Hetero- and homodimerization of Arabidopsis thaliana arginine decarboxylase AtADC1 and AtADC2.

The arginine decarboxylase enzyme (ADC) carries out the production of agmatine from arginine, which is the precursor of the first polyamine (PA) known as putrescine; subsequently, putrescine is turned into the higher PAs, spermidine and spermine. In Arabidopsis thaliana PA production occurs only from arginine and this step is initiated by two ADC paralogues, AtADC1 and AtADC2. PA production is essential for A. thaliana life cycle. Here, we analyzed the sub-cellular localization of AtADC1 and AtADC2 enzymes through GFP translational fusions. Our data revealed that the A. thaliana arginine decarboxylase enzymes exhibit a dual sub-cellular localization both in the cytosol and chloroplast. Moreover, we examined the protein dimer assembly using a Bimolecular Fluorescence Complementation (BiFC) approach, which showed that AtADC1 and AtADC2 proteins were able to form homodimers in the cytosol and chloroplast. Interestingly, we found the formation of AtADC1/AtADC2 heterodimers with similar sub-cellular localization than homodimers. This study reveals that both ADC proteins are located in the same cell compartments, and they are able to form protein interaction complexes with each other.