Abstract:

Objective To identify the function of DoDELLA2, the major gene of the DELLA gene family in Dendrobium officinale, in plant morphological development, and to investigate the downstream genes and signaling pathways regulated by the DoDELLA2 gene, so as to provide a theoretical basis for the molecular breeding of D. officinale. Method RT-qPCR was employed to analyze the tissue expressions of members of the DELLA gene family in D. officinale, and a potential major gene DoDELLA2 of the DELLA gene family in D. officinale was screened out. The full-length DoDELLA2 gene was synthesized, followed by the construction of the 35S-DoDELLA2 overexpressing vector for heterologous transformation into Arabidopsis thaliana. Functional studies were conducted by combining phenotypic observation with transcriptome data analysis. Result Compared with the wild type, A. thaliana overexpressing DoDELLA2 showed phenotypic differences in the growth period, including a 10-16 d delay in bolting time, a significant 40.04% reduction in plant height, elliptical leaf apices with deeper leaf margin serrations, and a significant increase in the number of siliques but a significant reduction in silique length. Transcriptome analysis revealed 696 differentially expressed genes (DEGs) between DoDELLA2-overexpressing A. thaliana and the wild type. Among these, the significantly enriched up-regulated genes mainly included protein-coding genes such as transporter proteins, gibberellin synthetases, and cysteine-rich secretory proteins. The significantly enriched down-regulated genes mainly included the peroxidase protein superfamily, cytochrome P450 protein superfamily, and plant pathogenesis-related protein (PR1). The DEGs were significantly enriched in biological processes such as lignin biosynthesis and the transition from vegetative to reproductive growth, as well as KEGG pathways including phenylpropane biosynthesis, flavonoid biosynthesis, and diterpenoid biosynthesis. Additionally, the expressions of key gibberellin biosynthesis enzyme genes AtGA₂₀OX2, AtGA₂₀OX3, and AtGA₃OX1 were upregulated, showing obvious feedback regulation. Conclusion The overexpression of the DoDELLA2 gene influenced the morphological development of A. thaliana by regulating downstream genes in the GA signaling pathway. Transcriptome differential analysis indicated that DoDELLA2 overexpression significantly affected the expressions of gibberellin synthase genes and certain resistance gene families, providing important targets and a theoretical foundation for molecular breeding practices aimed at improving the quality and traits of Dendrobium officinale.

Key words: Dendrobium officinale, DoDELLA2, tissue expression pattern, Arabidopsis thaliana, heterologous expression, dwarfing, transcriptome, differentially expressed genes