Biology subjects

Typas, M. A.

Publications and source records attributed to Typas, M. A..

4 recordsLinked to original sources

bioRxiv2021

The NADPH Oxidase A of Verticillium dahliae is Essential for Pathogenicity, Normal Development, and Stress Tolerance, and it Interacts with Yap1 to Regulate Redox Homeostasis

Maintenance of redox homeostasis is vital for aerobic organisms and particularly relevant to plant pathogens. These need to balance between endogenous ROS production that is required for their development and pathogenicity, and host-derived oxidative stress. Endogenous ROS in fungi are generated by the membrane-bound NADPH oxidase (NOX) complexes and the mitochondrial respiratory chain, while the transcription factor Yap1 is a major regulator of the antioxidant response. Here we investigated the roles of NoxA and Yap1 in fundamental biological processes of the important plant pathogen Verticillium dahliae. Deletion of noxA impaired growth and morphogenesis, compromised formation of hyphopodia, diminished penetration ability and pathogenicity, increased sensitivity against antifungal agents, and dysregulated expression of antioxidant genes. On the other hand, deletion of yap1 resulted in defects in conidial and microsclerotia formation, increased sensitivity against oxidative stress, and down-regulated antioxidant genes. Localized accumulation of ROS was observed before conidial fusion and during the heterokaryon incompatibility reaction upon nonself fusion. The frequency of inviable fusions was not affected by deletion of Yap1. Analysis of a double knockout mutant revealed an epistatic relationship between noxA and yap1. Our results collectively reveal instrumental roles of NoxA and ROS homeostasis in the biology of V. dahliae.

genetics↗

bioRxiv2021

Starvation-induced cell fusion and heterokaryosis frequently escape imperfect allorecognition systems to enable parasexual interactions in an asexual fungal pathogen

O_LIAsexual fungi include important pathogens of plants and other organisms, and their effective management requires understanding of their evolutionary dynamics. Genetic recombination is critical for species adaptability and could be achieved via heterokaryosis and the parasexual cycle in asexual fungi. Here, we investigate the extent and mechanisms of heterokaryosis in the asexual plant pathogen Verticillium dahliae. C_LIO_LIWe used live-cell imaging and genetic complementation assays of tagged V. dahliae strains to analyze the extent of nonself vegetative fusion, heterokaryotic cell fate and nuclear behavior. An efficient CRISPR/Cas9-mediated system was developed to investigate the involvement of autophagy in heterokaryosis. C_LIO_LIUnder starvation, nonself fusion of germinating spores occurs frequently regardless of the previously assessed vegetative compatibility of the partners. Supposedly "incompatible" fusions often establish viable heterokaryotic cells and mosaic mycelia, where nuclei can engage in fusion or transfer of genetic material. The molecular machinery of autophagy has a protective function against destruction of "incompatible" heterokaryons. C_LIO_LIOur results suggest an autophagy-mediated trade-off between parasexual interactions for genetic exchange and allorecognition systems possibly for mycelial protection from parasitic elements. Our study reveals unexpected capacity for heterokaryosis in V. dahliae and suggests, therefore, important roles of parasexuality in the evolution of asexual fungi. C_LI

genetics↗

bioRxiv2020

Conidial fusion in the asexual fungus Verticillium dahliae

Cell-to-cell fusion is a fundamental biological process across the tree of life. In filamentous fungi, somatic fusion (or anastomosis) is required for the normal development of their syncytial hyphal networks, and it can initiate non-sexual genetic exchange processes, such as horizontal genetic transfer and the parasexual cycle. Although these could be important drivers of the evolution of asexual fungi, this remains a largely unexplored possibility due to the lack of suitable resources for their study in these puzzling organisms. In this study, we report that the spores of the important asexual plant-pathogenic fungus Verticillium dahliae often engage in cell fusion via Conidial Anastomosis Tubes (CATs). We optimized appropriate procedures for their highly reproducible quantification and live-cell imaging, which were used to characterize their physiology and cell biology, and to start elucidating their underlying genetic machinery. Formation of CATs was shown to depend on growth conditions and require functional Fus3 and Slt2 MAP kinases, as well as the NADPH oxidase NoxA, whereas the GPCR Ste2 and the mating-type protein MAT1-2-1 were dispensable. We show that nuclei and other organelles can migrate through CATs, which often leads to the formation of transient dikaryons. Their nuclei have possible windows of opportunity for genetic interaction before degradation of one by a presumably homeostatic mechanism. We establish here CAT-mediated fusion in V. dahliae as an experimentally convenient system for the cytological analysis of fungal non-sexual genetic interactions. We expect that it will facilitate the dissection of sexual alternatives in asexual fungi.

microbiology↗

bioRxiv2020

Hex1, the Major Component of Woronin Bodies, is Required for Normal Development, Pathogenicity and Stress Response in the Plant Pathogenic Fungus Verticillium dahliae

Woronin bodies are membrane-bound organelles of filamentous ascomycetes that mediate hyphal compartmentalization by plugging septal pores upon hyphal damage. Their major component is the peroxisomal protein Hex1, which has also been implicated in additional cellular processes in fungi. Here, we analyzed the Hex1 homolog of Verticillium dahliae, an important asexual plant pathogen, and we report its pleiotropic involvement in fungal growth, physiology, stress response and pathogenicity. Alternative splicing of the Vdhex1 gene can lead to the production of two Hex1 isoforms, which are structurally similar to their Neurospora crassa homolog. We show that VdHex1 is targeted to the septum, consistently with its demonstrated function in sealing hyphal compartments to prevent excessive cytoplasmic bleeding upon injury. Furthermore, our investigation provides direct evidence for significant contributions of Hex1 in growth and morphogenesis, as well as in asexual reproduction capacity. We discovered that Hex1 is required both for normal responses to osmotic stress and factors that affect the cell wall and plasma membrane integrity, and for normal resistance to oxidative stress and ROS homeostasis. The Vdhex1 mutant exhibited diminished ability to colonize and cause disease on eggplant. Overall, we show that Hex1 has fundamentally important multifaceted roles in the biology of V. dahliae.

microbiology↗