LcEIL2/3 are involved in fruitlet abscission via activating genes related to ethylene biosynthesis and cell wall remodeling in litchi

Fruit crops are subject to precocious fruit abscission, during which the phytohormone ethylene (ET) acts as a major positive regulator. However, the molecular basis of ET-induced fruit abscission remains poorly understood. Here, we show that two ETHYLENE INSENSITIVE 3-like (EIL) homologs in litchi,LcEIL2andLcEIL3, play a role in ET-activated fruitlet abscission.LcEIL2/3were significantly upregulated in the fruit abscission zone (AZ) during the ET-induced fruitlet abscission in litchi. The presence ofLcEIL2/3in wild-type Arabidopsis andein3 eil1mutants can accelerate the floral organ abscission. Moreover, the electrophoretic mobility shift assay and dual luciferase reporter analysis illustrated that LcEIL2/3 directly interacted with the gene promoters to activate the expression of cell wall remodeling genesLcCEL2/8andLcPG1/2, and ET biosynthetic genesLcACS1/4/7andLcACO2/3. Furthermore, we showed thatLcPG1/2were expressed in the floral abscission zone of Arabidopsis, and constitutive expression ofLcPG2in Arabidopsis promoted the floral organ abscission. In conclusion, we propose that LcEIL2/3 are involved in ET-induced fruitlet abscission via controlling expression of genes related to ET biosynthesis and cell wall remodeling in litchi.