Hormonal and Transcriptomic Analysis Reveal Gibberellin-Induced Fruit Set in Jujube (Ziziphus jujuba Mill.)

Gibberellin (GA) is a crucial hormone that drives parthenocarpy and fruit set progression. However, it remains unknown whether GA participates in the parthenocarpy and fruit set in jujube (Ziziphus jujuba Mill.). In this study, we observed the morphology and effect of parthenocarpy in jujube flowers with GA3 treatment. Liquid chromatography tandem-mass spectrometry analysis was performed to detect the levels of endogenous hormones in sepal spread (H), filament wilting (S), and ovary inflation (G) stages of jujube flowers, and the GA3-induced differentially expressed genes (DEGs) were identified by RNA sequencing. We found that GA3 improved jujube parthenocarpic fruit set and that the morphology and size of flowers after GA3 treatment were superior to those in control flowers. GA3 treatment increased the levels of gibberellin, ABA, auxins, and cytokinins in jujube flowers. RNA sequencing revealed that GA3-induced DEGs expressed in the H, S, and G stages. Functional and pathway analyses demonstrated that these DEGs belong to plant development, including glucan metabolic processes and plant hormone signal transduction. Moreover, quantitative reverse transcription polymerase chain reaction validated the reliability of the sequencing data. Fruit set–related genes were significantly induced in the H, S, and G stages of jujube flowers. Our study confirmed that GA3 induced phytohormone production and fruit set by regulating the expression of endogenous hormones and related genes.