Studies on host specificity of the cucurbit anthracnose pathogen Colletotrichum orbiculare via comparative analyses with closely related pathogens

概要

CHAPTER I. Multiple Colletotrichum species commonly exhibit focal effector
accumulation in a biotrophic interface at the primary invasion sites in their host plants
Fungal plant pathogens deploy a suite of secreted proteins, called effectors, to
facilitate successful infection. Several fungal pathogens have been reported to secrete and
accumulate their effector proteins in the host–pathogen interfacial spaces. Colletotrichum
orbiculare strain 104-T was known to accumulate effectors in host–pathogen biotrophic
interfacial space around the neck of the primary invasive hyphae beneath the appressoria
to form ring-like signals. Here, to see whether the other strains or species in the genus
Colletotrichum exhibit similar accumulation patterns of effectors, I generated mCherrytagged CoDN3 effector expressing reporter lines of C. orbiculare MAFF306589, C.
trifolii MAFF305078, which infects alfalfa, and C. higginsianum MAFF305635, which
infects Brassicaceae plants. The immunoblotting analysis confirmed that these strains
secrete the CoDN3:mCherry protein from hyphal cells. Microscopic observations of these
strains showed that all tested reporter lines focally accumulated the CoDN3:mCherry
protein around the neck region of the primary hyphae, which were detected as ring-shaped
fluorescence signals, during their biotrophic interaction with their host plants. This result
suggested that ring-shaped effector accumulation at the hyphal neck region is a conserved
mechanism among the Colletotrichum genus and derived from their common ancestor.
This suggested that in planta effector secretion machinery of the genus Colletotrichum is
an evolutionarily conserved trait and is not related to the host specificity. ...