Regulates the Angle of Leaf Petiole by Affecting Endogenous Content of Auxin in Cucumber ( L.).

The leaf angle is an important factor determining plant shoot architecture that may boost crop yield by increasing photosynthetic efficiency and facilitating high-density planting. Auxin is an important phytohormone involved in leaf angle regulation. Here, we identified two Single-Nucleotide Polymorphisms (SNPs) in the Indoleacetic Acid (IAA) glucosyltransferase gene in 80 re-sequenced cucumber lines, of which the is the dominant allele associated with a small leaf pedicle angle (LPA), whereas is linked with a large LPA. was highly expressed in leaves and petioles. In natural cucumber populations, the expression of was negatively correlated with the LPA. The mutation of induced by the CRISPR-Cas9 system resulted in elevated free IAA levels and enlarged cell expansion on the adaxial side of the petiole base, thus producing a greater LPA. Consistently, exogenous IAA treatment led to increased LPA and cell size. Therefore, our findings suggest that functions as a negative regulator of LPA development via auxin-mediated cell expansion in cucumber, providing a valuable strategy for cucumber breeding with small LPAs.