Stafstrom, Joel P.
M.S. (Master of Science)
Department of Biological Sciences
Peas--Dormancy; Growth (Plants)--Regulation; Plant cell cycle
Apical dominance allows the use of a natural system to study the reversible dormancy/growth cycles found in pea axillary buds. Axillary buds on intact pea seedlings are dormant. After decapitation of the terminal bud, the axillary buds begin to grow rapidly. In this study, the cell cycle has been analyzed using phase-specific expression of cloned genes and flow cytometry. This information was used to determine the relationship between dormancy/growth cycles and regulation of the cell cycle. Several clones were sequenced and their patterns of expression were analyzed by RNA gel blotting. Clones that were identified by sequence similarity were homologs of ribosomal protein L34, histone H2A and histone H4. In small buds (second largest at node two), the expression of ribosomal protein L27 and L34 clones were correlated with the reversible dormancy to growth stages of axillary bud development. Flow cytometry analysis of cells in S-phase demonstrated that dormant buds contained both G1 and G2 cell populations at approximately a 3:1 ratio. Histone H2A and H4 mRNAs (S-phase markers) accumulated within 1 to 6 hours, indicating the G1 cell population had entered S-phase shortly after decapitation. This suggested a G1/S checkpoint that occurred immediately before the S-phase boundary. A peak of mitotic cells 3 hours after decapitation indicated the G2 cell population also began to proliferate shortly after decapitation. This suggested a second checkpoint located directly before the boundary into mitosis (G2/M). These two cell populations, located at the G1/S and G2/M checkpoints, proliferated (entered the cell cycle) shortly after decapitation of the terminal bud.
Devitt, Michelle L., "Development of pea axillary buds : gene expression and cell cycle analysis" (1994). Graduate Research Theses & Dissertations. 2197.
vii, 74 pages
Northern Illinois University
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