Nitric Oxide Associated Protein 1 (NOA1)

AtNOS1 encodes a protein with nitric oxide synthase (NOS) activity and that regulates growth and abscisic acid signaling in plants, yet is a distinct enzyme with no sequence similarities to any mammalian isoform. AtNOS1 is targeted to mitochondria by examining GFP and Mito-Tracker signals in transgenic plants carrying 35S AtNOS1-GFP constructs.

Atnos1 mutants show a higher level of H2O2 in leaves compared to wild type, indicating that AtNOS1 is a new player in regulating ROS levels in plant cells. It has been known that NO donors delay leaf senescence, which involves ROS. Atnos1 mutant exhibits accelerated leaf senescence, which can be reversed by SNP, a NO donor. These results establish a link between NO production by AtNOS1 in mitochondria and leaf senescence.