Molecular mechanisms of stress tolerance in plants

Environmental stress conditions such as drought, salt stress and pathogenic fungi affect negatively plant growth and productivity. Therefore, it is necessary to search for new genetic components and strategies for improving resistance and tolerance in crops. In the present thesis, we describe two different approaches that increase our understanding of mechanisms of stress tolerance in plants. The first approach is to study an extreme adaptation to dehydration tolerance from a plant than can "resurrect" after being completely dried. The second study addresses how plant might respond to two different stresses simultaneously, and how one stress can enhance the response to the other. In Chapter 2, we investigate the dehydration tolerance mechanism in the model resurrection grass species Sporobolus stapfianus using a large scale expression profiling of leaf tissues at full hydration, during drying and after re-watering. This study provides some important insights into the gene regulatory mechanisms used by this interesting plant during severe vegetative desiccation and subsequent recovering during re-watering. We also found some genes that are differentially expressed between S. stapfianus and its desiccation sensitive sister species S. pyramidalis. These genes are considered potential candidates for engineering drought tolerant crops. Previous studies have shown a positive effect of chitin (released from the fungal cell wall) on salinity tolerance. In Chapter 3, we explore the cross talk between salt stress and chitin-triggered immune responses. Our results demonstrate a physiological and biochemical link between salinity stress and chitin-triggered innate immunity. Chitin receptors, CERK1 and LYK4, and ANN1, a NaCl- induced calcium permeable channel, interact physically at the plasma membrane and are necessary to modulate early responses (e.g. Ca2+ signaling) to both stresses. Understanding these layers of cross-talk may lead to more sustainable methods to employ innate immunity to protect against both biotic and abiotic stress induced crop losses

An integrated approach to use genetic resources for resurrection plants to enhance drought tolerance in breeding-extension programs [abstract]

Only abstract of poster available.Track V: BiomassThe ultimate goals of this project are to gain a basic understanding of the unique gene and gene regulatory networks that are necessary and sufficient for vegetative tissues to withstand dehydration and then rapidly recover upon rehydration and to use the knowledge gained to develop crops, maize and forage grasses that maintain biomass production under drought condition. Our approach is to combine comparative genomics and phylogenetics to identify genes and gene networks that are adaptive and central to the tolerance of cellular dehydration. This involves the use of resurrection species as models for dehydration tolerance coupled with a suite of comparative bioinformatic tools that allows for the phylogenetic assessment of gene expression patterns in response to dehydration and rehydration. Once the key genetic elements have been identified and assessed we will use a transgenic functional assessment of their involvement in the phenotype, both at a molecular and physiological level, of drought tolerance. One of our key resurrection species is the South African grass Sporobolus stapfianus, which is capable of surviving -240 MPa of water deficit (a hundred times lower than most crop plants). This plant not only serves as a model for monocot crops such as maize and switchgrass, our major targets for crop improvement, but also serves as a direct possibility for an alternate forage grass and biomass source. The improvement of biomass production under drought conditions is not only important for sustainable biofuel production but also for food and energy security. Funded by a CSREES-NRI Grant of $450,000 over three years to PI Mel Oliver USDA-ARS-PGRU Columbia, CoPIs Robert Sharp, University of Missouri; John Cushman, University of Nevada, Reno; Paxton Payton, USDA-ARS-PSRU Lubbock

Agricultural Applications of Biotechnology and the Potential for Biodiversity Valorization in Latin America and the Caribbean

This article provides a brief account of key developments in agricultural applications of biotechnology in Latin American and Caribbean (LAC) countries; it also focuses on the potential of developing value-added products from the biological diversity harbored in the region. Most agricultural biotechnologies involve tissue culture and DNA-based markers for germplasm conservation, production of disease-free planting material, and assistance to genetic improvement. More recently, LAC countries such as Argentina, Brazil, Colombia, Honduras, Mexico, and Uruguay have commercially grown transgenic crops. Advanced biotechnologies, such as genetic sequencing and microarray genomics, are differentially utilized in some LAC countries, with Brazil being at the forefront, for characterization, mapping, and trait screening for important crops and pathogens. There is great potential for the integration of these technologies with chemical analyses in bioprospecting biodiversity. Implementation of effective regulatory frameworks for access, genetic resource benefit sharing, and biosafety need urgent attention in most countries.Includes bibliographical reference