Potentiates primary root protophloem differentiation (PubMed:22395740, PubMed:25049386, PubMed:28652362). Required, together with VCC, for embryo provasculature development and cotyledon vascular complexity and connectivity (PubMed:25149602). Regulates roots architecture (PubMed:25049386). Mediates the recruitment of ASK7/BIN2 to the plasma membrane (PubMed:28652362). Interacts with VCC. Polar localization at the apical side of the plasma membrane, shootward oriented, in developing root protophloem cells (PubMed:22395740, PubMed:28652362). Also found in the cytoplasm in the early, dividing. protophloem cells (PubMed:28652362). Expressed in provascular cells and phloem initials (e.g. protophloem, metaphloem, sieve element precursor cells and sieve element procambium precursor cells). First expressed in provascular cells, and upon vascular cell type specification becomes restricted to the phloem cell lineage. Phosphorylation at Ser-318 amplifies the promotion of protophloem differentiation. Short roots associated with both reduced cell division in the root meristem and altered root cell elongation. Early emergence of lateral roots at the root-hypocotyl junction (PubMed:22395740, PubMed:25049386, PubMed:28652362). Reductions in the complexity of vascular networks in cotyledons and discontinuous phloem differentiation (PubMed:25149602, PubMed:22395740, PubMed:25049386, PubMed:28652362). Impaired primary root protophloem differentiation during root development leading to altered phloem long-distance transport (PubMed:22395740). The double mutant vcc ops exhibits a complete loss of high-complexity vascular networks (PubMed:25149602). The double mutant brx ops double mutant has strongly reduced root length and meristem size, with missing protophloem strands (PubMed:28652362). Belongs to the OCTOPUS family.