The ConservedColletotrichumspp. Effector CEC3 Induces Nuclear Expansion and Cell Death in Plants

Abstract

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.

How activated NLRs induce anti-microbial defenses in plants

“…The mechanisms leading to the loss of cell integrity during ETI are not well studied. There are a few reports showing that NLR activation or the expression of viral, bacterial and fungal effectors can induce severe morphological cellular phenotypes, like the fusion of the vacuole with the plasma membrane [ 122 ], alterations of vacuolar structures (El Kasmi lab unpublished; [ 63 ]), the expansion of the nucleus [ 123 ], chloroplast clustering around the nucleus [ 124 ], cytoplasmic shrinkage, mitochondrial swelling and many more [ 125 ]. It is likely that these cellular changes and the loss of plasma membrane integrity is leading to a release or (calcium-) induced production of DAMPs [ 126 , 127 ], molecular signals that are known to be potent immune activators [ 128 ].…”

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

“…The names of the repository/repositories and accession number(s) can be found below: https://www. ncbi.nlm.nih.gov/nuccore/MW528236, MW528236; https:// www.ncbi.nlm.nih.gov/nuccore/MW528237, MW528237; and Tsushima et al (2021).…”

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

“…For other instances, the homologous effectors CoDN3 from C. orbiculare and ChEC3 from Colletotrichum higginsianum, a pathogen that causes anthracnose disease on Brassicaceae plants, suppress plant cell death induced by NIS1 and NLP1, respectively, when they are expressed together in N. benthamiana (Yoshino et al, 2012;Kleemann et al, 2012). Recently, a highly conserved Colletotrichum effector candidate that induces host nuclear expansion and cell death was identified (Tsushima et al, 2021). However, Colletotrichum effectors such that induce an immune response in the host plant have not been reported.…”