The effect of temperature changes and K supply on the reproduction and growth of Bolboschoenus planiculmis

温度变化和钾添加对扁秆藨草生长及繁殖的影响 人类活动导致的气候变暖和农业面源污染已被认为是影响湿地植物生长和繁殖的重要因素。为了预 测和缓解这些人类活动的影响,研究沼泽植物如何响应这些环境变化具有重要意义。本研究选取在欧亚 大陆广泛分布的莎草科球茎植物扁秆藨草(Bolboschoenus planiculmis)为研究对象,考察气温变化(恒温： 15、20、25 °C及交替温度：20/10和30/15 °C)和钾添加(0、1、3、9 和18 mmol/L)对其生长和繁殖性状 的影响。研究结果表明,高的恒温(20、25 °C)比高的交替温度(30/15 °C)更有利于扁秆藨草球茎的形成, 而地上生物量和株高一般在较高温度下(30/15、25 °C)达到最大值。扁秆藨草的繁殖和生长性状均与施钾量 呈驼峰型关系,最适施钾量在1–3 mmol/L K。高恒温效应和最适钾浓度的交互作用对繁殖性状的促进作 用最大,但是,较高的温度(30/15和25 °C)和0–9 mmol/L的钾浓度只促进了生长性状的生长。综上所述, 扁秆藨草的种群优势度可能受益于全球变暖和额外的钾添加。     

The coordination of spindle‐positioning forces during the asymmetric division of the Caenorhabditis elegans zygote

In Caenorhabditis elegans zygote, astral microtubules generate forces essential to position the mitotic spindle, by pushing against and pulling from the cortex. Measuring microtubule dynamics there, we revealed the presence of two populations, corresponding to pulling and pushing events. It offers a unique opportunity to study, under physiological conditions, the variations of both spindle‐positioning forces along space and time. We propose a threefold control of pulling force, by polarity, spindle position and mitotic progression. We showed that the sole anteroposterior asymmetry in dynein on‐rate, encoding pulling force imbalance, is sufficient to cause posterior spindle displacement. The positional regulation, reflecting the number of microtubule contacts in the posterior‐most region, reinforces this imbalance only in late anaphase. Furthermore, we exhibited the first direct proof that dynein processivity increases along mitosis. It reflects the temporal control of pulling forces, which strengthens at anaphase onset following mitotic progression and independently from chromatid separation. In contrast, the pushing force remains constant and symmetric and contributes to maintaining the spindle at the cell centre during metaphase.     

Production of phosphatidylinositol 5‐phosphate via PIKfyve and MTMR3 regulates cell migration

Although phosphatidylinositol 5‐phosphate (PtdIns5P) is present in many cell types and its biogenesis is increased by diverse stimuli, its precise cellular function remains elusive. Here we show that PtdIns5P levels increase when cells are stimulated to move and we find PtdIns5P to promote cell migration in tissue culture and in a Drosophila in vivo model. First, class III phosphatidylinositol 3‐kinase, which produces PtdIns3P, was shown to be involved in migration of fibroblasts. In a cell migration screen for proteins containing PtdIns3P‐binding motifs, we identified the phosphoinositide 5‐kinase PIKfyve and the phosphoinositide 3‐phosphatase MTMR3, which together constitute a phosphoinositide loop that produces PtdIns5P via PtdIns(3,5)P₂. The ability of PtdIns5P to stimulate cell migration was demonstrated directly with exogenous PtdIns5P and a PtdIns5P‐producing bacterial enzyme. Thus, the identified phosphoinositide loop defines a new role for PtdIns5P in cell migration.     

Diagnostics method for the rapid quantitative detection and identification of low-level contamination of high-purity water with pathogenic bacteria

High-purity water (HPW) can be contaminated with pathogenic microorganisms, which may result in human infection. Current culture-based techniques for the detection of microorganisms from HPW can be slow and laborious. The aim of this study was to develop a rapid method for the quantitative detection and identification of pathogenic bacteria causing low-level contamination of HPW. A novel internally controlled multiplex real-time PCR diagnostics assay was designed and optimized to specifically detect and identify Pseudomonas aeruginosa and the Burkholderia genus. Sterile HPW, spiked with a bacterial load ranging from 10 to 10³ cfu/100 ml, was filtered and the bacterial cells were removed from the filters by sonication. Total genomic DNA was then purified from these bacteria and subjected to testing with the developed novel multiplex real-time PCR diagnostics assay. The specific P. aeruginosa and Burkholderia genus assays have an analytical sensitivity of 3.5 genome equivalents (GE) and 3.7 GE, respectively. This analysis demonstrated that it was possible to detect a spiked bacterial load of 1.06 × 10² cfu/100 ml for P. aeruginosa and 2.66 × 10² cfu/100 ml for B. cepacia from a 200-ml filtered HPW sample. The rapid diagnostics method described can reliably detect, identify, and quantify low-level contamination of HPW with P. aeruginosa and the Burkholderia genus in <4 h. We propose that this rapid diagnostics method could be applied to the pharmaceutical and clinical sectors to assure the safety and quality of HPW, medical devices, and patient-care equipment.