Biology subjects

Espeso, E. A.

Publications and source records attributed to Espeso, E. A..

8 recordsLinked to original sources

bioRxiv2025

A TRAPPC2L/TRAPPC11/12/13 subcomplex directs TRAPPIII to autophagy

TRAPP complexes are master regulators of membrane trafficking. TRAPPs are targeted to different locales by pathway-specific subunits decorating a core hetero-heptamer to build TRAPPII (Golgi exit) and TRAPPIII (autophagosomes and ER-Golgi traffic). Metazoan and Arabidopsis TRAPPIII have three components, TRAPPC11/12/13 absent from the budding yeast. We studied TRAPPC11/12/13 in the related ascomycete Aspergillus nidulans, where TRAPPC11 and TRAPPC12 localize to pre-autophagosomes and their ablation impairs autophagy. Two stable subcomplexes containing Tca17/TRAPPC2L coexist, one including the TRAPPII-specific subunits Trs120/Trs130/Trs65 and another including the TRAPPIII-specific subunits TRAPPC11/12/13. Both are recruited to core TRAPP by Tca17/TRAPPC2L, which therefore plays a crucial role by determining the fate of TRAPP. TRAPPIII also comes in two versions, TRAPPIIIa and TRAPPIIIb, both containing Trs85/TRAPPC8, but only TRAPPIIIb containing TRAPPC11/12/13, which target TRAPPIII to autophagy. This study might help characterize potentially pathogenic mutations affecting human TRAPPC11/12/13, facilitating assessment of their functional consequences in a genetically amenable ascomycete.

cell biology↗

bioRxiv2025

Gene duplication drove functional divergence of two effectors in the maize anthracnose pathogen

Colletotrichum species rank among the most important fungal pathogens, threatening food security by infecting nearly all major crops worldwide. Colletotrichum graminicola, the causal agent of maize anthracnose, secretes effector proteins to manipulate host defences and promote colonization. Building on previous work characterizing the nuclear effector CgEP1, we characterized its paralog CgEP4, which is highly conserved across strains of C. graminicola. Phylogenetic analysis of the two genes and their homologs in other species revealed that they originated from a gene duplication event approximately 28 to 18 million years ago, predating the diversification of the Graminicola species complex. This timing aligns with the ecological expansion of C4 grasses, suggesting that the functional divergence of these effectors was an adaptive response to facilitate the colonization of emerging monocot hosts. Functional characterization using gene deletion mutants demonstrated that CgEP4 has a critical role in pathogenicity, characterized by a significant reduction in virulence, delayed penetration, enhanced papilla formation, and decreased fungal biomass. This virulence defect is associated with compromised host colonization and a failure to suppress basal host defences. In the absence of CgEP4, the pathogen also showed defects in general fungal physiology and stress tolerance. Overall, our findings establish CgEP4 as a new, essential nuclear-localized effector that promotes fungal entry and colonization by manipulating host responses. Our findings demonstrate that evolutionary analysis is a valuable tool for discovering new genes important for host adaptation and pathogen evolution.

plant biology↗

bioRxiv2025

The actin module of endocytic internalization in Aspergillus nidulans: a critical role of the WISH/DIP/SPIN90 family protein Dip1

Using fluorescent protein-tagged F-actin reporters we studied the actin cytoskeleton in Aspergillus nidulans. F-actin probes labeled endocytic patches, contractile actin rings and the Spitzenkorper (SPK), but not exocytic cables generated by the SPK-associated formin, illuminated only by tropomyosin. The SPK actin mesh contains tropomyosin and capping protein, but not fimbrin or Arp2/3, showing that it does not involve branched actin. Arp2/3 and fimbrin are recruited to endocytic patches at the end of their lifecycle, staying in them for 12-14 sec, coinciding with the burst of branched actin polymerization that powers vesicle internalization, whereas verprolin stays only during the first half of this actin phase. Hyphal growth requires endocytic recycling, which we exploited to assess the efficiency of endocytosis following genetic interventions. Ablation of SlaBSla2, Arp2/3, cofilin and fimbrin is lethal, whereas that of Srv2, verprolin and capping protein are debilitating, with the lifetime of actin in mutant patches roughly correlating with the extent of growth and endocytic defects. An outstanding problem is the origin of seed filaments required to prime Arp2/3 during endocytosis. Actin patches associate with cortical cables that give rise to long distance-moving "actin worms" that are different from tropomyosin-containing cables emanating from the SPK. Cables and worms are dependent on formin, yet inactivation of formin does not affect the F-actin patch lifecycle, arguing against formin playing an endocytic role. Ablation of the WISH/DIP/SPIN90 protein Dip1 priming Arp2/3 for the synthesis of linear actin delocalizes the endocytic machinery and severely impairs, but does not preclude, endocytosis. This establishes the existence of Dip1-independent mechanism(s) that synthesize seed filaments. Our data negate the possibility that this alternative mechanism results from a priming role of formin that is unmasked in dip1{Delta} cells, but do not exclude that cofilin-mediated filament severing could produce seed microfilaments for Arp2/3, as suggested for Schizosaccharomyces pombe. Authors summaryFilamentous fungi have a deep impact in our lives as friends and foes. Certain species are used as cell factories for the production of proteins or biopharmaceuticals. In contrast, phytopathogenic species, cause important losses in crops whereas those able to infect humans represent serious risks for global health. Filamentous fungi form tubular cells, denoted hyphae, that grow by apical extension. This requires the coupling between exocytosis and endocytosis in the so-called endocytic recycling pathway, which is needed, for example, to maintain the polarization of enzymes which synthesize the cell wall as growth proceeds. Remarkably, detailed studies on endocytosis in filamentous fungi are wanting. Here we report the characterization of the endocytic pathway in the genetic model Aspergillus nidulans, a filamentous ascomycete which is well-suited for genetic manipulation and in vivo fluorescence microscopy. Our study demonstrates that endocytosis is essential for filamentous fungal life and provides significant insight on how F-actin powers the internalization of endocytic vesicles, including an important physiological role of Dip1, a protein required to provide seed filaments for the formation of F-actin branching networks. Importantly, as yet unidentified Dip1-independent mechanisms that synthesize these seeds must exist, opening new avenues for future research.

cell biology↗

bioRxiv2023

Identification and functional characterization of the putative members of the CTDK-1 kinase complex as regulators of growth and development in the genus Aspergillus.

The genus Aspergillus includes industrially, medically and agriculturally important species. All of them, as do fungi in general, disperse to new niches principally by means of asexual spores. Regarding the genetic/molecular control of asexual development, Aspergillus nidulans is the main reference. In this species, two pathways control the production of conidiophores, the structures bearing asexual spores (conidia). The Upstream Developmental Activation (UDA) pathway transduces environmental signals, determining whether the Central Developmental Pathway (CDP) and the required morphological changes are induced. The transcriptional regulator BrlA links both pathways as loss-of-function mutations in flb (UDA) genes block brlA transcription and, consequently, conidiation. However, the aconidial phenotype of specific flb mutants is reverted under salt-stress conditions. Previously, we generated a collection of {Delta}flbB mutants unable to conidiate on culture medium supplemented with NaH2PO4 (0.65M). Here, we identified a Gly347Stop mutation within flpA as responsible for the FLIP57 phenotype. The putative cyclin FlpA and the remaining putative components of the C-terminal domain kinase-1 (CTDK-1) complex are necessary for proper germination, growth and developmental patterns in both A. nidulans and A. fumigatus. Cellular localization and functional interdependencies of the three proteins are also analyzed. Overall, this work links the putative CTDK-1 complex of aspergilli with growth and developmental control. One-sentence summaryIdentification of a mutation in flpA as inhibitor of conidiation in A. nidulans and functional characterization of FlpA, Stk47 and FlpB as putative members of the C-terminal domain kinase complex CTDK-1 in the genus Aspergillus.

microbiology↗

bioRxiv2023

Homeobox Transcription Factor HbxA Influences Expression of over One ThousandGenes in the Model Fungus Aspergillus nidulans

In fungi, conserved homeobox-domain (HD) proteins are transcriptional regulators governing development. In Aspergillus species, several HD transcription factor genes have been identified, among them, hbxA/hbx1. For instance, in the opportunistic human pathogen Aspergillus fumigatus, hbxA is involved in conidial production and germination, as well as virulence and secondary metabolism (SM), including production of fumigaclavines, fumiquinazolines, and chaetominine. In the agriculturally important fungus Aspergillus flavus, disruption of hbx1 results in fluffy aconidial colonies unable to produce sclerotia. hbx1 also regulates production of aflatoxins, cyclopiazonic acid and aflatrem. Furthermore, transcriptome studies revealed that hbx1 has a broad effect on the A. flavus genome, including numerous genes involved in SM. These studies underline the importance of the HbxA/Hbx1 regulator, not only in developmental processes but also in the biosynthesis of a broad number of fungal natural products, including potential medical drugs and mycotoxins. To gain further insight into the regulatory scope of HbxA in Aspergilli, we studied its role in the model fungus Aspergillus nidulans. Our present study of the A. nidulans hbxA-dependent transcriptome revealed that more than one thousand genes are differentially expressed when this regulator was not transcribed at wild-type levels, among them numerous transcription factors, including those involved in development as well as in SM regulation. Furthermore, our metabolomics analyses revealed that production of several secondary metabolites, some of them associated with A. nidulans hbxA-dependent gene clusters, was also altered in deletion and overexpression hbxA strains compared to the wild type, including synthesis of nidulanins A, B and D, versicolorin A, sterigmatocystin, austinol, dehydroaustinol, and three unknown novel compounds.

genetics↗

bioRxiv2020

Defining the transcriptional responses of Aspergillus nidulans to cation/alkaline pH stress and the role of the transcription factor SltA.

Fungi have developed the ability to overcome extreme growth conditions and thrive in hostile environments. The model fungus Aspergillus nidulans tolerates, for example, ambient alkalinity up to pH 10 or molar concentrations of multiple cations. The ability to grow under alkaline pH or saline stress depends on the effective function of, at least, three regulatory pathways mediated by high hierarchy zinc-finger transcription factors: PacC, which mediates the ambient pH regulatory pathway, the calcineurin-dependent CrzA and the cation-homeostasis responsive factor SltA. Using RNA sequencing, we determined the effect of external pH alkalinisation or sodium stress on gene expression. Data show that each condition triggers transcriptional responses with a low degree of overlap. By sequencing the transcriptomes of the null mutant, the role of SltA in the abovementioned homeostasis mechanisms was also studied. Results show that the transcriptional role of SltA is wider than initially expected and implies, for example, the positive control of the PacC-dependent ambient pH regulatory pathway. Overall, our data strongly suggest that the stress-response pathways in fungi include some common but mostly exclusive constituents, and that there is a hierarchy of authority among the main regulators of stress response, with SltA controlling pacC expression at least in A. nidulans.

microbiology↗

bioRxiv2019

Rewiring of transcriptional networks as a major event leading to the diversity of asexual multicellularity in fungi

Complex multicellularity (CM) is characterized by the generation of three-dimensional structures that follow a genetically controlled program. CM emerged at least five times in evolution, one of them in fungi. There are two types of CM programs in fungi, leading, respectively, to the formation of sexual or asexual spores. Asexual spores foment the spread of mycoses, as they are the main vehicle for dispersion. In spite of this key dependence, there is great morphological diversity of asexual multicellular structures in fungi. To advance the understanding of the mechanisms that control initiation and progression of asexual CM and how they can lead to such a remarkable morphological diversification, we studied 503 fungal proteomes, representing all phyla and subphyla, and most known classes. Conservation analyses of 33 regulators of asexual development suggest stepwise emergence of transcription factors. While velvet proteins constitute one of the most ancient systems, the central regulator BrlA emerged late in evolution (with the class eurotiomycetes). Some factors, such as MoConX4, seem to be species-specific. These observations suggest that the emergence and evolution of transcriptional regulators rewire transcriptional networks. This process could reach the species level, resulting in a vast diversity of morphologies.\n\nOne-sentence summaryA study of the evolution of regulators that control the production of asexual spores in fungi.

developmental biology↗

bioRxiv2018

Developmental regulators FlbE/D orchestrate the polarity site-to-nucleus dynamics of the fungal bZIP FlbB

Permanently polarized cells have developed transduction mechanisms linking polarity-sites with gene regulation in the nucleus. In neurons, one mechanism is based on long-distance retrograde migration of transcription factors (TFs). Aspergillus nidulans FlbB is the only known fungal TF shown to migrate retrogradely to nuclei from the polarized region of fungal cells known as hyphae. There, FlbB controls developmental transitions by triggering the production of asexual multicellular structures. FlbB dynamics in hyphae is orchestrated by regulators FlbE and FlbD. At least three FlbE domains are involved in the acropetal transport of FlbB, with a final MyoE/actin filament-dependent step from the subapex to the apex. Experiments employing a T2A viral peptide-containing chimera (FlbE::mRFP::T2A::FlbB::GFP) suggest that apical FlbB/FlbE interaction is inhibited in order to initiate a dynein-dependent FlbB transport to nuclei. FlbD controls the nuclear accumulation of FlbB through a cMyb domain and a C-terminal LxxLL motif. Overall, results elucidate a highly dynamic pattern of FlbB interactions, which enable timely developmental induction. Furthermore, this system establishes a reference for TF-based long-distance signaling in permanently polarized cells.

developmental biology↗