Abstract
Salicylic acid (SA) is a phytohormone that regulates a variety of physiological and developmental processes, including disease resistance. SA is a key signaling component in the immune response of many plant species. However, the mechanism underlying SA-mediated immunity is obscure in rice (Oryza sativa). Prior analysis revealed a correlation between basal SA level and blast resistance in a range of rice varieties. This suggested that resistance might be improved by increasing basal SA level. Here, we identified a novel UDP-glucosyltransferase gene, UGT74J1, which is expressed ubiquitously throughout plant development. Mutants of UGT74J1 generated by genome editing accumulated high levels of SA under non-stressed conditions, indicating that UGT74J1 is a key enzyme for SA homeostasis in rice. Microarray analysis revealed that the ugt74j1 mutants constitutively overexpressed a set of pathogenesis-related (PR) genes. An inoculation assay demonstrated that these mutants had increased resistance against rice blast, but they also exhibited stunted growth phenotypes. To our knowledge, this is the first report of a rice mutant displaying SA overaccumulation.
Highlights
Salicylic acid (SA), 2-hydroxy benzoic acid, is a small phenolic compound that was first isolated from willow bark
Nine unknown UGT74 proteins with significant homology to a previously characterized SA-glucosyltransferase, OsSGT1, were identified in the database (Figure 1). These UGT genes are clustered on chromosomes 4 and 9, suggesting they originated through gene duplications (Supplementary Figure S1)
Asterisks statistically significant differences compared with the wild type
Summary
Salicylic acid (SA), 2-hydroxy benzoic acid, is a small phenolic compound that was first isolated from willow bark. SA functions as a phytohormone and regulates many physiological processes, such as germination, cell growth, respiration, and senescence [1,2,3,4]. SA regulates tolerance against environmental stresses, including heat, chilling, salinity, and oxidative damage [5,6,7,8]. The most important role of SA is the regulation of disease resistance. The HR prevents the penetration and spread of pathogens from the site of infection [10]. Infected local tissues transmit a signal to distant healthy tissues to induce systemic acquired resistance (SAR) [11,12]. SAR confers resistance to a wide range of pathogens and requires biosynthesis of mobile signals such as methyl salicylate [13]
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