Venturia inaequalis is an ascomycete fungus responsible for apple scab, a disease that has invaded almost all apple growing regions worldwide, with the corresponding adverse effects on apple production. Monitoring and predicting the effectiveness of intervention strategies require knowledge of the origin, introduction pathways, and population biology of pathogen populations. Analysis of the variation of genetic markers using the inferential framework of population genetics offers the potential to retrieve this information. Here, we present a population genetic analysis of microsatellite variation in 1,273 strains of V. inaequalis representing 28 orchard samples from seven regions in five continents. Analysis of molecular variance revealed that most of the variation (88%) was distributed within localities, which is consistent with extensive historical migrations of the fungus among and within regions. Despite this shallow population structure, clustering analyses partitioned the data set into separate groups corresponding roughly to geography, indicating that each region hosts a distinct population of the fungus. Comparison of the levels of variability among populations, along with coalescent analyses of migration models and estimates of genetic distances, was consistent with a scenario in which the fungus emerged in Central Asia, where apple was domesticated, before its introduction into Europe and, more recently, into other continents with the expansion of apple growing. Across the novel range, levels of variability pointed to multiple introductions and all populations displayed signatures of significant post-introduction increases in population size. Most populations exhibited high genotypic diversity and random association of alleles across loci, indicating recombination both in native and introduced areas. Venturia inaequalis is a model of invasive phytopathogenic fungus that has now reached the ultimate stage of the invasion process with a broad geographic distribution and well-established populations displaying high genetic variability, regular sexual reproduction, and demographic expansion.

Background: Effector proteins function not only as toxins to induce plant cell death, but also enable pathogens to suppress or evade plant defense responses. NLP-like proteins are considered to be effector proteins, and they have been isolated from bacteria, fungi, and oomycete plant pathogens. There is increasing evidence that NLPs have the ability to induce cell death and ethylene accumulation in plants. Results: We evaluated the expression patterns of 11 targeted PcNLP genes by qRT-PCR at different time points after infection by P. capsici. Several PcNLP genes were strongly expressed at the early stages in the infection process, but the expression of other PcNLP genes gradually increased to a maximum at late stages of infection. The genes PcNLP2, PcNLP6 and PcNLP14 showed the highest expression levels during infection by P. capsici. The necrosis-inducing activity of all targeted PcNLP genes was evaluated using heterologous expression by PVX agroinfection of Capsicum annuum and Nicotiana benthamiana and by Western blot analysis. The members of the PcNLP family can induce chlorosis or necrosis during infection of pepper and tobacco leaves, but the chlorotic or necrotic response caused by PcNLP genes was stronger in pepper leaves than in tobacco leaves. Moreover, PcNLP2, PcNLP6, and PcNLP14 caused the largest chlorotic or necrotic areas in both host plants, indicating that these three genes contribute to strong virulence during infection by P. capsici. This was confirmed through functional evaluation of their silenced transformants. In addition, we further verified that four conserved residues are putatively active sites in PcNLP1 by site-directed mutagenesis. Conclusions: Each targeted PcNLP gene affects cells or tissues differently depending upon the stage of infection. Most PcNLP genes could trigger necrotic or chlorotic responses when expressed in the host C. annuum and the non-host N. benthamiana. Individual PcNLP genes have different phytotoxic effects, and PcNLP2, PcNLP6, and PcNLP14 may play important roles in symptom development and may be crucial for virulence, necrosis-inducing activity, or cell death during infection by P. capsici.

Most fungi display a mixed mating system with both asexual and sexual reproduction. The timing of the two modes of reproduction must be carefully coordinated through signal perception and coordination in the cell along with chromatin modification. Here, we investigated coordination of reproductive output by investigating the function of the histone chaperone anti-silencing factor 1 (ASF1) in a fungal species amenable to characterization of both asexual and sexual reproduction. We used knockout approach to show that SeASF1 influenced asexual and sexual reproduction in Stemphylium eturmiunum . SeASF1-deleted strains failed to produce pseudothecia, but produce abnormal conidia and showed an irregular distribution of nuclei in mycelium. Transcriptome sequencing was then used to identify genes with altered expression in the SeASF1-deleted strains. The transcriptional expression of the identified SeDJ-1 was strongly regulated by SeASF1. The interaction of SeDJ-1 and SeASF1 was confirmed using Y2H, Co-IP, and pull-down. Due to some components of phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway were known to interact with DJ-1 in mammals, we verified SePI3K, an element of PI3K/AKT signaling pathway in S. eturmiunum , was directly linked to SeDJ-1 and then these two proteins were defined as a coordinator of reproduction. However, knockout of SeDJ-1 or SePI3K altered the asexual and sexual reproduction, but SePI3K recovered the asexual and sexual development of ∆ Sedj-1 . The SeDJ-1-M6 segment of SeDJ-1 was essential for its interaction with SePI3K and played a critical role in restoring sexual reproduction in the ∆ Sepi3k , providing a deep understanding of the regulatory mechanism of SeDJ-1 in S. eturmiunum development. Summarily, SeASF1 is able to trigger SeDJ-1 and SeDJ-1can also activate SePI3K, which is orchestrally involved in asexual and sexual reproduction in S. eturmiunum . All these results reveal that SeASF1 manipulates asexual and sexual reproduction in S. eturmiunum by SeDJ-1 perception of PI3K/AKT signaling pathway. These data highlight the deep similarities in coordinating asexual and sexual processes in both fungi and eukaryotes in general.

During our continuous survey (2012–2016) of saprobic hyphomycetes from dead branches in the forest ecosystems of southern China, we collected several acrodictys-like species. Acrodictys-like species are characterized by darkly pigmented and muriform conidia produced from holoblastic conidiogenous cells on macronematous, mononematous, cylindrical and unbranched or infrequently branched conidiophores. Phylogenetic analyses of ncLSU, ncSSU, ITS andtub2sequence data lead us to propose two novel families in Sordariomycetes,AcrodictyaceaeandJunewangiaceae. In addition, a new species,Acrodictys hainanensis, two new combinations,Junewangia queenslandicaandDistoseptispora martinii, three new Chinese records,Acrodictys liputii,A. peruamazonensisandJunewangia sphaerosporaare introduced. Two names,Acrodictys globulosaandA. malabarica, are resurrected.

Diaporthales is an important group of fungi widely distributed worldwide as endophytes, pathogens, and saprobes on the various plants. Here, we collected and isolated 209 strains of the Diaporthales and then employed morphological characteristics and advanced techniques such as multigene phylogenetics, genomic phylogenetics, molecular clock estimates, and metabolic pathways annotations to explore the evolutionary diversification and metabolic pathways within the Diaporthales. Firstly, our study confirmed that Diaporthales occurred early with a mean stem age of 181.5 Mya and a mean crown age of 157.7 Mya. Secondly, two new families, Sinodisculaceae fam. nov. and Ternstroemiomycetaceae fam. nov., were introduced based on morphology, phylogeny, and divergence times. Thirdly, we further described multiple novel taxa or records including Anadiaporthostoma gen. nov. ( Diaporthostomataceae ), Lunatospora gen. nov. ( Sinodisculaceae ), Microphaeotubakia gen. nov. ( Tubakiaceae ), Neoplagiostoma gen. nov. ( Pseudoplagiostomataceae ), and Ternstroemiomyces gen. nov. ( Ternstroemiomycetaceae ), 55 new species, three new species complexes, 32 new host records, and three new combinations. Furthermore, we accepted 35 families within the Diaporthales based on analysis of multiple evidences. Additionally, high activity in universal pathways such as purine metabolism and ribosome across the order suggested a fundamental for robust growth and stress response in Diaporthales. These findings enrich fungal biodiversity and provide critical insights into the evolutionary processes in these communities.