Cloning and functional characterization of LiDXR gene from Oriental Lily (Lilium ‘Sorbonne’)

Floral scent is an important ornamental shape of garden plants. Monoterpenes in terpenoids are the main components of lily floral scents. 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) plays a role in the second enzymatic reaction of methylerythritol phosphate (MEP) pathway, which is responsible for monoterpene synthesis. However, the function of DXR gene in the floral monoterpene synthesis pathway of Lilium ‘Sorbonne’ remains unclear. In this study, the Lilium oriental ‘Sorbonne’ was used as the experimental material, and the differentially expressed LiDXR gene was selected using the early transcriptomic data. It was found that it had a high consistency with the rater rate process from synthesis to termination of floral substances in the flowering stage of lily. Therefore, the LiDXR gene was cloned and bioinformatics analyzed. A total of 472 amino acids are encoded. The expression of LiDXR gene was the highest at the Sorbonne half opening stage, and the expression of LiDXR gene in petals was significantly higher than that in other flower organs. The results of subcellular localization showed that LiDXR protein was localized in chloroplasts of leaf epidermal cells. A virus-induced gene silencing (VIGS) assay showed that silencing LiDXR can reduce monoterpene levels by down-regulating TPS gene expression downstream of the MEP pathway. Meanwhile, the results of HS-SPME-GC-MS showed that the total volatile terpene content of lily decreased significantly after silenced. The results of overexpressed plants A. thaliana and petunia showed that the transgenic plants had stronger growth potential and advanced flowering time. The GC-MS results of transgenic petunias showed that the content of volatile total terpenes in transgenic strains was 78% higher than that of wild type. Overexpression of LiDXR gene would affect the expression level of MEP pathway genes, and then affect the synthesis of terpenes including monoterpenes downstream of MEP pathway. The purpose of this study was to analyze the function of LiDXR gene and provide theoretical basis for floral breeding of lily and ornamental plants.