Early onset of the legume-rhizobia symbiosis: Detection of early nodulin gene activity in M. truncatula seeds following Nod Factor exposure.

RAMIREZ, G. A., BOSCHETTO, B. AND BRELLES-MARIÑO, G

Los Angeles, California, Estados Unidos de America

Simposio; Microbiology: Beyond Human Disease Symposium.Southern California Academy of Sciences (SCAS) Annual Meeting; 2010

Southern California Academy of Sciences

The Legume-Rhizobia symbiosis provides leguminous plants with reduced nitrogen forms that are directly incorporated into plant metabolic cycles.  This symbiotic interaction implies a sustainable agricultural practice that fertilizes crops and remediates nitrogen depleted soils. The symbiotic interaction is mediated by a complex molecular dialogue between Medicago plants and their respective prokaryotic symbionts.  Plant developmental changes needed for this symbiosis begin by the perception of rhizobial excreted signal molecules called Nod Factors (NFs).  In mature M. truncatula root systems, the expression of early nodulin (ENOD) genes is triggered by exposure to NFs.  Here we present results of the activity of M. truncatula ENOD genes, following NF exposure, in seeds.  Surface sterilized M. truncatula seeds were exposed to a 10-8 NF solution for 6hrs under vacuum infiltration.  Following NF exposure, total RNA was extracted from seed tissue and analyzed via RT PCR for the activity of the early nodulin genes ENOD11, ENOD12, ENOD16, ENOD20 and MtN21.  So far, we have detected NF induced activity of at least one ENOD gene, ENOD20, in M. truncatula seeds.  To our knowledge, this is the first time that ENOD gene activity has been detected at the seed level of plant development. These preliminary results suggest that NF perception mechanisms could be present at the seed developmental level and not be, as suggested by the current literature, exclusive to the root system found in mature M. truncatula plants.  Additional work, including the analysis of other M. truncatula ENOD genes, will be needed to confirm these preliminary observations.