Dual Roles of GSNOR1 in Cell Death and Immunity in Tetraploid .

S-nitrosoglutathione reductase 1 (GSNOR1) is the key enzyme that regulates cellular homeostasis of nitrosylation. Although extensively studied in , the roles of GSNOR1 in tetraploid species have not been investigated previously. To study the function of GSNOR1, we knocked out two genes simultaneously in 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 GSNOR1 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 (HO). This spontaneous cell death phenotype was not affected by knocking out two genes and thus was independent of the salicylic acid (SA) pathway. Unexpectedly, we found that the knockout plants displayed a significantly ( < 0.001) enhanced resistance to paraquat-induced cell death compared to WT plants, suggesting that GSNOR1 functions as a positive regulator of the paraquat-induced cell death. The increased resistance to the paraquat-induced cell death of the knockout plants was correlated with the reduced level of HO accumulation. Interestingly, whereas the gene-mediated resistance to (TMV) was significantly enhanced ( < 0.001), the resistance to pv. DC3000 was significantly reduced ( < 0.01) in the knockout lines. In summary, our results indicate that GSNOR1 functions as both positive and negative regulator of cell death under different conditions and displays distinct effects on resistance against viral and bacterial pathogens.