The OsMPK15 Negatively Regulates Magnaporthe oryza and Xoo Disease Resistance via SA and JA Signaling Pathway in Rice.

Yongbo Hong,Yue Zhang,Daibo Chen,Xiangyang Lou,Qunen Liu,Shihua Cheng,Yongrun Cao,Liyong Cao

doi:10.3389/fpls.2019.00752

Yongbo Hong, Yue Zhang + Show 6 more

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https://doi.org/10.3389/fpls.2019.00752

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Abstract

Mitogen-activated protein kinase (MAPK) cascades play central roles in response to biotic and abiotic stresses. However, the mechanisms by which various MAPK members regulate the plant immune response in rice remain elusive. In this article, to characterize the mechanisms, the knock-out and overexpression mutants of OsMPK15 were constructed and the disease resistance was investigated under the various fungal and bacterial inoculations. The knock-out mutant of OsMPK15 resulted in the constitutive expression of pathogenesis-related (PR) genes, increased accumulation of reactive oxygen species (ROS) triggered by the pathogen-associated molecular pattern (PAMP) elicitor chitin, and significantly enhanced the disease resistance to different races of Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae (Xoo), which cause the rice blast and bacterial blight diseases, respectively. On contrary, the expression of PR genes and ROS were down-regulated in the OsMPK15-overexpressing (OsMPK15-OE) lines. Meanwhile, phytohormones such as salicylic acid (SA) and jasmonic acid (JA) were accumulated in the mpk15 mutant lines but decreased in the OsMPK15-OE lines. The expression of SA- and JA-pathway associated genes were significantly upregulated in the mpk15 mutant, whereas it was down regulated in the OsMPK15-OE lines. We conclude that OsMPK15 may negatively regulate the disease resistance through modulating SA- and JA-mediated signaling pathway.

Highlights

The plant has evolved two-layered immune systems to fight off the pathogen attacks, including pattern-recognition receptors (PRRs) triggered immunity (PTI) and specific pathogen-derived effectors triggered immunity (ETI) that is activated by recognition of cytoplasmic resistance proteins (Monaghan and Zipfel, 2012)
To better understand the molecular mechanism of rice mitogen-activated protein kinase (MAPK) family underlying plant-microbe interaction and immune response, we explored the expression pattern of OsMPK15 in response to M. oryzae infection and phytohormone treatment
Since previous studies have pointed to the conclusions that the transcript of OsMPK15 was suppressed by virulent blast race earlier than 24 h while it was accumulated 48 h after inoculated with the avirulent race (Reyna and Yang, 2006) and that the transcript of OsMPK15 was accumulated by jasmonic acid (JA) treatment (Reyna and Yang, 2006), we hypothesized that OsMPK15 may be involved in the disease resistance

Summary

Introduction

The plant has evolved two-layered immune systems to fight off the pathogen attacks, including pattern-recognition receptors (PRRs) triggered immunity (PTI) and specific pathogen-derived effectors triggered immunity (ETI) that is activated by recognition of cytoplasmic resistance proteins (Monaghan and Zipfel, 2012). The mitogen-activated protein kinase (MAPK) cascade is one of the well-characterized and conserved signaling pathways that play vital importance in plant. Plant MAPK cascade signaling modules consist of three functionally intertwined protein kinases including MAPK kinase kinase (MPKKK), MAPK kinase (MPKK), and MAPK. The basic process is that MPKKK phosphorylate and activate MPKKs, which in turn phosphorylate and activate MAPKs. The activated MAPKs are commonly imported into nucleus, and further interact with specific downstream components such as transcription factors (Tena et al, 2001; Asai et al, 2002; Koo et al, 2009; Jalmi and Sinha, 2016). At least 17 rice MAPKs have been identified according to in silico search of rice genome database but still a large number of members remain yet to be characterized (Reyna and Yang, 2006)

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