CAREER: Roles for Indole-3-butyric Acid in Plant Development

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The plant hormone auxin regulates plant growth and development to control crop yield. Indole-3-butyric acid, or IBA, is an inactive auxin precursor whose transport throughout the plant and conversion to the active hormone is critical to auxin function. Despite the great importance of IBA to plant growth, the mechanisms controlling IBA input into the level of available auxin are not well understood. This proposal aims to increase our understanding of how IBA-derived auxin impacts plant growth; this understanding will provide new tools to alter plant growth and development for use in crop improvement. This CAREER proposal outlines experiments to elucidate developmental roles for indole-3-butyric acid (IBA) transport and IBA-derived auxin in the model plants Arabidopsis thaliana and Physcomitrella patens. Auxin is essential to plants, controlling cell division and cell expansion to orchestrate many developmental events and environmental responses. IBA is a biologically inactive molecule that is converted into the active auxin IAA (indole-3-acetic acid) by peroxisomal β-oxidation. IBA-derived auxin drives a wide range of seedling developmental processes, including cotyledon and root hair cell expansion, apical hook curvature, high-temperature-induced hypocotyl elongation, lateral root production, and root meristem maintenance. Similar to the active auxin IAA, the auxin precursor IBA is transported by carrier-mediated mechanisms.The proposed experiments focus on understanding roles for IBA transport and IBA-derived auxin in plant development with four specific aims: 1) To determine the tissue-specificity of IBA-to-IAA conversion. 2) To identify components of IBA transport. 3) To characterize TRANSPORTER OF IBA (TOB) family regulation of IBA transport and plant development. 4) To compare the roles of IBA-derived auxin and IBA transport in the nonvascular plant Physcomitrella patens. The proposed studies will advance our understanding of auxin regulation of plant development.This research will also support the creation of an inquiry-based laboratory to increase opportunities for undergraduate research at Washington U. This course addresses a critical need for a cell biology lab course in the curriculum; the primary objectives of this course are to increase student ability to form and test hypotheses and to raise student awareness of the diverse biological systems available for basic research. Aim 4 of this proposal will be directly integrated into the course and students will present their work at the WU Research Symposium at the end of the semester. In addition, this research will support the Missouri Local Auxin Meeting, co-organized by the PI to strengthen and expand the local auxin community, and additional K-12 outreach activities.