Sly‐miR159 regulates fruit morphology by modulating GA biosynthesis in tomato

Summary Fruit morphology is an important agronomical trait of many crops. Here, we identify Sly‐miR159 as an important regulator of fruit morphology in tomato, a model species of fleshy‐fruit development. We show that Sly‐miR159 functions through its target SlGAMYB2 to control fruit growth. Suppression of Sly‐miR159 and overexpression of SlGAMYB2 result in larger fruits with a reduced length/width ratio, while loss of function of SlGAMYB2 leads to the formation of smaller and more elongated fruits. Gibberellin (GA) is a major phytohormone that regulates fruit development in tomato. We show the Sly‐miR159‐SlGAMYB2 pathway controls fruit morphology by modulating GA biosynthesis. In particular, we demonstrate that Sly‐miR159 promotes GA biosynthesis largely through the direct repression of the GA biosynthetic gene SlGA3ox2 by SlGAMYB2. Together, our findings reveal the action of Sly‐miR159 on GA biosynthesis as a previously unidentified mechanism that controls fruit morphology in tomato. Modulating this pathway may have potential applications in tomato breeding for manipulating fruit growth and facilitating the process of fruit improvement.