Shoot bending promotes flower bud formation by mi RNA ‐mediated regulation in apple ( M alus domestica B orkh.)

Summary Flower induction in apple ( M alus domestica B orkh.) trees plays an important life cycle role, but young trees produce fewer and inferior quality flower buds. Therefore, shoot bending has become an important cultural practice, significantly promoting the capacity to develop more flower buds during the growing seasons. Additionally, micro RNA s (mi RNA s) play essential roles in plant growth, flower induction and stress responses. In this study, we identified mi RNA s potentially involved in the regulation of bud growth, and flower induction and development, as well as in the response to shoot bending. Of the 195 mi RNA s identified, 137 were novel mi RNA s. The mi RNA expression profiles revealed that the expression levels of 68 and 27 known mi RNA s were down‐regulated and up‐regulated, respectively, in response to shoot bending, and that the 31 differentially expressed novel mi RNA s between them formed five major clusters. Additionally, a complex regulatory network associated with auxin, cytokinin, abscisic acid ( ABA ) and gibberellic acid ( GA ) plays important roles in cell division, bud growth and flower induction, in which related mi RNA s and targets mediated regulation. Among them, mi R 396, 160, 393, and their targets associated with AUX , miR159, 319, 164, and their targets associated with ABA and GA , and flowering‐related mi RNA s and genes, regulate bud growth and flower bud formation in response to shoot bending. Meanwhile, the flowering genes had significantly higher expression levels during shoot bending, suggesting that they are involved in this regulatory process. This study provides a framework for the future analysis of mi RNA s associated with multiple hormones and their roles in the regulation of bud growth, and flower induction and formation in response to shoot bending in apple trees.