|Samac, Deborah - Debby|
Submitted to: North American Alfalfa Improvement Conference
Publication Type: Abstract Only
Publication Acceptance Date: 7/17/2000
Publication Date: N/A
Technical Abstract: The annual medic, Medicago truncatula (barrel medic), is the focus of functional and comparative genomic studies in a number of laboratories world wide. Functional genomic studies are currently focusing on plant- microbe interactions, particularly nodulation by Sinorhizobium meliloti, mycorrhizal interactions, and host-pathogen interactions. In our laboratories, five cDNA libraries were constructed from nitrogen-fixing nodules, senescent nodules, leaves and cotyledons, leaves infected with Colletotrichum trifolii, and roots infected with Phytophthora medicaginis. More than 2,400 clones have been sequenced from the 5' end from each library. The EST sequence data are available from the M. truncatula database (http://chrysie.tamu.edu/medicago.mtdb). To identify ESTs associated with plant-microbe interactions, several hundred ESTs were chosen to analyze on nylon filter macroarrays. Probes were prepared to compare expression in healthy roots to infected roots, mature nodules to senescent nodules, healthy leaves to infected leaves, and roots to nodules. The greatest differences were between roots and nodules in which 26 ESTs were down-regulated in nodules and 69 ESTs were up-regulated in nodules, including 44 ESTs of unknown function. In infected roots and leaves, 11 ESTs were up-regulated in both interactions and 5 ESTs were down-regulated indicating that these ESTs are involved in general host defense mechanisms. Seven ESTs were regulated similarly in infected tissues and nodules, adding support to the observation that symbiosis and pathogenesis share some common molecular processes. The similarities between genes of M. truncatula and alfalfa and common symbiotic and pathogenic interactions can be employed to facilitate alfalfa improvement.