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Suppression Of Phytoene Desaturase Gene Affects On The Function Of Photosynthesis

Posted on:2011-01-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:M WangFull Text:PDF
GTID:1100360308454603Subject:Biomolecular Engineering
Abstract/Summary:PDF Full Text Request
The plant carotenoid biosynthetic pathway is localized in the plastid and well elucidated in recent years. Carotenoids are essential components of the photosynthetic apparatus in plants, in which they significantly contribute both to the harvesting of light for subsequent photochemistry and to photoprotection of photosystems by dissipating excess light energy. It is known that photosynthesis apparatus work as a whole organization, especially the pigment-protein complexes which act in light reaction. Therefore it was deduced that the exact aggregation of pigments and proteins underlies the highly efficient photosynthetic apparatus in which the precisely quantified matching is a pre-requisite.Alterations to the pigments content were found in transgenic tobacco leaves with RNAi mediated suppression of phytoene desaturase gene (pds gene). Plants showed different degrees of albinism and PSII efficiency was decreased significantly in the blocky plants. The total carotenoid contents decreased. The ratio of chlorophyll (Chl) a to b was unchanged while the content of both of Chl a, b declined. The grana stacking of thylakoid in the green part of variegation section was the same as in the control and etioplast was found in the white sector of leaf. Native green gel analysis and pigments determination showed that the ratios of Chl a/b in PSI, PSII core, and LHCII were not altered in pds-silenced plants. SDS-PAGE indicated that the Chl-binding complexes of PSI and PSII core kept unchanged in transgenics, but LHCII complexes were altered. A new band around 50kDa was noted and the density of the protein around 18kDa significantly increased. Chl fluorescence kinetics showed that energy transferring and photosynthesis of pds-silenced plants were inhibited under both high and moderate light conditions. It can be deduced that the number of Chl molecules in every LHCII protein complex reduced, thus the energy transferring may be influenced, which resulted in the practical PSII efficiency declined severely. The antioxidant enzymes did not work in line with each other, which may explain why the albinism of the leaves appeared. These observations suggest the exact matching of pigments and proteins is important for energy absorption and transfer in photosynthesis and mismatching of them can cause malfunction of PSII.
Keywords/Search Tags:carotenoid, pds gene, photosynthesis, RNAi, Chlorophyll fluorescence
PDF Full Text Request
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