Plants sense and respond to changes in their environment. For example, elongation of the embryonic stem ensures seedlings reach light after they germinate. This critical stage in a plant’s life is highly regulated by hormones, including gibberellic acid (GA) and brassinosteroids (BRs). Using the model system Arabidopsis thaliana, we discovered GA and BRs interact to control stem elongation during early development. We found that treating seedlings with both hormones resulted in a synergistic growth response during some phases of development but not others. We are exploring the genetic basis of this response using seedlings mutant in different aspects of their GA and BR pathways. For example, DWF4ox seedlings over-express a gene that encodes a BR biosynthetic enzyme. These seedlings make more BRs and have an enhanced growth response. DELLAs (RGA and GAI) repress growth and are degraded by GA. Seedlings that have reduced DELLA (rga gai) function also have enhanced growth. We are testing the growth responses of the DWF4ox rga gai triple mutant looking at hypocotyl elongation rates. By using these and other mutants that have compromised GA and BR pathways we hope to better understand the molecular mechanism of the interaction between these two hormones.

Plants use hormone-signaling pathways to regulate growth and development. Brassinosteroids (BRs) are critical plant hormones that regulate growth such as the elongation of the embryonic stem. We study the specific mechanism of this process by testing the hormone-induced growth responses of both wild type and mutant Arabidopsis seedlings. We are testing whether growth repressor SPATULA is involved in BR growth response. We hypothesized that the growth repressor SPATULA is downstream of the BR pathway. To test this hypothesis, we acquired mutants that lack SPATULA function. After confirming the genotype of the mutants by PCR, we used a high-resolution camera to observe growth throughout early development in response to hormone treatments. Data is recorded by the camera over the course of 132 hours. The images are then analyzed and growth rates are calculated. Using these data, we determined if SPATULA is involved in the BR growth response.

Essentially all growth and developmental processes in plants require action of the hormone auxin. Auxin regulates gene expression by mediating the degradation of repressor proteins called Aux/IAAs. At low concentrations of auxin, these IAA proteins repress auxin-responsive genes by binding to auxin response factor (ARF) activating transcription factors. A subset of ARF and IAA proteins are involved in the initiation of new lateral roots, which are important for overall root architecture and function. Mutant phenotypes in these ARFs and IAAs fall into two separate classes. Based on this evidence, we hypothesize that the structural properties of specific ARF and IAA proteins cause them to have specific binding preferences. For example, we predict that ARF5 has stronger binding preference for IAA12 than IAA14, while ARF7 has stronger preference for IAA14. To test interactions between these proteins, we are expressing them in the yeast, S. cerevisiae. This allows us to look at individual protein interactions at single cell resolution, which is not possible using a plant based system due to the ubiquity of auxin responses and the presence of multiple IAAs and ARFs. We are using a bimolecular fluorescence complementation approach, in which two complementary halves of fluorescent proteins are fused to two interacting proteins of interest. Specifically, we have fused halves of different fluorescent proteins to IAAs and ARFs, such that each specific IAA-ARF complex exhibits a different color of fluorescence. Using this system, we will compete two different IAA proteins for binding of a single ARF. This approach will allow us to analyze the binding preferences of proteins through quantitative comparison of fluorescence of protein complexes. The results of my research may explain some of the specificities between ARF and IAA mutant phenotypes found in Arabidopsis and how distinct protein properties lead to differences in gene expression and development.

Despite an increasing US-born population, Asian-Americans are often regarded as perpetual foreigners and unrecognized as ‘American.’ The present research examines whether Asian-Americans that are heavier, a stereotype commonly associated with Americans, are perceived as more American than normal weight Asian-Americans. Sixty-eight students were randomly assigned to see a photo of one of three Asian-American women. The same three women were used in both conditions and photos were edited to reflect a change in weight (the weights estimated by participants differed on average by 46 pounds between conditions). Results showed that heavier Asian-Americans were rated as more likely to have been born in the US and rated as worse at math than normal weight Asian-Americans. This research suggests that weight may reduce the extent to which Asian-Americans are perceived as foreigners and increase acknowledgement of their American identity. 

Solar cells, through their ability to convert energy from light directly into electricity, pose a promising alternative for supplying our world’s growing demand for clean affordable energy. Many factors governing the efficiency of these photovoltaic devices are still being explored and improved upon through methods aimed at boosting photo-voltages, improving energy-conversion efficiency, and finding materials accessible for large-scale production and implementation. Here, I investigate the potential of a new type of solar cell that utilizes electron-impurity Auger de-excitation. I will discuss the effect of Auger de-excitation observed in Mn doped CdS quantum dots and explore the potential for boosting the photo-voltage via the harvesting of hot electrons. I will explain the processes involved in both synthesizing Mn:CdS quantum dots and fabricating quantum dot-based solid-state devices. I will show preliminary results from photoluminescence quenching measurements used to quantify Auger de-excitation in fabricated solid-state devices as well as device properties and characterization measurements. In the future, full-cell PV devices will be constructed and tested against the efficiencies of today’s leading solar cells.