Characterization of the wzc gene from Pantoea sp. strain PPE7 and its influence on extracellular polysaccharide production and virulence on Pleurotus eryngii.

To characterize of the pathogenicity gene from the soft rot pathogen Pantoea sp. PPE7 in Pleurotus eryngii, we constructed over 10,000 kanamycin-resistant transposon mutants of Pantoea sp. strain PPE7 by transposon mutagenesis. One mutant, Pantoea sp. NPPE9535, did not cause a soft rot disease on Pleurotus eryngii was confirmed by the pathogenicity test. The transposon was inserted into the wzc gene and the disruption of the wzc gene resulted in the reduction of polysaccharide production and abolished the virulence of Pantoea sp. strain PPE7 in P. eryngii. Analysis of the hydropathic profile of this protein indicated that it is composed of two main domains: an N-terminal domain including two transmembrane α-helices and a C-terminal cytoplasmic domain consisting of a tyrosine-rich region. Comparative analysis indicated that the amino acid sequence of Wzc is similar to that of a number of proteins involved in the synthesis or export of polysaccharides in other bacterial species. Purified GST-Wzc was found to affect the phosphorylation of tyrosine residue in vivo. These results showed that the wzc gene might play an important role in the virulence of Pantoea sp. strain PPE7 in P. eryngii.

Fungal MACPF-like proteins and aegerolysins: bi-component pore-forming proteins?

Proteins with membrane-attack complex/perforin (MACPF) domains are found in almost all kingdoms of life, and they have a variety of biological roles, including defence and attack, organism development, and cell adhesion and signalling. The distribution of these proteins in fungi appears to be restricted to some Pezizomycotina and Basidiomycota species only, in correlation with another group of proteins with unknown biological function, known as aegerolysins. These two protein groups coincide in only a few species, and they might operate in concert as cytolytic bi-component pore-forming agents. Representative proteins here include pleurotolysin B, which has a MACPF domain, and the aegerolysin-like protein pleurotolysin A, and the very similar ostreolysin A, which have been purified from oyster mushroom (Pleurotus ostreatus). These have been shown to act in concert to perforate natural and artificial lipid membranes with high cholesterol and sphingomyelin content. The aegerolysin-like proteins provide the membrane cholesterol/sphingomyelin selectivity and recruit oligomerised pleurotolysin B molecules, to create a membrane-inserted pore complex. The resulting protein structure has been imaged with electron microscopy, and it has a 13-meric rosette-like structure, with a central lumen that is ~4-5 nm in diameter. The opened transmembrane pore is non-selectively permeable for ions and smaller neutral solutes, and is a cause of cytolysis of a colloid-osmotic type. The biological significance of these proteins for the fungal life-style is discussed.

Molecular characterization and enzymatic activity of laccases in two Pleurotus spp. with different pathogenic behaviour.

Pleurotus eryngii and P. ferulae, two species belonging to the P. eryngii complex, synthesize laccases, ligninolytic enzymes that play a role in the host-pathogen interaction in the first step of infection. Ecological studies have shown that although both fungi have been recognized as saprophytes, P. eryngii weakly pathogenic when colonizing the roots and stems of Eryngium campestre, whereas P. ferulae is mostly pathogenic to Ferula communis. The paper describes the genomic organization of four putative laccase genes (lac1, lac2, lac3, and lac5-like gene; gene names were assigned on the basis of sequence homologies) of P. eryngii and P. ferulae. The mRNA expression and enzymatic activity of the laccases were analysed under culture conditions where a source of lignin (wheat bran) or lyophilized roots of E. campestre or F. communis were present. These experiments indicated that the four lac-like genes were differentially regulated in the two mushrooms. Specifically, the addition of the lyophilized roots of the respective host plant to the culture media induced an advance in the mRNA expression of the four lac-like genes and a seven-fold higher total laccase activity in P. ferulae than in P. eryngii. The results obtained are discussed in relation to the possible role of laccases in the interaction of P. eryngii and P. ferulae with their respective host.

Determinación de la toxicidad de Pleurotus ostreatus, Pleurotus pulmonarius y Paxillus involutus sobre Artemia salina

Se presentan los resultados obtenidos en un estudio sobre la toxicidad de losextractos etanólicos de Pleurotus ostreatus, Pleurotus pulmonarius y Paxillusinvolutus sobre Artemia salina. P. involutus presentó la mayor toxicidad(CL50 = 94,4 mg/ml), que fue similar a la observada con el patrón de dicromatode potasio. P. pulmonarius y P. ostreatus no presentaron toxicidad sobreA. salina en concentraciones inferiores a 1.000 mg/ml(AU)

We report the toxicity of ethanolic extracts in Pleurotus ostreatus, Pleurotuspulmonarius and Paxillus involutus over that obtained in Artemia salina.P. involutus showed the highest toxicity (LC50 = 94.4 mg/ml), similar to thatdetected using potassium dichromate pattern. P. pulmonarius and P. ostreatusdid not show toxicity over A. salina in concentrations lower than 1,000 mg/ml(AU)

[The research of the pathogen responsible for Pleurocybella porrigens related encephalopathy: investigation of 3-nitropropionic acid hypothesis].

Pleurocybella porrigens related encephalopathy exhibits consciousness disturbance and convulsion in the patients after taking and patients show bilateral basal ganglia lesion resulted in high mortality rate. This encephalopathy is a very similar to the moldy sugarcane encephalopathy epidemic in China in the past. We investigated the relationship between Pleurocybella porrigens related encephalopathy and 3-nitropropionic acid which had caused the moldy sugarcane encephalopathy. We have tried to detect 3-NPA in the various specimens from patients and Pleurocybella porrigens, but failed. Further examinations for elucidating the causation of Pleurocybella porrigens related encephalopathy are needed.