Plant nitric oxide synthase: a never-ending story?

In their report ‘Identification of a plant nitric oxide synthase gene involved in hormonal signaling’ [1], Nigel Crawford and colleagues reported on the discovery of a distinct nitric oxide synthase (AtNOS1) in Arabidopsis thaliana that regulates growth and hormonal signaling in plants. Arabidopsis mutants (Atnos1) were found to be impaired in NO production and organ growth. Although the AtNOS1 sequence has no similarities to any mammalian NOS isoform, the cloned and purified AtNOS1 protein was demonstrated to use the substrates arginine and nicotinamide adenine dinucleotide phosphate to produce NO.