Genetic and biochemical characterization of the maize mutants floury-2 and modified opaque-2

Persistent Link:
http://hdl.handle.net/10150/186409
Title:
Genetic and biochemical characterization of the maize mutants floury-2 and modified opaque-2
Author:
Lopes, Mauricio Antonio
Issue Date:
1993
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The maize mutations floury-2 (fl2) and opaque-2 (o2) reduce endosperm storage protein synthesis and lead to accumulation of protein fractions that are nutritionally more balanced. However, this advantage is offset by the soft and fragile texture of the endosperm, which gives the grain inferior quality for harvesting, storage, and processing. Further development and future usefulness of these materials may depend upon deciphering the genetic, biochemical and molecular mechanisms that affect seed physical structure and nutritional quality. The soft endosperm of the maize floury-2 (fl2) mutant is associated with a reduction in zein mRNA and protein synthesis, and enhanced levels of a 70-kD protein shown to be the maize homolog of the chaperonin BiP. An unusual alpha-zein protein of 24-kD was found to be consistently associated with the storage protein fraction from fl2 mutants. Increases in accumulation of this novel alpha-zein protein is correlated with increases in BiP accumulation and decreases in storage protein deposition. Also, an RFLP that is unique to fl2 was detected with a 22-KD alpha-zein probe. The synthesis of an abnormal alpha-zein protein in fl2 could explain many features of the mutant, such as abnormal protein body morphology, BiP induction and hypostasis to o2. These findings indicate that the effects of the fl2 mutation could be a response to accumulation of a defective protein that causes impairment of secretory protein synthesis. Breeding methods based on accumulation of o2 modifier genes led to the development of mutant germplasm with normal kernel phenotype and enhanced nutritional value. However, these modified mutants have not yet reached widespread commercial production because the components and mode of action of the genetic system involved in seed modification are largely unknown. Detailed genetic and biochemical characterization of endosperm modification in o2 indicated that two independent modifier genes act in a semidominant fashion to increase seed hardness and accumulation of the storage protein gamma-zein. Genetic mapping experiments together with molecular analysis indicated gamma-zein genes as components of the o2 modifier system. Also the use of RFLP, RAPD and bulked segregant analysis to locate a second endosperm modifier locus is described.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic.; Molecular biology.; Genetics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Plant Sciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Larkins, Brian

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleGenetic and biochemical characterization of the maize mutants floury-2 and modified opaque-2en_US
dc.creatorLopes, Mauricio Antonioen_US
dc.contributor.authorLopes, Mauricio Antonioen_US
dc.date.issued1993en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe maize mutations floury-2 (fl2) and opaque-2 (o2) reduce endosperm storage protein synthesis and lead to accumulation of protein fractions that are nutritionally more balanced. However, this advantage is offset by the soft and fragile texture of the endosperm, which gives the grain inferior quality for harvesting, storage, and processing. Further development and future usefulness of these materials may depend upon deciphering the genetic, biochemical and molecular mechanisms that affect seed physical structure and nutritional quality. The soft endosperm of the maize floury-2 (fl2) mutant is associated with a reduction in zein mRNA and protein synthesis, and enhanced levels of a 70-kD protein shown to be the maize homolog of the chaperonin BiP. An unusual alpha-zein protein of 24-kD was found to be consistently associated with the storage protein fraction from fl2 mutants. Increases in accumulation of this novel alpha-zein protein is correlated with increases in BiP accumulation and decreases in storage protein deposition. Also, an RFLP that is unique to fl2 was detected with a 22-KD alpha-zein probe. The synthesis of an abnormal alpha-zein protein in fl2 could explain many features of the mutant, such as abnormal protein body morphology, BiP induction and hypostasis to o2. These findings indicate that the effects of the fl2 mutation could be a response to accumulation of a defective protein that causes impairment of secretory protein synthesis. Breeding methods based on accumulation of o2 modifier genes led to the development of mutant germplasm with normal kernel phenotype and enhanced nutritional value. However, these modified mutants have not yet reached widespread commercial production because the components and mode of action of the genetic system involved in seed modification are largely unknown. Detailed genetic and biochemical characterization of endosperm modification in o2 indicated that two independent modifier genes act in a semidominant fashion to increase seed hardness and accumulation of the storage protein gamma-zein. Genetic mapping experiments together with molecular analysis indicated gamma-zein genes as components of the o2 modifier system. Also the use of RFLP, RAPD and bulked segregant analysis to locate a second endosperm modifier locus is described.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academic.en_US
dc.subjectMolecular biology.en_US
dc.subjectGenetics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePlant Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairLarkins, Brianen_US
dc.contributor.committeememberPenna, Dean Dellaen_US
dc.contributor.committeememberGalbraith, Daviden_US
dc.contributor.committeememberHelentjaris, Timen_US
dc.contributor.committeememberOishi, Karenen_US
dc.identifier.proquest9408484en_US
dc.identifier.oclc720654085en_US
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