Identification of Aspergillus niger Aquaporins Involved in Hydrogen Peroxide Signaling

Identification of mycoparasitism-related genes in Trichoderma harzianum T4 that are active against Colletotrichum musae

Trichoderma harzianum is a well-known biological control agent (BCA) that shows great potential in controlling many pathogenic fungi. To screen for genes associated with mycoparasitism, we sequenced and analyzed the transcriptome of T. harzianum T4 grown in dual culture with Colletotrichum musae. We analyzed differentially expressed genes (DEGs) of Trichoderma harzianum T4 in three different culture periods: before contact (BC), during contact (C) and after contact (AC). A total of 1453 genes were significantly differentially expressed compared to when T. harzianum T4 was cultured alone. During the three periods of double culture of T. harzianum T4 with C. musae, 74, 516, and 548 genes were up-regulated, respectively, and 11, 315, and 216 genes were down-regulated, respectively. The DEGs were screened using GO and KEGG enrichment analyses combined with differential expression multiples. Six gene categories related to mycoparasitism were screened: (a) pathogen recognition and signal transduction, (b) hydrolases, (c) ribosomal proteins and secreted proteins, (d) multidrug-resistant proteins and transporters, (e) heat shock proteins and detoxification, and (f) oxidative stress and antibiotics-related genes. The expression levels of 24 up-regulated genes during T. harzianum T4's antagonistic interaction with C. musae were detected via real-time fluorescence quantitative PCR (RT-qPCR). This study provided information on the transcriptional expression of T. harzianum T4 against C. musae. These results may help us to further understand the mechanism of mycoparasitism, which can provide a potential molecular target for improving the biological control capacity of T. harzianum T4.

The Transcriptome Response to Azole Compounds in Aspergillus fumigatus Shows Differential Gene Expression across Pathways Essential for Azole Resistance and Cell Survival

The opportunistic pathogen Aspergillus fumigatus is found on all continents and thrives in soil and agricultural environments. Its ability to readily adapt to novel environments and to produce billions of spores led to the spread of azole-resistant A. fumigatus across the globe, posing a threat to many immunocompromised patients, including critically ill patients with severe influenza or COVID-19. In our study, we sought to compare the adaptational response to azoles from A. fumigatus isolates that differ in azole susceptibility and genetic background. To gain more insight into how short-term adaptation to stressful azole compounds is managed through gene expression, we conducted an RNA-sequencing study on the response of A. fumigatus to itraconazole and the newest clinically approved azole, isavuconazole. We observed many similarities in ergosterol biosynthesis up-regulation across isolates, with the exception of the pan-azole-resistant isolate, which showed very little differential regulation in comparison to other isolates. Additionally, we found differential regulation of membrane efflux transporters, secondary metabolites, iron metabolism, and various stress response and cell signaling mechanisms.

Osmotically Activated Anion Current of Phycomyces Blakesleeanus-Filamentous Fungi Counterpart to Vertebrate Volume Regulated Anion Current

Studies of ion currents in filamentous fungi are a prerequisite for forming a complete understanding of their physiology. Cytoplasmic droplets (CDs), obtained from sporangiophores of Phycomyces blakesleeanus, are a model system that enables the characterization of ion currents in the native membrane, including the currents mediated by the channels not yet molecularly identified. Osmotically activated anionic current with outward rectification (ORIC) is a dominant current in the membrane of cytoplasmic droplets under the conditions of hypoosmotic stimulation. We have previously reported remarkable functional similarities of ORIC with the vertebrate volume regulated anionic current (VRAC), such as dose-dependent activation by osmotic difference, ion selectivity sequence, and time and voltage dependent profile of the current. Using the patch clamp method on the CD membrane, we further resolve VRAC-like ORIC characteristics in this paper. We examine the inhibition by extracellular ATP and carbenoxolone, the permeation of glutamate in presence of chloride, selectivity for nitrates, and activation by GTP, and we show its single channel behavior in excised membrane. We propose that ORIC is a functional counterpart of vertebrate VRAC in filamentous fungi, possibly with a similar essential role in anion efflux during cell volume regulation.