Abstract
Wild watermelon is a desert plant showing the strong tolerance to drought stress. This plant is unique in that development of its root system is significantly promoted in response to the onset of drought, which offers adaptive advantage for absorbing water from deep soil layer under water deficit conditions. However, molecular mechanism responsible for this physiological response has been largely uncharacterized. To gain information on the genetic factors involved in this process, change in the root transcriptome under drought was compared between wild and domesticated watermelon plants by microarray analysis. Out of 8,069 genes analyzed in this study, expression levels of 79 genes were found to be up-regulated by drought in the root of wild watermelon but unchanged in domesticated watermelon. These differentially-expressed genes included zinc-finger-type and myb-type transcriptional factors, raising the possibility that these genes may function as key regulators for promoting root growth in wild watermelon under drought. We are currently analyzing the function of these genes using transgenic approach in hairy root system for wild and domesticated watermelon plants.
