Fungal infections cause significant losses in the agronomic field, with tons of crops and ornamental plants affected every year. Similarly,
infections caused by members of the kingdom Fungi are among the most prevalent in humans, and systemic candidiasis, aspergillosis,
and cryptococcosis are associated with high morbidity and mortality rates. The lack of a vast repertoire of antifungal drugs to attack
phytopathogens and medically relevant fungi has led to the search for new potential targets to develop novel compounds to fight these
diseases. The search of virulence factors that confer the ability of these organisms to cause damage to the cells, and the identification of
the mechanisms of sensing by the host immunity and evasion of this by the fungus, are among the main aspects currently under study to
find new therapeutic targets. The synthesis of pigments like melanins, the capsule, the cell wall, secreted and membrane-bound proteins,
along with the secretion of extracellular vesicles are the first lines of contact with the host cells and these contribute to adhesion, colonization,
and ultimately to cell and tissue damage. Since most of these components are not synthesized by host cells, they are also part of the
elements that the defense mechanisms recognize to establish a protective immune response. Therefore, the balance between the effector
role of these fungal components and its recognition by the host will define the outcome of the interaction: control and clearance of the
fungal population or establishment of the disease. Here, we offer a collection of comprehensive review papers dealing with the current
progress in the study of virulence factors in phytopathogens and medically relevant fungi, the mechanisms behind their immune sensing
and the current strategies they have to avoid the host’s defense mechanisms.
When a capsule is absent, the cell wall is the outermost structure of the fungal cell and is the first in establishing contact with the host.
This interaction will be key to the development of the disease, as reported by Plaza et al. [1]. They present a thorough revision on the
relevance of glucans, chitin, chitosan, and cell wall glycoproteins in the interaction of both human and plant pathogens with the host,
highlighting the molecular bases and the signaling pathways involved in the synthesis of these wall components [1]; while García-Carnero
et al. describe the relevance of these polysaccharides and proteins during recognition by the host immunity [2]. Fabri et al. offer an analysis
of the Aspergillus fumigatus cell wall integrity and the high osmolarity glycerol signaling pathways, which regulate the synthesis of
plasma membrane sphingolipids, ergosterol, and phospholipids [3]. By comparative analysis with better studied fungal models, they proposed
that the study of these pathways could unveil targets for the development of new therapeutic options to control invasive pulmonary
aspergillosis [3]. Another strategy that is currently under study to find new sources of molecules that could assist in the therapy against
fungal pathogens is the identification and characterization of plant lectins with antifungal properties [4]. Del Rio et al. gathered the most
relevant information on this subject and highlighted lectins that have shown an effect on the cell wall, viability, biofilms, membrane permeabilization,
and inhibition of morphological transition of causative agents of mycoses in humans [4].
Sporotrichosis is a subcutaneous or deep-seated infection that affects mammals, including the human being. It is caused by members
of the pathogenic clade of genus Sporothrix and thus far, the most studied species is Sporothrix schenckii. At present, the virulence
factors this organism uses to establish interaction with the host and to cause damage are not well documented. Here, Tamez-
Castrellón et al. performed a comparative analysis of the S. schenckii genome with well-described virulence factors in Candida albicans,
Cryptococcus neoformans, and A. fumigatus [5]. They generated a list of S. schenckii genes likely to encode proteins involved in
morphological change, cell wall synthesis, immune evasion, thermotolerance, adhesion, biofilm formation, melanin production, nutrient
uptake, response to stress, extracellular vesicle formation, and toxin production [5].
One of the most thoroughly studied fungal models in medical mycology is C. albicans, and there is a vast amount of information
on virulence factors and how the fungal proteins provide advantages to the pathogen to cause disease and at the same time, how the
recognition by the host could help to establish strategies to control C. albicans cells [6]. Here, Staniszewska summarized the most
recent and relevant information not only on virulence factors found in C. albicans but also in other medically relevant species, like
Candida parapsilosis, Candida tropicalis, Candida glabrata, and Candida krusei [6].
Finally, Metarhizium is a fungal genus that includes organisms with the ability to colonize and cause an entomopathogenic interaction
with more than 200 insect species [7]. González-Hernández et al., present here a revision of the molecular mechanisms behind the
conidia attachment, appressorium formation, penetration, and colonization of insects by Metarhizium spp [7].
