The Cell Wall as a Barrier Against Water Loss and Plant Pathogens

The ability to survive a range of stresses is crucial to the survival of plants. Structural modifications in the cell wall through pectin cross linkages may be key to mitigating damage caused by stress. Pectin reduces cell wall permeability and increases rigidity through calcium ion crosslinks to carboxylate ions in galacturonic acid residues in homogalacturonan, and boron crosslinks to apiosyl residues in rhamnogalacturonan II side chains. The objective of this research was to understand the influence of calcium and boron in vitro, and how changes in viscosity and rigidity may translate to resistance to dehydration and fungal pathogens in Allium spp. and Arabidopsis pectin methylesterase/boron mutant genotypes. Allium spp. served as an ideal model to study dehydration stress as the cells are large and a single layer of epidermal cells can be easily separated. Arabidopsis was useful given the availability of mutant genotypes. CaCl2 and H3BO3 were both found to significantly (p0.05) and Colletotrichum higginsianum infection (p<0.05). Because of the mechanism of infection, the rapid rate of Colletotrichum higginsianum infection in bor1 is indicative of a weak cell wall. While the response to stress is highly complex, collectively this thesis indicates calcium, boron, pectin and the cell wall in general may play important but relatively under researched roles in plant resistance to both abiotic and biotic stress

Discrete brittle to distributed shearing; Results from analysis of the deep portions of the Cajon Pass Drill Hole

We performed systematic structural and geochemical analyses on a suite of cored rocks from the vertical Cajon Pass, California drill hole to characterize the deformation and alteration of fault-related rocks. The drill hole lies 4 km northeast of the San Andreas Fault (SAF), and observations of deformed crystalline rock in core and outcrop provide a sample of a 5-km vertical column adjacent to the steeply dipping Cleghorn fault and span the brittle to semi-brittle deformational regime at hydrothermal conditions. The rocks in the upper 500 m of the borehole are composed of sandstones and granitoid augen gneiss, with narrow fault and fracture zones coated with thin seams of laumontite. Below 500 m depth in the core, tonalite gneiss and migmatite contain well-developed discrete brittle faults and fracture zones. Thirty-seven faults are recognized in the core and borehole data; eleven are newly identified here, eight were previously identified in the core, and the remainder are interpreted from borehole image log data. The size of the fault zones intersected by the core controls the extent and nature of deformation. Distribution of faults in the core increase with depth, and fracture densities are greater around fault zones. In the upper 2600 m of the hole, the faults and fractures are typically narrow with thin coatings of alteration products. Prominent fault zones at 2100 - 2300 and 2500 - 2600 m measured depth dip moderately to steeply, and within this fault distributed shearing and alteration textures are common. Microstructures in these fault zones primarily include shear fractures containing a matrix of laumontite with angular to sub-angular clasts within the matrix and record multiple cycles of deformation and alteration. Laumontite mineralization indicates moderate- to high-temperature fluids interacting with the rocks throughout most of the column. The most significant fault observed in the core is an indurated, steep-dipping zone at 3,402 m depth that exhibits evidence of a mixture of brittle and semi-brittle deformation and abundant mineralization and alteration of potassium feldspar and epidote. This fault correlates well with the left-lateral steeply dipping Cleghorn fault, and reflects the interaction between hydrothermal metasomatic alteration and brittle fracture, cataclastic flow, to incipient plastic deformation processes at depth. The interpretation that the fault zone at the bottom of the hole is the Cleghorn fault agrees with stress orientation measurements made there by M D. Zoback and coworkers and indicates that the faults in the drill hole reflect active deformation and alteration associated with northeast-oriented maximum horizontal stress that may drive the left-lateral oblique motion on the Cleghorn fault. The data also show that damage zones associated with faults are present here, and may consist of mixed mode deformation, indicating a long-lived presence of the deformed and altered zones of reduced elastic moduli associated with faults. Simple modeling of the thermodynamics of syntectonic reactions in the fault zones indicate that earthquakes can be the source of heat to drive the reactions, and thus earthquake energy may be consumed in the fault core and damage zone by focused alteration

The personalized advantage index: Translating research on prediction into individualized treatment recommendations. A demonstration

Background: Advances in personalized medicine require the identification of variables that predict differential response to treatments as well as the development and refinement of methods to transform predictive information into actionable recommendations. Objective: To illustrate and test a new method for integrating predictive information to aid in treatment selection, using data from a randomized treatment comparison. Method: Data from a trial of antidepressant medications (N = 104) versus cognitive behavioral therapy (N = 50) for Major Depressive Disorder were used to produce predictions of post-treatment scores on the Hamilton Rating Scale for Depression (HRSD) in each of the two treatments for each of the 154 patients. The patient's own data were not used in the models that yielded these predictions. Five pre-randomization variables that predicted differential response (marital status, employment status, life events, comorbid personality disorder, and prior medication trials) were included in regression models, permitting the calculation of each patient's Personalized Advantage Index (PAI), in HRSD units. Results: For 60% of the sample a clinically meaningful advantage (PAI≥3) was predicted for one of the treatments, relative to the other. When these patients were divided into those randomly assigned to their "Optimal" treatment versus those assigned to their "Non-optimal" treatment, outcomes in the former group were superior (d = 0.58, 95% CI .17-1.01). Conclusions: This approach to treatment selection, implemented in the context of two equally effective treatments, yielded effects that, if obtained prospectively, would rival those routinely observed in comparisons of active versus control treatments. © 2014 DeRubeis et al