A STRESS-RESPONSIVE NAC1-regulated protein phosphatase gene rice protein phosphatase18 modulates drought and oxidative stress tolerance through abscisic acid-independent reactive oxygen species scavenging in rice.

Jun You,Jinghua Xiao,Wei Zong,Honghong Hu,Lizhong Xiong,Xianghua Li

doi:10.1104/pp.114.251116

Abstract

Plants respond to abiotic stresses through a complexity of signaling pathways, and the dephosphorylation mediated by protein phosphatase (PP) is an important event in this process. We identified a rice (Oryza sativa) PP2C gene, OsPP18, as a STRESS-RESPONSIVE NAC1 (SNAC1)-regulated downstream gene. The ospp18 mutant was more sensitive than wild-type plants to drought stress at both the seedling and panicle development stages. Rice plants with OsPP18 suppressed through artificial microRNA were also hypersensitive to drought stress. Microarray analysis of the mutant revealed that genes encoding reactive oxygen species (ROS) scavenging enzymes were down-regulated in the ospp18 mutant, and the mutant exhibited reduced activities of ROS scavenging enzymes and increased sensitivity to oxidative stresses. Overexpression of OsPP18 in rice led to enhanced osmotic and oxidative stress tolerance. The expression of OsPP18 was induced by drought stress but not induced by abscisic acid (ABA). Although OsPP18 is a typical PP2C with enzymatic activity, it did not interact with SNF1-RELATED PROTEIN KINASE2 protein kinases, which function in ABA signaling. Meanwhile, the expression of ABA-responsive genes was not affected in the ospp18 mutant, and the ABA sensitivities of the ospp18 mutant and OsPP18-overexpressing plants were also not altered. Together, these findings suggest that OsPP18 is a unique PP2C gene that is regulated by SNAC1 and confers drought and oxidative stress tolerance by regulating ROS homeostasis through ABA-independent pathways.

Highlights

Plants respond to abiotic stresses through a complexity of signaling pathways, and the dephosphorylation mediated by protein phosphatase (PP) is an important event in this process
To test whether STRESSRESPONSIVE NAC1 (SNAC1) can bind to the promoter of OsPP18, a genomic fragment of the OsPP18 promoter containing the core DNA-binding sequence (CDBS) located upstream of the start codon (Fig. 1C) was fused upstream of the HIS3 minimal promoter to serve as a reporter construct, designated as pHIS2-POsPP18, and the pGAD-SNAC1 plasmid was used as the effecter construct
The cotransformants were able to grow on synthetic dropout/Leu2/Trp2/His2 medium with 30 mM 3-amino-1, 2, 4-Triazole, whereas the negative control could not (Fig. 1D), indicating that SNAC1 could bind to the OsPP18 promoter in yeast

Summary

Introduction

Plants respond to abiotic stresses through a complexity of signaling pathways, and the dephosphorylation mediated by protein phosphatase (PP) is an important event in this process. The expression of ABA-responsive genes was not affected in the ospp mutant, and the ABA sensitivities of the ospp mutant and OsPP18-overexpressing plants were not altered Together, these findings suggest that OsPP18 is a unique PP2C gene that is regulated by SNAC1 and confers drought and oxidative stress tolerance by regulating ROS homeostasis through ABA-independent pathways. These findings suggest that OsPP18 is a unique PP2C gene that is regulated by SNAC1 and confers drought and oxidative stress tolerance by regulating ROS homeostasis through ABA-independent pathways Abiotic stresses, such as drought or salinity, cause intensive losses to agricultural production worldwide. The group B member ARABIDOPSIS SER/ THR PHOSPHATASE OF TYPE 2C 1 (AP2C1) inactivates the mitogen-activated protein kinases (MAPKs) MPK4 and MPK6 involved in regulating stress hormone levels and defense responses (Schweighofer et al, 2007). A significant finding is that OsPP18 mediates drought and oxidative stress responses by regulating ROS homeostasis through ABA-independent pathways

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Results

Conclusion