| In ornamental plant, especially orchids, the floral color and fragrance are crucial to their ornamental and commercial value and play important roles in attracting pollinators. Phalaenopsis type dendrobium usually refer to "Phalaenopsis" Dendrobium series, the main floral color of which is purple. Most of the cultivated varieties do not have the aroma, but they have a high ornamental value and are important tropical orchid cut-flowers and potted products and widely used as garlands and table flowers.To clarify the relationship between the floral color, pigments and the related genes of Den. phalaenopsis varieties, the color phenotype, total flavonoid and total anthocyanins of dendrobium petals was measured, and real-time quantitative PCR (qRT-PCR) was used to analyse. Then key genes of regulating the floral color of Den. phalaenopsis was selected, and a particle bombardment was used to test the functions of these genes. The results are as follows:(1) Via color pigments and petal color phenotype analysis of 18 different varieties, the total anthocyanin and total flavonoids contents were both had a significant negative correlation with L*, b*.and C*,which indicated that with the increase of total anthocyanin and total flavonoid content, the color deepened, the brightness reduced, the blue hue increased, and the color turned less vivid; the total anthocyanin content and a* values showed a significant positive correlation, which demonstrated that the accumulation of anthocyanins helped to improve the degree of red.(2) Through the relative expression of 28 color related genes of 18 varieties with different floral colors and 3 varieties with anthocyanin distinctively accumulated in labellum tissues, the transcription factor gene MYB4, bHLH1, enzyme genes in anthocyanin biosynthesis pathway DFR, ANSI, F3H,7GT1, F3'H1 were found to play a decisive role in white colored dendrobium, and the transcription factor gene MYB4, bHLHl as well as enzyme genes DFR, ANSI,7GT1,7GT2,7GT3 were found to play a decisive role in pink colored dendrobium.(3) The key transcription factor MYB4, MYB8, MYB10 and bHLHl was selected. By particle bombardment, MYB4 and bHLHl was found to contribute to the anthocyanin synthesis. Besides, MYB4 plays a positive role in the regulation through transaction activity detected in yeast heterogenous expression.To identify the causes of floral scent of phalaenopsis type dendrobium with different kinds of flavor and the expression profiles of synthase genes related with terpene components, the solid-phase microextraction (SPME) and gas chromatography coupled with mass spectrometry (GC-MS) were employed to analyze the key volatile components of different varieties, and the relative expression level of those genes were analyzed using qRT-PCR assay. The results are as follows:(1) Five aroma cultivars and two non-fragrant varieties of dendrobium were selected, and bloom flowers were chosen. The results showed that there were 45 volatiles identified in seven varieties, including 34 kinds of terpenes,9 kinds of aromatics and 2 kinds of esters. Five aroma varieties volatile components mostly was terpene, and the terpene played an important role in formatting aroma of dendrobium. By comparison: the main volatiles of 5 aroma dendrobium were 3-carene, linalool, a-copaene. The volatiles and relative contents of different specie were significantly different. The main components of Den. Hand Green and Den. Burana Sunrise No.2 were 3-carene, while the emission rate of Den. Burana Sunrise No.2 was about 3 times of Den. Hand Green's; main volatiles of Den. K.B. White 607's were 3-carene, ?-copaene, and linalool; In Den. Blue Sapphine 256, the relative contents of ?-farnesene is highest; Den. Burana Charming's main volatiles were ?-copaene, followed by 1,2-Benzenedicarboxylic acid, bis (2-methylpropyl) ester. There were identified less volatiles in two non-fragrant vavieties, the main volatiles emission rate of which were also smaller; Den. Red Bull's main volatile was homosalate; and the most important volatile was isoeugenol in Den. Sunya Sunshine. The main volatile components played a decisive role of aroma of different varieties.(2) The major perfuming tissue was petal in Den. Hand Green and Den. K.B. White 607, followed by the lip. In Den. Burana Sunrise No.2 the main tissue was sepal followed by the petal and lip followed. And in Den. Blue Sapphine 256 the main tissue was petal, sepal and lip followed. The probable terpene synthesis gene is TS1?TS2?LS in Den. Hand Green, TS2?TS3?LS in Den. Burana Sunrise, RS in Den. Blue Sapphine 256. Flower petal was the major perfuming tissue, but the column was seldom perfuming. Floral volatile components were influenced by the sampling time and the flower development. The expression pattern of 8 scent related genes in various cultivars, and tissues were different. The relation between expressions of gene and accumulation of terpene content in dendrobium needs further study.The research found the key enzyme genes and regulator genes which controlled the formation of different floral color dendrobium, and cleared main floral volatiles of several phalaenopsis type dendrobium varieties and the main perfuming tissues. The research provides some theoretical basis for future study of genetic engineering of color and scent in dendrobium. |
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