NO signalling in cytokinin‐induced programmed cell death

Cell death can be induced by cytokinin 6‐benzylaminopurine (BA) at high dosage in suspension‐cultured Arabidopsis cells. Herein, we provide evidence that BA induces nitric oxide (NO) synthesis in a dose‐dependent manner. A reduction in cell death can be observed when the cytokinin is supplemented with the NO scavenger 2‐(4‐carboxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide (cPTIO) or the nitric oxide synthase (NOS) inhibitors: 2‐aminoethyl‐isothiourea (AET) and NG.‐monomethyl‐ l‐arginine ( l‐NMMA), which suggests that NO is produced via a NOS and is a signalling component of this form of programmed cell death. In BA‐treated cells, mitochondrial functionality is altered via inhibition of respiration. This inhibition can be prevented by addition of either cPTIO or AET implying that NO acts at the mitochondrial level.