Leaf biomechanical properties in Arabidopsis thaliana polysaccharide mutants affect drought survival.

Individual sugars are the building blocks of cell wall polysaccharides, which in turn comprise a plant׳s overall architectural structure. But which sugars play the most prominent role in maintaining a plant׳s mechanical stability during large cellular deformations induced by drought? We investigated the individual contributions of several genes that are involved in the synthesis of monosaccharides which are important for cell wall structure. We then measured drought tolerance and mechanical integrity during simulated drought in Arabidopsis thaliana. To assess mechanical properties, we designed a small-scale tensile tester for measuring failure strain, ultimate tensile stress, work to failure, toughness, and elastic modulus of 6-week-old leaves in both hydrated and drought-simulated states. Col-0 mutants used in this study include those deficient in lignin, cellulose, components of hemicellulose such as xylose and fucose, the pectic components arabinose and rhamnose, as well as mutants with enhanced arabinose and total pectin content. We found that drought tolerance is correlated to the mechanical and architectural stability of leaves as they experience dehydration. Of the mutants, S096418 with mutations for reduced xylose and galactose was the least drought tolerant, while the arabinose-altered CS8578 mutants were the least affected by water loss. There were also notable correlations between drought tolerance and mechanical properties in the diminished rhamnose mutant, CS8575 and the dehydrogenase-disrupted S120106. Our findings suggest that components of hemicellulose and pectins affect leaf biomechanical properties and may play an important role in the ability of this model system to survive drought.

Pandemic (H1N1) 2009-associated deaths detected by unexplained death and medical examiner surveillance.

During the pandemic (H1N1) 2009 outbreak, Minnesota, New Mexico, and Oregon used several surveillance methods to detect associated deaths. Surveillance using unexplained death and medical examiner data allowed for detection of 34 (18%) pandemic (H1N1) 2009-associated deaths that were not detected by hospital-based surveillance.

The 2009 H1N1 influenza pandemic and Minnesota's K-12 schools: public health lessons learned.

Prior to 2009, influenza pandemic planners had primarily planned for a virus that would originate in a location other than North America, giving public health officials in the United States time to determine its severity before widespread disease occurred here. Thus, response plans for schools focused on closure in the case of a severe pandemic and potential closure in the event of a moderate one. The 2009 H1N1 pandemic, however, presented a different scenario. The severity of 2009 H1N1 was initially unknown and later was determined to be mild to moderate. Thus, as the pandemic unfolded, state and national public health entities found themselves adapting their recommendations for school closure. This article reviews Minnesota's experience with 2009 H1N1, focusing on the pandemic among school-aged children during the spring (April to August 2009) and fall (September 2009 to April 2010), and it chronicles how outbreak surveillance policies and recommendations for K-12 schools changed over the course of the pandemic.