Characterization of lncRNAs in mycorrhizal tomato and elucidation of the role of lncRNA69908 in disease resistance.

Long noncoding RNAs (lncRNAs) have attracted widespread attention because of their meaningful roles in various plant biological processes. However, the potential functions of lncRNAs in the plant-beneficial microorganism interactions have not been fully explored. Arbuscular mycorrhiza (AM) symbiosis is accompanied by the systemic induction of defense responses in the host leaves. In the present study, we globally profiled lncRNA expression and explored their potential regulatory roles in AM fungi-inoculated tomato leaves. Among 851 differentially expressed lncRNAs, a novel lncRNA (lncRNA69908) that was significantly downregulated in the leaves of AM fungi inoculated tomato, affected tomato resistance after pathogen infection. One of the competing endogenous RNA networks, lncRNA69908-sly-miR319c, was verified by using a coexpression system. Silencing of lncRNA69908 or overexpression of sly-miR319c enhanced tomato resistance to Phytophthora infestans, whereas overexpression of lncRNA69908 decreased the reactive oxygen species scavenging. As above, we speculated that lncRNA69908 may be involved in mycorrhiza-induced defense responses. Our findings can broaden the knowledge on the potential regulatory roles of ncRNAs in AM symbiosis.