**5.3 lncRNA**

The role of lncRNAs has been well-investigated in the context of plant defense against fungal, bacterial and viral pathogens [89–94]. Furthermore, the functions of a number of plant lncRNAs intricated in plant defenses are experimentally validated. For instance, it has been observed that the lncRNA-ACOD1 is dispensable for viral entrance but not for viral replication in the host [95]. Moreover, when turnip crinkle virus infection occurs in *Arabidopsis*, the expression of the long intergenic ncRNA LINC-AP2 gene is negatively regulated [89]. LncRNA33732 has been characterized to function as a positive regulator in tomatoes, enhancing the expression of the respiratory burst oxidase gene and raising H2O2 build-up, thereby increasing tomato resistance to *Phytophthora infestans* [96]. Also, lncRNA23468 in tomato can compete with endogenous RNA to regulate the NBS-LRR gene by feeding on miRNA482b, thereby controling tomato resistance to *P. infestans* pathogenesis [90]. Numerous lncRNAs have been identified as being modulated in drought, nitrogen-stress and phosphate depletion in maize [97–99]. The maize inbred line B73 tissues were subjected more than 700 high-fidelity RNA-Seq studies, which identified nearly 18,165 maize

lncRNAs [100]. Although lncRNAs are involved in the regulation of plant-microbe interactions, there are no available reports characterizing lncRNA responses to AM fungi, so far as the experimental evidence is considered.
