The molecular mechanism of apical hook development in dicot plant

After the seeds of the dicot model plant Arabidopsis germinate in the soil, the tip of the hypocotyl will form a specialized structure called apical hooks to protect the cotyledons and shoot apical meristems from the mechanical damage during the soil emerging process. The development process of the apical hook is divided into three stages: the apical hook formation, maintenance, and opening. In recent decades, studies have shown that different kinds of plant hormones and environmental signals play a vital role in the development of the apical hook. As the downstream of a variety of signals, the asymmetric distribution of auxin and the signal transduction pathways play a decisive role in the development of the apical hook. However, the detailed mechanism of the asymmetric signal transduction pathway of the cells on both sides of the apical hook is still unclear. In this review, we summarize the molecular mechanisms of the development of apical hook and further refine the role of auxin in the development of apical hook, and prospect for future research directions in this field.