Document Type

Thesis - University Access Only

Award Date

2012

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Donald Auger

Abstract

The Ac/ Ds transposable element system and B-A tertiary trisomies are two key components in a strategy to generate and maintain mutations that are lethal to the maize gametophyte. The transposition rate of Ac is low in the W22 inbred background so we tested to see if various hybrid combinations would increase the trans-acting effect of Ac upon a Ds reporter gene. Our results indicate that, among the hybrids tested, the W22/W23 hybrid resulted in the most Ds transpositions per ear. We also attempted to establish a baseline transmission rate of a trisomic B-A chromosome (triB-5Sc) from one generation to the next. Interestingly, the transmission rates of this trisomic chromosome were not homogeneous among a sample of 105 testcrosses, but appeared to be clustered around two or more means. These results indicates that our B-A transmission was affected by one or more uncontrolled factors, which could be genetic, epigenetic or environmental. Finally, on a project unrelated to generating gametophyte mutations, we present data on the cDNA sequences of the maize sbel (starch branch enzyme 1) gene from two maize lines: GEMS-0067 and H99. These two lines show a substantial difference in V endosperm amylose composition and sbel appears to be a strong candidate gene. We found twelve polymorphisms between the two at the DNA level and this translated into six amino acid polymorphisms. One amino acid change in the a-amylase domain was particularly interesting. This change was from alanine in H99 to aspartic acid in GEMS-0067. Comparisons to other reference sequences showed that B73, another low amy lose maize inbred, possessed alanine at this position, but that seven unrelated species showed the same amino acid as GEMS-0067. This may indicate that the GEMS-0067 allele is more ancestral.

Library of Congress Subject Headings

Corn -- Genetics
Corn -- Mutation breeding

Publisher

South Dakota State University

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Rights Statement

In Copyright