Plants are continuously exposed to deleterious biotic and abiotic stresses. In rice, WRKY45 is a crucial transcription factor in the salicylic acid defense signaling pathway, on which several chemical-defense inducers act. We have developed transgenic rice lines using WRKY45 that are resistant to multiple diseases, and during that work, found that the extremely strong disease resistance that results from the overexpression of WRKY45 renders rice hypersensitive to low temperature and high salinity due to antagonistic crosstalk of defense signaling against abiotic stress signaling. Here, we introduce molecular mechanisms underlying the trade-off between disease resistance and abiotic stress responses, highlighting strategies involving crosstalk between signaling pathways.
Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most economically devastating diseases of food crops worldwide. Approaches to controlling blast disease have mainly been via the deployment of nucleotide-binding leucine-rich repeat receptors (NLRs). M. oryzae secretes a battery of small effector proteins to manipulate host functions for its successful infection, and some of them are recognized by host NLR proteins as avirulence effectors (AVRs), which turns on strong immunity. Therefore, the analysis of interactions between AVRs and their cognate NLR proteins provide crucial insights into the molecular basis of plant–fungal interactions.
A new disease of bird’s-nest fern (Asplenium nidus, cv. Emerald) with dark-green, water-soaked lesions on the leaves has been found in Fukuoka Prefecture, Japan since approximately 1996. The lesions gradually extended from the lower part of the leaves near the soil to the tip of the leaves under high humidity. Affected leaves and petioles softened, turned dark-brown and dry. When severely infected, plants had rotted petioles and withered. A causal fungus was isolated from the infected tissues, and these isolates caused the same symptoms on cvs. Abis and Emerald of bird’s-nest fern in inoculation tests. The pathogen was identified as Rhizoctonia solani based on the morphological and cultural characteristics, and the hyphal anastomosis group and the cultural type were determined as AG-1 IB, confirmed with PCR analysis using specific DNA primer sets for the anastomosis groups. The name leaf blight was proposed for this disease on bird’s-nest fern.