Extended Data Fig. 1: Markers used for sorting phloem pole cells and new CC genes identified.

a) MAKR5 translational fusion highlights all the cells surrounding PSE⁷³ from the quiescent centre (QC) (often stronger from cell number 3) until the differentiation zone, where it becomes weaker. Some weak expression is also found in PSE. In mature parts of the root this marker spreads to the whole pericycle. Published marker was fused to 3xYFP to increase signal. S17¹ is expressed in PPP from the unloading zone. pAPL::3xYFP is expressed first in PSE and after enucleation switches to all the cells around PSE, stronger in CC. This line is not fully reflecting ALTERED PHLOEM DEVELOPMENT (APL) endogenous expression, since it has some expression in the outer layers but it is a very strong phloem pole marker. sAPL is expressed in CC and MSE (weaker) from 90–120 µm from the QC. pPEAR1(del)::3xYFP is a modified version of the PEAR1 promoter that is expressed in early PSE, MSE and a procambial cell resulting from the same division plus columella cells. See Roszak et al.³³ for the detailed expression pattern b) Newly identified genes expressed in CC (PLC5, At5g58690, and At2g38640). c) Expression of mature CC (NAKR1, SUC2), mature PSE (NAC086, NAC045) and mature PPP (S17, MES7) genes at the terminal clusters. UMAPs show the particular cluster-weighted normalised expression of each gene in the phloem pole cell atlas and microscopy pictures are representative images of the transcriptional reporter lines where the gene promoter is fused to VENUSer. Scale bar in the longitudinal sections is 25 µm while it is 10 µm in the cross sections. White arrowheads point to PSE cells as a reference point. The numbers in each panel indicate samples with similar results, of the total independent biological samples observed.