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41.
With radical global climate change and global warming, high temperature stress has become one of major factors exerting a major influence on crop production. In the cotton (Gossypium hirsutum L.)-growing areas of China, especially in the Yangtze River valley, unexpected periodic episodes of extreme heat stress usually occur in July and August, the peak time of cotton flowering and boll loading, resulting in lower boll set and lint yield. Breeding programs for screening high temperature-tolerant cotton germplasm and cultivars are urgent in order to stabilize yield in the current and future warmer weather conditions. In the present study, 14 cotton cultivars were quantified for in vitro pollen germination and pollen tube growth in response to temperatures ranging from 10 to 50 ℃ at 5 ℃ intervals. Different cotton genotypes varied in their in vitro pollen germination and pollen tube length responses to the different temperatures. Maximum pollen germination and pollen tube length ranged from 25.2% to 56.2% and from 414 to 682 μm, respectively.The average cardinal temperatures (Tmin, Topt, and Tmax) also varied among the 14 cultivars and were 11.8,27.3, and 42.7 ℃ for pollen germination and 11.8, 27.8, and 44.1 ℃ for maximum pollen tube length. Variations in boll retention and boll numbers per plant in field experiments were found for the 14 cotton cultivars and the boll retention and boll retained per plant on 20 August varied considerably in different years according to weather conditions. Boll retention on 20 August was highly correlated with maximum pollen germination (R2=0.84) and pollen tube length (R2=0.64). A screening method based on principle component analysis of the combination of pollen characteristics in an in vitro experiment and boll retention testing in the field environment was used in the present study and, as a result, the 14 cotton cultivars could be classified as tolerant, moderately tolerant, moderately susceptible and susceptible to high temperature.  相似文献   
42.
Diaprepes abbreviatus is an important pest that causes extensive damage to citrus in the USA. Analysis of an expressed sequence tag (EST) library from the digestive tract of larvae and adult D. abbreviatus identified cathepsins as major putative digestive enzymes. One class, sharing amino acid sequence identity with cathepsin L’s, was the most abundant in the EST dataset representing 14.4% and 3.6% of the total sequences in feeding larvae and adults, respectively. The predominant cathepsin (Da-CTSL1) among this class was further studied. Three dimensional modeling of the protein sequence showed that the mature Da-CTSL1 protein folds into an expected cathepsin L structure producing a substrate binding pocket with appropriate positioning of conserved amino acid residues. A full-length cDNA was obtained and the proCTSL1 encoding sequence was expressed in Rosetta™ Escherichia coli cells engineered to express tRNAs specific for eukaryotic codon usage. The Da-CTSL1 was expressed as a fusion protein with GST and His6 tags and purified in the presence of 1% Triton X-100 by Ni-NTA affinity and size exclusion chromatography. Recombinant mature Da-CTSL1 (23 KDa) exhibits optimal activity at pH 8, rather than at acidic pH that was shown of all previously characterized cathepsins L. Substrate specificity supports the hypothesis that Da-CTSL1 is a unique basic cathepsin L and protease inhibitor studies also suggest unique activity, unlike other characterized acidic cathepsin Ls. This paper describes for the first time a prokaryotic expression system for the production of a functional eukaryotic cathepsin L1 from larval gut of D. abbreviatus.  相似文献   
43.
The German government has adopted a law that requires sewage plants to go beyond the recovery of phosphorus from wastewater and to promote recycling. We argue that there is no physical global short‐ or mid‐term phosphorus scarcity. However, we also argue that there are legitimate reasons for policies such as those of Germany, including: precaution as a way to ensure future generations’ long‐term supply security, promotion of technologies for closed‐loop economics in a promising stage of technology development, and decrease in the current supply risk with a new resource pool.  相似文献   
44.
Abstract Stable polymorphisms are commonly observed in experimental bacterial populations grown in homogeneous media. Evidence is accumulating that metabolic interactions might be the main mechanism underlying the emergence and maintenance of such polymorphisms. To date, however, attempts to model the evolution of bacterial polymorphism have not considered metabolism as a possible component of polymorphism maintenance. Here, we propose a simulation approach to model the evolution of selected polymorphisms in a bacterial population. Using recent knowledge of the relationship between bacterial fitness and metabolism, we build a simple metabolic model and test the effect of resource competition on polymorphism. Without making an a priori hypothesis on fitness functions, we show that stable polymorphic situations could be observed under high nutrient competition, and we propose a functional, metabolism‐based explanation to the debated issue of polymorphism maintenance.  相似文献   
45.
46.
锥花莸 (CaryopterispaniculataB .C .Clarke)属莸属 (CaryopterisBunge)的假莸组 (Sect.PseudocaryopterisBriq .)。亚热带分布 ,产印度东北部、尼泊尔、不丹、缅甸北部、泰国 ,我国产云南东南、西南及南部 ,广西、四川、贵州也有分布。生长于海拔 6 50— 2 30 0m的常绿阔叶林、混交林、箐沟疏林下 ,也常见于林缘、路旁、石灰岩山、干草地以及荒地等群落中。莸属不仅系统位置存在争议 (Cantino ,1 992 ) ,且近年来孢粉学 (Mones等 ,1 993)、形态学 (…  相似文献   
47.
Computational fluid dynamics (CFD) modelling based on a commercial package, FLUENT, has been used in the present study. The primary aim of this study is to develop a novel implant by employing CFD techniques. Firstly, CFD analyses on the best design commercially available, which is the Ahmed Glaucoma Valve (AGV®), are accomplished. In the light of the results, the new design focus is selected as the valve. The new design is analysed using GAMBIT and FLUENT software. CFD analyses of the new design and the AGV® are compared and the strengths of the new design are revealed. The results are also compared with the experimental studies AGV® in the literature. It is deduced that the proposed model shows a nonlinear pressure drop response, which is quite similar to that of AGV®. The optimum combination would be a flow rate of 2.5 μl/min and a pressure drop of 1054.58 Pa for the proposed model.  相似文献   
48.
抗菌肽因其具有广谱抗菌活性、不容易引起抵抗性,被认为是先天免疫系统对抗微生物感染的多功能工具。然而,天然抗菌肽存在抗菌活性低、稳定性低、溶血性高等问题,使其较难应用于临床,所以研究人员对抗菌肽进行改良设计以期获得更高抗菌活性、更低溶血活性的新型抗菌肽。另外,天然抗菌肽作为一类免疫效应因子而被发现,其表现出的抑菌、免疫调节、内毒素中和等作用,使得研究人员对抗菌肽在抗炎作用的研究表现出极大的兴趣。就抗菌肽的药物设计方法及抗炎作用机制进行综述。  相似文献   
49.
SnS2 nanoplatelet electrodes can offer an exceptionally high pseudocapacitance in an organic Na+ ion electrolyte system, but their underlying mechanisms are still largely unexplored, hindering the practical applications of pseudocapacitive SnS2 anodes in Na‐ion batteries (SIBs) and Na hybrid capacitors (SHCs). Herein, SnS2 nanoplatelets are grown directly on SnO2/C composites to synthesize SnS2/graphene‐carbon nanotube aerogel (SnS2/GCA) by pressurized sulfidation where the original morphology of carbon framework is preserved. The composite electrode possessing a large surface area delivers a remarkable specific capacity of 600.3 mA h g?1 at 0.2 A g?1 and 304.8 mA h g?1 at an ultrahigh current density of 10 A g?1 in SIBs. SHCs comprising a SnS2/GCA composite anode and an activated carbon cathode present exceptional energy densities of 108.3 and 26.9 W h kg?1 at power densities of 130 and 6053 W kg?1, respectively. The in situ transmission electron microscopy and the density functional theory calculations reveal that the excellent pseudocapacitance originates from the combination of Na adsorption on the surface/Sn edge of SnS2 nanoplatelets and ultrafast Na+ ion intercalation into the SnS2 layers.  相似文献   
50.
Many models of honest signaling, based on Zahavi's handicap principle, predict that if receivers are interested in a quality that shows continuous variation across the population of signalers, then the distribution of signal intensities will also be continuous. However, it has previously been noted that this prediction does not agree with empirical observation in many signaling systems, where signals are limited to a small number of levels despite continuous variation in the trait being signaled. Typically, there is a critical value of the trait, with all individuals with trait values on one side of the threshold using the same cheap signal, and all those with trait values on the other side of the threshold using the same expensive signal. It has already been demonstrated that these classical models naturally predict such "all-or-nothing signaling" if it is additionally assumed that receivers suffer from perceptual error in evaluating signal strength. We show that such all-or-nothing signaling is also predicted if receivers are limited to responding to the signals in one of two ways. We suggest that many ecological situations (such as the decision to attack the signaler or not, or mate with the signaler or not) involve such binary choices.  相似文献   
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