Development of disease-resistant rice using regulatory components of induced disease resistance

Abstract

Infectious diseases cause huge crop losses annually. In response to pathogen attacks, plants activate defense systems that are mediated through various signaling pathways. The salicylic acid (SA) signaling pathway is the most powerful of these pathways. Several regulatory components of the SA signaling pathway have been identified, and are potential targets for genetic manipulation of plants’ disease resistance. However, the resistance associated with these regulatory components is often accompanied by fitness costs; that is, negative effects on plant growth and crop yield. Chemical defense inducers, such as benzothiadiazole and probenazole, act on the SA pathway and induce strong resistance to various pathogens without major fitness costs, owing to their ‘priming effect.’ Studies on how benzothiadiazole induces disease resistance in rice have identified WRKY45, a key transcription factor in the branched SA pathway, and OsNPR1/NH1. Rice plants overexpressing WRKY45 were extremely resistant to rice blast disease caused by the fungus Magnaporthe oryzae and bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo), the two major rice diseases. Disease resistance is often accompanied by fitness costs; however, WRKY45 overexpression imposed relatively small fitness costs on rice because of its priming effect. This priming effect was similar to that of chemical defense inducers, although the fitness costs were amplified by some environmental factors. WRKY45 is degraded by the ubiquitin–proteasome system, and the dual role of this degradation partly explains the priming effect. The synergistic interaction between SA and cytokinin signaling that activates WRKY45 also likely contributes to the priming effect. With a main focus on these studies, I review the current knowledge of SA-pathway-dependent defense in rice by comparing it with that in Arabidopsis, and discuss potential strategies to develop disease-resistant rice using signaling components.

4-Coumarate-CoA Ligase-Like Gene OsAAE3 Negatively Mediates the Rice Blast Resistance, Floret Development and Lignin Biosynthesis

“…Fungus-induced rice blast is a potential threat to the rice production, which is characterized by sporadic and unpredictable outbreaks, leading to significant yield loss (Takatsuji, 2014). However, to protect themselves from pathogen invasion, plants have to effectively integrate extracellular and intracellular signals to activate the physiological and biochemical responses by enhancing the hormone defense pathway, switching off the plant growth and regulating the expressions of immunity-related genes and proteins (Lozano-Durán and Zipfel, 2015).…”

Quantifying the Impacts of Systemic Acquired Resistance to Pitch Canker on Monterey Pine Growth Rate and Hyperspectral Reflectance

“…Slower growth could heighten the risk of a tree being over-topped by faster growing con-specifics, reducing access to light and ultimately the capacity to produce seed. Previous work has shown that SAR may or may not be associated with reduced growth [12,25], whereas enhanced growth is also possible [15]. Most studies on SAR have involved annual plants [13] and thus do not provide information on long term effects of induced resistance.…”

CC-NBS-LRR-Type R Proteins for Rice Blast Commonly Interact with Specific WRKY Transcription Factors

“…However, Pb1 encodes an R protein-like CC-NB-LRR protein with atypical NB domain . Our recent studies showed that Pb1 specifically interacts with rice WRKY45 (Shimono et al 2007(Shimono et al , 2012Takatsuji et al 2010;Nakayama et al 2013;Akagi et al 2014;Takatsuji 2014), a TF that plays a major role in the salicylic acid signaling pathway, and that the blast resistance due to Pb1 is dependent on WRKY45 . Rice WRKY45 is regulated by ubiquitin-proteasome degradation in the nuclei to suppress untimely defense activation in the absence of pathogen infection .…”