Degree Type

Dissertation

Date of Award

1995

Degree Name

Doctor of Philosophy

Department

Zoology and Genetics

First Advisor

Randy C. Shoemaker

Abstract

The entire soybean Sle gene family was cloned and characterized. The five Sle genes (Sle1-5) could be divided into two classes based on sequence identity. Sle1-4 map to 4 different linkage groups. Sle1 and Sle5 are expressed weeks earlier in seed development than Sle2 and Sle3. Sle4 is a pseudogene. Maximal levels of Sle mRNA accumulate in the seeds, before desiccation had occurred, and decline rapidly upon seed imbibition. Desiccation does not induce Sle expression in seeds. Unlike most of its homologs, ABA is not necessary to induce Sle expression in cultured embryos and only moderately increases Sle mRNA levels. Sle expression is confined to embryo tissues and Sle mRNA accumulates at similar levels in both the embryo axis and in the cotyledons. Neither ABA nor desiccation induce expression of the Sle genes in vegetative tissues;The DNA sequence of the promoter region of four Sle genes was examined and several putative regulatory motifs were identified. Transcriptional fusion of the Sle1 promoter was able to drive GUS gene expression on both embryo and endosperm of transgenic tobacco seeds. Mutated versions of the Sle1 promoter were also analyzed. Neither the two G-box core or a third ACGT containing motif appeared to be major sites for proper promoter regulation in tobacco seeds. Rather, the Sphl box and its flanking CCACAT repeats play a major positive role on this response;Taken together these results suggest that an ABA-dependent transduction pathway, acting upon the G-box core motifs or on the proximal ACGT core, does not appear to be the main regulatory pathway controlling the Sle1 gene expression during soybean late embryo development. Therefore, other yet unknown pathway(s) acting upon the Sphl box and its flanking sequences CCACAT sequence is likely to play a major role in Sle1 promoter function.

DOI

https://doi.org/10.31274/rtd-180813-10007

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Éberson Sanches Calvo

Language

en

Proquest ID

AAI9540879

File Format

application/pdf

File Size

116 pages

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