Dual Roles of GSNOR1 in Cell Death and Immunity in Tetraploid Nicotiana tabacum

Zhen-Chao Li; Qian-Wei Ren; Yan Guo; Jie Ran; Xiao-Tian Ren; Ni-Ni Wu; Hui-Yang Xu; Xia Liu; Jian-Zhong Liu

doi:10.3389/fpls.2021.596234

Dual Roles of GSNOR1 in Cell Death and Immunity in Tetraploid Nicotiana tabacum

Front Plant Sci. 2021 Feb 10:12:596234. doi: 10.3389/fpls.2021.596234. eCollection 2021.

Authors

Zhen-Chao Li¹, Qian-Wei Ren¹, Yan Guo¹, Jie Ran¹, Xiao-Tian Ren¹, Ni-Ni Wu¹, Hui-Yang Xu¹, Xia Liu^{1

2}, Jian-Zhong Liu^{1

2}

Affiliations

¹ College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, China.
² Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, Zhejiang Normal University, Jinhua, China.

Abstract

S-nitrosoglutathione reductase 1 (GSNOR1) is the key enzyme that regulates cellular homeostasis of S-nitrosylation. Although extensively studied in Arabidopsis, the roles of GSNOR1 in tetraploid Nicotiana species have not been investigated previously. To study the function of NtGSNOR1, we knocked out two NtGSNOR1 genes simultaneously in Nicotiana tabacum using clustered regularly interspaced short palindromic repeats (CRISPR)/caspase 9 (Cas9) technology. To our surprise, spontaneous cell death occurred on the leaves of the CRISPR/Cas9 lines but not on those of the wild-type (WT) plants, suggesting that NtGSNOR1 negatively regulates cell death. The natural cell death on the CRISPR/Cas9 lines could be a result from interactions between overaccumulated nitric oxide (NO) and hydrogen peroxide (H₂O₂). This spontaneous cell death phenotype was not affected by knocking out two Enhanced disease susceptibility 1 genes (NtEDS11a/1b) and thus was independent of the salicylic acid (SA) pathway. Unexpectedly, we found that the NtGSNOR1a/1b knockout plants displayed a significantly (p < 0.001) enhanced resistance to paraquat-induced cell death compared to WT plants, suggesting that NtGSNOR1 functions as a positive regulator of the paraquat-induced cell death. The increased resistance to the paraquat-induced cell death of the NtGSNOR1a/1b knockout plants was correlated with the reduced level of H₂O₂ accumulation. Interestingly, whereas the N gene-mediated resistance to Tobacco mosaic virus (TMV) was significantly enhanced (p < 0.001), the resistance to Pseudomonas syringae pv. tomato DC3000 was significantly reduced (p < 0.01) in the NtGSNOR1a/1b knockout lines. In summary, our results indicate that NtGSNOR1 functions as both positive and negative regulator of cell death under different conditions and displays distinct effects on resistance against viral and bacterial pathogens.

Keywords: S-nitrosoglutathione reductase; cell death; disease resistance; hypersensitive responses; nitric oxide; reactive oxygen species.