Honors Theses

Date of Award


Document Type

Undergraduate Thesis



First Advisor

Sarah Liljegren

Relational Format



Arabidopsis thaliana, a model plant species, has been heavily studied to determine the genetic contributions that lead to gynoecium development. The Arabidopsis fruit is created from two carpels that form a gynoecium, which contains the stigma, style, and ovary. The ovary is divided into two sub-compartments by a septum, and the ovules develop within the ovary. The fruit’s purpose is to protect, nurture, and eventually disperse the mature ovules, or seeds, and if the septum does not fuse properly, the plant’s fertility will be impacted. SHOOT MERISTEMLESS (STM) and ARABIDOPSIS THALIANA HOMEOBOX GENE1 (ATH1) are two genes that are known to be involved in fruit development, specifically meristem maintenance and organ boundary specification. Plants with mutations in both STM and ATH1 produce fruit with multiple developmental defects. To investigate the effects of stm and ath1 mutations on septum development, I analyzed the septa of stm, ath1, stm/+ ath1, and stm ath1 fruit in comparison to wild-type fruit. Because STM maintains the stem cell population in flower meristems and induces the biosynthesis of cytokinin in the carpel margin meristem (which includes the septum), I hypothesized that stm mutant fruit would display moderate septum defects. Also, because previous studies have shown that ATH1 and STM act redundantly in promoting fruit development, I hypothesized that the stm ath1 double mutant fruit would have enhanced septum defects compared to the stm single mutant. To evaluate the septum fusion defects, I measured the amount of septum surface area missing in relation to the total potential septum surface area for each fruit. This study revealed that 50 of the 51 stm single mutant fruit had septa fusion defects, while none of the ath1-5 fruit had abnormal septa. In addition, I found that the fusion defects present in the stm ath1-5 double mutant were not significantly enhanced relative to the stm single mutant. These results suggest that STM alone plays a critical role in fusion of the septum during fruit development.

Included in

Biochemistry Commons



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