Abstract
BackgroundRice blast disease is one of the most destructive diseases of rice worldwide. We previously cloned the rice blast resistance gene Pid2, which encodes a transmembrane receptor-like kinase containing an extracellular B-lectin domain and an intracellular serine/threonine kinase domain. However, little is known about Pid2-mediated signaling.ResultsHere we report the functional characterization of the U-box/ARM repeat protein OsPUB15 as one of the PID2-binding proteins. We found that OsPUB15 physically interacted with the kinase domain of PID2 (PID2K) in vitro and in vivo and the ARM repeat domain of OsPUB15 was essential for the interaction. In vitro biochemical assays indicated that PID2K possessed kinase activity and was able to phosphorylate OsPUB15. We also found that the phosphorylated form of OsPUB15 possessed E3 ligase activity. Expression pattern analyses revealed that OsPUB15 was constitutively expressed and its encoded protein OsPUB15 was localized in cytosol. Transgenic rice plants over-expressing OsPUB15 at early stage displayed cell death lesions spontaneously in association with a constitutive activation of plant basal defense responses, including excessive accumulation of hydrogen peroxide, up-regulated expression of pathogenesis-related genes and enhanced resistance to blast strains. We also observed that, along with plant growth, the cell death lesions kept spreading over the whole seedlings quickly resulting in a seedling lethal phenotype.ConclusionsThese results reveal that the E3 ligase OsPUB15 interacts directly with the receptor-like kinase PID2 and regulates plant cell death and blast disease resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0442-4) contains supplementary material, which is available to authorized users.
Highlights
IntroductionWe previously cloned the rice blast resistance gene Pid, which encodes a transmembrane receptor-like kinase containing an extracellular B-lectin domain and an intracellular serine/threonine kinase domain
Rice blast disease is one of the most destructive diseases of rice worldwide
According to the rice genome annotation database, OsPUB15 is annotated as a putative ARM repeat family protein composed of 824 amino acids with a molecular mass of approximate 90 kD
Summary
We previously cloned the rice blast resistance gene Pid, which encodes a transmembrane receptor-like kinase containing an extracellular B-lectin domain and an intracellular serine/threonine kinase domain. Plants respond to pathogen infection using their innate immunity system, which includes two layers, pathogen/ microbe-associated molecular pattern (PAMP/MAMP)triggered immunity (PTI) and effector-triggered immunity (ETI) [1,2]. PTI, known as the plant basal defense, is mediated by plant pattern recognition receptors (PRRs) through recognizing the conserved microbial features. Compared to ETI, PTI mediates a relatively weaker immune response with broad-spectrum defense against pathogens. When pathogens develop specific effectors to suppress PTI, plants evolve corresponding resistance proteins to recognize these effectors and lead to ETI, a much more rapid and robust immune response [8]. Besides the signaling process present in PTI, hypersensitive response (HR), a form of localized programmed cell death (PCD) at the infection sites of plant to prevent the spread of pathogens, is usually accompanied
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