Multifaceted controls on auxin metabolism during cellular reprogramming and organ regeneration in plants

Regenerative responses of plants are primarily triggered by injury in natural conditions, while desirable regenerative responses are often achieved in vitro in the presence of exogenous hormone application. The phytohormone auxin plays key roles in both naturally occurring regeneration and tissue culture-based in vitro regeneration. Here in this review, we provide an overview of the multifaceted metabolic controls on the major natural auxin, indole-3-acetic acid (IAA), which enable successful regeneration. Recent studies revealed the significance of IAA biosynthesis for the appropriate auxin patterning in pluripotent callus formation and de novo root regeneration. Wounding signals and environmental factors impact regenerative responses via modifying IAA metabolism. Further understanding of the regulation of IAA availability is expected to open an avenue to improve regeneration efficiency.