Invertebrates as model organisms for research on aging biology

Invertebrate model systems, such as nematodes and fruit flies, have provided valuable information about the genetics and cellular biology involved in aging. However, limitations of these simple, genetically tractable organisms suggest the need for other model systems, some of them invertebrate, to facilitate further advances in the understanding of mechanisms of aging and longevity in mammals, including humans. This paper introduces 10 review articles about the use of invertebrate model systems for the study of aging by authors who participated in an ‘NIA-NIH symposium on aging in invertebrate model systems’ at the 2013 International Congress for Invertebrate Reproduction and Development. In contrast to the highly derived characteristics of nematodes and fruit flies as members of the superphylum Ecdysozoa, cnidarians, such as Hydra, are more ‘basal’ organisms that have a greater number of genetic orthologs in common with humans. Moreover, some other new model systems, such as the urochordate Botryllus schlosseri, the tunicate Ciona, and the sea urchins (Echinodermata) are members of the Deuterostomia, the same superphylum that includes all vertebrates, and thus have mechanisms that are likely to be more closely related to those occurring in humans. Additional characteristics of these new model systems, such as the recent development of new molecular and genetic tools and a more similar pattern to humans of regeneration and stem cell function suggest that these new model systems may have unique advantages for the study of mechanisms of aging and longevity.     

丝状真菌的细胞凋亡

凋亡是一种程序性细胞死亡类型,为多细胞生物发育和维持生命所必需的,也普遍存在于细菌等原核生物和酵母、丝状真菌等真核生物中。丝状真菌既具有酵母和哺乳动物共有的凋亡同源蛋白,也具有酵母所不具备的哺乳动物凋亡同源蛋白,所以其凋亡机制较酵母更为复杂,而又较哺乳动物简单。凋亡在丝状真菌的发育、繁殖、衰老等过程中具有重要的作用。近年,丝状真菌作为新的凋亡研究的模式生物被广泛研究,而且进展迅速。综述丝状真菌的凋亡现象和检测方法,丝状真菌中凋亡的生物学功能,丝状真菌凋亡的诱导条件,以及丝状真菌凋亡相关基因的功能研究进展。     

Autophagy in filamentous fungi

Autophagy is a ubiquitous, non-selective degradation process in eukaryotic cells that is conserved from yeast to man. Autophagy research has increased significantly in the last ten years, as autophagy has been connected with cancer, neurodegenerative disease and various human developmental processes. Autophagy also appears to play an important role in filamentous fungi, impacting growth, morphology and development. In this review, an autophagy model developed for the yeast Saccharomyces cerevisiae is used as an intellectual framework to discuss autophagy in filamentous fungi. Studies imply that, similar to yeast, fungal autophagy is characterized by the presence of autophagosomes and controlled by Tor kinase. In addition, fungal autophagy is apparently involved in protection against cell death and has significant effects on cellular growth and development. However, the only putative autophagy proteins characterized in filamentous fungi are Atg1 and Atg8. We discuss various strategies used to study and monitor fungal autophagy as well as the possible relationship between autophagy, physiology, and morphological development.     

Assessment of the microbody luminal pH in the filamentous fungus Penicillium chrysogenum

The enzymes of the penicillin biosynthetic pathway in Penicillium chrysogenum are located in different subcellular compartments. Consequently, penicillin pathway precursors and the biologically active penicillins have to cross one or more membranes. The final enzymatic step that is mediated by acyltransferase takes place in a microbody. The pH of the microbody lumen in penicillin producing cells has been determined with fluorescent probes and mutants of the green fluorescent protein and found to be slightly alkaline.     

Nitric oxide as a developmental and metabolic signal in filamentous fungi

The short-lived hydrophobic gas nitric oxide (NO) is a broadly conserved signaling molecule in all domains of life, including the ubiquitous and versatile filamentous fungi (molds). Several studies have suggested that NO plays a vast and diverse signaling role in molds. In this review, we summarize NO-mediated signaling and the biosynthesis and degradation of NO in molds, and highlight the recent advances in understanding the NO-mediated regulation of morphological and physiological processes throughout the fungal life cycle. In particular, we describe the role of NO in molds as a signaling molecule that modulates asexual and sexual development, the formation of infection body appressorium, and the production of secondary metabolites (SMs). In addition, we also summarize NO detoxification and protective mechanisms against nitrooxidative stress.     

Aquaporins in yeasts and filamentous fungi

Recently, genome sequences from different fungi have become available. This information reveals that yeasts and filamentous fungi possess up to five aquaporins. Functional analyses have mainly been performed in budding yeast, Saccharomyces cerevisiae, which has two orthodox aquaporins and two aquaglyceroporins. Whereas Aqy1 is a spore-specific water channel, Aqy2 is only expressed in proliferating cells and controlled by osmotic signals. Fungal aquaglyceroporins often have long, poorly conserved terminal extensions and differ in the otherwise highly conserved NPA motifs, being NPX and NXA respectively. Three subgroups can be distinguished. Fps1-like proteins seem to be restricted to yeasts. Fps1, the osmogated glycerol export channel in S. cerevisiae, plays a central role in osmoregulation and determination of intracellular glycerol levels. Sequences important for gating have been identified within its termini. Another type of aquaglyceroporin, resembling S. cerevisiae Yfl054, has a long N-terminal extension and its physiological role is currently unknown. The third group of aquaglyceroporins, only found in filamentous fungi, have extensions of variable size. Taken together, yeasts and filamentous fungi are a fruitful resource to study the function, evolution, role and regulation of aquaporins, and the possibility to compare orthologous sequences from a large number of different organisms facilitates functional and structural studies.     

丝状致病真菌的分子生物学研究进展

随着分子生物学技术的飞速发展和日益成熟,有关丝状致病真菌的分子生物学和基因的研究日渐增多。目前,从分子水平研究丝状致病真菌的主要目标是探讨致病真菌的致病性因子、分生机制及寻求抗真菌药物、分子进化等。作者综述了近年来在这一领域的新进展。！致病毒素因子研究较为广泛、透彻的丝状真菌致病毒素因子是黄曲霉毒素蛋白。该毒素BI、BZ是一组由黄曲霉、寄生曲霉产生的有毒性和致癌作用的次级代谢产物。目前,黄曲霉毒素的生物合成途径已经研究确立,但其调节机制仍不清楚［'］。主要研究途径有三条：（l）先分离特殊的合成酶的mR…     

Meiotic recombination in filamentous fungi

The exchange of genes by crossing over and by gene conversion is a basic process in eukaryotes. Fungi have played a special role in the study of this process because they permit tetrad analysis, which provides complete information on the distribution of genes and chromosomes in meiosis. Recombination is detected by new combinations of genetic markers. The first observation gave only the simple picture of a crossover provided by two segregating loci far apart on the chromosome. Later the discovery of recombination between sites within a gene led to a revolution in our knowledge of this process. Today we carry the resolution a step further with RFLP markers, which can detect the details of recombination down to nucleotide distances. I review here observations on filamentous fungi, which have contributed to this pursuit at each stage of the emerging synthesis.     

Nuclear movement in filamentous fungi

One of the most striking features of eukaryotic cells is the organization of specific functions into organelles such as nuclei, mitochondria, chloroplasts, the endoplasmic reticulum, vacuoles, peroxisomes or the Golgi apparatus. These membrane-surrounded compartments are not synthesized de novo but are bequeathed to daughter cells during cell division. The successful transmittance of organelles to daughter cells requires the growth, division and separation of these compartments and involves a complex machinery consisting of cytoskeletal components, mechanochemical motor proteins and regulatory factors. Organelles such as nuclei, which are present in most cells in a single copy, must be precisely positioned prior to cytokinesis. In many eukaryotic cells the cleavage plane for cell division is defined by the location of the nucleus prior to mitosis. Nuclear positioning is thus absolutely crucial in the unequal cell divisions that occur during development and embryogenesis. Yeast and filamentous fungi are excellent organisms for the molecular analysis of nuclear migration because of their amenability to a broad variety of powerful analytical methods unavailable in higher eukaryotes. Filamentous fungi are especially attractive models because the longitudinally elongated cells grow by apical tip extension and the organelles are often required to migrate long distances. This review describes nuclear migration in filamentous fungi, the approaches used for and the results of its molecular analysis and the projection of the results to other organisms.     

Mitochondrial dynamics in filamentous fungi

Mitochondria are essential organelles of eukaryotic cells. They grow continuously throughout the cell cycle and are inherited by daughter cells upon cell division. Inheritance of mitochondria and maintenance of mitochondrial distribution and morphology require active transport of the organelles along the cytoskeleton and depend on membrane fission and fusion events. Many of the molecular components and cellular mechanisms mediating these complex processes have been conserved during evolution across the borders of the fungal and animal kingdoms. During the past few decades, several constituents of the cellular machinery mediating mitochondrial behavior have been identified and functionally characterized. Here, we review the contributions of fungi, with special emphasis on the filamentous fungus Neurospora crassa, to our current understanding of mitochondrial morphogenesis and inheritance.     

Challenges and opportunities of the bio-pesticides production by solid-state fermentation: filamentous fungi as a model

In recent years, production and use of bio-pesticides have increasing and replacing some synthetic chemical pesticides applied to food commodities. In this review, biological control is focused as an alternative, to some synthetic chemical treatments that cause environmental, human health, and food quality risks. In addition, several phytopathogenic microorganisms have developed resistance to some of these synthetic chemicals and become more difficult to control. Worldwide, the bio-pesticides market is growing annually at a rate of 44% in North America, 20% in Europe and Oceania, 10% in Latin and South American countries and 6% in Asia. Use of agro-industrial wastes and solid-state fermentation (SSF) technology offers an alternative to bio-pesticide production with advantages versus conventional submerged fermentations, as reduced cost and energy consumption, low production of residual water and high stability products. In this review, recent data about state of art regarding bio-pesticides production under SSF on agroindustrial wastes will be discussed. SSF can be defined as a microbial process that generally occurs on solid material in the absence of free water. This material has the ability to absorb water with or without soluble nutrients, since the substrate must have water to support the microorganism’s growth and metabolism. Changes in water content are analyzed in order to select the conditions for a future process, where water stress can be combined with the best spore production conditions, obtaining in this way an inexpensive biotechnological option for modern agriculture in developing countries.     

植物病原丝状真菌G蛋白偶联受体的研究进展

通过对丝状真菌G蛋白偶联受体(GPCR)的结构、分类以及功能方面进行综述,以期明确丝状真菌与其他模式生物GPCR之间的关系。基于已报道的模式生物及丝状真菌等不同生物中的GPCR,通过SMART保守结构域分析,以及利用Clustal X、MEGA等软件对上述GPCR进行遗传关系分析。明确丝状真菌典型GPCR具有七跨膜结构域,新型GPCR则含有PIPK、RGS等保守结构域,明确不同学者对于GPCR的分类情况,以及新型GPCR所具有的特殊功能,明确模式生物GPCR、丝状真菌GPCR分别各自聚类。丝状真菌中GPCR的数量较模式生物少,不同分类单元中真菌之间GPCR的数量也不尽相同,同时,丝状真菌GPCR除具有典型的七跨膜结构域外,还含有一些其他保守的结构域,上述研究为进一步开展其功能研究提供重要的理论基础。     

Protein targeting and secretion in filamentous fungi

Although the application of filamentous fungi, such asAspergillus niger for the production of extracellular proteins is well established for several decades, hardly any information is available about the molecular mechanisms of the process of protein secretion in these organisms.Two lines of research initiated towards a systematic analysis of the mechanism of protein targeting and secretion are presented in this paper.1 — To study routing and targeting of proteins in filamentous fungi the availability of a versatile reporter/carrier protein will be of considerable importance. Experiments towards the identification of such a protein are presented.2 — In analogy to the situation inSaccharomyces cerevisiae, the availability of defined (conditional) mutations in the secretion pathway will provide very important information about the organisation of the pathway. Therefore, based on results obtained inS. cerevisiae, the cloning of several fungal secretion genes was started. The results of the cloning and characterisation of one of these genes is presented.