Inheritance of freezing resistance in interspecific F1 hybrids of Eucalyptus

Summary The inheritance of freezing resistance in interspecific F₁ hybrid families of Eucalyptus encompassing 27 different species combinations and a range of levels of hardiness was examined. Freezing resistance was assessed by determining the temperatures required to cause either 30% (T30), 40% (T40), or 50% (T50) leakage of electrolytes from excised leaf discs subjected to artificial freezing. Highly significant variation in freezing resistance occurred between species; the maximum difference between parents in any specific combination was over 9°C (E. gunnii x E. globulus). Freezing resistance was inherited in a predominantly additive manner in interspecific hybrids, although there was a tendency towards partial dominance toward the more sensitive species in some combinations (e.g., E. nitens x E. Globulus, E. nitens x E. camaldulensis, E. gunnii x E. globulus). The full expression of this genetic variation appeared to increase with hardiness and in some cases appeared to vary with ontogeny. Estimates of individual narrow-sense heritability of freezing resistance for pure E. nitens families were h ² = 0.66±0.44 and 0.46±0.44. Across all species combinations examined, the heritability of F₁ family means estimated from midparent regression was h ² = 0.76±0.06 and h ² = 0.89±0.06 for T40 and T50 values, respectively. The advantage of using selected parents for interspecific hybridization is demonstrated and the implications of these results for breeding for freezing resistance in Eucalyptus are discussed.     

Synthesis of spoIIA and spoVA mRNA in Bacillus subtilis

The expression of the spoIIA and spoVA sporulation loci of Bacillus subtilis was examined by using DNA-RNA hybridization to detect the time of appearance of their corresponding mRNA molecules in wild-type and asporogenous mutants of B. subtilis. From the size of the mRNA molecules it is clear that both the spoIIA and spoVA loci are polycistronic operons. Neither of the mRNA molecules is polyadenylated. The results also indicate the spoIIA operon is regulated by two promoters which become functional at different times.     

基于土地利用变化与生态系统服务供需的中国野生亚洲象时空迁移特征分析

2021年4月,我国15头野生亚洲象(Elephas maximus)从西双版纳一路北迁至昆明市受到了全世界的关注,分析我国野生亚洲象分布区土地利用变化、生态系统服务供需关系如何影响野生亚洲象分布,对保护亚洲象与提高当地人类福祉具有重要的意义。利用生态系统服务价值当量因子法和生态系统服务需求模型计算中国野生亚洲象分布区1990、2005、2015年生态系统服务供给价值与需求指数,通过空间标准化匹配出四种生态系统服务供需模式,探究我国野生亚洲象偏好分布的供需模式。结果表明,林地、草地和耕地是最主要的土地利用类型,1990—2015年,林地、草地和耕地的面积变化率分别为1.09%、-4.82%、-4.86%。1990、2005、2015年生态系统供给总价值分别为6108.55亿元、7434.41亿元、13973.37亿元;生态系统服务需求不断提高,整体呈现中间高,四周低的分布格局。在研究的25年内,亚洲象分布于高供给-高需求与高供给-低需求区域,且有向高供给-高需求区域迁徙的趋势。     

The topology of chromatin-binding domains in the NuRD deacetylase complex

Class I histone deacetylase complexes play essential roles in many nuclear processes. Whilst they contain a common catalytic subunit, they have diverse modes of action determined by associated factors in the distinct complexes. The deacetylase module from the NuRD complex contains three protein domains that control the recruitment of chromatin to the deacetylase enzyme, HDAC1/2. Using biochemical approaches and cryo-electron microscopy, we have determined how three chromatin-binding domains (MTA1-BAH, MBD2/3 and RBBP4/7) are assembled in relation to the core complex so as to facilitate interaction of the complex with the genome. We observe a striking arrangement of the BAH domains suggesting a potential mechanism for binding to di-nucleosomes. We also find that the WD40 domains from RBBP4 are linked to the core with surprising flexibility that is likely important for chromatin engagement. A single MBD2 protein binds asymmetrically to the dimerisation interface of the complex. This symmetry mismatch explains the stoichiometry of the complex. Finally, our structures suggest how the holo-NuRD might assemble on a di-nucleosome substrate.     

Structure of a bacterial type IV secretion core complex at subnanometre resolution

Type IV secretion (T4S) systems are able to transport DNAs and/or proteins through the membranes of bacteria. They form large multiprotein complexes consisting of 12 proteins termed VirB1‐11 and VirD4. VirB7, 9 and 10 assemble into a 1.07 MegaDalton membrane‐spanning core complex (CC), around which all other components assemble. This complex is made of two parts, the O‐layer inserted in the outer membrane and the I‐layer inserted in the inner membrane. While the structure of the O‐layer has been solved by X‐ray crystallography, there is no detailed structural information on the I‐layer. Using high‐resolution cryo‐electron microscopy and molecular modelling combined with biochemical approaches, we determined the I‐layer structure and located its various components in the electron density. Our results provide new structural insights on the CC, from which the essential features of T4S system mechanisms can be derived.     

Unravelling mitochondrial retrograde regulation in the abiotic stress induction of rice ALTERNATIVE OXIDASE 1 genes

Mitochondrial retrograde regulation (MRR) is the transduction of mitochondrial signals to mediate nuclear gene expression. It is not clear whether MRR is a common regulation mechanism in plant abiotic stress response. In this study, we analysed the early abiotic stress response of the rice OsAOX1 genes, and the induction of OsAOX1a and OsAOX1b (OsAOX1a/b) was selected as a working model for the stress‐induced MRR studies. We found that the induction mediated by the superoxide ion (O_2·^‐)‐generating chemical methyl viologen was stronger than that of hydrogen peroxide (H₂O₂). The addition of reactive oxygen species (ROS) scavengers demonstrated that the stress induction was reduced by eliminating O_2·^‐. Furthermore, the stress induction did not rely on chloroplast‐ or cytosol‐derived O_2·^‐. Next, we generated transgenic plants overexpressing the superoxide dismutase (SOD) gene at different subcellular locations. The results suggest that only the mitochondrial SOD, OsMSD, attenuated the stress induction of OsAOX1a/b specifically. Therefore, our findings demonstrate that abiotic stress initiates the MRR on OsAOX1a/b and that mitochondrial O_2·^– is involved in the process.     

Identification of Legionella spp. in Environmental Water Samples by ScanVIT-Legionella™ Method in Spain

Rapid and more sensitive methods for the detection and quantification of viable Legionella cells have been developed. In this paper, a comparative analysis of environmental water samples using the ScanVIT-Legionella? method and the traditional “gold standard” method of culturing is realised indicating the usefulness of the ScanVIT method. The ScanVIT-Legionella? method was performed on environmental water samples from different locations of Huesca region (Spain). Legionella micro-colonies should appear green colour and Legionella pneumophila micro-colonies appear red. Twenty-one environmental water samples analysed by standard culture plus five control samples (Two sterile water samples with Legionella as positive controls and three sterile water samples as negative controls). All of them were used to apply ScanVIT-Legionella? method. From of 21 environmental samples eleven were positive, six negative with both methods and four samples were negative for culture method and positive for ScanVIT-Legionella? method. The positive control samples were positive and the negative were negative for both methods. A comparative analysis of the results obtained with two methods showed a strong positive determination coefficient (R² = 0.99753). The results demonstrate the usefulness of the ScanVIT-Legionella? method as a rapid diagnostic tool in order to provide a diagnosis as quick as possible. ScanVIT-Legionella? method offers a series of advantages such as quickly diagnosis, higher sensitivity and the possibility to identify Legionella spp. and L. pneumophila simultaneously.     

Clostridium perfringens epsilon toxin H149A mutant as a platform for receptor binding studies

Clostridium perfringens epsilon toxin (Etx) is a pore‐forming toxin responsible for a severe and rapidly fatal enterotoxemia of ruminants. The toxin is classified as a category B bioterrorism agent by the U.S. Government Centres for Disease Control and Prevention (CDC), making work with recombinant toxin difficult. To reduce the hazard posed by work with recombinant Etx, we have used a variant of Etx that contains a H149A mutation (Etx‐H149A), previously reported to have reduced, but not abolished, toxicity. The three‐dimensional structure of H149A prototoxin shows that the H149A mutation in domain III does not affect organisation of the putative receptor binding loops in domain I of the toxin. Surface exposed tyrosine residues in domain I of Etx‐H149A (Y16, Y20, Y29, Y30, Y36 and Y196) were mutated to alanine and mutants Y30A and Y196A showed significantly reduced binding to MDCK.2 cells relative to Etx‐H149A that correlated with their reduced cytotoxic activity. Thus, our study confirms the role of surface exposed tyrosine residues in domain I of Etx in binding to MDCK cells and the suitability of Etx‐H149A for further receptor binding studies. In contrast, binding of all of the tyrosine mutants to ACHN cells was similar to that of Etx‐H149A, suggesting that Etx can recognise different cell surface receptors. In support of this, the crystal structure of Etx‐H149A identified a glycan (β‐octyl‐glucoside) binding site in domain III of Etx‐H149A, which may be a second receptor binding site. These findings have important implications for developing strategies designed to neutralise toxin activity.     

新生儿肺炎的临床表现及x线特征的探讨

目的：探讨新生儿肺炎（neonatal pneumonia,NP）的临床表现及x线特征,以提高对NP的临床认识。方法：选择2011年6月至2012年10月在我院确诊为NP的新生儿73例,均经x线检查,回顾性分析患儿的临床资料,总结并分析患儿的临床表现及x线特征。结果：NP患儿的临床症状主要表现为呼吸急促、发绀、咳嗽、吐沫、呛奶和三凹征,部分患儿体温正常;NP的x线影像表现具有多样性,以不同程度的支气管肺炎多见,主要表现为肺纹理增多增密,局部肺野透光度降低或透光度增强。结论：NP患儿的临床症状以呼吸急促、发绀、咳嗽、吐沫、呛奶和三凹征为主,x线检查可为NP的早期诊断提供重要的临床信息,临床医师应根据NP患儿的x线影像的多样性,密切结合患儿的临床症状,做出综合分析。     

异丙酚和氯胺酮对大鼠离体缺血再灌注损伤心肌脂质过氧化的影响

目的：比较异丙酚和氯胺酮对大鼠离体缺血再灌注损伤心肌脂质过氧化的影响。方法：成年Wistar大鼠18只,雌雄不拘。体重240-300g,随机分为3组（T1=6）：心肌缺血再灌注损伤组（I／R组）,异丙酚组（P组）,氯胺酮组（K组）。采用Langendorff灌装置建立离体心脏缺血再灌注模型,将心脏连接至Langendorff逆灌装置,3组均以K-H液平衡灌注10min后,再分别以K．H液、含30μmol/L。异丙酚的K-H液、含10μmol-L-1氯胺酮的K-H液灌注10min,然后全心停灌25min,再分别以停灌前相同的灌注液恢复灌注30min。留取冠脉流出液测定总LDH活性;灌注末取左室心肌组织置于2．5％的戊二醛固定,观察心肌的超微结构;心尖部心肌组织留待检测8-异前列腺素和SOD活性。结果：与I／R组比较,P组8-异前列腺素含量降低,SOD活性升高,LDH活性降低（P〈0．05）;K组8-异前列腺素含量,SOD及LDH活性均无统计学意义（P〉0．05）;与P组比较,K组8-异前列腺素含量升高,SOD及LDH活性降低（P〈0．05）;P组心肌超微结构损伤较m组和K组也明显改善。结论：异丙酚可显著减轻心肌缺血再灌注损伤大鼠的脂质过氧化和心肌缺血再灌注损伤,而氯胺酮没有抗心肌缺血再灌注损伤心肌脂质过氧化的作用。