CRISPR/Cas9 editing of two adenine phosphoribosyl transferase coding genes reveals the functional specialization of adenine salvage proteins in common bean.

Adenine metabolism is important for common bean (Phaseolus vulgaris L) productivity since this legume uses ureides derived from the oxidation of purine nucleotides, as their primary nitrogen storage molecules. Purine nucleotides are produced from de novo synthesis or through salvage pathways. Adenine phosphoribosyl transferase (APRT) is the enzyme dedicated to adenine nucleobase salvage for nucleotide synthesis, but it also acts on the inactivation of cytokinin bases. In common bean, the APRT enzyme is encoded by four genes. Gene expression analysis, biochemical properties and subcellular location suggest functional differences among the common bean APRT isoforms. CRISPR/Cas9 targeted downregulation of two of the four PvAPRTs followed by metabolomics and physiological analyses of targeted hairy roots reveals that, although the two proteins have redundant functions, PvAPRT1 mostly participates in the salvage of adenine, whereas PvAPRT5 is the predominant form in the regulation of cytokinin homeostasis and stress responses with a high impact in root and nodule growth.