Fig. 1

CKX2-overexpressing tomato plants display increased shoot branching and alters cytokinin accumulation and responses. A. Phenotype of CKX2 overexpressing (OE) lines (#1, #2 and #3) in tomato Micro-Tom (MT) background. B. AtCKX2 gene expression analysis. Transcript accumulation was estimated compared to CKX2-OE#1 in axillary buds (0.5 to 1.0 cm) harvested from the 3rd and 4th node of vegetative plants. Data are means ± se of three biological samples. Letters indicate significant differences among the transgenic lines. C. Schematic representation of axillary shoot branching in the sympodial axis at anthesis. Squares represent individual leaf axils and columns represent single plants. Oldest (#1 at the bottom) to the youngest (#10 at the top) leaves are shown within the column. Gray squares indicate absence of axillary branch; yellow (< 0.5 cm), pale green (≥ 0.5 cm to ≤3 cm) and dark green (> 3 cm) squares indicate growing branches. D and E. Concentration of endogenous cytokinin t-Zeatin (A) and iP (B) in vegetative shoots and roots in CKX2-OE#2 and MT plants. Data are means ± se (n = 3 for shoot and n = 5 for root). F and G. Root growth inhibition in response to 2iP (E) or TDZ (F) in CKX2-OE#2 compared with the MT. 2iP, N⁶-(2-Isopentenyl) adenine; TDZ, thidiazuron. Total root length (primary and lateral roots for MT; primary, lateral and adventitious roots for CKX2-OE#2) was measured 7 days after treatment; Data are means ± se (n = 12). H. Transcript levels of cytokinin-biosynthesis, −activation and -response genes in CKX2-OE#2 and MT shoot buds. Transcript accumulation was measured in axillary buds (0.5 to 1.0 cm) harvested from the 3rd and 4th node of vegetative plants. Asterisks indicate significant differences between genotypes (*P < 0.05**, P < 0.01, ***P < 0.001). B: Tukey test; D, E and H: Student’s t-test; F and G: Mann Whitney test