Isolating and characterizing components in phytochrome signaling networks.
Item
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Title
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Isolating and characterizing components in phytochrome signaling networks.
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Identifier
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AAI3127912
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identifier
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3127912
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Creator
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Qiu, Caihong.
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Contributor
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Adviser: Timothy W. Short
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Date
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2004
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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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Biology, Cell | Biology, Molecular | Biology, Plant Physiology
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Abstract
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Light is life for plants. At least three classes of photoreceptors, red/far-red light sensing phytochromes, blue/UV-A light absorbing cryptochromes and phototropins, and at least one UV-B light receptor, have been found to regulate plant growth and development.;By screening for the most severe phenotypes that severely affect light signaling, various alleles of different photoreceptor mutations and their downstream components have been isolated. There mutations completely block one or more branches of light signaling responses. Using a novel screen of an EMS mutagenized pool for less severe phenotypes under white light, three mutants, designated deficient photomorphogenesis---dep1, dep2 and dep3 have been isolated.;Upon characterizing the mutants, it was demonstrated that dep1 and dep2 display intermediate phenotypes of several light-regulated responses involving red, far-red, and even blue light, whereas dep3 displayed much stronger deficiencies than either dep1 or dep2 for all phenotypes investigated, especially in FR-regulated responses, and approaching those of phyA null mutants. All dep mutants express wild type levels of PHYA apoprotein, and normal phyA degradation kinetics once photoconverted to the active form, indicating that dep mutants do not affect chromophore synthesis, its attachment to phytochromes, or the photoconvertability of phyA. DEP1 and DEP2 may represent two components downstream of shared light signaling pathways, and DEP3 is strongly affected in phyA signaling but also participates in other parts of the phytochrome transduction network.;Using SSLP, CAPs, AFLP, and SNP mapping techniques, DEP1 and DEP3 have been mapped to two different sites on the top of chromosome 1, and DEP2 maps to the bottom of chromosome 4.;dep3 has been cloned and found to encode a novel mutant allele of phyA, designated phyA-401, with two missense changes in conserved amino acids within the chromophore binding pocket region. Spectrophotometry and Western Blotting data suggest that phyA-401 produces defective phyA that is not photoreversible because it is impaired in light-induced conversion of Pfr (light unstable form) to Pr (stable), and leading to the rapid degradation of phyA upon its conversion to Pfr.
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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.
