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 <i>LcGA2ox</i> genes (<i>LcGA2ox1</i>-<i>LcGA2ox9</i>) were identified within the litchi (<i>Litchi chinensis</i> Sonn.) genome. Bioinformatics analyses revealed that the proteins encoded by these genes uniformly possess 2OG-Fe (II)_Oxy and DIOX_N 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 <i>cis</i>-regulatory elements implicated in light signaling, hormonal pathways, abiotic stress responses, and developmental processes. The <i>LcGA2ox</i> 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: <i>LcGA2ox1/6/7</i> are predominantly expressed in flowers, <i>LcGA2ox8</i> in fruits, and <i>LcGA2ox9</i> in buds. Notably, <i>LcGA2ox6/7</i> are key regulators of male and female flower development in litchi, exhibiting a negative correlation with the female flower genes <i>AGL1</i> and <i>SPT</i>. The overexpression studies conducted in <i>Arabidopsis</i> have demonstrated that <i>LcGA2ox6</i> acts as an inhibitor of both vegetative and reproductive development. This study characterizes the <i>LcGA2ox</i> family, establishing a theoretical basis for understanding GA regulation in litchi reproductive development and genetic improvement.