A genetic, molecular, and developmental study of transposable elements in Sorghum bicolor
Abstract
The candystripe variety of Sorghum bicolor displays a variegated pattern of red pigmented tissues in the pericarps, leaves, and stigmas. My dissertation encompasses different studies which are linked by a common theme--the investigation of transposable elements in sorghum. This work can be divided into three parts: a genetic characterization of the candystripe transposable element of sorghum, a molecular genetic study of two transposable elements cloned from sorghum, and a study of sorghum development utilizing the candystripe transposable element. In the first part of my study, I characterized the candystripe transposable element system and pigmentation genes involved in the candystripe phenotype. The variegated pattern appears to be caused by a transposable element inserted into the sorghum Y gene, producing an unstable allele, y-cs. I also found that the y-cs allele controls the pigmentation of the pericarps, leaves, and stigmas of candystripe sorghum plants. In the second part of my study, I molecularly isolated a putative transposable element from candystripe sorghum. This element is a homologue of the maize Activator transposable element family. This sorghum Activator homologue shares the consensus sequence for the 11 bp terminal inverted repeats of Activator elements, and also has 8 bp direct repeats. This homologue has a large deletion within the coding region of the transposase, and it appears to be a non-autonomous element similar to Ds. This region of Activator homology is adjacent to another region that appears to be an element with 150 nucleotide terminal inverted repeats, and appears to be similar to MITEs such as the Tourist element. The third part of my study was an investigation of sorghum vegetative and floral development utilizing the clonally-derived sectors of red tissue produced by the reversion of the y-cs allele. Through clonal analysis, I have determined that there is little compartmentalization of cell lineages in the sorghum apical meristem. The somatic tissues of the sorghum inflorescence and the vegetative structures share closely related cell lineages. However, the cell lineages of the gametophytic tissues of the inflorescence diverge from that of the somatic tissues of the pericarps early in the development of the panicle, and before the divergence of the pericarps and leaves. These data show that the development of the sorghum panicle is more similar to the development of the maize tassel than the maize ear.
Degree
Ph.D.
Advisors
Bennetzen, Purdue University.
Subject Area
Genetics|Molecular biology|Botany
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