Overexpression of SlIMP3 gene increased cell wall thickness and delayed fruit softening in Ailsa Craig tomato. (a, b) Total ascorbate and reduced ascorbate contents in different tomato tissues (L leaf, S stem, IMG immature green fruit, MG mature green fruit, BF break fruit, OF orange fruit, RF red fruit) of ACWT (Ailsa Craig wild type) and overexpression (OESlIMP3‐1, OESlIMP3‐9) lines. (c) Red fruits of ACWT and OESlIMP3‐1 lines were stored at 25°C for 0, 8, 15 and 30 days. Scale bars, 5 mm. (d) Water loss rate of ACWT and OESlIMP3‐1 lines. Statistics of water loss rate every five days. (e) Firmness of fruits at different developmental stages: GF green fruit, BF break fruit, OF orange fruit, RF red fruit. (f, g) The difference in cell wall thickness between ACWT and OESlIMP3 lines. The cell wall of fruit pericarp cells was observed by transmission electron microscope, and the cell wall thickness was measured with ImageJ software. Scale bars, 1 μm. All data contain three replicates and SD was given by error bar. Statistical significance between ACWT and OESlIMP3 lines was indicated by an asterisk (*P < 0.05, **P < 0.01, ***P < 0.001).