Analysis Of Evolution And Infection Mechanism Of Nematophagous Fungus Drechmeria Coniospora At The Genome And Transcoriptome Level

Annual crop losses to plant-parasitic nematodes are estimated at $157 billion worldwide. However, chemical pesticides are harmful for environment. As being environment-friendly, nematophagous fungi play a key role in the area of biological control of nematode, and have received great attention in recent years. Nematophagous fungi are divided into three groups according to their infection strategy, namely, nematode-trapping fungi, egg parasites and endoparasites fungi. Amongst three groups, endoparasites fungi are more specific to their host than others. However, there exist limited reports of this kind of fungi. Drechmeria coniospora is a kind of typically near obligate endoparasitic fungus, and it can infect many kinds of nematodes. In this study, we present an analysis of evolution and adaption mechanism in D. coniospora, moreover, revealed some infection related genes, then, characterized fungal subtilisin-like serine proteases Pr1 C subfamily. The results are as follows:1. Using Solexa, Roche 454, PacBio RS II platform and optical mapping, we got the high quality genome sequencing result of D. coniospora, sequencing coverage of 457.9-fold and scaffold N50 of 4.14 Mb. The D. coniospora genome has 3 chromosomes, totally 32.5 Mb. It has 8 281 protein-encoding genes and an active repeat-induced point mutation（RIP） system. Phylogenesis analysis showed that it derived from an entomopathogenic ancestor, which provide infection elements to this fungus. In order to adapt to the near-obligate nematode endoparasitic trophic mode, D.coniospora contracte its genome and invent/obtain some new genes, e.g transporter gene.2. D.coniospora has a series of potential virulence factor genes. According to genome and transcription analysis, it has 312 SSP genes totally, 210 showed infection activity; 14.3% genes of its genome are pathogen-host interaction coding gene; during evoling D.coniospora gradually acculmulate pathogenicity-related genes, instead of acquisite large pathogenicity islands. What’s more, the surface proteins, including agglutinin-like surface（ALS） proteins, hydrophobins, adhesin and CFEM-domain or GLEYA-domain containing proteins, encoded in the D. coniospora genome are candidates for host surface recognition and adhesion. Moreover, subtilases, metalloproteases and acid phosphatases have been implicated in D. coniospora in the softening of the nematode cuticle. Furthermore, D.coniospora genome includes 17 gene clusters organized around PKS, NRPS and NRPS-PKS genes. One of secondary metabolites, drechmerins, showed bioactivity, which was produced by DcPKS1-DcPKS2-DcNRPS1, and the structure was determined by MS that it contains the non-canonical amino acid analogues AIB, AHMOD and AMD.3. Totally, D. coniospora has 26 subtilisin-like proteins, of which 13 are subtilisin-like serine proteases Pr1 C. We analyzed Pr1 C domain and motif organizations and constructed its phylogenetic tree with other subtilases. We found that Pr1 C not only shares catalytic core of peptidase_S8 domain with other Pr1 proteins, but also possess an fn3₅ domain. Our study confirms that Pr1 C in fungal belongs to pyrolysin family, and all Pr1 C could be divided into three types according to the length of peptidase_S8 domain. Pr1 C has its specific marker sequence containing fn3₅ and C-terminal motif. We alignment all the Pr1 C marker sequence in this study and create an HMM model, which contributes to fungal genome annotation.This study focus on the genome of near obligate endoparasitic nematophagous fungus D. coniospora, reveal the basic mechanism of infection process, and made a foundation for further molecular and application research.