LIF-dependent survival of embryonic stem cells is regulated by a novel palmitoylated Gab1 signalling protein.

The cytokine leukaemia inhibitory factor (LIF) promotes self-renewal of mouse embryonic stem cells (ESCs) through activation of the transcription factor Stat3. However, the contribution of other ancillary pathways stimulated by LIF in ESCs, such as the MAPK and PI3K pathways, is less well understood. We show here that naive-type mouse ESCs express high levels of a novel effector of the MAPK and PI3K pathways. This effector is an isoform of the Gab1 (Grb2-associated binder protein 1) adaptor protein that lacks the N-terminal pleckstrin homology (PH) membrane-binding domain. Although not essential for rapid unrestricted growth of ESCs under optimal conditions, the novel Gab1 variant (Gab1ß) is required for LIF-mediated cell survival under conditions of limited nutrient availability. This enhanced survival is absolutely dependent upon a latent palmitoylation site that targets Gab1ß directly to ESC membranes. These results show that constitutive association of Gab1 with membranes through a novel mechanism promotes LIF-dependent survival of murine ESCs in nutrient-poor conditions.

The genus Rachicladosporium: introducing new species from sooty mould communities and excluding cold adapted species.

The fungal genus Rachicladosporium (Cladosporiales, Cladosporiaceae), typified by cladosporium-like Rachicladosporium luculiae, includes a morphologically diverse assemblage of species. The species of this genus were reported from different substrates, habitats and environments, including plant leaves and needles, twig, black mould on baobab trees, rocks and insects. In this study, four new Rachicladosporium species (R. europaeum, R. ignacyi, R. kajetanii, R. silesianum) isolated from sooty mould communities covering leaves and needles of trees and shrubs in Poland are described. The new species are delineated based on morphological characteristics and molecular phylogenetic analyses using concatenated ITS, LSU, and rpb2 sequences. All newly described species are nested in the main Rachicladosporium lineage (centred around the type species), which contains species that are able to grow at 25 °C. By contrast, four cold adapted, endolithic species known from Antarctica (R. antarcticum, R. aridum, R. mcmurdoi) and Italian Alps (R. monterosanum) form distant phylogenetic lineage and do not grow at this temperature. Therefore, they are accommodated in the new genus Cryoendolithus, typified by Cryoendolithus mcmurdoi.

Discovery of Formicomyces microglobosus gen. et sp. nov. strengthens the hypothesis of independent evolution of ant-associated fungi in Trichomeriaceae.

Different groups of fungi have been reported to interact with ants. Recent studies have shown that fungi of the order Chaetothyriales are important components of ant-fungus networks, including members of the family Trichomeriaceae, which is particularly rich in fungi isolated from carton ants nests. One of the still understudied ant-related environments are ants' infrabuccal pockets and pellets, which often contain fungal matter. The aim of this work was to determine the systematic and phylogenetic position of two slow growing strains of Trichomeriaceae isolated from infrabuccal pellets of Formica polyctena ants. Molecular analyses based on maximum likelihood and bayesian inference, using sequences of two ribosomal DNA markers: ITS and LSU have shown that the isolated strains form a monophyletic clade within the family Trichomeriaceae, sister to a clade formed by representatives of the genus Trichomerium. Morphological analyses additionally justified distinctiveness of the isolated strains, which have different morphology of conidia and conidiophores than Trichomerium representatives. Therefore, our results show that the isolated strains represent a new species within a not yet described fungal genus. Due to the strains' isolation source and their close relatedness to a fungal strain isolated from a carton nest of Lasius fuliginosus, we propose a name Formicomyces microglobosus Siedlecki & Piatek for this fungus. While our discovery strengthens a hypothesis of the multiple, independent evolution of ant-associated fungi in the family Trichomeriaceae, the ecology of F. microglobosus still remains to be characterized.

Salinomyces polonicus: A moderately halophilic kin of the most extremely halotolerant fungus Hortaea werneckii.

A clade where the most halotolerant fungus in the world - Hortaea werneckii, belongs (hereafter referred to as Hortaea werneckii lineage) includes five species: Hortaea werneckii, H. thailandica, Stenella araguata, Eupenidiella venezuelensis, and Magnuscella marina, of which the first species attracts increasing attention of mycologists. The species diversity and phylogenetic relationships within this lineage are weakly known. In this study two moderately halophilic black yeast strains were isolated from brine of graduation tower in Poland. Molecular phylogenetic analyses based on the rDNA ITS1-5.8S-ITS2 (=ITS), rDNA 28S D1-D2 (=LSU), and RNA polymerase II (rpb2) sequences showed that the two strains belong to Hortaea werneckii lineage but cannot be assigned to any described taxa. Accordingly, a new genus and species, Salinomyces and Salinomyces polonicus, are described for this fungus. Furthermore, molecular phylogenetic analyses have revealed that Hortaea thailandica is more closely related to S. polonicus than to H. werneckii. A new combination Salinomyces thailandicus is proposed for this fungus.