G C A T T A C G G C A T genes Article Genome-Wide Transcriptional Changes and Lipid Profile Modifications Induced by Medicago truncatula N5 Overexpression at an Early Stage of the Symbiotic Interaction with Sinorhizobium meliloti Chiara Santi 1, Barbara Molesini 1, Flavia Guzzo 1, Youry Pii 2 ID , Nicola Vitulo 1 and Tiziana Pandolfini 1,* ID 1 Department of Biotechnology, University of Verona, 37134 Verona, Italy;
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[email protected]; Tel.: +39-045-8027918 Received: 30 October 2017; Accepted: 11 December 2017; Published: 19 December 2017 Abstract: Plant lipid-transfer proteins (LTPs) are small basic secreted proteins, which are characterized by lipid-binding capacity and are putatively involved in lipid trafficking. LTPs play a role in several biological processes, including the root nodule symbiosis. In this regard, the Medicago truncatula nodulin 5 (MtN5) LTP has been proved to positively regulate the nodulation capacity, controlling rhizobial infection and nodule primordia invasion. To better define the lipid transfer protein MtN5 function during the symbiosis, we produced MtN5-downregulated and -overexpressing plants, and we analysed the transcriptomic changes occurring in the roots at an early stage of Sinorhizobium meliloti infection. We also carried out the lipid profile analysis of wild type (WT) and MtN5-overexpressing roots after rhizobia infection. The downregulation of MtN5 increased the root hair curling, an early event of rhizobia infection, and concomitantly induced changes in the expression of defence-related genes.