Characterization of Putative Factors Involved in CO2-mediated Stomatal Signaling in Arabidopsis thaliana

With atmospheric CO2 levels steadily increasing, it is important for humans to understand how plants utilize CO2 and release O2 in the air we breathe. Several CO2 signaling components have been characterized, but there are still many unknown components of the CO2 signaling pathway. This thesis characterizes candidate mutant plants from a comprehensive artificial microRNA (amiRNA) forward genetic screen designed to isolate putative mutants involved in CO2 signaling. Each mutant carried an amiRNA specifically designed to downregulate a few genes in Arabidopsis thaliana. 39 putative mutants were isolated and confirmed at the T3 generation. This project aims to elucidate the role of these genes in CO2-mediated stomatal responses and stomatal development. Gas exchange assays under defined changes in CO2 concentrations were performed to quantify the stomatal conductance and kinetic responses of the candidates. Stomatal density assays were performed to quantify the number of stomata of the candidates. The database ePlant and a Python script were utilized to determine potential interactions between the targeted amiRNA loci and known CO2-mediated stomatal signaling components. The results highlight 15 candidate mutants with unique responses to imposed shifts in CO2 concentration and varying stomatal densities compared to HsMYO (wild-type control) plants. 6 of the putative mutants show an inhibited response to defined changes in CO2 concentration or are affected in stomatal development and warrant further investigation. The 6 putative mutants have been retransformed in wild-type plants and will be examined to verify the robustness of the mutant phenotypes seen in this thesis

α-Arrestin ARRDC3 tumor suppressor function is linked to GPCR-induced TAZ activation and breast cancer metastasis.

The α-arrestin domain containing protein 3 (ARRDC3) is a tumor suppressor in triple-negative breast carcinoma (TNBC), a highly metastatic subtype of breast cancer that lacks targeted therapies. Thus, understanding the mechanisms and targets of ARRDC3 in TNBC is important. ARRDC3 regulates trafficking of protease-activated receptor 1 (PAR1, also known as F2R), a G-protein-coupled receptor (GPCR) implicated in breast cancer metastasis. Loss of ARRDC3 causes overexpression of PAR1 and aberrant signaling. Moreover, dysregulation of GPCR-induced Hippo signaling is associated with breast cancer progression. However, the mechanisms responsible for Hippo dysregulation remain unknown. Here, we report that the Hippo pathway transcriptional co-activator TAZ (also known as WWTR1) is the major effector of GPCR signaling and is required for TNBC migration and invasion. Additionally, ARRDC3 suppresses PAR1-induced Hippo signaling via sequestration of TAZ, which occurs independently of ARRDC3-regulated PAR1 trafficking. The ARRDC3 C-terminal PPXY motifs and TAZ WW domain are crucial for this interaction and are required for suppression of TNBC migration and lung metastasis in vivo. These studies are the first to demonstrate a role for ARRDC3 in regulating GPCR-induced TAZ activity in TNBC and reveal multi-faceted tumor suppressor functions of ARRDC3. This article has an associated First Person interview with the first author of the paper

Exploring the Potential of a School Impact on Pupil Weight Status: Exploratory Factor Analysis and Repeat Cross-Sectional Study of the National Child Measurement Programme.

Schools are common sites for obesity prevention interventions. Although many theories suggest that the school context influences weight status, there has been little empirical research. The objective of this study was to explore whether features of the school context were consistently and meaningfully associated with pupil weight status (overweight or obese). Exploratory factor analysis of routinely collected data on 319 primary schools in Devon, England, was used to identify possible school-based contextual factors. Repeated cross-sectional multilevel analysis of five years (2006/07-2010/11) of data from the National Child Measurement Programme was then used to test for consistent and meaningful associations. Four school-based contextual factors were derived which ranked schools according to deprivation, location, resource and prioritisation of physical activity. None of which were meaningfully and consistently associated with pupil weight status, across the five years. The lack of consistent associations between the factors and pupil weight status suggests that the school context is not inherently obesogenic. In contrast, incorporating findings from education research indicates that schools may be equalising weight status, and obesity prevention research, policy and practice might need to address what is happening outside schools and particularly during the school holidays.This article is freely available online via Open Access. Click on the 'Additional Link' above to access the full-text via the publisher's site