Na⁺/H⁺ exchanger 1 participates in tobacco disease defence against Phytophthora parasitica var. nicotianae by affecting vacuolar pH and priming the antioxidative system.

Xianyang Chen,Yinxin Li,Weitao Jia,Jie Guo,Lingling Nie,Ping Jiang,Hexigeduleng Bao,Juanjuan Feng,Sulian Lv,Fang Tai

doi:10.1093/jxb/eru351

Xianyang Chen, Yinxin Li + Show 8 more

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https://doi.org/10.1093/jxb/eru351

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Abstract

Despite the importance of NHX1 (Na(+)/H(+) exchanger 1) in plant salt tolerance, little is known about its other functions. In this study, intriguingly, it was found that NHX1 participated in plant disease defence against Phytophthora parasitica var. nicotianae (Ppn) in Nicotiana benthamiana. NbNHX1 was originally isolated from N. benthamiana, and characterized. The subcellular localization of NbNHX1 with its C-terminus fused with green fluorescent protein indicated that NbNHX1 localized primarily to the tonoplast. Tobacco rattle virus-induced NbNHX1 silencing led to reduced H(+) efflux from the vacuole to cytoplasts, and decreased Ppn resistance in N. benthamiana. After attack by Ppn, NbNHX1-silenced plants exhibited impaired ability to scavenge reactive oxidative species (ROS) induced by the pathogen. Pea early browning virus-mediated ectopic expression of SeNHX1 (from Salicornia europaea) or AtNHX1 (from Arabidopsis thaliana) both conferred enhanced Ppn resistance to N. benthamiana, with a lower H2O2 concentration after Ppn inoculation. Further investigation of the role of NHX1 demonstrated that transient overexpression of NbNHX1 improved the vacuolar pH and cellular ROS level in N. benthamiana, which was coupled with an enlarged NAD(P) (H) pool and higher expression of ROS-responsive genes. In contrast, NbNHX1 silencing led to a lower pH in the vacuole and a lower cellular ROS level in N. benthamiana, which was coupled with a decreased NAD(P) (H) pool and decreased expression of ROS-responsive genes. These results suggest that NHX1 is involved in plant disease defence; and regulation of vacuolar pH by NHX1, affecting the cellular oxidation state, primes the antioxidative system which is associated with Ppn resistance in tobacco.

Highlights

Due to their sessile nature, plants have developed vari- homeostasis in response to abiotic and biotic stresses, and the ous biochemical and physiological processes to respond redox state is regarded as one of the most important indito environmental stresses
Hydropathy plot analysis showed that NbNHX1 is similar to SeNHX1 as well as AtNHX1 containing 12 transmembrane domains typical for a vacuolar-type Na+/ H+ antiporter
The phylogenetic analysis showed that NbNHX1 and SeNHX1 are more closely related to AtNHX1 compared with other NHX members in Arabidopsis (Fig. 1B)

Summary

Introduction

Due to their sessile nature, plants have developed vari- homeostasis in response to abiotic and biotic stresses, and the ous biochemical and physiological processes to respond redox state is regarded as one of the most important indito environmental stresses They efficiently regulate redox cators for evaluating the situation of the cell Overexpression of a gene related to the NAD(P)H pool in rice improves the resistance to hydrogen peroxide (H2O2) and disease (Hayashi et al, 2005)

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