Regulation of Medicago truncatula GH3 Genes Expression by Auxin and Macrophomina phaseolina Infection

Macrophomina phaseolina is a soil-borne necrotrophic fungus that causes charcoal rot disease in a wild range of plant hosts. Currently, there is no effective management approach to control the disease, and genetic engineering of resistant crop is hindered by our limited knowledge on the molecular mechanisms of the disease. To better understand the molecular interactions between M. phaseolina and its plant hosts, we established a model pathosystem using Medicago truncatula. Plant hormone auxin has been shown to be involved in plant disease development. Mutations in several GH3 genes that encode IAA-amido synthases for maintaining auxin homeostasis resulted in changes in disease responses to various pathogens. In this study, we characterized the expression of seven GH3 genes identified in Medicago genome. Using real-time quantitative PCR (RT-qPCR), we investigated the expression of Medicago GH3 genes in response to auxin and M. phaseolina infection. We hope that these findings will lead to a better understanding on the compatible interaction between M. phaseolina and its plant hosts.