Carbon regulation of environmental pH by secreted small molecules that modulate pathogenicity in phytopathogenic fungi

[EN]Fruit pathogens can contribute to the acidification or alkalinization of the host environment. This capability has been used to divide fungal pathogens into acidifying and/or alkalinizing classes. Here, we show that diverse classes of fungal pathogens—Colletotrichum gloeosporioides, Penicillium expansum, Aspergillus nidulans and Fusarium oxysporum—secrete small pH-affecting molecules. These molecules modify the environmental pH, which dictates acidic or alkaline colonizing strategies, and induce the expression of PACC-dependent genes. We show that, in many organisms, acidification is induced under carbon excess, i.e. 175 mm sucrose (the most abundant sugar in fruits). In contrast, alkalinization occurs under conditions of carbon deprivation, i.e. less than 15 mm sucrose. The carbon source is metabolized by glucose oxidase (gox2) to gluconic acid, contributing to medium acidification, whereas catalysed deamination of non-preferred carbon sources, such as the amino acid glutamate, by glutamate dehydrogenase 2 (gdh2), results in the secretion of ammonia

LaeA regulation of secondary metabolism modulates virulence in Penicillium expansum and is mediated by sucrose

Penicillium expansum, the causal agent of blue mould rot, is a critical health concern because of the production of the mycotoxin patulin in colonized apple fruit tissue. Although patulin is produced by many Penicillium species, the factor(s) activating its biosynthesis are not clear. Sucrose, a key sugar component of apple fruit, was found to modulate patulin accumulation in a dose-responsive pattern. An increase in sucrose culture amendment from 15 to 175 mm decreased both patulin accumulation and expression of the global regulator laeA by 175- and five-fold, respectively, whilst increasing expression of the carbon catabolite repressor creA. LaeA was found to regulate several secondary metabolite genes, including the patulin gene cluster and concomitant patulin synthesis in vitro. Virulence studies of laeA mutants of two geographically distant P. expansum isolates (Pe-21 from Israel and Pe-T01 from China) showed differential reduction in disease severity in freshly harvested fruit, ranging from no reduction for Ch-Pe-T01 strains to 15%-25% reduction for both strains in mature fruit, with the laeA strains of Is-Pe-21 always showing a greater loss in virulence. The results suggest the importance of abiotic factors in LaeA regulation of patulin and other secondary metabolites that contribute to pathogenicity

Westland ecosystems of Sokolov regoin and their using in school practise

"The wetland ecosystems of Sokolov region and their using in school practice" The topic of the thesis is to monitor the biodiversity of wetland ecosystems, with a focus on protected species at selected localities of Sokolov region. Localities that were studied - Nadlesí, Stará Ovčárna and pískovna Erika, have been selected with regard to their accessibility for schools. The objective of the thesis was also to propose the possibility of the didactic use of localities for the natural science and biology at primary schools, therefore, for each a site excursion was propose; with a follow up creation of worksheets. The theoretical part contains the definition of the term wetlands, Sokolov region characteristics and it also summarizes the previous inventory research conducted at the given localities. In the practical part, the floristic and zoological inventory is determined along with methodology and didactic applications, i.e. the descriptions of excursions, the real-life testing of the excursions in school practice and the worksheets

Additional file 10: Table S1. of Fungal and host transcriptome analysis of pH-regulated genes during colonization of apple fruits by Penicillium expansum

Fungal primers used in this study. (DOCX 13 kb