Abstract
Lesion mimic mutants have become an effective material for understanding plant-microbe interactions and the immune mechanism in plants. Although many mechanisms responsible for the lesion mimic phenotype have been clarified in plants, the mechanism by which lesion mimic is regulated by posttranslational modification remained largely elusive, especially in rice. In this study, a mutant with the lesion mimic phenotype was obtained and named lmp1-1. Physiological measurements and quantitative real-time PCR analysis showed that the defense response was activated in the mutants. Transcriptome analysis showed that the phenylalanine ammonia lyase (PAL) pathway was activated in the mutant, causing the accumulation of salicylic acid (SA). The results of mapping based cloning showed that OsLMP1 encodes a deubiquitinase. OsLMP1 can cleave ubiquitination precursors. Furthermore, OsLMP1 epigenetically modifies SA synthetic pathway genes by deubiquitinating H2B and regulates the immune response in rice. In summary, this study deepens our understanding of the function of OsLMP1 in the plant immune response and provides further insight into the relationship between plants and pathogenic microorganisms.
Highlights
Rice, one of the main food crops in the world, supports half of the world’s population
A cross test between lmp1-1 and wild-type plants showed that the segregation ratio in the F2 progeny of wild-type (156) and mutant-like (50) plants reached 3:1 (x2 = 0.81, x20.05,1), indicating that lmp1-1 is controlled by a single recessive nuclear locus
An infection experiment at the flowering stage using four bacterial blight strains and one M. oryzae strain showed that the lmp1-1 t plants were more resistant to the bacterial blight strain and M. oryzae strain than the wild-type plants, similar to most of the lesion mimic mutants (Figure 1D and Supplementary Figure 1)
Summary
One of the main food crops in the world, supports half of the world’s population. Pathogenic microorganism invasion often decreases grain weight and the seed setting rate, which seriously affects the yield and quality of crops. Lesion mimic is a phenomenon in which local cell necrosis occurs spontaneously in plants without invasion by external pathogens. Most lesion mimic mutants show increased disease resistance to at least one microorganism; they are good materials with which to study the mechanism of the plant defense response (Wu et al, 2008). As an increasing number of disease resistance genes have been cloned and their functions elucidated, the mechanism responsible for the lesion mimic phenotype can be summarized by the following four observations. The resistance genes nucleotide binding site/leucine rich repeats (NBS-LRRs) were found to lead to the disorder of signaling pathways in the defense
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