Ubiquitin E3 Ligase AaBre1 Responsible for H2B Monoubiquitination Is Involved in Hyphal Growth, Conidiation and Pathogenicity in Alternaria alternata

Progress on H2B as a multifunctional protein related to pathogens

Histone H2B is a member of the core histones, which together with other histones form the nucleosome, the basic structural unit of chromosomes. As scientists delve deeper into histones, researchers gradually realize that histone H2B is not only an important part of nucleosomes, but also plays a momentous role in regulating gene transcription, acting as a receptor and antimicrobial action outside the nucleus. There are a variety of epigenetically modified sites in the H2B tail rich in arginine and lysine, which can occur in ubiquitination, phosphorylation, methylation, acetylation, etc. When stimulated by foreign factors such as bacteria, viruses or parasites, histone H2B can act as a receptor for the recognition of these pathogens, and induce an intrinsic immune response to enhance host defense. In addition, the extrachromosomal histone H2B is also an important anti-microorganism agent, which may be the key to the development of antibiotics in the future. This review aims to summarize the interaction between histone H2B and etiological agents and explore the role of H2B in epigenetic modifications, receptors and antimicrobial activity.

Functional Role of RING Ubiquitin E3 Ligase VdBre1 and VdHrd1 in the Pathogenicity and Penetration Structure Formation of Verticillium dahliae

Verticillium dahliae, a virulent soil-borne fungus, elicits Verticillium wilt in numerous dicotyledonous plants through intricate pathogenic mechanisms. Ubiquitination, an evolutionarily conserved post-translational modification, marks and labels proteins for degradation, thereby maintaining cellular homeostasis. Within the ubiquitination cascade, ubiquitin ligase E3 demonstrates a unique capability for target protein recognition, a function often implicated in phytopathogenic virulence. Our research indicates that two ubiquitin ligase E3s, VdBre1 and VdHrd1, are intrinsically associated with virulence. Our findings demonstrate that the deletion of these two genes significantly impairs the ability of V. dahliae to colonize the vascular bundles of plants and to form typical penetration pegs. Furthermore, transcriptomic analysis suggests that VdBre1 governs the lipid metabolism pathway, while VdHrd1 participates in endoplasmic-reticulum-related processes. Western blot analyses reveal a significant decrease in histone ubiquitination and histone H3K4 trimethylation levels in the ΔVdBre1 mutant. This research illuminates the function of ubiquitin ligase E3 in V. dahliae and offers fresh theoretical perspectives. Our research identifies two novel virulence-related genes and partially explicates their roles in virulence-associated structures and gene regulatory pathways. These findings augment our understanding of the molecular mechanisms inherent to V. dahliae.

Post-Translational Modifications of Histones Are Versatile Regulators of Fungal Development and Secondary Metabolism

Chromatin structure is a major regulator of DNA-associated processes, such as transcription, DNA repair, and replication. Histone post-translational modifications, or PTMs, play a key role on chromatin dynamics. PTMs are involved in a wide range of biological processes in eukaryotes, including fungal species. Their deposition/removal and their underlying functions have been extensively investigated in yeasts but much less in other fungi. Nonetheless, the major role of histone PTMs in regulating primary and secondary metabolisms of filamentous fungi, including human and plant pathogens, has been pinpointed. In this review, an overview of major identified PTMs and their respective functions in fungi is provided, with a focus on filamentous fungi when knowledge is available. To date, most of these studies investigated histone acetylations and methylations, but the development of new methodologies and technologies increasingly allows the wider exploration of other PTMs, such as phosphorylation, ubiquitylation, sumoylation, and acylation. Considering the increasing number of known PTMs and the full range of their possible interactions, investigations of the subsequent Histone Code, i.e., the biological consequence of the combinatorial language of all histone PTMs, from a functional point of view, are exponentially complex. Better knowledge about histone PTMs would make it possible to efficiently fight plant or human contamination, avoid the production of toxic secondary metabolites, or optimize the industrial biosynthesis of certain beneficial compounds.