黄曲霉Ste50衔接子蛋白对生长发育及致病性的影响

[目的] Ste50是真菌中重要的衔接子蛋白,在多个MAPK级联通路中起重要的信号衔接与传递作用。本研究鉴定出了黄曲霉AflSte50蛋白,并发现了其对黄曲霉的生长、产孢、致病能力和响应渗透压胁迫等方面的影响。[方法] 首先通过生物信息学方法在黄曲霉NRRL 3357中鉴定出ste50基因,并通过同源重组的方法构建了ste50基因的敲除和互补突变体菌株。而后,对基因敲除在黄曲霉生长发育、次级代谢产物合成和胁迫响应等方面的作用进行了研究。[结果] 与野生型相比,△Aflste50菌株生长速度和AFB₁合成量降低且不能产生菌核,同时对花生、玉米种子的致病能力下降。该基因在渗透胁迫条件下正调控MAP激酶的磷酸化水平,但对细胞壁胁迫无响应。[结论] Ste50（AFLA_002340）是黄曲霉衔接子蛋白,影响黄曲霉的生长、发育和AFB₁的合成,能够响应渗透压胁迫,在HOG通路中发挥作用。     

禾谷镰刀菌蛋白激酶研究进展

由禾谷镰刀菌引起的小麦赤霉病是小麦生产最重要的真菌病害之一,除了造成严重的产量损失外,其病原菌还会产生多种真菌毒素危害人畜健康。蛋白激酶在禾谷镰刀菌生长发育、植物侵染和胁迫应答等方面具有重要作用。综述了禾谷镰刀菌主要蛋白激酶在生物学功能和分子作用机制等方面的研究进展,并对未来禾谷镰刀菌蛋白激酶的研究趋势进行了展望,以期为今后禾谷镰刀菌蛋白激酶的研究与小麦赤霉病的防治提供理论参考。     

Enquêtes sur l'archipel de la Maddalena (Sardaigne NE): la flore et le paysage végétal de l'[icaron]le des Bisce

Abstract

Presented herevin are the results of research on the flora and vegetable landscape of the isola delle Bisce (NE Sardinia). The flora was found to be composed of 230 entities (1 Gymnospermae, 229 Angiospermae) belonging to 47 families and included in 156 genera. Failure to find numerous species is underscored and an overview of the vegetation landscape based on aerial photography is presented, with the identification of the vegetation formations and sites on the islands most sensitive to anthropic impact.     

Stipa valdemonensis (Poaceae), a new species from Sicily

Abstract

A new species of Stipa, endemic to Sicily, named Stipa valdemonensis is described here. The new taxon is related to Stipa crassiculmis. Owing to the small number of individuals observed, in few restricted localities only, it is assigned the IUCN threat status “vulnerable”.     

Mammalian Prion protein expression in yeast; a model for transmembrane insertion

The prion protein (PrP), a GPI-anchored glycoprotein, is inefficiently secreted by mammalian microsomes, 50% being found as transmembrane (TM) proteins with the central TM1 segment spanning the membrane. TM1 hydrophobicity is marginal for lateral membrane insertion, which is primarily driven by hydrophobic interaction between the ER translocon and substrates in transit. Most inserted TM1 has its N-terminus in the ER lumen (Ntm orientation), as expected for arrest of normal secretion. However, 20% is found in inverted Ctm orientation. These are minor species in vivo, presumably a consequence of efficient quality control. PrP mutations that increase TM1 hydrophobicity result in increased Ctm insertion, both in vitro and in mouse brain, and a strong correlation is found between CtmPrP insertion and neuropathology in transgenic mice; a copper-dependent pathogenicity mechanism is suggested. PrP fusions with a C-terminal epitope tag, when expressed in yeast cells at moderate levels, appear to interact efficiently with the translocon, providing a useful model for testing the effects of PrP mutations on TM insertion and orientation. However, secretion of PrP by the mammalian translocon requires the TRAP complex, absent in yeast, where essentially all PrP ends up as TM species, 85–90% Ntm and 10–15% Ctm. Although yeast is, therefore, an incomplete mimic of mammalian PrP trafficking, effects on Ctm insertion of mutations increasing TM1 hydrophobicity closely reflect those seen in vitro. Electrostatic substrate-translocon interactions are a major determinant of TM protein insertion orientation and the yeast model was used to investigate the role of the large negative charge difference across TM1, a likely cause of translocation delay that would favor TM insertion and Ctm orientation. An increase in ΔCh from −5 to −7 caused a marked increase in Ctm insertion, while a decrease to −3 or −1 allowed 35 and about 65% secretion, respectively. Utility of the yeast model and the role of this charge difference in driving PrP membrane insertion are confirmed.     

Length-weight relationship of twelve mesopelagic fishes from the western Tropical Atlantic

Length-weight relationship parameters were calculated for twelve mesopelagic fish species from the western Tropical Atlantic: Diretmus argenteus, Melamphaes polylepis, Bolinichthys distofax, Diaphus lucidus, Diaphus splendidus, Electrona risso, Hygophum taaningi, Taaningichthys bathyphilus, Melanolagus bericoides, Winteria telescopa, Diplophos taenia, Astronesthes similus. Data was collected off northeastern Brazil from April 9th to May 6th, 2017. Hauls were conducted during day and night at 47 stations by using a micronekton trawl (body mesh: 40 mm, cod-end mesh: 10 mm) from 10 to 1,113 m depth. The material was fixed in a 4% formalin solution for 1 month and then preserved in a 70% alcohol solution for proximally 6 months before processing for length (nearest 0.1 cm of standard length) and weight (nearest 0.01 g of total weight). A new maximum standard length for Winteria telescopa is also provided.     

Advances on Vibrio parahaemolyticus research in the postgenomic era

Vibrio parahaemolyticus is a leading cause of seafood-borne bacterial gastroenteritis in humans. Since its discovery in 1950, this bacterium has been isolated in widespread outbreaks and in sporadic cases of gastroenteritis worldwide. Although the exotoxin, thermostable direct hemolysin, had been the focus of extensive research on the pathogenicity of V. parahaemolyticus, the whole-genome sequencing of a clinical isolate, RIMD2210633 strain, was a breakthrough in this field. The possession of two sets of gene clusters for type III secretion systems (T3SS1 and T3SS2) was unveiled by that genome project. T3SS is a protein export apparatus that delivers bacterial proteins, called effectors, directly into the host's cytosol, to disrupt host cell function. The subsequent studies have established that T3SS2, which is encoded in an 80 kb pathogenicity island called V. parahaemolyticus pathogenicity island (Vp-PAI), is closely related to enteropathogenicity. Recent functional analyses of Vp-PAI-encoded genes revealed the sophisticated mechanisms in V. parahaemolyticus for sensing the intestinal environment and host cell contact, and a dozen T3SS2-exported proteins encoded in Vp-PAI. In this review, we summarize recent advances in V. parahaemolyticus research regarding the control of the expression of Vp-PAI-encoded genes, structural components and the secretory regulation of T3SS2, and the biological activities of T3SS2-exported effectors. Thus, Vp-PAI-encoded T3SS2 becomes an important key in the postgenomic era to shed light on the enteropathogenic mechanism of V. parahaemolyticus.     

Genome-Wide Association Analysis Identifies a Genetic Basis of Infectivity in a Model Bacterial Pathogen

Knowledge of the genetic architecture of pathogen infectivity and host resistance is essential for a mechanistic understanding of coevolutionary processes, yet the genetic basis of these interacting traits remains unknown for most host–pathogen systems. We used a comparative genomic approach to explore the genetic basis of infectivity in Pasteuria ramosa, a Gram-positive bacterial pathogen of planktonic crustaceans that has been established as a model for studies of Red Queen host–pathogen coevolution. We sequenced the genomes of a geographically, phenotypically, and genetically diverse collection of P. ramosa strains and performed a genome-wide association study to identify genetic correlates of infection phenotype. We found multiple polymorphisms within a single gene, Pcl7, that correlate perfectly with one common and widespread infection phenotype. We then confirmed this perfect association via Sanger sequencing in a large and diverse sample set of P. ramosa clones. Pcl7 codes for a collagen-like protein, a class of adhesion proteins known or suspected to be involved in the infection mechanisms of a number of important bacterial pathogens. Consistent with expectations under Red Queen coevolution, sequence variation of Pcl7 shows evidence of balancing selection, including extraordinarily high diversity and absence of geographic structure. Based on structural homology with a collagen-like protein of Bacillus anthracis, we propose a hypothesis for the structure of Pcl7 and the physical location of the phenotype-associated polymorphisms. Our results offer strong evidence for a gene governing infectivity and provide a molecular basis for further study of Red Queen dynamics in this model host–pathogen system.