Apoplastic proteome seems to be particularly interesting when considering the distribution of NO in plant cells.
Available literature data [29,30] and our analyses [12,26] indicate that the cell wall area is the compartment most
enriched in NO within a plant cell. This may result from the activity of membrane enzymes, nitrite:NO reductase and
plasma membrane-bound nitrate reductase, which are the main source of NO in plant cells apart from nitrate reductase
[15complement
this picture, cell walls are the site of release of superoxide
anion by apoplastic peroxidases [31].,16]. Moreover, it was also shown that NO can be produced in the walls via non-enzymatic pathway [14].