Cytospotones A-D, four new polyketones from the endophytic fungus Cytospora sp. A879

Three new α-pyrone derivatives cytospotones A-C (1-3) and a new cyclohexenone derivative cytospotone D (4) together with four known α-pyrones were isolated from the endophytic fungus Cytospora sp. A879 of Pogostemon cablin (Blanco) Benth. The structures of 1-4 were elucidated primarily by spectroscopic methods (1D, 2D NMR and HRESIMS), ECD spectra analyses, and ECD calculations. Furthermore, the four new compounds (1-4) were evaluated for their anti-inflammatory and α-glucosidase inhibitory activities. The results showed that compound 1 had moderate inhibitory effect on LPS-induced NO production in RAW 264.7 macrophages.

First Report of Olive Branch Dieback in Croatia Caused by Cytospora pruinosa Défago

Olive (Olea europaea L.) is a very important crop grown in the Mediterranean part of Croatia. Olive branch and fruit dieback symptoms were observed in two olive orchards in Istria, Croatia. The samples from symptomatic trees were collected and brought to the laboratory for analysis. Based on their morphological characterization, isolated fungi were identified as Cytospora sp. Two representative isolates (one per orchard) were taken for molecular analysis, and based on DNA sequence data of the ITS and TUB gene regions, and phylogenetic analysis of the sequences, the isolates were identified as Cytospora pruinosa Défago. To determine pathogenicity, pathogenicity tests were conducted on detached olive branches and two-year-old olive trees in the greenhouse. This is the first report of C. pruinosa causing olive branch and fruit dieback in Croatia.

Cytospyrone and Cytospomarin: Two New Polyketides Isolated from Mangrove Endophytic Fungus, Cytospora sp

Two new polyketides, cytospyrone (1), cytospomarin (2), together with three known metabolites dimethoxyphtalide (3), integracin A (4) and integracin B (5), were isolated from the culture of Cytospora sp. from the Chinese mangrove Ceriops tagal. Their structures were elucidated by extensive spectroscopic analyses and time dependent density functional theory (TDDFT), calculation of electronic circular dichroism (ECD) and optical rotation (OR) data. Compound 2 displayed weak inhibitory activity against Escherichia coli GIM1.201 (minimum inhibitory concentration (MIC) value of 0.35 mM). Compounds 4 and 5 displayed significant cytotoxicity against human cancer cell line HepG2 (IC₅₀ values of 5.98 ±  0.12 µM and 9.97 ± 0.06 µM, respectively), more potent than the positive control 5-fluorouracil (IC₅₀ value of 43.50 ± 3.69 µM).

A new antimicrobial sesquiterpene isolated from endophytic fungus Cytospora sp. from the Chinese mangrove plant Ceriops tagal

Chemical examination of Chinese mangrove Ceriops tagal endophytic Cytospora sp., yielded a new biscyclic sesquiterpene seiricardine D (1), and eight known metabolites, xylariterpenoid A (2a), xylariterpenoid B (2b) and regiolone (3) 4-hydroxyphenethyl alcohol (4), (22E, 24R)5, 8-epidioxy-5α, 8α-ergosta-6,22E-dien-3ß-ol (5), (22E, 24R)5, 8-epidioxy-5α, 8α-ergosta-6,9(11), 22-trien-3 ß-ol (6), ß-sitosterol (7) and stigmast-4-en-3-one (8). These structures were unambiguously elucidated on the basis of extensive NMR spectroscopic and mass spectrometric analyses. The antimicrobial activities of compounds 1-8 and their effects on a panel of plant and human pathogens were evaluated.

Unconventional Recombination in the Mating Type Locus of Heterothallic Apple Canker Pathogen Valsa mali

Sexual reproduction in filamentous ascomycetes is controlled by the mating type (MAT) locus, including two idiomorphs MAT1-1 and MAT1-2 Understanding the MAT locus can provide clues for unveiling the sexual development and virulence factors for fungal pathogens. The genus Valsa (Sordariomycetes, Diaporthales) contains many tree pathogens responsible for destructive canker diseases. The sexual stage of these ascomycetes is occasionally observed in nature, and no MAT locus has been reported to date. Here, we identified the MAT locus of the apple canker pathogen Valsa mali, which causes extensive damage, and even death, to trees. V. mali is heterothallic in that each isolate carries either the MAT1-1 or MAT1-2 idiomorph. However, the MAT structure is distinct from that of many other heterothallic fungi in the Sordariomycetes. Two flanking genes, COX13 and APN2, were coopted into the MAT locus, possibly by intrachromosomal rearrangement. After the acquisition of foreign genes, unequal recombination occurred between MAT1-1/2 idiomorphs, resulting in a reverse insertion in the MAT1-2 idiomorph. Evolutionary analysis showed that the three complete MAT1-1-2, COX13, and APN2 genes in this region diverged independently due to different selection pressure. Null hypothesis tests of a 1:1 MAT ratio of 86 V. mali isolates from four different provinces showed a relatively balanced distribution of the two idiomorphs in the fields. These results provide insights into the evolution of the mating systems in Sordariomycetes.

[Screening, identification and biocontrol effect of antagonistic actinomycetes against the pathogen of Cytospora sp. for apple tree]

The pathogen of Cytospora sp. was considered as the target fungus to evaluate the bio-control potential of antagonistic actinomycetes against Cytospora sp. in the present study, which was isolated from the rhizosphere soil of apple tree. Moreover, the antagonistic effect of actinomycetes against Cytospora sp. growth was determined by the method of confrontation and growth rate, and the screened antagonistic strain was identified by the method of morphology and molecular biology. Also, the inhibitory activity of strain ZZ-9 against the conidium germination and mycelia growth of Cytospora sp. was determined in vivo, and its bio-control effect on Cytospora sp. growth was determined in detached apple twigs. The results showed that fifteen strains of actinomycetes had the inhibitory effect on Cytospora sp. growth, among all the isolated strains, which accounted for 18.8% and especially the inhibitory rate of eight strains was more than 50%. In addition, among all the screened strains, the strain ZZ-9 presented the highest inhibitory rate of 96.4%, which was significantly higher than those of the other isolated strains. The strain ZZ-9 was initially identified as Streptomyces rochei according to cultural characteristics, physiological and biochemical properties and 16S rDNA analysis. The nucleotide sequences in GenBank accession number was registered as KT986228. Different dilution of ZZ-9 fermentation had significant inhibitory effect on Cytospora sp. conidium germination and mycelia growth. The inhibitory rates of the 50 times fermentation on both conidium germination and mycelia growth were more than 80%. The inhibited mycelia's color was deepened, the mycelia branches were increased, and the ends of hyphae were swelled and deformed, even the protoplasm was concentrated and released. The bio-control effect of the ZZ-9 stock solution on Cytospora sp. growth was more than 75% in detached apple twigs. Thus, our results indicated that the strain ZZ-9 could be used for controlling apple tree Valsa canker in vivo and vitro.