Comprehensive characterization of gibberellin oxidase gene family in Brassica napus reveals BnGA2ox15 involved in hormone signaling and response to drought stress

Brassica napus is a well-known allopolyploid oil crop with high commercial potential. Gibberellin oxidase (GAox) is an essential enzyme that activates gibberellins, which regulate plant growth, and development, and have a significant impact on plant responses to abiotic stress. However, the comprehensive understanding of GAox genes and their evolution in Brassica plants remains elusive. Using advanced bioinformatics tools, this study identified 125 candidate GAox genes from the whole genomes of three key Brassica species. This study also investigated sequence characteristics, conserved motifs, exon/intron structures, cis-acting elements, syntenic analysis, duplication events and expression patterns. Subcellular localization analysis showed that the BnGA2ox14 and BnGA2ox15 proteins are located in the nucleus, whereas BnGA2ox26 is specifically localized to the chloroplast. Yeast one-hybrid and dual-luciferase assays demonstrated that MYELOCYTOMATOSIS 4 (BnMYC4) and ABA-INDUCIBLE BHLH-TYPE TRANSCRIPTION FACTOR (BnAIB) bind to the BnGA2ox15 promoter and activate its transcription. Molecular docking analysis further elucidated their interaction structures and identified potential binding sites. Roots transformations show that overexpression of BnGA2ox15 increased sensitivity to PEG-6000 treatment in rapeseed. In brief, this study reveals that BnGA2ox15 is a downstream target in JA and ABA signaling pathways, functioning as a negative regulator in responding to drought stress.