The Evolutionary and Functional Paradox of Cerato-platanins in Fungi

Abstract

Cerato-platanins (CPs) form a family of fungal small secreted cysteine-rich proteins (SSCPs) and are of particular interest not only because of their surface activity but also their abundant secretion by fungi. We performed an evolutionary analysis of 283 CPs from 157 fungal genomes with the focus on the environmental opportunistic plant-beneficial and mycoparasitic fungus Trichoderma. Our results revealed a long evolutionary history of CPs in Dikarya fungi that have undergone several events of lateral gene transfer and gene duplication. Three genes were maintained in the core genome of Trichoderma, while some species have up to four CP-encoding genes. All Trichoderma CPs evolve under stabilizing natural selection pressure. The functional genomic analysis of CPs in Trichoderma guizhouense and Trichoderma harzianum revealed that only epl1 is active at all stages of development but that it plays a minor role in interactions with other fungi and bacteria. The deletion of this gene results in increased colonization of tomato roots by Trichoderma spp. Similarly, biochemical tests of EPL1 heterologously produced by Pichia pastoris support the claims described above. Based on the results obtained, we conclude that the function of CPs is probably linked to their surfactant properties and the ability to modify the hyphosphere of submerged mycelia and, thus, facilitate the nutritional versatility of fungi. The effector-like functions do not sufficiently describe the diversity and evolution of these proteins in fungi, as they are also maintained, duplicated, or laterally transferred in the genomes of nonherbivore fungi. IMPORTANCE Cerato-platanins (CPs) are surface-active small proteins abundantly secreted by filamentous fungi. Consequently, immune systems of plants and other organisms recognize CPs and activate defense mechanisms. Some CPs are toxic to plants and act as virulence factors in plant-pathogenic fungi. Our analysis, however, demonstrates that the interactions with plants do not explain the origin and evolution of CPs in the fungal kingdom. We revealed a long evolutionary history of CPs with multiple cases of gene duplication and events of interfungal lateral gene transfers. In the mycoparasitic Trichoderma spp., CPs evolve under stabilizing natural selection and hamper the colonization of roots. We propose that the ability to modify the hydrophobicity of the fungal hyphosphere is a key to unlock the evolutionary and functional paradox of these proteins.

Plant recognition byTrichoderma harzianumelicits upregulation of a novel secondary metabolite cluster required for colonization

“…Considering fungus-plant interaction, also the more than 5fold up-regulation of Triha_398864, encoding a homologue of Epl1/Sm1 is interesting. These ceratoplatanin-like proteins play a role in colonization of plant roots and as effectors (Gao et al, 2020). In T. harzianum, Epl1 regulates virulence of the plant pathogen Botrytis cinerea, mycoparasitism as well as plant immunity at early stages of root colonization (Gomes et al, 2015;Gomes et al, 2017), which is in perfect agreement with our hypotheses.…”

Characterization of an Exceptional Fungal Mutant Enables the Discovery of the Specific Regulator of a Silent PKS–NRPS Hybrid Biosynthetic Pathway

“…This result revealed a relatively complete and similar gene composition of the BGCs in these fungi (Figure ). Additionally, we reconstructed a multi-loci species phylogeny for 171 representative fungi (Figure S13) as described in our previous study. , Besides the Harzianum species complex of Trichoderma, the complete hac BGC is present in T. asperellum and only a few plant-pathogenic hypocrealean fungi (Fusarium spp.…”

“…Additionally, we reconstructed a multi-loci species phylogeny for 171 representative fungi (Figure S13) as described in our previous study. 47,48 Besides the Harzianum species complex of Trichoderma, the complete hac BGC is present in T. asperellum and only a few plant-pathogenic hypocrealean fungi (Fusarium spp. and Cylindrodendrum hubeiense), but other Trichodermaspp.…”

“…The best amino acid substitution model was searched by ModelFinder integrated in IQ-TREE according to the Bayesian Information Criterion . The evolutionary analysis was performed by using NOTUNG version 2.9.1.5 to infer the gene loss (GL), gene duplication (GD), and lateral gene transfer (LGT) events, as described in our previous studies. − …”

The Hydrophobin Gene Family Confers a Fitness Trade-off between Spore Dispersal and Host Colonization in Penicillium expansum

“…3 ). The requirement of adding SDS and EDTA into water droplets in order to observe the wettable phenotypes suggests that P. expansum contains other amphipathic proteins with hydrophobic properties, as found in other fungi, including cero-platanins ( 24 ), repellent proteins found in Ustilago maydis ( 25 , 26 ), or CFEM (Common in several Fungal Extracellular Membrane) proteins in Candida species ( 27 ).…”