Abstract
Background Magnaporthe oryzae, the rice blast fungus, might secrete certain proteins related to plant-fungal pathogen interactions.Methodology/Principal FindingsIn this study, we report the purification, characterization, and gene cloning of a novel hypersensitive response-inducing protein elicitor (MoHrip1) secreted by M. oryzae. The protein fraction was purified and identified by de novo sequencing, and the sequence matched the genomic sequence of a putative protein from M. oryzae strain 70-15 (GenBank accession No. XP_366602.1). The elicitor-encoding gene mohrip1 was isolated; it consisted of a 429 bp cDNA, which encodes a polypeptide of 142 amino acids with a molecular weight of 14.322 kDa and a pI of 4.53. The deduced protein, MoHrip1, was expressed in E. coli. And the expression protein collected from bacterium also forms necrotic lesions in tobacco. MoHrip1 could induce the early events of the defense response, including hydrogen peroxide production, callose deposition, and alkalization of the extracellular medium, in tobacco. Moreover, MoHrip1-treated rice seedlings possessed significantly enhanced systemic resistance to M. oryzae compared to the control seedlings. The real-time PCR results indicated that the expression of some pathogenesis-related genes and genes involved in signal transduction could also be induced by MoHrip1.Conclusion/SignificanceThe results demonstrate that MoHrip1 triggers defense responses in rice and could be used for controlling rice blast disease.
Highlights
In nature, plants face a broad range of potential pathogens, including viruses, bacteria, fungi, oomycetes, nematodes and insects, which have different life cycles and infection strategies
Purification and characterization of the Magnaporthe oryzae hypersensitive response-inducing protein 1 (MoHrip1) protein Crude protein from a culture filtrate of M. oryzae was put through dialysis and anion exchange chromatography, and final extracts were eluted with a NaOH gradient
Infiltration of MoHrip1 into mature tobacco leaves resulted in rapid macroscopic changes
Summary
Plants face a broad range of potential pathogens, including viruses, bacteria, fungi, oomycetes, nematodes and insects, which have different life cycles and infection strategies. The other type of defense, named gene-for-gene resistance, acts mainly inside the plant cell, using the recognition between the resistance (R) proteins and the effectors, including elicitors secreted by pathogens [5] This R protein-mediated defense is called effector-triggered immunity (ETI); it occurs only in living host tissues but not in necrotrophs [6,7] and accompanies some early events, such as the hypersensitive response (HR), oxidative bursts, nitric oxide (NO) generation, extracellular pH increase, cell wall strengthening and expression of pathogenesis-related proteins [8,9,10], in plant cells. Magnaporthe oryzae, the rice blast fungus, might secrete certain proteins related to plant-fungal pathogen interactions
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