Measurement Of Content Of Benzyl Isothiocyanate And Temporal And Spacial Expression Of Myrosinase Gene Of Papaya

Isothiocyanates(ITCs)being cancer preventive and anticarcinogenic, are important secondary metabolites of cruciferous plants. It's high biological activity has received much attention from food scientist, medical scientist and biologist. Papaya (Carica papaya L.) a large evergreen perennial herbs, is highly nutritional tropical and subtropical fruit. In recent years, aromatic alkyl side chain isothiocyanates components-benzyl isothiocyanate (benzyl isothiocyanate, BITC) has been detected in papaya.In order to systematically investigate BITC content in different organ of papaya, gas chromatography was used to determine the BITC content in roots, stems, leaves, flowers, pulp and seeds of papaya. The results showed that the BITC components could be detected only in flowers and seeds, the content of BITC in the seeds and flowers are 0.111mg/g,0.605mg respectively. Besides, The BITC content also were measured in pulp and seeds at four different developing stages. The results showed that BITC components can be detected in four different developing stage of the seeds. The BITC content in stageⅠ→Ⅳperiod (tender→old) are 0.577mg/g, 0.631mg/g,0.815mg/g,0.605mg/g respectively, obviously, it was the highest in stageⅢ, lowest in stageⅠ. No BITC was detected in pulp.The BITC in Papaya is a enzymatic hydrolysis of benzyl glucosinolate by thioglucosidase (thioglucoside glucosidases, TGG) which is commonly known as mustard thioglucosidase enzyme (Myrosinase, EC). By now, Southern-blot method indicates that there are only two myrosinase genes tgg1, tgg2 in papaya.In order to understand the relationship between the expression level of tggl and tgg2 and the BITC content in papaya, real-time fluorescence quantitative PCR (Real-time PCR) was employed to analyze the temporal-spatial expression of tggl and tgg2 in roots, stems, leaves, flowers, pulp and seeds of papaya. The results show that, tggl is hardly expressed in root, therefore, taking the expression of tggl in root as a reference, the expression of tggl in stems, leaves, flowers, fruit and seeds can all be detected. The highest level of expression of tggl was detected in the stem. Whereas tgg2 is specifically expressed in roots. To sum up, the different expression of tgg1, tgg2 in different organs of papaya suggests that the expression of tggl and tgg2 are tissue-specific. In addition, according to the measurement of BITC content, BITC content can be detected in the flowers and seeds, and the expression level of tggl is high in flowers and seeds. We conclude that the tggl may plays a key role in the hydrolysis process of benzyl glucosinolat releasing the BITC, but the mechanism needs to be further explored.In this study, we investigated the content of BITC in different organ of Papaya and the content of BITC in seeds and pulp at four stages during the fruit developing and maturing process. In addition, real-time quantitative expression of tggl and tgg2 was also studied. This work lay a foundation for research of regulation mechanism of BITC synthesis in Papaya,as well as quality improvement, product development of papaya.