Ethylene promotes branch formation but inhibits tendril development in cucumber

Ethylene coordinates numerous plant growth processes, particularly in cucurbit crops, yet its role in vegetative growth regulation remains largely unexplored. Here, we report the function of ethylene in controlling branch and tendril development in cucumber. We find that ethylene promotes branches formation but inhibits tendrils development in a dose-dependent manner. CRISPR-Cas9-generated gene-edited Csein2 and Csein3/Cseil1 mutants exhibit few branches and more tendrils. Exogenous ethylene can recover the branch/tendril defective phenotypes of the Csein3 and Cseil1 mutants but not those of the Csein2 mutant or the Csein3/Cseil1 double mutant. Transcriptomic and metabolic analyses reveal that CsCYP707A4 and CsTL are the key downstream targets of ethylene signaling. We show that CsEIN3 can bind to its promoters to activate the expression of CsCYP707A4 but inhibit the expression of CsTL, which leads to the opposite effect on branch and tendril development. The study sets the foundation for designing ideal plant architecture to increase production efficiency.