Osa‐miR398b boosts H₂O₂ production and rice blast disease‐resistance via multiple superoxide dismutases

Abstract

Summary mi RNA s contribute to plant resistance against pathogens. Previously, we found that the function of miR398b in immunity in rice differs from that in Arabidopsis. However, the underlying mechanisms are unclear. In this study, we characterized the mutants of miR398b target genes and demonstrated that multiple superoxide dismutase genes contribute to miR398b‐regulated rice immunity against the blast fungus Magnaporthe oryzae . Out of the four target genes of miR398b, mutations in Cu/Zn‐Superoxidase Dismutase1 ( CSD 1 ), CSD 2 and Os11g09780 ( Superoxide DismutaseX , SODX ) led to enhanced resistance to M. oryzae and increased hydrogen peroxide (H 2 O 2 ) accumulation. By contrast, mutations in Copper Chaperone for Superoxide Dismutase ( CCSD ) resulted in enhanced susceptibility. Biochemical studies revealed that csd1 , csd2 and sodx displayed altered expression of CSD s and other superoxide dismutase ( SOD ) family members, leading to increased total SOD enzyme activity that positively contributed to higher H 2 O 2 production. By contrast, the ccsd mutant showed CSD protein deletion, resulting in decreased CSD and total SOD enzyme activity. Our results demonstrate the roles of different SOD s in miR398b‐regulated resistance to rice blast disease, and uncover an integrative regulatory network in which miR398b boosts total SOD activity to upregulate H 2 O 2 concentration and thereby improve disease resistance.

circRNAs Are Involved in the Rice-Magnaporthe oryzae Interaction

“…Fully expanded leaves of 3-week-old seedlings were challenged with spores (2 3 10 5 spore mL 21 ) of M. oryzae eGFP-tagged Zhong8-10-14 (GZ8) through punch inoculation or spraying inoculation methods (Park et al, 2012;Li et al, 2019). The disease phenotype was photographed at 7 d postinoculation.…”

“…Disease lesions were measured with ImageJ software. Relative fungal biomass was quantified as previously described (Park et al, 2012;Li et al, 2019).…”

“…Genome-wide small RNA analyses have revealed a number of candidate miRNAs responsive to M. oryzae infection or elicitors (Campo et al, 2013;Li et al, 2014;Li et al, 2016;Wang et al, 2018). Transgenic approaches further confirm miRNAs, such as miR7695, miR398b, miR160a, and miR166k-166h (Campo et al, 2013;Li et al, 2014Li et al, , 2019Salvador-Guirao et al, 2018), positively regulate rice blast resistance; on the contrary, miR169a, miR164a, miR319b, miR396, and miR167d Wang et al, 2018;Zhang et al, 2018;Chandran et al, 2019;Zhao et al, 2019) act as negative regulators of rice immunity against the blast pathogen. miRNAs exert their biological functions via targeting mRNAs with sequence complementarity (Seitz, 2009); meanwhile, binding of miRNAs to their targets could be interfered with by endogenous noncoding RNAs, such as target mimics (Wu et al, 2013) and circular RNAs (circRNAs; Hansen et al, 2013).…”

“…miRNAs exert their biological functions via targeting mRNAs with sequence complementarity (Seitz, 2009); meanwhile, binding of miRNAs to their targets could be interfered with by endogenous noncoding RNAs, such as target mimics (Wu et al, 2013) and circular RNAs (circRNAs; Hansen et al, 2013). Target mimics have been reported to regulate rice immunity against the blast pathogen Chandran et al, 2019;Li et al, 2019), but it is unknown whether circRNAs are involved in the rice-M. oryzae interaction.…”

Osa‐miR167d facilitates infection of Magnaporthe oryzae in rice

“…Increasing evidence indicates that miRNAs play important roles in the regulation of rice‐blast interactions by effectively and accurately regulating the expression of their target genes. For example, miR398b positively regulates rice immunity against M. oryzae (Li et al ), and coordinates multiple pathways to boost H 2 O 2 accumulation via multiple Superoxide Dismutase ( SOD ) family genes (Li et al ). In addition, miR396 , miR444b.2 , miR169 , miR319b and miR164a negatively regulate (Li et al ; Li et al ; Xiao et al ; Wang et al ; Zhang et al ), whereas, miR160a , miR7695 and miR166k‐miR166h positively regulate rice immunity against M. oryzae (Campo et al ; Li et al ; Salvador‐Guirao et al ).…”