| Summary: | 博士 === 國立臺灣大學 === 農業化學研究所 === 95 === The effects of the endocrine disrupter, di-n-butyl phthalate (DBP), on the growth of leaf vegetable Bok choy (Brassica rapa subsp. chinensis) and Chinese cabbage (Brassica rapa var. chinensis) were investigated. The results showed that leaves of Bok choy became white in color with the occurrence of chlorosis and necrosis upon treating with 30 mg L-1 DBP in hydroponic culture for 42 days. Transmission electron microscopic images revealed that changes in the chloroplast structures accompanied the chlorosis. In addition, a decrease in biomass and chlorophyll, and accumulation of DBP, were found in DBP-treated Bok choy.
The proteome of the leaf tissue was analyzed using 2-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS). Six protein spots were identified from 2-DE that showed reproducible differences in expression between the normal control and the DBP-treated Bok choy. Based on proteome level studies two protein spots increased were identified as superoxide dismutase (SOD) and peroxidase 21 precursor. These proteins are believed to increase in expression in response to free radical exposure as a detoxification mechanism. The other four protein spots disappeared on the leaf of treatment with DBP were identified as heat shock cognate protein 80, protein disulfide isomerase precursor, apocytochrome f precursor, and RNA polymerase beta subunit. These results are indicated that DBP might affect the polypeptide folding, electron transport chain and DNA transcription in the Bok choy cell and cause the restriction of growth and development in Bok choy.
Besides, the results of Chinese cabbage showed that leaves turned yellow in color with the occurrence of etiolation upon treating with 50 mg L-1 DBP for 42 days. Examination of grana structure in chloroplast under the TEM revealed the organelle unchanged in the tissue of yellow leaf. In addition, a decrease in biomass and chlorophyll, and accumulation of DBP, were found in DBP-treated Chinese cabbage.
There are also six protein spots were identified in 2-DE that showed reproducible differences in expression between the normal control and the DBP-treated Chinese cabbage. Three proteins were found or increased in amount and another three proteins were decreased or disappeared. Three protein spots increased were identified as acyl-[acyl-carrier-protein] desaturase (acyl-ACP desaturase), root phototropism protein 3 (RPT3) and ferredoxin-nitrite reductase (Fd-NiR). The three are responsible for the fatty acid biosynthesis, signal transduction of the phototropic response and nitrate assimilation in plant cells. These results are indicated that DBP seems to induce some physiological reactions increasing in the Chinese cabbage cell.
The other three protein spots that disappeared in Chinese cabbage on treatment with DBP were identified as dihydroflavonol-4-reductase (DFR), aminoacyl-tRNA synthetase (aaRS) and ATP synthase subunit beta. The results in this part revealed some damages or disorder of metabolism inside the Chinese cabbage cell that may partially be attributed to the change in the amounts of some proteins in the cell. Decrease of DFR indicated that DBP might affect the flavonoid biosynthesis and floral color development in the Chinese cabbage cell. This effect might the cause of Chinese cabbage leaf change to yellow. Decrease of aaRS indicated that DBP might affect the aminoacylation of tRNA and other transcriptional or translational regulation in the Chinese cabbage cell. This effect might cause some disorders of regular metabolism or development of Chinese cabbage. Decreased of ATP synthase subunit beta indicated that ATP synthesis in the Chinese cabbage cell might be affected by DBP and cause the restriction of growth and development in Chinese cabbage. From our results, we might say that DBP seems to induce some physiological reactions increasing and also cause the restriction of growth and development in Chinese cabbage. These results seem partially the same as that of Bok choy.
This study indicated that the growth and morphology of Bok choy and Chinese cabbage showed a significant dose-response relationship upon treatment with DBP in a hydroponic culture medium. Furthermore, DBP also affects the proteome formation as well as the physiology and the morphology of Bok choy and Chinese cabbage during growth.
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