Important but understudied: recent advances of peptide hormones in horticultural plants

Plant peptide hormones are signaling molecules, produced from small proteins named precursors through proteolytic processing. A peptide hormone normally contains 10–20 amino acids with particular posttranslational modifications. After being secreted into the apoplast, plant peptide hormones are perceived by their specific receptor(s) on the surface of the plasma membrane to induce downstream signaling transduction. Since the isolation of the first peptide hormone systemin in tomato, multiple peptide hormone families have been identified in plants. Moreover, peptide hormones together with their receptor complexes have been revealed to modulate almost all biological processes throughout plant life, such as root growth and development, reproduction, regeneration, and immune responses, indicating their critical roles in plants. Distinct from previous articles, this review focused on peptide hormones in horticultural plants, which are represented by many fruits and vegetables with high economic significance. Here, we summarized current knowledge about identification strategies and maturation processes of peptide hormones. Furthermore, we introduced the functions of important peptide hormone families in horticultural plants, highlighting future perspectives and challenges of peptide hormone research in horticultural plants.