Transcription factor required for phloem identity. Has a dual role both in promoting phloem differentiation and in repressing xylem differentiation during vascular development. Regulates the expression of the transcription factor NAC045 (AC A4VCM0). May activate the transcription of specific genes involved in phosphate uptake or assimilation (PubMed:15592750). Promotes flowering through transcriptional activation of both FT and its transport machinery component, FTIP1 (PubMed:26239308). Expressed in shoots and roots, specifically in the developing protophloem sieve elements (PubMed:14614507). Detected in phloem and/or cambium (PubMed:15923329). Expressed in the phloem tissues of various organs, including leaves and cotyledons, during vegetative growth (PubMed:26239308). Specifically expressed in the developing protophloem sieve elements soon after the phloem-specific cell divisions have taken place. Also found in the companion cells and metaphloem sieve elements. May not be necessary for the initial steps of protophloem differentiation. Up-regulated by phosphate deficiency. Differentiation of tracheary-like elements of xyleme at the site of the phloem pole leading to seedling lethality. May be due to an intron retention. Belongs to the MYB-CC family.