Peroxisomal plant nitric oxide synthase (NOS) protein is imported by peroxisomal targeting signal type 2 (PTS2) in a process that depends on the cytosolic receptor PEX7 and calmodulin

Nitric oxide (NO) production in plant peroxisomes by l-arginine-dependent NO synthase activity has been proven. The PEX5 and PEX7 PTS receptors, which recognize PTS1- and PTS2-containing proteins, are localized in the cytosol. Using AtPex5p and AtPex7p knockdown in Arabidopsis by RNA interference (RNAi) designated as pex5i and pex7i, we found that the l-arginine-dependent protein responsible for NO generation in peroxisomes appears to be imported through an N-terminal PTS2. Pharmacological analyzes using a calcium channel blocker and calmodulin (CaM) antagonist show that the import of the peroxisomal NOS protein also depends on calcium and calmodulin.