Plant vascular development: from early specification to differentiation

Key Points Owing to recent advances, plant vascular developmental can now be described from early specification during embryogenesis up to late differentiation events. Plant vascular tissues display both deterministic and plastic properties during development. Most of the molecular pathways controlling vascular tissue patterning involve mobile signals. Although a rather elaborate transcriptional network has been established for xylem differentiation processes, very little is known about phloem differentiation. We propose a model in which two distinctly regulated orthogonal meristems each controls a separate axis of growth to sustain tissue development as a whole. Recent studies in Arabidopsis thaliana have identified interconnected signalling networks that regulate plant vascular development. These findings have increased our understanding of vascular development from early cell specification during embryogenesis to the latest stages of differentiation of the phloem and xylem. Vascular tissues in plants are crucial to provide physical support and to transport water, sugars and hormones and other small signalling molecules throughout the plant. Recent genetic and molecular studies have identified interconnections among some of the major signalling networks that regulate plant vascular development. Using Arabidopsis thaliana as a model system, these studies enable the description of vascular development from the earliest tissue specification events during embryogenesis to the differentiation of phloem and xylem tissues. Moreover, we propose a model for how oriented cell divisions give rise to a three-dimensional vascular bundle within the root meristem.