Comprehensive Analysis of the Gibberellin Oxidase Gene Family and Their Response to Exogenous Gibberellins in Flax Stem Development

Gibberellin oxidase (GAox) are central to both the biosynthesis and inactivation of gibberellins. While GAox genes have been characterized in numerous plant species, their functions in flax (Linum usitatissimum L.) remain comparatively unexplored. In this study, we conducted a systematic analysis of the LuGAox gene family in flax, identifying 91 putative LuGAox genes. Our results classified the LuGAox genes into seven distinct subfamilies, each exhibiting conserved motif architectures. Furthermore, transcriptomic sequencing (RNA-seq) data uncovered tissue-specific expression patterns among LuGAox genes. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis of 14 selected LuGAox genes revealed distinct expression profiles across various stem tissues in response to treatment with different concentrations of gibberellin (GA3). The genes LuGA2ox11, LuGA20ox5, LuGA20ox44, LuGA20ox50, LuGA20ox72, LuGA3ox1, and LuGA3ox2 have been selected as key candidate genes for further study of flax stem development. Co-expression network analysis indicated significant co-expression between LuGA20ox5, LuGA20ox44, and LuKNOX family members, suggesting potential interactions. In a parallel physiological investigation, exogenous application of GA3 demonstrated that treatment with a concentration of 100 mg/L significantly altered stem cell wall composition. It reduced lignin and pectin content while promoting the accumulation of cellulose and hemicellulose, thereby modifying key chemical parameters associated with fiber processing performance.