Permanent fixation of an I/d-Spm insertion

Abstract

INTRODUCTION 1 2. LITERATURE REVIEW 2.1. Discovery of Transposable Elements 5 2.1.1. Variegation in plants 5 2.1.2. McClintock's pioneering work in maize 2.2. General features of Transposable Elements 2.2.1. Genetic traits 2.2.2. Molecular traits 2.3. Transposable Element Systems in Maize 2.3.1. Basis of classification of systems 2.3.2. Summary of the systems identified in maize 2.4. The £r7/Spm Transposable Element System of Maize 2.4.1. Discovery of £r?/Sp/77 system 2.4.2. Molecular Cloning of fn/Spm element 2.4.3. Genetic functions of £f7/Sp/77 and their molecular basis 2.4.3.1. S function 20 2.4.3.2. M Function 2.4.3.3. A function 2.4.3.4. The Coex function 2.4.4. Model for En/Spm transposition 2.4.5. Regulation of En/Spm expression 34 2.4.5.1. Negative regulation of f/7/Sp/77 2.4.5.2. Positive regulation of En/Spm expression 40 2.4.5.3. Autoregulation of En/Spm 2.4.5.4. Modifiers of En/Spm expression 2.4.5.5. Environmental effect on En/Spm expression 43 2.5. States of Transposable Element function 43 2.5.2. The basis of states 46 2.5.2.1. The position hypothesis 46 2.5.2.2. The composition hypothesis 46 2.5.2.3. Genetic and molecular evidence 46 2.6. Transposable Elements as Introns 49 2.6.1. General features of introns 49 2.6.2. Features of introns in plants 50 2.6.3. Certain transposable element inserts behave as introns in maize 52 2.6.4. Relation to origin of introns 55 iii 2.7. Stability of Transposable Elements 2.7.1. Identification of stable inserts 2.7.2. Causes for stability 2.7.2.1. Stability related to methylation of transposable elements 2.7.2.2. Stability related to changes in the cis determinants of transposition 2.7.2.3. Stability related to size of the insert 2.7.3. Degree of stability of the transposable element inserts. . 2.8. Pervasiveness of Transposable Element Inserts in Maize 2.9. Consequences of Transposition Events 2.9.1. Chromosomal rearrangements 2.9.2. Footprints as sources of genetic variation 2.9.3. Transposons as gene tags 3. MATERIALS AND METHODS 3.1. Maize Kernel 3.1.1. Genes expressed in aleurone 3.