Evolutionary Profiling of Group II Pyridoxal-Phosphate-Dependent Decarboxylases Suggests Expansion and Functional Diversification of Histidine Decarboxylases in Tomato

Pyridoxal phosphate (PLP)-dependent enzymes are one of the most important enzymes involved in plant N metabolism. Here, we explored the evolution of group II PLP-dependent decarboxylases (PLP_deC), including aromatic L-amino acid decarboxylase, glutamate decarboxylase, and histidine decarboxylase in the plant lineage. Gene identification analysis revealed a higher number of genes encoding PLP_deC in higher plants than in lower plants. Expression profiling of PLP_deC orthologs and syntelogs in Arabidopsis thaliana (L.) Heynh., pepper (Capsicum annuum L.), and tomato (Solanum lycopersicum L.) pointed toward conserved as well as distinct roles in developmental processes such as fruit maturation and ripening and abiotic stress responses. We further characterized a putative promoter of tomato ripening-associated gene (SlHDC10) operating in a complex regulatory circuit. Our analysis provides a firm basis for further in-depth exploration of the PLP_deC gene family, particularly in the economically important Solanaceae family.