Genome-wide identification and integrated analysis of gibberellin oxidase genes associated with branch angle and internode elongation in tea plants (Camellia sinensis)

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Introduction Gibberellin oxidases (GAoxs) are key enzymes involved in maintaining gibberellin (GA) homeostasis and therefore play important roles in regulating plant architecture. However, the GAox genes associated with branch angle and internode elongation in tea plants ( Camellia sinensis ) remain largely uncharacterized. Methods In this study, 33 CsGAox genes were identified in the genome of the tea cultivar `Longjing 43' and classified into four subfamilies. Comparative genomic analysis across eight Camellia genomes was performed, and phenotypic measurements were integrated with endogenous GA quantification, transcriptome profiling, qRT-PCR analysis, and exogenous GA₃ treatment. Results Whole-genome or segmental duplication contributed substantially to the expansion of the CsGAox family, with duplicated gene pairs in `Longjing 43' predominantly undergoing purifying selection. The levels of GA₁, GA₉, and GA₂₀ were higher in the lateral buds of the draped cultivar than in those of the upright cultivars and were positively correlated with branch angle. CsGA20ox4.3 expression was positively associated with branch angle and the levels of those GAs, whereas CsGA2ox5.3 exhibited the opposite relationships. Exogenous GA₃ application significantly increased branch angle and was accompanied by the upregulation of CsGA20ox4.3 and CsGA20ox.un3 and the downregulation of CsGA2ox5.3 . Integrated analyses across cultivars and developmental stages further showed that CsGA20ox4.3 and CsGA3ox3.3 were positively associated with internode elongation, whereas CsGA2ox1.1 , CsGA2ox5.2 , and CsGA2ox.un1 generally exhibited negative associations. Discussion These findings identify candidate CsGAox genes associated with branch angle and internode elongation, providing a basis for future functional studies and further evaluation in tea plant architecture breeding.

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