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关键词： helminths   trematodes   parasites   cathepsins   proteases   vaccines   immunology   biochemistry  

摘要： Fasciola hepatica secretes cathepsin L proteases that facilitate the penetration of the parasite through the tissues of its host, and also participate in functions such as feeding and immune evasion. The major proteases, cathepsin L1 (FheCL1) and cathepsin L2 (FheCL2) are members of a lineage that gave rise to the human cathepsin Ls, Ks and Ss, but while they exhibit similarities in their substrate specificities to these enzymes they differ in having a wider pH range for activity and an enhanced stability at neutral pH. There are presently 13 Fasciola cathepsin L cDNAs deposited in the public databases representing a gene family of at least seven distinct members, although the temporal and spatial expression of each of these members in the developmental stage of F. hepatica remains unclear. Immunolocalisation and in situ hybridisation studies, using antibody and DNA probes, respectively, show that the vast majority of cathepsin L gene expression is carried out in the epithelial cells lining the parasite gut. Within these cells the enzyme is packaged into secretory vesicles that release their contents into the gut lumen for the purpose of degrading ingested host tissue and blood. Liver flukes also express a novel multi-domain cystatin that may be involved in the regulation of cathepsin L activity. Vaccine trials in both sheep and cattle with purified native FheCL1 and FheCL2 have shown that these enzymes can induce protection, ranging from 33 to 79%, to experimental challenge with metacercariae of F. hepatica, and very potent anti-embryonation/hatch rate effects that would block parasite transmission. In this article we review the vaccine trials carried out over the past 8 years, the role of antibody and T cell responses in mediating protection and discuss the prospects of the cathepsin Ls in the development of first generation recombinant liver fluke vaccines. (C) 2003 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

关键词： Non-programmatic  

摘要： Discusses the effect of flooding on roots' ability to absorb water. Molecular basis for the paradox; Key role of aquaporins in water uptake by roots; Factors gating aquaporins; Effect of decreased cytosolic pH on root permeability.

关键词： Animals   Arthropods/physiology   Bacteria/growth & development   Carbon/metabolism   Coniferophyta   Coniferophyta   Ecosystem   Ecosystem   Environment   Fungi/growth & development   Geography   Invertebrates/physiology   Lauraceae   Lauraceae   Liliaceae/growth & development   Liliaceae/growth & development   Nematoda/physiology   New Zealand   New Zealand   Nitrogen/metabolism   Oligochaeta/physiology   Phosphorus/metabolism   Population Density   Soil   Species Specificity   Trees   Vitex   Vitex  

摘要： Although island attributes such as size and accessibility to colonizing organisms can influence community structure, the consequences of these for ecosystem functioning are little understood. A study of the suspended soils of spatially discrete epiphytes or treetop "islands" in the canopies of New Zealand rainforest trees revealed that different components of the decomposer community responded either positively or negatively to island size, as well as to the tree species that the islands occurred in. This in turn led to important differences between islands in the rates of ecosystem processes driven by the decomposer biota. This system serves as a model for better understanding how attributes of both real and habitat islands may affect key ecosystem functions through determining the community structure of organisms that drive these functions.

关键词： Changnienia amoena   Bombus (Diversobombus) trifasciatus   deceptive pollination   stalk elongation  

摘要： Changnienia amoena Chien is a monotypic species and endemic to China, and was listed on the Chinese Red Book in 1992. The species was once abundant but has become rare and endangered in recent years because of the habitat fragmentation and unduly commercial collections. Previous observation showed that this species has very low and even no fruit set, and the pollinators are not observed before this report. The present observation was conducted at the Shennongjia, Hubei Province during the spring of 2002. The results showed that Bombus (Diversobombus) trifasciatus Smith, B. imitator Pittion and one species of Apis visited the flowers of the orchid, but only B. tritasciatus could carry pollinaria on its body and was the legitimate pollinators of C amoena. During 113 h of observation, only nine visitations were recorded. The bumblebees mainly appeared during 12:00-15:00 during the day. Bumblebees stayed in a flower only a few seconds and never more than ten seconds. The flowers would persist in fresh for about three weeks when they were not pollinated, but 3 or 4 d after pollinated, the pollinated flowers underwent a series of color and morphological changes including stalk elongation and ovary swelling. Therefore, stalk elongation can be considered an index of fruits set. Artificial pollination indicated that C amoena is a highly self-compatible and outcrossing species, but dependent on pollinators for fruit set. Based on the field observations, we concluded that pollination system of C amoena is deceptive. The fruit set in nature is not very low (26.98% on average) compared to other deceptive orchids, which may be related to small population sizes. The number of pollinia removal is much higher than that of fruit set, indicating that there are some degrees of pollinia wasting in C amoena.

关键词： 植物   多酚氧化酶   分子生物学   PPO   分子结构   分子量   活性   基因   克隆   蛋白质   序列保守性   内含子   翻译   表达  

摘要： 本文综述了近年来植物多酚氧化酶在分子生物学如分子结构,分子量,基因克隆、结构、特征与表达调控等方面的研究进展以及植物多酚氧化酶的应用前景。

关键词： 稀有观赏植物   舞草   生物学特性   繁殖技术   播种育苗   扦插育苗  

摘要： 舞草(Codariocalyx motorius)属蝶形花科、舞草属.是一种世界上濒临绝迹的珍稀植物,为多年生阳性小灌木,3小叶,或兼有单小叶,高达1.8 m.

关键词： 景东报春   地理分布   生态生物学特性   报春花科  

摘要： Primula interjacens Chen, an endemic and rare species to China, is restrictively distributed in Mt. Wuliangshan of Yunnan Province. Only three populations are found. The species has been fallen into endangered condition. Its present state of distribution, biological and ecological characteristics are investigated. In addition, the factors causing this species endangered and conservation strategies are analyzed briefly.

关键词： .homology   make   chapters   population genetic   phenotypic variation   Microevolutionary   Developmental Genetics   Evo-Devo   macroevolutionary patterns  

摘要： Developmental Genetics and Plant Evolution is reviewed.

关键词： 《植物有性生殖实验研究四十年》   植物生殖生物学研究   科学家精神   杨弘远  

摘要： 由武汉大学出版社出版的荣获第十三届中国图书奖的学术著作<植物有性生殖实验研究四十年>,是作者长期潜心研究的重大成果,也是我国植物生殖生物学发展的里程碑.

关键词： Florida   invasive species   Lygodium   reproductive biology   Schizaeaceae   selfing  

摘要： The effect of culture system and population source on sexual expression and sporophyte production was examined for two invasive fern species in Florida, USA, Lygodium microphyllum and L. japonicum (Schizaeaceae). Both species are currently spreading through Florida. Long-distance dispersal of ferns is thought to rely on successful intragametophytic selling. Given the rate of spread observed in both Lygodium species, we hypothesized that both species are capable of intragametophytic selfing. To test this hypothesis, gametophytes of both species were grown in vitro as isolates, pairs, and groups. Both species were capable of intragametophytic selfing;78% of L. microphyllum isolates produced sporophytes and over 90% of the L. japonicum isolates produced sporophytes. Lygodium microphyllum also displayed the ability to reproduce via intergametophytic crossing, facilitated by an antheridiogen pheromone. Sporophyte production was rapid across mating systems for both species, an advantage in Florida's wet and dry seasonal cycles. The high intragametophytic selfing rate achieved by both species has likely facilitated their ability to colonize and spread through Florida. The mixed mating system observed in L. microphyllum appears to give this species the ability to invade distant habitats and then adapt to local conditions.