Nitric oxide synthase (NOS)-dependent nitric oxide generation is involved in putrescine-induced chilling tolerance of Anthurium andraeanum

Previous studies have demonstrated the positive effects of exogenous putrescine (Put) on the chilling tolerance of Anthurium andraeanum. In the present study, anthurium seedlings were pretreated with Put and Put in combination with NO scavenger cPTIO, nitric oxide synthase (NOS) inhibitor L -NAME, or nitrate reductase (NR) inhibitor Na2WO4 solutions for four weeks and then subjected to chilling stress (6 degrees C) for three days, followed by recovery (25 degrees C) for one day. NO fluorescence, endogenous NO content, and activities of NOS, NR, and copper amine oxidase (CuAO), as well as physiological indexes, were assessed during the experiment. The results were further confirmed at the transcriptional level via transcriptome sequencing and qRT-PCR. Results indicated that the application of Put prompted the accumulation of endogenous NO, and the NOS-dependent pathway probably played a vital role in the endogenous NO generation. The enhancement of chilling tolerance induced by exog-enous Put could be notably reversed by the combined application of (L)-NAME. Moreover, transcriptome sequencing and gene expression analyses confirmed the contribution of the NOS-dependent pathway to the accumulation of endogenous NO and the effects of endogenous NO on the mediation of chilling tolerance. In summary, the NOS-dependent pathway was the primary source of endogenous NO in the Put-pretreated anthurium. Furthermore, endogenous NO was involved in the chilling response of anthurium, playing a syner-gistic role in the mediation of chilling tolerance with exogenous Put.