Unique and unifying themes in the mechanisms regulating the expression of the arabidopsis thaliana PR-1 and Solanum tuberosum PR-10a inducible defense genes

Arabidopsis is a model plant used to study disease resistance; Solanum tuberosum or potato is a crop species. Both plants possess inducible defense mechanisms that are deployed upon recognition of pathogen invasion. Transcriptional reprogramming is crucial to the activation of defense responses. The Pathogenesis-Related (PR) genes are activated in these defense programs. Expression of Arabidopsis PR-l and potato PR-10a serve as markers for the deployment of defense responses in these plants. PR-l expression indicates induction of systemic acquired resistance (SAR). Activation of SAR requires accumulation of salicylic acid (SA), in addition to the interaction of the non-expressor of pathogenesis-related genes I (NPRI), with the TGA transcription factors. The PR-10a is activated in response to pathogen invasion, wounding and elicitor treatment. PR-10a induction requires recruitment of the Whirly I (Whyl) activator to the promoter. This locus is also negatively regulated by the silencer element binding factor (SEBF). We established that both the PR-l and PR-10a are occupied by repressors under non-inducing conditions. TGA2 was found to be a constitutive resident and repressor of PR-l, which mediates repression by forming an oligomeric complex on the promoter. The DNA-binding activity of this oligomer required the TGA2 N-terminus (NT). Under resting conditions we determined that the PR-10a is bound by a repressosome containing SEBF and curiously the activator Pto interacting protein 4 (Pti4). In the context of this repressosome, SEBF is responsible for PR-10a binding, yet rWe also showed that PR-l and PR-10a are activated by different means. In PR-l activation the NPRI NT domain alleviates TGA2-mediated repression by interacting with the TGA2 NT. TGA2 remains at the PR-l but adopts a dimeric conformation and forms an enhanceosome with NPRl. In contrast, the PR-10a is activated by evicting the repressosome and recruiting Why! to the promoter. These results advance our understanding of the mechanisms regulating PR-l and PR-10a expression under resting and inducing conditions. This study also revealed that the means of regulation for related genes can differ greatly between model and crop s

Starvation Induces Expression of the Plant-Adhesin Gene, Mad2, of the Entomopathogenic Fungus Metarhizium robertsii.

Metarhizium robertsii is an entomopathogenic fungus that is additionally plant rhizosphere competent. Two adhesin-encoding gens, Mad1 and Mad2, are involved in insect pathogenesis or plant root colonization, respectively. This study examined differential expression of the Mad genes for M robertsii grown on a variety of insectand plant-related substrates. Mad1 was up regulated in response to insect cuticles and up regulation of Mad2 resulted from root exudates, tomato stems and non-preferred carbohydrates. A time course analysis that compared water, minimal media, and nutrient rich broth revealed Mad2 gene expression increased as nutrient availability decreased. The regulation of Mad2 compared to known stress-related genes (Hsp30, Hsp70 and ssgA) under various stresses (nutrient, pH, osmotic, oxidative, temperature) revealed Mad2 to be generally up regulated by nutrient starvation only. Examination of the Mad2 promoter region revealed two copies of a stress-response element (S TRE) known to be regulated under the general stress response pathway.

Genetic and Electrophysiological Correlates of Self-Regulation in Adolescence

Self-regulation is considered a powerful predictor of behavioral and mental health outcomes during adolescence and emerging adulthood. In this dissertation I address some electrophysiological and genetic correlates of this important skill set in a series of four studies. Across all studies event-related potentials (ERPs) were recorded as participants responded to tones presented in attended and unattended channels in an auditory selective attention task. In Study 1, examining these ERPs in relation to parental reports on the Behavior Rating Inventory of Executive Function (BRIEF) revealed that an early frontal positivity (EFP) elicited by to-be-ignored/unattended tones was larger in those with poorer self-regulation. As is traditionally found, N1 amplitudes were more negative for the to-be-attended rather than unattended tones. Additionally, N1 latencies to unattended tones correlated with parent-ratings on the BRIEF, where shorter latencies predicted better self-regulation. In Study 2 I tested a model of the associations between selfregulation scores and allelic variations in monoamine neurotransmitter genes, and their concurrent links to ERP markers of attentional control. Allelic variations in dopaminerelated genes predicted both my ERP markers and self-regulatory variables, and played a moderating role in the association between the two. In Study 3 I examined whether training in Integra Mindfulness Martial Arts, an intervention program which trains elements of self-regulation, would lead to improvement in ERP markers of attentional control and parent-report BRIEF scores in a group of adolescents with self-regulatory difficulties. I found that those in the treatment group amplified their processing of attended relative to unattended stimuli over time, and reduced their levels of problematic behaviour whereas those in the waitlist control group showed little to no change on both of these metrics. In Study 4 I examined potential associations between self-regulation and attentional control in a group of emerging adults. Both event-related spectral perturbations (ERSPs) and intertrial coherence (ITC) in the alpha and theta range predicted individual differences in self-regulation. Across the four studies I was able to conclude that real-world self-regulation is indeed associated with the neural markers of attentional control. Targeted interventions focusing on attentional control may improve self-regulation in those experiencing difficulties in this regard.