Plant xylem tissues serve an important dual role during growth and development of plants as they are required for both physical support and water transport. Moreover, modulation of xylem characteristics like size and number of xylem vessels provides a vital mechanism to cope with environmental stress. Hence, a comprehensive understanding of the regulatory network of xylem development can greatly benefit plant health and crop yield. Although xylem development has been investigated over the past decades, one key aspect found in most highly differentiated plant tissues has been neglected in the field of vascular development thus far: the switch from mitosis to endoreduplication. My preliminary results suggest that endoreduplication onset not only occurs in maturing xylem cells, but also that inhibition leads to alterations in xylem morphology. The aim of this research proposal is thus to identify and characterize the molecular players controlling endoreduplication onset during xylem differentiation by i) validating the impact of mitosis-to-endoreduplication switch for xylem development, ii) identifying regulators of endoreduplication onset by inferring and validating Gene Regulatory Networks, iii) functionally characterizing these new regulators and iv) assessing the physiological relevance of a timely endoreduplication onset under abiotic stress conditions. The outcomes of the proposed project will thus shed light on xylem differentiation from a new perspective.