Abstract:In this study, the flower of a sweet osmanthus cultivar ‘Rixiang Gui’ was used as experimental material, the cloning of OfRAP212 gene were conducted by RTPCR, and bioinformatic analysis was performed to comprise its expression in different tissues, flower development stages and daily cycles in two sweet osmanthus cultivars ‘Rixiang Gui’ with a light aroma and ‘Boye Jinui’ with a strong aroma, by identifying the subcellular location of the encoded protein, and further analyzing the correlation between gene expression and the content of floral scent to explore its relationship with floral scent. The relationship lays a foundation for the research on the molecular mechanism of sweet osmanthus floral scent. The results showed: (1) the OfRAP212 gene of Osmanthus fragrans was successfully cloned. The length of the target fragment was 1 367 bp, containing an ORF of 966 bp in length, encoding 321 amino acids. (2) Sequence and phylogenetic analyses showed that OfRAP212 contained the conserved domain of RAP212, belonging to ERF subfamily, from the core Eudicots and was clustered into the Oleaceae clade, showing a lineagespecific trait. (3) Online prediction results shows that OfRAP212 protein is located in the nucleus, and mainly distributed in the plasma membrane (69%) and endoplasmic reticulum membrane (64%); the 35S∷OfRAP212GFP fusion protein expression vector was constructed, and infected the epidermis of tobacco leaves by bacillusmediated method. Two days later, the laser confocal microscope observation revealed that the 35S∷OfRAP212GFP fusion protein can be clearly observed on the nucleus and the plasma membrane with green fluorescent signal. (4) qRTPCR analysis showed that OfRAP212 exhibited a distinct tissue expression pattern between the two cultivars, ‘Rixiang Gui’ showing the highest expression in the stems, while ‘Boye Jinui’ had the highest expression in the flowers. During flower development stages of the two cultivars, the gene expression level in primary blooming stage was higher than that in other three stages, exhibiting generally an upward trend followed by a downward trend. The daily analysis found that OfRAP212 existed significant diurnal changes. (5) The correlation analysis showed that the expression of OfRAP212 was consistent with the release of ocimene, and ocimene derivatives. Our results proposed OfRAP212 as a possible candidate gene involving in the regulating of the synthesis of aroma substances. The results showed that OfRAP212 may be involved in the regulation of the synthesis of aroma in sweet osmanthus, and lay the foundation for the molecular mechanism of it. The study showed that OfRAP212 protein of O. fragrans is localized in the nucleus and plasma membrane. The expression trend of OfRAP212 gene is consistent with the release of O. fragrans floral scent, and OfRAP212 may participate in the synthesis and regulation of O. fragrans aroma.