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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

R. Neil Reese


While soybeans (Glycine max [L.] Merr.) produce an abundance of flowers, a rather large portion of them, 32 to 82%, are shed before the seeds begin to fill. This abortion of flowers can occur anywhere on the raceme, but generally the more proximal flowers set and the distal flowers abort (Dybing et al., 1986; Huff and Dybing, 1980). Removal of proximal flowers can induce increased setting of the distal flowers at or before anthesis. In addition, direct application of the synthetic growth regulator benzyladenine or other cytokinins to racemes has been shown to increase pod set by preventing abortion of ovaries that are either pre- or post-anthesis (Dybing and Westgate, 1989; Dyer et al., 1987). Soybean plants were grown in the field in the summer of 1991. Raceme tissues were manipulated to increase set through removal of proximal flowers and/ or exogenous application of cytokinin. Time-course studies of proteins extracted from raceme tissue were conducted and have shown changes in protein synthesis in setting versus aborting racemes. To elucidate the molecular mechanisms involved in floral set, proteins were extracted from treated soybean racemes and separated on polyacrylamide gels. Coomassie blue staining of these gels demonstrated the presence of the 29kD protein in both setting and aborting raceme tissue. However, 35S-methionine incorporation studies indicated that the 29kD protein was only being actively translated in setting as compared to aborting tissue. Western blot analysis demonstrated that the 29kD protein was a soybean Vegetative Storage Protein (VSP), a transient storage protein which is preferentially lost from leaves during seed development (Staswick, 1989b). To study the temporal regulation of transcription of the 29kD VSP, Northern blot analysis was attempted. RNA was isolated from raceme tissue, separated with formaldehyde agarose gel electrophoresis and blotted onto a nylon membrane. A probe specific for VSP29 RNA was propagated, isolated, and successfully labeled with photobiotin. The labeled probe was then hybridized to the northern blots. Failure to detect either the positive controls or the RNA on the membrane, despite repeated attempts, indicated that the detection system of choice lacked adequate sensitivity. Currently work is being done to label the probe with 32P, a more easily detected marker than photobiotin. Elucidation of these mechanisms may lead to a comprehensive understanding of the processes involved in floral set and abortion, and provide insight into the physiological and molecular regulation of plant reproduction, growth and development.

Library of Congress Subject Headings

Soybean -- Flowering




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