Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

James T. Colbert


The regulation of oat phytochrome A (phyA) mRNA stability and the photoregulation of germination of tobacco seeds containing the oat phyA gene was examined using oat phyA containing transgenic tobacco. Oat phyA mRNA has been previously shown to be a relatively unstable mRNA. The intent of this research was to identify elements within the phyA mRNA responsible for rendering the message unstable. The approach taken was to use tobacco transformed with either the full-length or truncated versions of the oat phyA gene and examine the half-lives of the resulting oat phyA mRNAs in transgenic tobacco. RNA blot analysis of oat phyA in both oats and in tobacco transformed with the oat phyA gene showed a pattern of oat phyA hybridizable fragments smaller than the full-length mRNA band. These fragments were thought to be degradation products indicative of a short-lived message. The half-lives of the truncated oat phyA mRNAs were found to be between 90 minutes and four hours. The full-length oat phyA mRNA had a half-life of about four hours in transgenic tobacco. Determination of the half-life of both truncated and full-length oat phyA mRNAs in transgenic tobacco suggests that the amount of oat phyA hybridizable fragments does not correlate with mRNA half-life. Germination of seeds from wild-type tobacco plants requires light. Approximately 20% of the seeds from transgenic tobacco plants containing the oat phyA gene and grown under fluorescent lighting were found to germinate in the dark. Seeds from transgenic tobacco grown under fluorescent and incandescent lighting did not germinate in darkness. A higher percentage of seeds from both wild-type and transgenic plants were found to germinate when imbibed in the presence of nitrate. About 50% of the seeds from transgenic plants grown in the presence of incandescent lighting and imbibed in the presence of nitrate germinated in darkness. The higher level of phytochrome in the transgenic seedlings promoted germination and was sensitive to the light conditions under which the parent plants were grown. These findings suggest that phyA plays a role in promoting germination in tobacco seeds.



Digital Repository @ Iowa State University,

Copyright Owner

Linda Joanne Barnes



Proquest ID


File Format


File Size

80 pages