Natural regulatory variations of MdIAA14b links auxin signalling to fruit cell density and firmness in apple.

Natural cis-regulatory variations of MdIAA14b are linked to differences in apple fruit firmness, with high-expression alleles associated with increased firmness and cell density.

• Why it matters: Understanding how auxin signaling influences fruit firmness can improve apple quality and shelf life, addressing gaps in knowledge about auxin's role beyond ethylene regulation in fruit texture.
• What they did: Researchers identified allele-specific expression of MdIAA14b through RNA-seq, revealing promoter insertions that affect gene activation, and demonstrated that high-expression alleles correlate with firmer fruit and smaller cells.
• The result: Overexpression of MdIAA14b in tomato increased cell number and fruit firmness, suggesting that cis-regulatory variations in MdIAA14b can be targeted to enhance fruit texture in apple breeding programs.