Biology subjects

Narusaka, M.

Publications and source records attributed to Narusaka, M..

3 recordsLinked to original sources

bioRxiv2021

Guanosine-specific single-stranded ribonuclease effectors of a phytopathogenic fungus potentiate host immune responses

Plants activate immunity upon recognition of pathogen-associated molecular patterns. Although phytopathogens have evolved a set of effector proteins to counteract plant immunity, some effectors are perceived by hosts and induce immune responses. Here, we show that two secreted ribonuclease effectors, SRN1 and SRN2, encoded in a phytopathogenic fungus, Colletotrichum orbiculare, induce cell death in a signal peptide- and catalytic residue-dependent manner, when transiently expressed in Nicotiana benthamiana. The pervasive presence of SRN genes across Colletotrichum species suggested the conserved roles. Using a transient gene expression system in cucumber (Cucumis sativus), an original host of C. orbiculare, we show that SRN1 and SRN2 potentiate host pattern-triggered immunity. Consistent with this, C. orbiculare SRN1 and SRN2 deletion mutants exhibited increased virulence on the host. In vitro analysis revealed that SRN1 specifically cleaves single-stranded RNAs at guanosine, leaving a 3'-end phosphate. This activity has not been reported in plants. Importantly, the potentiation of C. sativus responses by SRN1 and SRN2 depends on the signal peptide and ribonuclease catalytic residues, suggesting that secreted SRNs cleave RNAs in apoplast and are detected by the host. We propose that the pathogen-derived apoplastic guanosine-specific single-stranded endoribonucleases lead to immunity potentiation in plants.

microbiology↗

bioRxiv2021

The Conserved Colletotrichum spp. Effector CEC3 Induces Nuclear Expansion and Cell Death in Plants

Plant pathogens secrete small proteins, known as effectors, that promote infection by manipulating host cells. Members of the phytopathogenic fungal genus Colletotrichum collectively have a broad host range and generally adopt a hemibiotrophic lifestyle that includes an initial biotrophic phase and a later necrotrophic phase. We hypothesized that Colletotrichum fungi use a set of conserved effectors during infection to support the two phases of their hemibiotrophic lifestyle. This study aimed to examine this hypothesis by identifying and characterizing conserved effectors among Colletotrichum fungi. Comparative genomic analyses using genomes of ascomycete fungi with different lifestyles identified seven effector candidates that are conserved across the genus Colletotrichum. Transient expression assays showed that one of these conserved effectors, CEC3, induces nuclear expansion and cell death in Nicotiana benthamiana, suggesting that CEC3 is involved in promoting host cell death during infection. Nuclear expansion and cell death induction were commonly observed in CEC3 homologs from four different Colletotrichum species that vary in host specificity. Thus, CEC3 proteins could represent a novel class of core effectors with functional conservation in the genus Colletotrichum.

microbiology↗

bioRxiv2020

Subtelomeric regions and a repeat-rich chromosome harbor multicopy effector gene clusters with variable conservation in multiple plant pathogenic Colletotrichum species

Members of the Colletotrichum gloeosporioides species complex are causal agents of anthracnose in a wide range of commercially important plants. To provide an in-depth overview of its diversity, we sequenced the genomes of fungi belonging to this group, including multiple strains of C. fructicola (Cf) and C. siamense (Cs), as well as representatives of three previously unsequenced species, C. aenigma (Ca), C. tropicale and C. viniferum. Comparisons between multiple Cf and Cs strains led to the identification of accessory regions that show variable conservation in both lineages. These accessory regions encode effector candidate genes, including homologs of previously characterized effectors, organized in clusters of conserved synteny with copy number variations in different strains of Cf, Cs and Ca. Analysis of highly contiguous assemblies of Cf, Cs and Ca strains revealed the association of such accessory effector gene clusters with subtelomeric regions and repeat-rich minichromosomes and provided evidence of gene transfer between these two genomic compartments. In addition, expression analysis indicated that paralogs associated with clusters of conserved synteny showed a tendency for correlated gene expression. These data highlight the importance of subtelomeric regions and repeat-rich chromosomes to the genome plasticity of Colletotrichum fungi.

genomics↗