Chromosome‐level genome assembly of the greenhouse whitefly (Trialeurodes vaporariorum Westwood)

The greenhouse whitefly, Trialeurodes vaporariorum Westwood, is an agricultural pest of global importance. Here we report a 787‐Mb high‐quality draft genome sequence of T. vaporariorum assembled from PacBio long reads and Hi‐C chromatin interaction maps, which has scaffold and contig N50 lengths of 70 Mb and 500 kb, respectively, and contains 18,275 protein‐coding genes. About 98.8% of the assembled contigs were placed onto the 11 T. vaporariorum chromosomes. Comparative genomic analysis reveals significantly expanded gene families such as aspartyl proteases in T. vaporariorum compared to Bemisia tabaci Mediterranean (MED) and Middle East‐Asia Minor 1 (MEAM1). Furthermore, the cytochrome CYP6 subfamily shows significant expansion in T. vaporariorum and several genes in this subfamily display developmental stage‐specific expression patterns. The high‐quality T. vaporariorum genome provides a valuable resource for research in a broad range of areas such as fundamental molecular ecology, insect–plant/insect–microorganism or virus interactions and pest resistance management.     

A green and effective method for the determination of metalaxyl enantiomers in tobacco and soil by supercritical fluid chromatography–tandem mass spectrometry

We reported a new methodology for the stereoselective determination of metalaxyl enantiomers in tobacco and soil. The QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was used for the extraction and clean-up of the tobacco and soil samples. Separation of the metalaxyl enantiomers was performed on an ACQUITY UPC2 Trefoil CEL1 chiral column coupled with supercritical fluid chromatography with tandem mass spectrometry (SFC-MS/MS), and the run time was only 5 minutes. Under the optimized conditions, the recoveries for the enantiomers were between 78.2% and 93.3% with intraday relative standard deviations (RSDs) ranging from 1.1% to 5.4%. The limit of detection (LOD) for the enantiomers in tobacco and soil varied from 0.005 to 0.007 mg/kg, and the limit of quantitation (LOQ) ranged from 0.017 to 0.020 mg/kg. In this method, only a small amount of methanol was consumed to obtain a rapid stereoselective separation. This proposed method showed good accuracy and precision and might be suitable for fast enantioselective determination of metalaxyl in food and environmental samples. The developed method was further validated by application to the analysis of authentic samples.     

Integrative structure and function of the yeast exocyst complex

Exocyst is an evolutionarily conserved hetero‐octameric tethering complex that plays a variety of roles in membrane trafficking, including exocytosis, endocytosis, autophagy, cell polarization, cytokinesis, pathogen invasion, and metastasis. Exocyst serves as a platform for interactions between the Rab, Rho, and Ral small GTPases, SNARE proteins, and Sec1/Munc18 regulators that coordinate spatial and temporal fidelity of membrane fusion. However, its mechanism is poorly described at the molecular level. Here, we determine the molecular architecture of the yeast exocyst complex by an integrative approach, based on a 3D density map from negative‐stain electron microscopy (EM) at ~16 Å resolution, 434 disuccinimidyl suberate and 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride cross‐links from chemical‐crosslinking mass spectrometry, and partial atomic models of the eight subunits. The integrative structure is validated by a previously determined cryo‐EM structure, cross‐links, and distances from in vivo fluorescence microscopy. Our subunit configuration is consistent with the cryo‐EM structure, except for Sec5. While not observed in the cryo‐EM map, the integrative model localizes the N‐terminal half of Sec3 near the Sec6 subunit. Limited proteolysis experiments suggest that the conformation of Exo70 is dynamic, which may have functional implications for SNARE and membrane interactions. This study illustrates how integrative modeling based on varied low‐resolution structural data can inform biologically relevant hypotheses, even in the absence of high‐resolution data.     

江苏省不同种植年限的西/甜瓜农田土壤线虫群落特征

在江苏省主要西/甜瓜产区,采集不同种植年限的西/甜瓜农田土壤,采用线虫形态学的鉴定方法,分析了不同种植年限西/甜瓜农田土壤线虫的数量、群落结构及相关生态指数的变化。结果表明:所有调查样点中,共发现土壤线虫54属,平均682条·100 g^-1干土,其中原杆属线虫、拟丽突属线虫和矮化属线虫在不同种植年限的西/甜瓜农田土壤中均为优势属;随着种植年限的增加,土壤线虫的总数量虽无显著变化,但其中食细菌类线虫和杂食-捕食类线虫数量显著减少,而植物寄生类线虫数量显著增加;植物寄生类线虫中的矮化属、根结属线虫数量不断增加;随着种植年限的增加,土壤线虫的多样性指数(H)、瓦斯乐斯卡指数(WI)、自由生活线虫成熟度指数(MI)显著降低,线虫通道指数(NCR)、植物寄生线虫成熟度指数(PPI)、PPI/MI显著升高,其他指数无显著变化;相关性分析结果显示,土壤线虫数量与土壤pH、速效磷、有效锌和有效硼均呈显著正相关;土壤p H、有机质、全氮、速效钾、有效硼和有效锌对土壤优势属线虫的影响较大;连续种植西/甜瓜会增加土壤植物寄生类线虫数量,进而可能造成西/甜瓜连作障碍的发生;连续种植6~10年,土壤线虫的多样性最低、稳定性最差,土壤环境已趋于恶化。     

小叶锦鸡儿天然居群叶形态性状变异研究

为揭示小叶锦鸡儿(Caragana microphylla)天然居群叶形态性状的变异规律及其生态适应性特征,该研究以10个小叶锦鸡儿天然居群为对象,通过多重比较、巢式方差分析、相关性分析、聚类分析和主成分分析等方法,对7个叶形态性状进行分析。结果表明：(1)小叶锦鸡儿叶形态性状在居群内和居群间均存在极显著差异(P < 0.01),平均变异系数为10.13%,不同性状的变异幅度为6.23%~12.78%;平均叶形态性状的表型分化系数为43.62%,居群内变异(30.09%)大于居群间变异(24.91%),说明居群内是其叶形态性状变异的主要来源。(2)相关性分析表明,环境因子对小叶锦鸡儿的叶形态性状变异有很大的影响,在地理空间上主要呈现出沿海拔梯度的变异模式;主成分分析的结果显示,小叶宽、叶柄宽和叶柄长对小叶锦鸡儿叶形态变异起主导作用;利用欧式距离对小叶锦鸡儿居群进行UPGMA聚类分析结果显示,基于叶形态性状和环境因子可分别将小叶锦鸡儿10个居群分为3类和2类,Mantel检验结果表明,小叶锦鸡儿的叶形态性状变异不存在地理连续性。研究结果为小叶锦鸡儿的适应性进化和开发利用提供了理论依据。     

外源水杨酸对NaCl胁迫下白榆幼苗光合作用及离子分配的影响

以1年生白榆幼苗为研究对象,设置0、0.5、1.0和2.0 mmol·L^-1水杨酸(SA)与0、50、100和150 mmol·L^-1 NaCl处理组合,考察盐胁迫下白榆幼苗生物量、光合色素含量、光合作用参数及根叶离子含量、分配、运输的情况,探讨外源SA对NaCl胁迫下白榆幼苗耐盐生理特征的影响。结果表明:(1)NaCl胁迫显著抑制了白榆幼苗的生长、光合色素含量及光合能力,并破坏了白榆体内离子平衡。(2)喷施外源SA使盐胁迫下白榆幼苗的干重和根冠比均不同程度升高,0.5和2.0 mmol·L^-1 SA不同程度提高了50和100 mmol·L^-1 NaCl处理组幼苗叶片光合色素含量。(3)0.5 mmol·L^-1 SA显著提升了50 mmol·L^-1 NaCl处理组白榆幼苗的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr),1.0和2.0 mmol·L^-1 SA对150 mmol·L^-1 NaCl处理组幼苗净光合速率改善效果较好,外源SA对100 mmol·L^-1 NaCl处理组幼苗的光合作用参数无显著影响。(4)NaCl胁迫下,外源SA处理的白榆幼苗叶和根Na^+含量及Na^+/K^+、Na^+/Ca^2+和Na^+/Mg^2+显著降低,离子选择运输系数SK,Na、SCa,Na和SMg,Na升高,从而促进了幼苗K^+、Ca^2+和Mg^2+由根向叶片的转运;隶属函数分析发现对白榆幼苗叶和根中离子含量改善效果最好的SA浓度分别为1.0和2.0 mmol·L^-1。因此,适宜浓度的外源水杨酸能够有效改善NaCl胁迫下白榆幼苗的光合能力,有效调节白榆幼苗体内离子状态,从而增强白榆对NaCl胁迫的抗性。     

睾酮对鸟类繁殖影响研究进展

类固醇激素睾酮是影响鸟类繁殖最重要的性激素之一,与鸟类的繁殖行为的各个方面息息相关。睾酮通过影响鸟类的羽色、鸣声等来影响鸟类的配偶选择,同时睾酮可以调节配偶选择和繁殖投入之间的平衡。睾酮水平影响出雏数、出飞数、孵化率成功率等繁殖成效。睾酮还对个体的免疫活性和个体的存活率等产生影响。目前关于睾酮对鸟类繁殖影响的研究大多是通过外源性植入睾酮的方式来改变个体睾酮的浓度,其研究结果也常出现相互矛盾之处,对于自然状态下影响睾酮水平变化的因素尚缺乏了解,睾酮对雌雄鸟在繁殖过程中的影响也不尽相同,有必要继续深入研究。