Genetic and physiological characterizations of the ripening-related never-ripe (Nr) and high-pigment (hp) mutants of tomato /
Mutations at the tomato Never-ripe (Nr) or high-pigment (hp)
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739364581&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Mutations at the tomato Never-ripe (Nr) or high-pigment (hp) loci result in aberration of normal fruit ripening. Nr is pleiotropic, influencing many aspects of plant growth and development such as senescence, abscission, and fruit ripening. It has been reported to be dominant. Using the triple response assay, Nr seedlings were observed to be partially insensitive to erogenous ethylene in concentrations as low as 1 ppm. The residual response to ethylene in Nr is much more attenuated than observed in wild type. Heterozygous Nr displays intermediate ethylene insensitivity. This co-dominant phenotypic marker was used to score a segregating population and thus Nr was placed on the tomato RFLP map. The placement of NR and an Arabidopsis ETR1-like sequence at the same locus in the tomato genetic map facilitated the rapid identification and cloning of the NR gene. A tomato genomic clone which is homologous to Arabidopsis ETRI cosegregates with NR in a segregating population. Collaborators have shown via genetic complementation that the tomato NR gene is a homolog of ETRI which is an ethylene receptor. The recessive hp mutation also produces pleiotropic symptoms and is characterized by increased pigment accumulation in most tissues. The hp- related overproduction of anthocyanin in germinating seedlings is intensified by red light. This phenotype was employed to facilitate RFLP mapping of the hp locus. It is suggested that phytochrome responses are amplified in the hp mutant which maintains normal levels of phytochrome. Three RAPD markers linked to hp were identified and indicated that hp is located on chromosome 2 of the tomato map rather than chromosome 12 as previously reported. Relocation of the hp locus was confirmed by linkage analysis of RFLP markers on chromosome 2. The closest flanking markers are 1.6 and 5.0 cM away from both sides of hp locus. A map-based cloning strategy could partially be adopted to isolate the HP gene. HP is suggested to be a negative regulator controlling phytochrome responses in the tomato light signal transduction pathway. |
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| Item Description: | Vita. "Major Subject: Plant Physiology". |
| Physical Description: | xi, 148 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 120-147. |