-9 activation reveal that the antiapoptotic property of Hualpha-Syn in neuronal cell lines is associated with the attenuation of caspase-3 activity without affecting the caspase-9 activity or the levels of cleaved, active caspase-3. We conclude that Hualpha-Syn modulates the activity of cleaved caspase-3 product in neuronal cell lines.     

Design of wide-spectrum inhibitors targeting coronavirus main proteases

The genus Coronavirus contains about 25 species of coronaviruses (CoVs), which are important pathogens causing highly prevalent diseases and often severe or fatal in humans and animals. No licensed specific drugs are available to prevent their infection. Different host receptors for cellular entry, poorly conserved structural proteins (antigens), and the high mutation and recombination rates of CoVs pose a significant problem in the development of wide-spectrum anti-CoV drugs and vaccines. CoV main proteases (M^pros), which are key enzymes in viral gene expression and replication, were revealed to share a highly conservative substrate-recognition pocket by comparison of four crystal structures and a homology model representing all three genetic clusters of the genus Coronavirus. This conclusion was further supported by enzyme activity assays. Mechanism-based irreversible inhibitors were designed, based on this conserved structural region, and a uniform inhibition mechanism was elucidated from the structures of M^pro-inhibitor complexes from severe acute respiratory syndrome-CoV and porcine transmissible gastroenteritis virus. A structure-assisted optimization program has yielded compounds with fast in vitro inactivation of multiple CoV M^pros, potent antiviral activity, and extremely low cellular toxicity in cell-based assays. Further modification could rapidly lead to the discovery of a single agent with clinical potential against existing and possible future emerging CoV-related diseases.     

应用CRISPRi技术敲低耻垢分枝杆菌异柠檬酸脱氢酶基因

成簇的规律间隔的短回文重复序列干扰(clustered regularly interspaced short palindromic repeat interference,CRISPRi)是一种新型转录抑制技术,该系统包含RNA介导的DNA内切酶dCas9和针对目的基因的特异性单向导RNA(single guide RNA,sgRNA),通过形成DNA识别复合物特异性识别相应DNA序列以抑制目的基因的转录。异柠檬酸脱氢酶(isocitrate dehydrogenase,ICD)是三羧酸循环中的关键代谢酶,在分枝杆菌的碳代谢过程中发挥重要作用。本研究利用CRISPRi高效抑制分枝杆菌特定基因表达的方法构建耻垢分枝杆菌icd敲低(icd knockdown,ICD-KD)株。定量聚合酶链反应(quantitative polymerase chain reaction,qPCR)和蛋白免疫印迹检测结果显示,耻垢分枝杆菌中icd转录水平与ICD蛋白表达水平显著下降,表明采用CRISPRi技术成功构建了耻垢分枝杆菌ICD-KD株。进一步研究ICD-KD株的生长情况,测定其在固体培养基点板及液体培养基中的生长曲线,结果均显示ICD-KD株生长速率明显减慢,同时菌体内ICD酶活显著降低,提示ICD对分枝杆菌的生长存活起重要作用。本研究使用CRISPRi技术快速构建了分枝杆菌必需基因的敲低菌株,为后续研究分枝杆菌ICD在碳源代谢通路中的功能和碳通量流向调控机制提供了重要基础。     

云杉雌球花与枝条同源的直观材料

在中学高中生物学教学中,因学生的“植物学”知识欠缺,理解雌球花与枝条同源等概念非常困难。笔者在指导学生研究性学习的备课过程中,发现了罕见的云杉雌球花发育逆转和大孢子叶的多态现象,遂采集了标本,用数码相机拍了照片,并作了进一步的探究,深感是直观教学的良好资料,愿与同行分享。1我校学生对校园云杉的认识云杉(Picea asperata)属裸子植物(Gymnospermae)、球果纲(Coniferopsida)、松科(Pinaceae)、云杉属(Picea),是我校校园绿化的优势树种,所以也是历届学生植物学研究性学习的必选“材料”。根据以往学生的调查记录:我校园内云杉4月中下旬开花,雌球花呈穗状,紫红色,多生于树冠中上部主、侧枝端,较雄球花迟1周     

Levamisole enhances immunity in ducklings vaccinated against Riemerella anatipestifer

Oil‐adjuvant‐inactivated vaccine is one of the most cost‐effective vaccines used to protect ducklings against RA infection; however, it does not provide complete protection in very young ducklings with immature immune systems. In the current study, LMS was used as an immunopotentiator to improve the immune system in ducklings. Serum immunoglobulin (Ig)G titers and the secretions of both Th1‐type (IFN‐γ and IL‐2) and Th2‐type (IL‐4 and IL‐10) cytokines were higher in ducklings that had been vaccinated with LMS. In addition, a significantly higher T‐lymphocyte proliferation rate was obtained with the addition of LMS. Furthermore, all of the ducklings vaccinated with LMS were protected against RA on the 9th day post‐vaccination, whereas only 69.2% of the ducklings were protected in the group that did not receive LMS. These results suggest that LMS might be a useful adjuvant to enhance the immune response of ducklings. The use of LMS may also alleviate local injection lesions, caused by the oil‐emulsion vaccine, by reducing the dose of the vaccine.