THE ROLE OF ABA IN THE FLORAL TRANSITION: SITE AND MECHANISM OF ACTION

The reproductive success of plants depends on their developmental plasticity that is the ability to modulate their growth in response to exogenous and endogenous stimuli. Plants efficiently integrate these signals to coordinate their life cycle according to the best conditions to increase their fitness. Light and water availability is a limiting factor for plants sustenance and growth. In Arabidopsis thaliana day length (photoperiod) and water status influence flowering time. In particular, water deficit accelerates flowering thus enabling the drought escape (DE) responses. Interestingly, such DE responses only occurs under inductive long day conditions (LDs, typical of spring and summer seasons) but not short day conditions (SDs) highlighting a link between photoperiod perception and drought responses. The phytohormone abscisic acid (ABA) mediates the DE response, by promoting the upregulation of the florigen genes FLOWERING LOCUS T (FT) and its paralogue TWIN SISTER OF FT (TSF), whose expression is activated mainly by LDs. The role of ABA in flowering regulation is controversial as the literature describes both positive and negative roles for ABA in flowering. My PhD work supports the idea that ABA acts as florigen-stimulating molecule under LDs and its activity depends on prior activation of the photoperiodic pathway. I demonstrated that the ABA-dependent activation of FT requires GIGANTEA (GI) and CONSTANS (CO) functions, two main components of the photoperiodic pathway that control florigen expression. The generation of transgenic plants over-expressing tagged versions of GI or CO proteins in different ABA genetic backgrounds allowed me to directly asses their activity and measure their accumulations under varying levels of ABA signalling. My results indicate that ABA promotes GI and CO function without affecting their protein stability. An intriguing perspective of my work is that ABA might regulate GI and/or CO accessibility to the FT promoter. Further studies are however necessary to test this hypothesis and to decipher the molecular mechanism by which ABA allow plants to coordinate flowering time according to the prevailing watering conditions

Secondary Transition Predictors of Postschool Success: An Update to the Research Base

Research suggests youth with disabilities are less likely to experience positive outcomes compared to peers without disabilities. Identification of in-school predictors of postschool success can provide teachers (e.g., special education, general education, career technical education), administrators, district-level personnel, and vocational rehabilitation counselors with information to design, evaluate, and improve transition programs. The purpose of this systematic literature review was to examine secondary transition correlational literature to identify additional evidence to support existing predictors and identify new predictors of postschool success. Results provided additional evidence for 14 existing predictors and identified three new predictors. Limitations and implications for research, policy, and practice are discussed

ABA-dependent control of GIGANTEA signalling enables drought escape via up-regulation of FLOWERING LOCUS T in Arabidopsis thaliana

One strategy deployed by plants to endure water scarcity is to accelerate the transition to flowering adaptively via the drought escape (DE) response. In Arabidopsis thaliana, activation of the DE response requires the photoperiodic response gene GIGANTEA (GI) and the florigen genes FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF). The phytohormone abscisic acid (ABA) is also required for the DE response, by promoting the transcriptional up-regulation of the florigen genes. The mode of interaction between ABA and the photoperiodic genes remains obscure. In this work we use a genetic approach to demonstrate that ABA modulates GI signalling and consequently its ability to activate the florigen genes. We also reveal that the ABA-dependent activation of FT, but not TSF, requires CONSTANS (CO) and that impairing ABA signalling dramatically reduces the expression of florigen genes with little effect on the CO transcript profile. ABA signalling thus has an impact on the core genes of photoperiodic signalling GI and CO by modulating their downstream function and/or activities rather than their transcript accumulation. In addition, we show that as well as promoting flowering, ABA simultaneously represses flowering, independent of the florigen genes. Genetic analysis indicates that the target of the repressive function of ABA is the flowering-promoting gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), a transcription factor integrating floral cues in the shoot meristem. Our study suggests that variations in ABA signalling provide different developmental information that allows plants to co-ordinate the onset of the reproductive phase according to the available water resources.Matteo Riboni, Alice Robustelli Test, Massimo Galbiati, Chiara Tonelli, Lucio Cont

The relationship between habitual physical activity status and executive function in individuals with Alzheimer’s disease: a longitudinal, cross-lagged panel analysis

To determine whether habitual physical activity status specifically influences executive function change in Alzheimer’s disease (AD) over 1 year. In this longitudinal cohort study, 45 participants with AD were recruited and provided follow-up data approximately 1 year later. Executive function measures (map search task, digit symbol substitution task, controlled oral word association task, verbal fluency task) and habitual physical activity measures (Physical Activity Scale for the Elderly (PASE) and handgrip strength) were taken at baseline and follow-up. Individual composites were subsequently created. Additional demographic, lifestyle, and neuropsychiatric measures were also taken. In a structural equation model (χ2(26) = 9.84, p = .998, comparative fit index = 1.00, root mean square error of approximation = .00), a significant association was found between habitual physical activity and executive function change (β = .27, p = .04). In a cross-lagged panel analysis, a significant path was found between the PASE score and executive change (β = .22, p = .01). As higher habitual physical activity levels were associated with reduced executive function change, the promotion of low-intensity habitual physical activities in individuals with a diagnosis of AD may be warranted. Further research is needed, however, to explore the impact of habitual physical activity on the trajectory of change across cognitive domains, and how this relates to the progression of the underlying pathology associated with this disease

Updating the Secondary Transition Research Base: Evidence- and Research-Based Practices in Functional Skills

Transition education should be grounded in quality research. To do so, educators need information on which practices are effective for teaching students with disabilities transition-related skills. The purpose of this systematic literature review was to identify evidence-based and research-based practices in secondary special education and transition for students with disabilities. This systematic review resulted in the identification of nine secondary transition evidence-based practices and 22 research-based practices across more than 45 different transition-related skills. The range of effects for each of the secondary transition evidence-based and research-based practices identified are also included. Limitations and implications for future research, policy, and practice are discussed

Molecular Basis of the ABA Dependent Modulation of CONSTANS Activity in Drought Escape Response

Plants ability to adapt their development in response to environmental changes is one key factor underlying their evolutionary success. Phytohormones modulate different plant\u2013environment interactions, namely the regulation of flowering time that is crucial to synchronize the onset of the reproductive phase with the most favorable conditions. In Arabidopsis thaliana the plant hormone abscisic acid (ABA), known to regulate various drought stress responses, promotes flowering under long day but not short day conditions. Genetic analyses support a model where ABA signals interact with the photoperiodic pathway, upstream of the flowering gene FLOWERING LOCUS T. Aims of my project are to define how ABA and photoperiod signaling interact. My genetic data indicates that ABA promotes flowering by modulating the activity of the FT activator CONSTANS (CO) rather than its transcriptional regulation. Initial data about the molecular basis of this ABA\u2013CO interaction will be presented. Our study point to CO as the key integrator between ABA signals and the photoperiodic pathway, allowing plants to coordinate flowering time according to the prevailing watering conditions