非生物胁迫下植物表观遗传变异的研究进展

植物在整个生命过程中固着生长,不能主动躲避外界不良环境的危害,需要通过自身的防御机制来抵御和适应外界胁迫,而表观遗传修饰在调控植物应对不良环境胁迫中起重要作用。该文从DNA甲基化、组蛋白修饰、染色质重塑和非编码RNA等方面进行了综述,主要阐述了近年来国内外有关非生物胁迫下植物的表观遗传变化,以期为利用表观遗传变异提高植物的抗胁迫能力提供参考。     

Optimization of <i>Agrobacterium tumefaciens</i>-Mediated Genetic Transformation of Maize

Immature embryos of inbred maize (Zea mays) lines (H8183, H8184, and H8185) were used for Agrobacterium infection. We used the β-glucuronidase gene (GUS) as the target gene and the glufosinate resistance gene (bar) as the selection marker. We conducted research on several aspects, such as different genotypes, coculture conditions, screening agent concentrations, and concentrations of indole-3-butytric acid (IBA), 6-benzylaminopurine (6-BA), and ascorbic acid (Vc) in the differentiation medium. We optimized the genetic transformation system, and the obtained results indicated that among the three lines studied, the induction rate of H8185 was the highest at 93.2%, followed by H8184, with H8183 having the lowest induction rate (80.1%). The best coculture method was that using the N6 coculture medium layered with a sterile filter paper. Using orthogonal analysis, we found that the optimal combination of the three factors in the differentiation medium was A₃ (1 mg mL⁻¹ IBA), B₃C₁ (1.6 mg mL⁻¹ 6-BA), and D₃ (1.5 mg mL⁻¹ Vc). Through GUS staining analysis, Bar test-strip analysis, and polymerase chain reaction, five transgenic plants were finally obtained. This study established the optimal conditions for genetic transformation in maize.     

An Efficient Correction Algorithm for Eliminating Image Misalignment Effects on Co-Phasing Measurement Accuracy for Segmented Active Optics Systems

The misalignment between recorded in-focus and out-of-focus images using the Phase Diversity (PD) algorithm leads to a dramatic decline in wavefront detection accuracy and image recovery quality for segmented active optics systems. This paper demonstrates the theoretical relationship between the image misalignment and tip-tilt terms in Zernike polynomials of the wavefront phase for the first time, and an efficient two-step alignment correction algorithm is proposed to eliminate these misalignment effects. This algorithm processes a spatial 2-D cross-correlation of the misaligned images, revising the offset to 1 or 2 pixels and narrowing the search range for alignment. Then, it eliminates the need for subpixel fine alignment to achieve adaptive correction by adding additional tip-tilt terms to the Optical Transfer Function (OTF) of the out-of-focus channel. The experimental results demonstrate the feasibility and validity of the proposed correction algorithm to improve the measurement accuracy during the co-phasing of segmented mirrors. With this alignment correction, the reconstructed wavefront is more accurate, and the recovered image is of higher quality.     

Formation Mechanism and Occurrence Law of Pod Shattering in Soybean: A Review

Seed shattering refers to the phenomenon in which the pods split along the abdominal and back sutures before the crop is received, so that the seeds are spread. Seed shattering is vital to the reproduction of their offspring in wild plants, but it is also the main cause of crop yield loss reason. Pod-explosion resistance is a complex process of physical and physiological and biochemical reactions. Soybean seed shattering phenomenon is widespread, which severely restricts the development of soybean industry. Seed shattering (pod cracking or fruit dropping) is essential for the reproduction of its offspring in wild plants, but it is also the main cause of crop yield loss. This article analyzes the morphology and structure of pods related to seed shattering from the morphology of pods. On the basis of the regularity of the occurrence of seed shattering and the summary of phenotypic index identification methods, physiologically introduced the regulation mechanism of key enzymes and endogenous hormones on seed shattering. The localization, labeling and cloning of seed shattering genes are introduced in molecular biology. The study focused on reviewing the latest advances in the research on soybean seed shattering characteristics, and discussed with the research results of related crops. Finally, the research and application of soybean seed shattering resistance were prospected for several aspects.     

Discovery and optimization of potent and selective imidazopyridine and imidazopyridazine mTOR inhibitors

mTOR is a critical regulator of cellular signaling downstream of multiple growth factors. The mTOR/PI3K/AKT pathway is frequently mutated in human cancers and is thus an important oncology target. Herein we report the evolution of our program to discover ATP-competitive mTOR inhibitors that demonstrate improved pharmacokinetic properties and selectivity compared to our previous leads. Through targeted SAR and structure-guided design, new imidazopyridine and imidazopyridazine scaffolds were identified that demonstrated superior inhibition of mTOR in cellular assays, selectivity over the closely related PIKK family and improved in vivo clearance over our previously reported benzimidazole series.     

变性高效液相色谱检测沙门氏菌、空肠弯曲菌和肠出血性大肠杆菌

应用多重PCR 反应(multiplex PCR,mPCR)结合变性高效液相色谱(denaturing high-performance liquid chromatography,DHPLC)技术建立食品中沙门氏菌、空肠弯曲菌和肠出血性大肠杆菌O157:H7的快速检测方法.以编码沙门氏菌的fimY基因、编码空肠弯曲菌的gyrA基因和编码肠出血性大肠杆菌O157:H7的rfbE基因为靶基因,选择3对引物,建立并优化了快速鉴别沙门氏菌、空肠弯曲菌和肠出血性大肠杆菌O157:H7的多重PCR体系,扩增产物分别为284、159和499 bp,并验证了该多重PCR具有特异性.沙门氏菌、空肠弯曲菌和肠出血性大肠杆菌O157:H7标准菌株稀释成不同梯度,做灵敏度检测.试验结果表明该方法有很好的特异性,且灵敏度高,检测限可达到:沙门氏菌1.5 CFU/ml、空肠弯曲菌15 CFU/ml、肠出血性大肠杆菌O157:H7 15 CFU/ml.在随机采集的226份冷冻鸡肉类样品中,检出了7份样品为沙门氏菌阳性、10份为空肠弯曲菌阳性、1份为肠出血性大肠杆菌O157:H7阳性.研究建立的多重PCR-DHPLC方法可特异、灵敏地实现对沙门氏菌、空肠弯曲菌和肠出血性大肠杆菌O157:H7的快速检测.