真菌的老化和质粒

真菌老化的研究工作在过去的三十五年中已有了很大的进展,本文综述了几种典型真菌老化的生长特征,以及线粒体 DNA 的部分缺失和部分扩增与老化发生的相关性。并且着重强调了 plDNA 的产生与插入可能是造成老化的一个重要原因。plDNA 的产生与反录酶有关,plDNA 可以自我复制,并能在菌丝中转移。因此,它极相似于在其它植物中被发现的转座子。本文中还介绍了几种老化发生机制的理论,并列举了迄今为止已发现的真菌质粒。     

The two‐component histidine kinase Fhk1 controls stress adaptation and virulence of Fusarium oxysporum

Fungal histidine kinases (HKs) have been implicated in different processes, such as the osmostress response, hyphal development, sensitivity to fungicides and virulence. Members of HK class III are known to signal through the HOG mitogen‐activated protein kinase (MAPK), but possible interactions with other MAPKs have not been explored. In this study, we have characterized fhk1, encoding a putative class III HK from the soil‐borne vascular wilt pathogen Fusarium oxysporum. Inactivation of fhk1 resulted in resistance to phenylpyrrole and dicarboximide fungicides, as well as increased sensitivity to hyperosmotic stress and menadione‐induced oxidative stress. The osmosensitivity of Δfhk1 mutants was associated with a striking and previously unreported change in colony morphology. The Δfhk1 strains showed a significant decrease in virulence on tomato plants. Epistatic analysis between Fhk1 and the Fmk1 MAPK cascade indicated that Fhk1 does not function upstream of Fmk1, but that the two pathways may interact to control the response to menadione‐induced oxidative stress.     

Hydrocortisone selectively inhibits IgE-dependent arachidonic acid release from rat peritoneal mast cells

Purified rat mast cells were used to study the effects of anti-inflammatory steroids on the release of [1-¹⁴C]-arachidonic acid ([1-¹⁴C]AA) and metabolites. Mast cells were incubated overnight with glucocorticoids, [1-¹⁴C]AA incorporated into cellular phospholipids and the release of [1-¹⁴C]AA, and metabolites determined using a variety of secretagogues. Release of [1-¹⁴C]AA and metabolites by concanavalin A, the antigen ovalbumin and anti-immunoglobulin in E antibody was markedly reduced by glucocorticoid treatment. Neither the total incorporation of [1-¹⁴C]AA nor the distribution into phospholipids was altered by hydrocortisone pretreatment. Glucocorticoid pretreatment did not alter [1-¹⁴C]AA release stimulated by somatostatin, compound 48/80, or the calcium ionophore, A23187. These data indicate that antiinflammatory steroids selectively inhibit immunoglobulin dependent release of arachidonic acid from rat mast cells. These findings question the role of lipomodulin and macrocortin as general phospholipase inhibitors and suggest that they may be restricted to immunoglobulin stimuli.     

Seasonal Trends of Nitrate Reductase, Carboxylating Enzymes, and Water-soluble Proteins in Two Field-grown Cultivars of Triticum

Nitrate reductase, RuDP¹ carboxylase, PEP carboxylase, and water-solubleproteins have been studied during the vegetative cycles of onesoft and one hard wheat cultivar. Nitrate reductase was similarin amount and in pattern of variation in both varieties, thevariations being related to the phenological state of the plant,because the seasonal trend was not in phase in the two varieties.The pattern of change in water-soluble proteins was significantlydifferent in the two cultivars, namely in the consistent declineshown by the upper leaves of soft wheat. RuDP carboxylase was almost identical in amount and absolutelyin phase between the two varieties, showing a dependence onseasonal factors, possibly through a photoperiodic effect. Thechanges in PEP carboxylase were similar in the two wheats andgenerally synchronous. The fluctuation in the RuDP carboxylase/PEPcarboxylase ratio was due primarily to the increase in RuDPcarboxvlase activity.     

Upper-lethal-temperature relations of the nymphs of the stonefly,paragnetina media

Summary Continuous water flow and static test apparatus were used in evaluating the influence of acclimation temperature, size, sex, season, life stage, current velocity, and testing method upon the upper-lethal temperature of the nymphal stage of the stonefly, Paragnetina media Walker.Lethal temperature was raised by acclimation to higher temperatures throughout the thermal range examined. The rate of gain of heat resistance was approximately 5°C per day. Acclimation to colder temperatures was much slower.Body size had no significant effect on upper-lethal temperature in summer or autumn, whereas in winter and spring larger nymphs were significantly less tolerant than smaller nymphs. This difference was attributed to sex, not body size per se.Tolerance was significantly less in static waters than in flowing water, faster current significantly increasing heat resistance at all lethal temperatures examined.Upper-lethal temperatures showed seasonal differences independent of acclimation, with nymphs least tolerant in spring, when temperature resistance was influenced by sex, molting condition, and proximity of emergence. The most temperature-sensitive stage was the period immediately following egg hatching.The direct effect of upper-lethal temperature is apparently not a limiting factor for P. media in the environment in which it is found. Temperature increases do, however, effect final stages of nymphal development, emergence patterns, and survival after hatching.Contribution No. 213, W. K. Kellogg Biological Station of Michigan State University. This investigation was supported in part by Research Grant WP 01178 from the Federal Water Pollution Control Administration.     

胶州湾滨海湿地枯落物分解对土壤活性有机碳含量及其三维荧光特性的影响

通过室内试验模拟胶州湾滨海湿地碱蓬、芦苇、互花米草枯落物的分解过程,测定土壤活性有机碳(可溶性有机碳、微生物生物量碳)含量变化,并利用三维荧光技术对可溶性有机碳(DOC)进行光谱分析.结果表明: 土壤活性有机碳含量呈先增加后降低最终趋于稳定的变化趋势;不同枯落物类型和添加方式对土壤活性有机碳的影响不同,表现为碱蓬＞互花米草＞芦苇,且原状混合＞表面覆盖;光谱分析表明,分解过程各三维荧光光谱的荧光峰数量、荧光中心位置和荧光强度都存在一定差异,添加枯落物后土壤未发现类酪氨酸峰;芳香类蛋白物质占比最高,腐殖质类物质次之.枯落物分解是以微生物分解作用为主导、枯落物性质为本质要素、多重因子综合作用的结果,其对提高土壤活性有机碳含量、增强土壤碳库的稳定性具有促进作用;该过程通过改变DOC的结构和化学组分,提高其在土壤中的迁移转化能力,增强生物可降解性和可利用性,促进微生物内源DOC的产生,加快湿地土壤碳循环.     

基于高速逆流色谱的大极性海参多肽分离方法研究

本文通过对HEMWat溶剂体系中28种常用溶剂系统单相以及整体极性进行系统分析,探讨了无法用常规J型逆流色谱实现对大极性化合物实现有效分离的原因。根据分析结果建立了一种以分离物质理化性质为基础选择潜在改性剂,样品在溶剂系统上相中的溶解程度为判断指标进行筛选逆流色谱溶剂系统改性剂,进而得到适宜的溶剂系统对大极性海参多肽样品进行系统分段方法。经过两步分离,共得到8个随极性分布的海参多肽片段,为海参多肽最佳活性物质的追踪和筛选提供了技术支持。