Study of the role of type III LTPs during the symbiotic interaction between Sinorhizobium meliloti and Medicago truncatula.

Lipid transfer proteins (LTPs) are small basic proteins that constitute a large family characterized by the ability to transfer phospholipids between a donor and an acceptor membrane. Numerous plant LTPs have been characterized for their antimicrobial activity, suggesting for these proteins a direct role in the protection against pathogenic microorganisms. Another group of LTPs seems to be involved in structural events in the extracellular matrix through binding and transport of hydrophobic molecules. Recently it has been demonstrated that MtN5, a non specific LTPs (ns-LTPs) classified as type III (Wang et al., 2012), is involved in the symbiotic interaction between legumes and rhizobia (Pii et al. 2009, Pii et al., 2012). MtN5 is a nod factor responsive gene expressed at a very early phase of rhizobial symbiosis in epidermal cells and root hairs. There are evidences that MtN5 positively regulates the nodulation process. Interestingly, two other putative type III ns-LTPs (Medtr3g055250 and Medtr7g052640) have been identified in Medicago truncatula genome. The aim of this study is to shed light on the role of these ns-LTPs in the symbiotic interaction between M. truncatula and Sinorhizobium meliloti.