Microbodies in fungi: a review

Summary Microbodies are ubiquitous organelles in fungal cells, occurring in both vegetative hyphae and spores. They are bounded by a single membrane and may contain a crystalloid inclusion with subunits spaced at regular intervals. Typically, they contain catalase which reacts with the cytochemical stain 3,3-diaminobenzidine to yield an electron-opaque product, urate oxidase,l--hydroxy acid oxidase andd-amino acid oxidase. Their fragility and the necessity to disrupt the tough fungal cell wall before isolating them make them difficult to isolate. Analysis of enzymes in purified or partially purified microbodies from fungi indicates that they participate in fatty acid degradation, the glyoxylate cycle, purine metabolism, methanol oxidation, assimilation of nitrogenous compounds, amine metabolism and oxalate synthesis. In organisms where microbodies are known to contain enzymes of the glyoxylate cycle, they are known as glyoxysomes; where they are known to contain peroxidatic activity, they are known as peroxisomes. In some cases microbodies contain enzymes for only a portion of a pathway or cycle. Thus, they must be involved in metabolic cooperation with other organelles, particularly mitochondria. The number, size and shape of microbodies in cells, their buoyant density and their enzyme contents may vary with the composition of the medium; their proliferation in cells is regulated by the growth environment. The isolation from the same organism of microbodies with different buoyant densities and different enzymes suggests strongly that more than one type of microbody can be formed by fungi.     

Arabidopsis: Sensitivity of growth to high temperature

Arabidopsis thaliana seedlings as measured by an electrolyte leakage assay, have been found to be extremely sensitive to high temperature stress as compared to a high temperature tolerant variety (Tracy) of soybean. Over 50% ion leakage occurred in Arabidopsis leaves during a 15-minute exposure to 50°C, indicating a heat killing time of less than 15 minutes. In contrast, the heat killing time for soybean at 50°C was over five times longer. When soybean or Arabidopsis seedlings in culture plates were exposed to 37°C for 2 hours and then returned to 23°C, they suffered no apparent short-term or long-term damage. Soybean seedlings given a 42°C, treatment for 2 hours also showed no damage. Arabidopsis seedlings after a 42°C treatment for 2 hours showed no apparent immediate damage, but 48 hours after return to 23°C severe damage symptoms were visible and after 96 hours all the seedlings were dead. Both soybean and Arabidopsis seedlings synthesize heat shock proteins (hsps) when exposed to 42°C for 2 hours. The hsps synthesized are of similar molecular weights, although the relative abundances of the different size classes are very different in the two plants. Even though hsps are produced in Arabidopsis seedlings after a 2 hour exposure to 42°C their presence is not sufficient for the seedlings to recover from the effects of rhe heat shock when returned to 23°C. Our results show that Arabidopsis has a heat sensitive genotype. This along with its other characteristics should make it a good model system in which to assay in transgenic plants, the functions of homologous and heterologous genes that might be candidates for determining heat tolerance in plants.     

Influence of galls of Phanacis taraxaci on carbon partitioning within common dandelion, Taraxacum officinale

We examined how leaf galls, induced by the cynipid wasp Phanacis taraxaci, influence the partitioning of photoassimilates within the host, the common dandelion, Taraxacum officinale. Galled and ungalled plants were exposed to ¹⁴CO₂ and the labelled photoassimilates accumulating within galls and other parts of the host were measured. During the growth phase of the gall they were physiological sinks for photoassimilates, accumulating 9% to 70% of total carbon produced by the host, depending upon the number of galls per plant. High levels of ¹⁴C assimilation in the leaves of galled plants compared to controls, suggest that galls actively redirect carbon resources from unattacked leaves of their host plant. This represents a significant drain on the carbon resources of the host, which increases with the number and size of galls per plant. Active assimilation of ¹⁴C by the gall is greatest in the growth phase and is several orders of magnitude lower in the maturation phase. This finding is consistent with physiological and anatomical changes that occur during the two phases of gall development and represents a key developmental strategy by cynipids to ensure adequate food resources before larval growth begins.     

Waxes enhance Plutella xylostella oviposition in response to sinigrin and cabbage homogenates

Oviposition by the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), on substrates treated with host stimuli (cabbage homogenate or sinigrin) and/or waxes (paraffin or a mixture of 10 single chain n-alkanes) was quantified using continuous observations and endpoint bioassays. Paraffin or an n-alkane mixture applied over cabbage homogenate or sinigrin caused an increase in oviposition compared to that on any single stimulus in choice tests. Sinigrin alone at 10^–5 M to 10^–2 M is an ovipositional stimulant; addition of alkane over sinigrin made all sinigrin concentrations (10^–6 M to 10^–2 M) significantly more stimulatory than controls. Waxes alone do not stimulate oviposition. In choice tests, insect movement between sinigrin/alkane treatment combinations was random, however, once encountered, visit duration was significantly longer on sinigrin with alkane than on sites treated with either stimulus alone. Given the ubiquity of waxes on plant surfaces and the interaction between waxes and host-specific chemical stimuli, waxes should be included when considering factors that significantly influence herbivore host acceptance.     

Torque generation in the flagellar motor of Escherichia coli: evidence of a direct role for FliG but not for FliM or FliN.

Among the many proteins needed for assembly and function of bacterial flagella, FliG, FliM, and FliN have attracted special attention because mutant phenotypes suggest that they are needed not only for flagellar assembly but also for torque generation and for controlling the direction of motor rotation. A role for these proteins in torque generation is suggested by the existence of mutations in each of them that produce the Mot- (or paralyzed) phenotype, in which flagella are assembled and appear normal but do not rotate. The presumption is that Mot- defects cause paralysis by specifically disrupting functions essential for torque generation, while preserving the features of a protein needed for flagellar assembly. Here, we present evidence that the reported mot mutations in fliM and fliN do not disrupt torque-generating functions specifically but, instead, affect the incorporation of proteins into the flagellum. The fliM and fliN mutants are immotile at normal expression levels but become motile when the mutant proteins and/or other, evidently interacting flagellar proteins are overexpressed. In contrast, many of the reported fliG mot mutations abolish motility at all expression levels, while permitting flagellar assembly, and thus appear to disrupt torque generation specifically. These mutations are clustered in a segment of about 100 residues at the carboxyl terminus of FliG. A slightly larger carboxyl-terminal segment of 126 residues accumulates in the cells when expressed alone and thus probably constitutes a stable, independently folded domain. We suggest that the carboxyl-terminal domain of FliG functions specifically in torque generation, forming the rotor portion of the site of energy transduction in the flagellar motor.     

东方法老蛛雌蛛的描述（蜘蛛目：跳蛛科）

报道采自甘肃文县的东方法老蛛雌蛛,为该种雌蛛的首次记述。     

以淀粉珠为载体的亲和层析法分离纯化高温α淀粉酶

 以淀粉珠为载体的亲和层析法分离纯化高温α淀粉酶张学忠,宋伦,王群,吴晓霞,唐锌进（吉林大学酶工程国家重点实验室,长春１３００２３;南京师范大学生物系,南京２１００２４）金凤燮等人从酒曲中筛选出高产热稳定α淀粉酶的菌株,命名为Ｂａｃｉｌｌｕｓｓｐ－ＪＦ...     

Bi（Ⅲ）与金属硫蛋白作用性质研究

 Ｂｉ（Ⅲ）与金属硫蛋白作用性质研究张保林,黄辉,朱凌燕,岳晟,唐雯霞（南京大学配位化学研究所,配位化学国家重点实验室,南京２１００９３）如何降低顺铂或其它抗癌铂的毒性,一直是癌症化疗中的重要课题之一,最近研究发现预先给大鼠或肺癌病人服用铋盐,可以极大...     

湿地松粉蚧夏季数量凋落的原因分析

利用生命表技术及其相应的控制指数分析方法,对新侵入害虫湿地松粉蚧Ｏｒａｏｅｌｌａａ－ｃｕｔａ（Ｌｏｂｄｅｌｌ）夏季数量凋落的某些因子进行了量化分析。结果表明：在广东南部的新侵入区,夏季高温引起的松梢迅速老化,上代为害以后引起的营养质量的变化、拥挤以及煤污病的严重发生等,均对湿地松粉蚧夏季种群数量的凋落有着明显的影响,其总的排除作用控制指数ＥＩＰＣ为４６．８９,如果排除这几个因子的作用,下代种群的数量将为当代的４６．８９倍。