Localization and expression of carotenoid biosynthetic enzymes in endosperms of Zea mays and Oryza sativa.
Item
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Title
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Localization and expression of carotenoid biosynthetic enzymes in endosperms of Zea mays and Oryza sativa.
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Identifier
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AAI9917719
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identifier
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9917719
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Creator
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Yu, Jia.
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Contributor
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Adviser: Eleanore T. Wurtzel
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Date
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1999
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry | Biology, Molecular | Biology, Cell
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Abstract
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Carotenoids are essential pigments existing in all green tissues, that also accumulate in the endosperm of maize (Zea mays) but not in rice (Oryza sativa). To investigate the difference in carotenoid accumulation between maize and rice, I carried out parallel studies where I measured carotenoid levels, and expression and localization of two carotenoid biosynthetic enzymes. To study the expression of the carotenoid enzymes phytoene synthase (PSY) and phytoene desaturase (PDS), I generated antisera specific to maize PSY and PDS proteins. The antisera detected antigens in both maize and rice; the antigens were predicted to be the processed forms as found in plastids.;In developing maize endosperm, the onset of carotenoid accumulation appeared to correlate with expression of PSY between 10 to 20 days after pollination suggesting that PSY may be a rate limiting enzyme in the carotenoid biosynthetic pathway during early stages of endosperm development. Differences in PSY level detected in various maize tissues suggested that PSY accumulation is under tissue-specific regulation. PSY and PDS proteins were detected in an amyloplast fraction of maize endosperm. Using confocal microscopy, PSY was localized to the envelope, and PDS was present both on the envelope and in the stroma of maize endosperm amyloplasts.;In rice, PSY accumulated at a similar level in embryo and endosperm, but was not detectable in leaf. PSY was not associated with an amyloplast fraction of rice endosperm. Using western analysis and confocal microscopy, I showed that PSY protein was present on the envelope of plastids in the rice embryo, but was found in the cytoplasm of rice endosperm cells. These results suggest that the compound amyloplasts in rice endosperm may be unable to retain the PSY protein. The improper localization of PSY may be the critical reason that carotenoids do not accumulate in rice endosperm.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
