Dear Editor,rnThe second messenger cyclic nucleotide 3’,5’-cyclic guanosine monophosphate (cGMP) is increasingly recognized as a key signaling molecule that mediates many physiological and developmental processes in plants (Supplemental Figure 1A).While cGMP-dependent phosphorylation of Arabidopsis proteins is a known phenomenon (Isner et al.,2012),a quantification of the cGMP-dependent protein phosphorylation at the system level has not been reported previously.