Transcriptional regulation by the Velvet complex during development in Neurospora crassa

• Autores: Sara Cea Sánchez
• Directores de la Tesis: Luis María Corrochano Peláez (dir. tes.), David Cánovas López (dir. tes.)
• Lectura: En la Universidad de Sevilla ( España ) en 2023
• Idioma: español
• Número de páginas: 195
• Enlaces
  • Tesis en acceso abierto en: Idus
• Resumen

  • Developmental transitions in fungi are key to their success in colonizing new habitats and adapting to stressful environmental conditions. Developmental transitions are regulated by environmental factors such as light. Neurospora crassa is an ascomycete heterothallic filamentous fungus and a model organism for research on several aspects of fungal biology, including the study of light sensing and morphogenesis during development. The life cycle of N. crassa includes asexual development with the formation of vegetative conidia that are easily dispersed, and sexual development, a complex process involving the formation of sexual reproductive structures (perithecia), were the ascospores (meiotic products) are formed. The velvet complex is a fungal-specific protein complex that participates in the regulation of gene expression in response to environmental signals such as light, as well as developmental processes, pathogenesis, and secondary metabolism. In this thesis, we have characterized the role of the velvet complex (the velvet proteins VE-1 and VE-2, and the methyltransferase LAE-1) during different stages of the life cycle of N. crassa. We first started studying the role of this complex during asexual development. Mutations in ve-1 or ve-2, but not in lae-1 led to shorter height of aerial tissue and an increased development of macroconidia. Additionally, when ve-1 or ve-2 mutations were combined with mutations in the transcription factor gene fl, which is an activator of macroconidiation, lead to increased microconidiation. VE-2 and LAE-1 were detected during vegetative growth and conidiation, unlike VE-1 which was mostly observed in samples obtained from submerged vegetative hyphae. We propose that VE-1 is the limiting component of the velvet complex during conidiation and has a major role in the transcriptional regulation of conidiation. Characterization of the role of VE-1 by RNA seq experiments during mycelial growth and asexual development (conidiation) allowed the identification of a set of genes regulated by VE-1, most notably the transcription factor genes vib-1 and fl, that participate in the regulation of conidiation. We propose that VE- 1 and VE-2 regulate the development of aerial tissue and the balance between macro- and microconidiation in coordination with FL and VIB-1. During sexual development, strains lacking VE-1 and/ or VE-2 display a markedly delayed and reduced sexual development with fewer fruiting bodies compared to the wildtype strain. Alterations in the development of female structures, protoperithecia, in the ve-1 and ve-2 mutants suggested that the VE-1/VE-2 complex should regulate transcription during sexual development. We have characterized the transcriptome of wild-type and Dve-1 mutant strains over the time course of sexual development in both dark and light. Among the misregulated genes, we detected genes that are essential for sexual development, such as mitogen-activated protein kinase (MAPK) signaling pathways, cell-cell fusion genes (ham genes) and transcription factor genes. Electrophoretic mobility shift essays of the promoter regions of the four MAPK genes suggest that VE-1 could be regulating sexual development by binding directly to promoters of these key regulatory genes. Furthermore, we detected transcription of ve-1, ve-2, and lae-1 during all stages of sexual development, but the three proteins were not detected in the later stages of development (4 and 6 days after fertilization), suggesting a major role for the velvet complex in the early stages of sexual development. Our results provide key insights into the control of multistage development processes by the regulatory velvet complex in the fungus N. crassa, and will help to understand how environmental signals are integrated in the fungal cell to regulate development.