Gene expression response of Medicago truncatula roots treated with Nod-LCOs

Legumes interact with rhizobia, leading to the development of root nodules. Diffusible rhizobial signals were identified as Nod-LCOs. Applying Nod-LCOs on plantlet roots, we used GeneChips to detail the global programme of gene expression in response to the external application of Nod-LCOs. To harvest tissues for transcriptome profiling, three biological replicates consisting of 10 plantlets per treatment were selected. After 6 h of incubation in the climate chamber, 10 plantlets per batch were removed from the treatment (Nod-LCOs) or control solutions and harvested. During harvest, one mm of the root tip of each plantlet was removed and discarded. The remaining 2 to 2.5 cm of the distal root region were cut off and directly frozen in liquid nitrogen.