Lipid signalling in pathogenic fungi

In recent years, the study of lipid signalling networks has significantly increased. Although best studied in mammalian cells, lipid signalling is now appreciated also in microbial cells, particularly in yeasts and moulds. For instance, microbial sphingolipids and their metabolizing enzymes play a key role in the regulation of fungal pathogenicity, especially in Cryptococcus neoformans, through the modulation of different microbial pathways and virulence factors. Another example is the quorum sensing molecule (QSM) farnesol. In fact, this QSM is involved not only in mycelial growth and biofilm formation of Candida albicans, but also in many stress related responses. In moulds, such as Aspergillus fumigatus, QSM and sphingolipids are important for maintaining cell wall integrity and virulence. Finally, fungal cells make oxylipins to increase their virulence attributes and to counteract the host immune defences. In this review, we discuss these aspects in details.     

Lipid signaling

Various lipids are involved in mediating plant growth, development and responses to biotic and abiotic cues, and their production is regulated by lipid-signaling enzymes. Lipid-hydrolyzing enzymes play a pivotal role both in the production of lipid messengers and in other processes, such as cytoskeletal rearrangement, membrane trafficking, and degradation. Studies on the downstream targets and modes of action of lipid signals in plants are still in their early stages but distinguishing features of plant lipid-based signaling are being recognized. Phospholipase D enzymes and phosphatidic acid may play a broader role in lipid signaling in plants than in other systems.     

Programmed cell death in pathogenic fungi

Greater understanding of programmed cell death (PCD) responses in pathogenic fungi may offer a chance of exploiting the fungal molecular death machinery to control fungal infections. Clearly identifiable differences between the death machineries of pathogens and their hosts, make this a feasible target. Evidence for PCD in a range of pathogenic fungi is discussed alongside an evaluation of the capacity of existing antifungal agents to promote apoptosis and other forms of cell death. Information about death related signalling pathways that have been examined in pathogens as diverse as Candida albicans, Aspergillus fumigatus, Magnaporthe grisea and Colletotrichum trifolii are discussed.     

Hybrid histidine kinases in pathogenic fungi

Histidine kinases (HK) sense and transduce via phosphorylation events many intra‐ and extracellular signals in bacteria, archaea, slime moulds and plants. HK are also widespread in the fungal kingdom, but their precise roles in the regulation of physiological processes remain largely obscure. Expanding genomic resources have recently given the opportunity to identify uncharacterised HK family members in yeasts and moulds and now allow proposing a complex classification of Basidiomycota, Ascomycota and lower fungi HK. A growing number of genetic approaches have progressively provided new insight into the role of several groups of HK in prominent fungal pathogens. In particular, a series of studies have revealed that members of group III HK, which occur in the highest number of fungal species and contain a unique N‐terminus region consisting of multiple HAMP domain repeats, regulate morphogenesis and virulence in various human, plant and insect pathogenic fungi. This research field is further supported by recent shape‐function studies providing clear correlation between structural properties and signalling states in group III HK. Since HK are absent in mammals, these represent interesting fungal target for the discovery of new antifungal drugs.     

The RAM network in pathogenic fungi

The regulation of Ace2 and morphogenesis (RAM) network is a protein kinase signaling pathway conserved among eukaryotes from yeasts to humans. Among fungi, the RAM network has been most extensively studied in the model yeast Saccharomyces cerevisiae and has been shown to regulate a range of cellular processes, including daughter cell-specific gene expression, cell cycle regulation, cell separation, mating, polarized growth, maintenance of cell wall integrity, and stress signaling. Increasing numbers of recent studies on the role of the RAM network in pathogenic fungal species have revealed that this network also plays an important role in the biology and pathogenesis of these organisms. In addition to providing a brief overview of the RAM network in S. cerevisiae, we summarize recent developments in the understanding of RAM network function in the human fungal pathogens Candida albicans, Candida glabrata, Cryptococcus neoformans, Aspergillus fumigatus, and Pneumocystis spp.     

Insertional mutagenesis of pathogenic fungi

Screening insertional mutants for loss of virulence is an effective method for investigating the molecular genetic basis of bacterial pathogenesis, but has only recently been applied to fungal pathogens. For many pathogenic fungi transformation with heterologous plasmid DNA results in complex integration events. This problem can now be circumvented for some species using restriction enzyme mediated integration. Insertional mutagenesis of Fusarium oxysporum using the naturally occurring fungal transposon impala has been described, but transposon tagging for other fungi has yet to be developed. Although insertional mutagenesis has recently identified important virulence determinants of fungal phytopathogens, the lack of suitable screening strategies has so far limited its applicability for fungal pathogens of humans.     

植物病原真菌的菌核研究进展

真菌菌核是相关真菌在特殊环境下由营养体菌丝交织和聚集形成的具有抵御恶劣环境能力的休眠结构,在真菌生活史及病原真菌的病害循环中具有重要的生物学和生态学意义。许多引起严重植物病害的病原真菌能够形成菌核,这类真菌通过菌核度过逆境。菌核在适宜条件下萌发形成子囊盘和孢子或菌丝,造成植物的侵染。本文从形成菌核的真菌种类、生物学特性、黑色素及分子生物学等方面进行综述,旨在为深入研究真菌菌核及其在真菌学、植物病理学及药用真菌学等领域应用提供研究思路和参考依据。     

病原性丝状真菌的菌种保藏方法

目的 探讨常见病原性丝状真菌的菌种保藏方法.方法将73株病原性丝状真菌经过纯化后,接种于马铃薯葡萄糖琼脂斜面分别在4℃和-80℃冷冻管保存,均用10％ (v/v)的丙三醇作为保护剂.结果经过1 a左右的保存,将菌株复活,发现4℃斜面保藏法菌株的存活率为100％,-80℃冷冻管保藏法菌株的存活率为98.6％,有些毛癣菌属...     

Studies on pathogenic dematiaceous fungi

Two hundred and twenty-six samples of woody materials, vegetable matter and soil were processed by the direct plating and mouse inoculation technique for the isolation of pathogenic dematiaceous fungi. The species of fungi isolated were Fonsecaea pedrosoi — 13, Cladosporium carrionii — 7 and Phialophora verrucosa — 4 isolates. The mouse inoculation technique was found to be much better than direct plating for the recovery of these fungi. Woody plant materials proved to be a good sample source for pathogenic dematiaceous fungi contributing about 90% of the isolates. All the isolates were pathogenic for mice as evidenced by the presence of dark nodular lesions containing fungal elements in the organs of experimentally infected animals.     

Lipid rafts in cytokine signaling

Lipid rafts are established as critical structures for a variety of cellular processes, including immune cell activation. Beyond their importance for initial immune cell activation at the immunological synapse, lipid rafts are now also being recognized as important sites for cytokine and growth factor signal transduction, both in immune cells as part of secondary regulatory processes, and in non-immune cells. This review summarizes current knowledge regarding the roles of rafts in cytokine signaling and emphasizes the need for measures to better standardize the study of rafts.     

Lipid signaling in embryo implantation

A reciprocal interaction between the implantation-competent blastocyst and the receptive uterus is required for successful implantation. Although various molecular pathways are known to participate in this cross-talk, a comprehensive understanding of the implantation process is still missing. Gene expression studies and genetically engineered mouse models have provided evidence that lipid mediators serve as important signaling molecules in coordinating the series of events during early pregnancy including preimplantation embryo formation and development, implantation and postimplantation growth. This review focuses on the roles of two groups of lipid mediators, prostaglandins (PGs) and endocannabinoids, during early pregnancy. Our laboratory has shown that while PGs generated by the cPLA2-cyclooxygenase (COX) system are essential to ovulation, fertilization, and implantation, endocannabinoids are important for synchronizing preimplantation embryo development with uterine receptivity for implantation. A better understanding of these molecular signaling pathways is hoped to generate new strategies to correct implantation failure and improve pregnancy rates in women.     

Lipid signaling in Drosophila photoreceptors

Drosophila photoreceptors are sensory neurons whose primary function is the transduction of photons into an electrical signal for forward transmission to the brain. Photoreceptors are polarized cells whose apical domain is organized into finger like projections of plasma membrane, microvilli that contain the molecular machinery required for sensory transduction. The development of this apical domain requires intense polarized membrane transport during development and it is maintained by post developmental membrane turnover. Sensory transduction in these cells involves a high rate of G-protein coupled phosphatidylinositol 4,5 bisphosphate [PI(4,5)P(2)] hydrolysis ending with the activation of ion channels that are members of the TRP superfamily. Defects in this lipid-signaling cascade often result in retinal degeneration, which is a consequence of the loss of apical membrane homeostasis. In this review we discuss the various membrane transport challenges of photoreceptors and their regulation by ongoing lipid signaling cascades in these cells. This article is part of a Special Issue entitled Lipids and Vesicular Transport.