Molecular cloning and heterologous expression of TeGA3ox, a gibberellin biosynthesis gene from Tagetes erecta L.

Abstract

Plant height is a critical agronomic trait of marigold (Tagetes erecta L.). Gibberellins (GAs) are central regulators of plant height, with gibberellin 3-oxidase (GA3ox) serving as a rate-limiting enzyme governing GA biosynthesis. In this study, we characterized the TeGA3ox gene and investigated its functional role in modulating plant height through GA biosynthesis. The full-length cDNA of TeGA3ox is 1343 bp, encoding a hydrophobic, unstable protein of 371 amino acids. Subcellular localization analysis revealed that the GA3ox protein is distributed in both the nucleus and the cytoplasm. The protein contains two conserved domains, 2OG-FeII_Oxy and DIOX_N, which are highly conserved among members of the Asteraceae family. Quantitative real-time PCR (qRT-PCR) analysis indicated that the highest transcript levels of TeGA3ox were predominantly observed at the late growth stage. Tissue-specific expression profiling showed that leaves consistently exhibited the highest expression among all tissues examined in all three lines. To further elucidate its function, overexpression vectors carrying TeGA3ox were constructed and transformed into Nicotiana tabacum. Compared with wild-type plants, transgenic tobacco lines overexpressing TeGA3ox displayed increased plant height, enlarged leaf area, early stem lignification, prominent auricular stipules, and elevated contents of bioactive gibberellins. Anatomical observations of stem and leaf cross-sections revealed that the cellular alterations in transgenic plants were consistent with the observed phenotypic changes. Collectively, these findings demonstrate that TeGA3ox plays a central role in the regulation of plant height in marigold, providing a mechanistic basis for GA-mediated growth regulation in this ornamental species.