1. A Xylem Transcript level by microarray * * C B ChIP-PCR assay RT-PCR assay of IAA16 Fold enrichment Relative transcript level shr-2 WT pIAA16 IAA16 Fig S4. IAA16 is a direct SHR target that is repressed by SHR in the stele IAA16 expression pattern according to the Root Map. Asterisks mark the cell types in which IAA16 expression level is lowest. LRC, lateral root cap; Epi, epidermis; Atrichoblast, non-root hair cell; QC, quiescent center; Endo, endodermis; P-Peri, phloem-associated pericycle; X-Peri, xylem-associated pericycle; Peri-m, pericycle in the maturation zone; P-Phloem, protophloem; companion, companion cell; Xylem-m, xylem in the maturation zone; LR initial, lateral root initial cells. ChIP-PCR assay confirming SHR binding to the IAA16 promoter (left bar). As a control, the IAA16 coding region (right bar) was also amplified. RT-PCR assay of IAA16 transcript level in shr-2 and wild-type root.