Biology subjects

Aden, M.

Publications and source records attributed to Aden, M..

4 recordsLinked to original sources

bioRxiv2026

Verticillium dahliae ubiquitin-specific proteases coordinate key developmental processes and pathogenicity

Ubiquitin is a posttranslational modifier that is conserved among eukaryotes. Ubiquitination alters stability and folding of cellular proteins. Deubiquitinases (DUBs) reverse ubiquitination and often function as part of protein complexes. There are 32 predicted DUB-encoding genes present in the soil-borne phytopathogenic fungus Verticillium dahliae. Nuclear ubiquitin-specific protease 3 (Usp3) is a member of the Spt-Ada-Gcn5 acetyltransferase (SAGA) complex, whereas Usp1 is predicted to associate with the COP9 signalosome (CSN), which controls specificities of cellular E3 ubiquitin ligase activities. A proteomics approach using biotin capture and identification (BioID) supports that Usp3 regulates gene expression beyond the transcription level. Western experiments showed a dysregulation in ubiquitinated cellular proteins in corresponding deletion strains. Usp3 and Usp1 are both required for fungal development. They regulate microsclerotia formation based on different environmental cues and provide redundant functions in controlling conidiation. Absence of both corresponding genes resulted in significant impairment of conidiospore formation, which is required for fungal propagation within the plant vascular system. This paralysed spreading ability reduced virulence on tomato plants (Solanum lycopersicum). In summary, V. dahliae responds to environmental cues by Usp3- and Usp1-mediated adjustment of gene expression and protein stability. This is important for key developmental processes of the V. dahliae disease cycle and its virulence towards the host plant. Author summaryUbiquitination and deubiquitination of proteins enable cells to rapidly react to environmental cues and adjust protein stabilities and subsequently transcriptomic profiles. Usp3 is a nuclear deubiquitinase subunit of the Spt-Ada-Gcn5 acetyltransferase (SAGA) transcriptional coactivator complex. Usp1 is predicted to be associated with the COP9 signalosome that regulates substrate specificities of the ubiquitin-proteasome system. BioID experiments suggest that other SAGA complex subunits, histone proteins, spliceosomal proteins, ribosomal proteins, a protein that tackles transcriptionally stalled RNAPII, and a protein that degrades mRNA with premature stop codons locate proximal to Usp3 within the cell. Deletion of USP3 led to the dysregulation of protein ubiquitination. A single deletion of USP1 did not significantly change ubiquitination profiles, however, a double deletion of USP1/3 significantly affected the ubiquitin-proteasome system. The altered ubiquitination profile correlated with a dysregulation of key developmental processes. Microsclerotia formation was decoupled from environmental cues in the {Delta}USP3 strain, whereas an additional deletion of USP1 reconnected it in a media-dependent manner. USP3 and USP1 contribute to a common governing process in conidiation, and the defect in spreading of the {Delta}USP1/3 strain is reflected by a significant reduction in plant pathogenicity.

microbiology↗

bioRxiv2025

The adapt-to-nutrient NRPS-like secondary metabolite gene cluster facilitates Verticillium dahliae adaptation to different nutrient environments

Filamentous fungi produce a wide range of secondary metabolites to adapt to changing environments. RNA sequencing revealed that nine biosynthetic gene clusters (BGCs) of the phytopathogenic Verticillium dahliae react to different nutrient environments. The adapt-to-nutrient NRPS-like (ANN) cluster contributes to antibacterial activity and developmental processes important for the early biotrophic life cycle, but is dispensable for virulence on tomato (Solanum lycopersicum). Transcription of the core biosynthetic enzyme-encoding ANN3 is highly induced in nutrient-poor environment. ANN3 is transcriptionally controlled by global and in-cluster transcription factors. ANN3 is activated by early colonisation transcription factors Som1 and Vta2, but repressed by Mtf1, which governs late stages of disease progression. The in-cluster transcription factor Ann1, which represses ANN3, is less stable in nutrient-poor environment or when V. dahliae encounters antagonists. Ann1 promotes resting structure formation but suppresses conidiation and antibacterial activity. Possible products of the ANN cluster were revealed by comparing metabolites extracted from ANN3 regulator mutants and from the bacterial-fungal interaction zone. Our findings revealed that V. dahliae perceives different nutrient environments and changes its survival strategy by differential expression of the ANN secondary metabolite gene cluster. Author summaryVerticillium dahliae is an economically significant phytopathogen that is widely distributed. The fungus adjusts and adapts its survival strategy according to the surrounding environment. Transcriptome data revealed that the core biosynthetic gene ANN3 of the adapt-to-nutrient NRPS-like (ANN) cluster is most expressed in nutrient-poor environments. The expression of ANN3 is governed by in-cluster repressor Ann1 and global transcriptional regulators that regulate other metabolic processes. Transcription factors Som1 and Vta2 are involved in the early plant-root infection process, whereas Mtf1 regulates late stage of disease development. ANN3 is activated by Som1 and Vta2, but repressed by Mtf1. The repressor Ann1 is less stable in nutrient-poor environments or when bacterial competitors are present. Ann1 promotes dormancy and represses spreading by conidiation. Vegetative growth is reduced but antibacterial activity is promoted when ANN1 is deleted. Possible chemical products of the ANN cluster were identified by comparing the metabolites extracted from the regulator mutant strains and the bacterial-fungal interaction zone. In summary, our findings show how V. dahliae react to environmental signals to balance growth, survival, and competition through the ANN cluster.

genetics↗

bioRxiv2025

The homeobox transcription factor HbxB coordinates distinct gene regulatory networks for asexual development and secondary metabolism in Aspergillus nidulans

Formation of conidia as asexual spores and sometimes worldwide distribution through the air is a very important feature of the fungal life style. This process is controlled by several regulatory proteins, including homeobox domain transcription factors. HbxB is one such regulator with implications in the control of development, secondary metabolism and various stress responses in the filamentous fungus Aspergillus nidulans. However, the molecular mechanism of the regulatory role of HbxB during asexual development is still elusive. Here we show that HbxB is a nuclear localized protein with great impact on asexual sporogenesis. Employment of high throughput assays like chromatin immunoprecipitation (ChIP-seq) and transcriptomics (RNA-seq), elucidated the in vivo binding landscape of HbxB in a genome-wide scale. A set of 238 genes as direct targets of HbxB were identified. A nine bases DNA motif where HbxB prefers to bind in vivo was discovered as HbxB response element (HRE). HbxB is influencing the expression of genes encoding master regulators of the asexual development such as SclB, PpoC, FlbA and FlbC. Moreover, the direct transcriptional control of the secondary metabolites sterigmatocystin and emericellamides biosynthesis by HbxB was discovered. Lastly also a previously elusive mutual regulatory control circuit between HbxB and two major regulators of the asexual development SclB and MsnA was found. Both of these regulators can directly induce the expression of hbxB. This study provides a detailed molecular mechanism on how HbxB controls A. nidulans asexual sporulation. ImportanceFungal distribution mainly relies on the formation of spores that are subsequently dispersed in different media to ensure colonization of substrates and the survival of the fungus. The asexual developmental program is a widely used strategy in the fungal kingdom for production of spores (conidia). The HbxB transcription factor is a nuclear localized, homeobox domain protein, with a strong impact on asexual sporulation of presumably numerous fungal species. This study enhances our understanding of the mechanism with which HbxB exerts its regulatory actions. HbxB is binding in vivo to specific DNA regulatory elements of genes encoding proteins with key roles in asexual development (like SclB, MsnA and PpoC), secondary metabolism (such as genes from the sterigmatocystin and emericellamide clusters) and stress response/tolerance. Overall, these findings open a window into how Hbx regulators orchestrate and coordinate fungal asexual developmental programs genome-wide at the molecular level.

molecular biology↗

bioRxiv2025

Molecular circuit between Aspergillus nidulans transcription factors MsnA and VelB to coordinate fungal stress and developmental responses

Development and secondary metabolism of the filamentous fungus Aspergillus nidulans are tightly controlled by concerted actions of several master regulator transcription factors. The connection between fungal development and cellular stress response programs is often elusive. Here we show that the MsnA zinc finger transcription factor, which controls salt-stress response, is a novel major player in fungal development. A molecular circuit among MsnA and the velvet domain regulator VelB was discovered, which mutually fosters the actions of both regulatory proteins during development. MsnA controls the expression of several genes encoding master transcriptional regulators of asexual as well as sexual development. In addition, MsnA affects directly and indirectly the synthesis of specific secondary metabolites relevant for fungal defense against other organisms and growth, in addition to salt-stress responses. Moreover, the expression of genes encoding the epigenetic regulators VapA and VipC are also directly controlled by MsnA. These subunits of the VapA-VipC-VapB methyltransferase signal transduction complex promote asexual differentiation. MsnA is therefore placed at a novel prominent position of the central regulatory network, which coordinates stress responses with the developmental and metabolic fate of the fungus.

microbiology↗