Figure 2.

Stele-specific transcriptome analysis and differentially expressed cell cycle genes in response to local high nitrate (local HN) stimulation. A, Shoot-borne roots were manually dissected in three tissues: 5 mm of root tip (5 mm), stele covering all central cell types covered by the pericycle (5–25 mm of stele), and cortex covering all radial tissues between endodermis and epidermis (5–25 mm). B, Frequency of differentially expressed genes normalized according to log₂ Fc with FDR ≤ 5% and │Fc│ ≥ 2. Homo LN, Homogeneous low nitrate. C, RNA-Seq revealed differentially expressed cell cycle genes. CDKB and CYCB genes (G2/M transition; left) were induced by local HN, whereas KRP genes were inhibited by local HN (G1/S transition; right). D, Heat map of selected cell cycle genes (CDKB1;1, CDKB2;1, CYCB1;1, CYCB1;3, CYCB2;1, CYCB2;2, KRP1, KRP2, KRP3, and KRP4) in the stele determined by qRT-PCR after a time-course experiment of 36 h. Transcript abundance was normalized to myosin and expressed in base log₂ values (GenBank accession no. 486090G09.x1). E, Expression of cell cycle genes (CDKB1;1, CDKB2;1, KRP1, KRP2, CYCB1;1, and CYCB2;1) in pericycle cells at the phloem poles determined by qRT-PCR 24 h after local HN stimulation. Error bars represent se for four biological replicates. Asterisks denote a significant difference according to paired Student’s t test. *, P ≤ 0.05; **, P ≤ 0.01.