Title

The role of ethylene in auxin-mediated root development and isolation and characterization of Arabidopsis mutants with altered auxin-responsive gene expression

Date of Completion

January 2002

Keywords

Biology, Molecular|Biology, Plant Physiology

Degree

Ph.D.

Abstract

Plant hormone auxin plays an important role in many aspects of plant growth and development. One of the major challenges in understanding auxin action is to understand the mechanisms of interaction between auxin and other hormones. For example, it has been shown that both auxin and ethylene regulate plant root growth and development and auxin stimulates ethylene production in the plant. Therefore, a role of ethylene in auxin actions has been suggested. The availability of a large number of auxin and ethylene related mutants in Arabidopsis provide us an ideal experimental system for elucidating the interaction between these two hormones. Using ethylene and auxin related mutants and ethylene biosynthesis and action inhibitors, we have shown in the present study that both ethylene dependent and independent pathways exist in auxin-mediated inhibition of root elongation. Also, both endogenous ethylene and exogenous auxin-induced ethylene play a role in lateral root formation of Arabidopsis. ^ Since isolation and characterization of mutants is widely used for studying auxin signaling. To further understand the auxin actions in plant growth and development, we have isolated four recessive mutants of Arabidopsis with altered expression of the auxin-inducible GH3 gene promoter/GUS reporter gene. All mutants isolated show dramatic changes in morphology that is related to lateral meristem development and were roughly mapped. Since GH3 gene is a primary auxin-response gene, further characterization of these mutants at molecular level may lead to the identification of components in the signal transduction pathways leading to the expression of auxin-inducible GH3 genes. ^