Genome-Wide Identification of the LcGA2ox Gene Family in Litchi (Litchi chinensis Sonn.) and Its Functional Analysis in Gibberellin Metabolism and Reproductive Development

Gibberellin 2-oxidase (GA2ox) is instrumental in gibberellin (GA) catabolism and the modulation of plant growth. In this investigation, nine LcGA2ox genes (LcGA2ox1-LcGA2ox9) were identified within the litchi (Litchi chinensis Sonn. ) genome. Bioinformatics analyses revealed that the proteins encoded by these genes uniformly possess 2OG-Fe (II) Oxy and DIOXN domains, exhibiting a range of physicochemical properties and subcellular localizations. Phylogenetic analysis categorized these genes into three subgroups, C19-GA2ox-I, C19-GA2ox-II, and C20-GA2ox-I, with each subgroup characterized by specific motif compositions and gene structures. These gene promoters harbor cis-regulatory elements implicated in light signaling, hormonal pathways, abiotic stress responses, and developmental processes. The LcGA2ox gene family contributes to the maintenance of GA metabolic homeostasis through interactions with GA synthases, receptors, and repressors. This gene family demonstrates distinct tissue-specific and spatiotemporal expression patterns: LcGA2ox1/6/7 are predominantly expressed in flowers, LcGA2ox8 in fruits, and LcGA2ox9 in buds. Notably, LcGA2ox6/7 are key regulators of male and female flower development in litchi, exhibiting a negative correlation with the female flower genes AGL1 and SPT. The overexpression studies conducted in Arabidopsis have demonstrated that LcGA2ox6 acts as an inhibitor of both vegetative and reproductive development. This study characterizes the LcGA2ox family, establishing a theoretical basis for understanding GA regulation in litchi reproductive development and genetic improvement.