Honors Theses

Date of Award


Document Type

Undergraduate Thesis



First Advisor

Sarah Liljegren

Relational Format



The purpose of this project was to explore the function of SHOOTMERISTEMLESS (STM) and ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1), two transcription factors in Arabidopsis thaliana that play a role in the molecular pathways that establish organ boundaries in flowers. Prior research has shownthat mutations in the STM and ATH1 genes cause defects in the boundaries formed between floral organs and the stem of the plant. My study was designed to investigate whether ATH1 and STM also control the boundaries found between adjacent floral organs. I predicted that stm ath1-3 double mutant flowers would display a significant number of stamen-stamen and sepal-sepal fusion events compared to wild-type flowers, which would indicate that the boundaries between these organs had been compromised. Stem cells found in flower meristems are required for a full set of floral organs to develop. Since STM are ATH1 are known to play roles in maintaining the population of stem cells in both shoot and flower meristems, stm ath1-3 double mutant flowers were also expected to produce fewer organs compared to wild-type flowers. I found that 15 percent of the stamens in stm and ath1-3 single mutant flowers, and 51 percent of the stamens in stm ath1-3 double mutant flowers were fused to another stamen. I also found that 95 percent of the sepals in the double mutant flowers were fused to a neighboring sepal. The stm ath1-3 mutant flowers produced three fewer petals and three fewer stamens on average. These results indicate that STM and ATH1 redundantly regulate boundaries formed between stamens and petals. They also demonstrate that STM and ATH1 regulate the size of the flower meristem and that their functions are required for that meristem to correctly produce all of its organs.

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