Plant pathogens deliver different effector proteins into plant cells to inhibit host immune responses. Because the effectors are thought to target important immune factors in plant cells, screening for host factors that interact with the effectors is a useful approach to discover uncharacterized immune factors. In fact, many immune factors have already been identified as targets of effectors. We isolated a rice receptor-like cytoplasmic kinase OsRLCK185 as an interactor with Xanthomonas oryzae effector Xoo1488. OsRLCK185 is directly phosphorylated by the immune receptor OsCERK1, and transmits immune signals to downstream components to induce a series of immune responses including MAPK activation.
The incidence of strawberry anthracnose, caused by Glomerella cingulata (Colletotrichum gloeosporioides), is increasing nationwide in Japan. The fungus, which overwinters in latently infected strawberry plants can act as an inoculum source in nursery beds next year. We monitored isolation frequency of the fungus on semiselective medium from latently infected plants in December, February and April and studied the effect of cold conditions on mycelial growth and the influence of long-term cold storage on infected strawberry plants. The isolation frequency of G. cingulata from plants latently infected with strawberry anthracnose was remarkably decreased after overwinter. The isolation frequency from infected strawberry plants placed in open field was lower than those placed in a plastic house. To further study this reduction, we pre-incubated colonies of G. cingulata on PSA and stored them at −2°C, then transferred a 6-mm mycelial disk from each colony to PSA at 25°C; after 21 days, the fungus had died. The isolation frequency of G. cingulata from pre-inoculated petioles and from pre-inoculated plants remarkably decreased after cold storage at −2°C for over 90 days. And after cold storage for 180 days, the fungus of G. cingulata was not isolated from any part of the plant (leaves, petioles, base of petioles or crowns). These results show that the infection frequency of strawberry anthracnose is significantly reduced by long-term cold storage and indicate that latently infected strawberry plants can become pathogen-free by this treatment.
The pathogenicity and mycological aspects of blast fungi isolated from Festuca arundinacea in Miyagi Prefecture, northern Japan, were studied. They typically formed elliptical lesions with pointed ends, a whitish-grey center and reddish-brown margin on their host and on Italian ryegrass, but they did not form lesions on rice or crabgrass. They produced the dihydropyriculol, but not the pyrichalasin H which is characteristic toxin of crabgrass blast fungi. The RFLP band patterns of the β-tubulin gene from the isolates corresponded to those of Pyricularia oryzae; no products were amplified by Digitaria-specific primers. Thus, isolates from F. arundinacea were assessed to be P. oryzae.