Graduate research assistant, PhD candidate University of Tennessee-Knoxville Knoxville, Tennessee
Body of Abstract: Ethylene is a gaseous plant hormone involved in the regulation of growth and development of plants. Regulation of ethylene has been widely used in controlling crop yield and post-harvest storage. The “triple response assay” of dark grown seedlings is characterized by a shorter hypocotyl and root, thickened hypocotyl, and exaggerated apical hook and is often used to screen for ethylene-related mutants. While conducting a triple response screen, we observed that when seedlings were transferred from dark to light and ethylene-free conditions, the ethylene pretreated seedlings grew larger compared to seedlings not pretreated with ethylene. This included increased primary root growth, higher lateral root length and density, and greater leaf fresh weight. These effects last for the lifetime of the plant. The growth enhancement correlates with an increase in the expression of genes involved in photosynthesis and carbohydrate metabolism, higher carbon assimilation, and increased levels of glucose, starch, and other sugars. Because of this we have termed this ethylene-mediated metabolic priming. This growth enhancement effect occurs in other species of plants including cucumber, tomato, and wheat showing that this priming likely occurs in Angiosperms. Paradoxically, we also found that ethylene-primed seedlings have an increased tolerance against several abiotic stresses like salt, heat, hypoxia, and copper. We exposed 5–7 days old seedlings to these above-mentioned stresses and found a greater percentage of survival in the ones primed with ethylene compared to control seedlings that were unprimed. To understand the underlying mechanism, we are studying core stress genes as well as specific stress genes to determine if ethylene-priming acts similarly on all or only a subset of these stresses.