Tarek Moussa

This study aimed to compare the fungal rhizosphere communities of Rhazya stricta, Enneapogon desvauxii, Citrullus colocynthis, Senna italica, and Zygophyllum simplex, and the gut mycobiota of Poekilocerus bufonius (Orthoptera, Pyrgomorphidae, “Usherhopper”). A total of 164,485 fungal reads were observed from the five plant rhizospheres and Usherhopper gut. The highest reads were in S. italica rhizosphere (29,883 reads). Species richness in the P. bufonius gut was the highest among the six samples. Ascomycota was dominant in all samples, with the highest reads in E. desvauxii (26,734 reads) rhizosphere. Sordariomycetes and Dothideomycetes were the dominant classes detected with the highest abundance in C. colocynthis and E. desvauxii rhizospheres. Aspergillus and Ceratobasidium were the most abundant genera in the R. stricta rhizosphere, Fusarium and Penicillium in the E. desvauxii rhizosphere and P. bufonius gut, Ceratobasidium and Myrothecium in the C. colocynthis rhizosphere, Aspergillus and Fusarium in the S. italica rhizosphere, and Cochliobolus in the Z. simplex rhizosphere. Aspergillus terreus was the most abundant species in the R. stricta and S. italica rhizospheres, Fusarium sp. in E. desvauxii rhizosphere, Ceratobasidium sp. in C. colocynthis rhizosphere, Cochliobolus sp. in Z. simplex rhizosphere, and Penicillium sp. in P. bufonius gut. The phylogenetic results revealed the unclassified species were related closely to Ascomycota and the species in E. desvauxii, S. italica and Z. simplex rhizospheres were closely related, where the species in the P. bufonius gut, were closely related to the species in the R. stricta, and C. colocynthis rhizospheres.

The transcription factors families (TFs) play a critical role in the response regulation of plants to abiotic stresses. The three plant lineages (E. desvauxii, C. colocynthis & Z. simplex) can be separated on the PC1 level, while R. stricta and S. Italica can be distinguished from each other on the PC2 level. A unique 225 transcripts in each of R. stricta and E. desvauxii, 85 transcripts in C. colocynthis, 92 transcripts in S. Italica, and 41 transcripts in Z. simplex were identified. All five plants were shared in only 15 transcripts. Genes had significant gene ontology (GO), R. stricta (450), E. desvauxii (475), C. colocynthis (197), S. Italica (223), and Z. simplex (75) were significantly assigned with GO terms for 29 transcriptional processes. The most abundant TF families in the five plants were MYB followed by, MYB-related, bHLH, and AP2-EREBP (1105, 803, 53 & 472 transcripts, respectively). The zinc TF families were the most transcribed and represented by 8 TF families (PLATZ, C2C2-CO-like, C3H, VOZ, C2C2-GATA, C2C2-DOF, C2H2 & ZF-HD), with the highest one (C3H TF family, 99 transcripts in both R. stricta & Z. simplex). The regulatory network showed that as heat response, 12 genes were upregulated in R. stricta and controlled several genes in some vital processes inside the plant, while E. desvauxii and S. Italica respond to heat by upregulation of 6 genes for each, C. colocynthis by regulation of 3 genes and the least one was Z. simplex by upregulation of two genes only.

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Iron is essential for a wide range of cellular processes. Here we show that the bZIP-type regulator HapX is indispensable for the transcriptional remodeling required for adaption to iron starvation in the opportunistic fungal pathogen Aspergillus fumigatus. HapX represses iron-dependent and mitochondrial-localized activities including respiration, TCA cycle, amino acid metabolism, iron-sulfur-cluster and heme biosynthesis. In agreement with the impact on mitochondrial metabolism, HapX-deficiency decreases resistance to tetracycline and increases mitochondrial DNA content. Pathways positively affected by HapX include production of the ribotoxin AspF1 and siderophores, which are known virulence determinants. Iron starvation causes a massive remodeling of the amino acid pool and HapX is essential for the coordination of the production of siderophores and their precursor ornithine. Consistent with HapX-function being limited to iron depleted conditions and A. fumigatus facing iron starvation in the host, HapX-deficiency causes significant attenuation of virulence in a murine model of aspergillosis. Taken together, this study demonstrates that HapX-dependent adaption to conditions of iron starvation is crucial for virulence of A. fumigatus.