Emergence of plant vascular system: roles of hormonal and non-hormonal regulatory networks

•Vascular system emergence is the most critical step for land plant evolution.•Sugar may be the first signaling molecule, although its mode of action is unknown.•Ancient phytohormones trigger vascular formation.•Newly emerged phytohormones may facilitate integration of developmental cues.•Interplay between metabolic and hormonal networks enables emergence of vasculature.

The divergence of land plants followed by vascular plants has entirely changed the terrestrial ecology. The vascular system is a prerequisite for this evolutionary event, providing upright stature and communication for sink demand-source capacity and facilitating the development of plants and colonization over a wide range of environmental habitats. Various hormonal and non-hormonal regulatory networks have been identified and reviewed as key processes for vascular formation; however, how these factors have evolutionarily emerged and interconnected to trigger the emergence of the vascular system still remains elusive. Here, to understand the intricacy of cross-talks among these factors, we highlight how core hormonal signaling and transcriptional networks are coalesced into the appearance of vascular plants during evolution.