sRNAs involved in the regulation of plant developmental processes are altered during the root-knot nematode interaction for feeding site formation

Plant parasitic root- knot nematodes (RKNs; Meloidogyne spp.) are a significant threat for the agriculture as they infect multiple crops, causing severe economic losses worldwide. Most of the effective chemical nematicides have been or are in the process of being banned on the basis of their harmful effect to the environment and human health. These nematodes penetrate the root, migrate intercellularly and establish in the vascular cylinder. Then, nematode effectors delivered into the plant cells alter the plant development to induce their feeding cells, called giant cells (GCs) that serve to nourish them till life cycle completion. The GCs are embedded into a swelling in the root, called gall, formed by the proliferation and/or hypertrophy of the surrounding tissues. Further studies on the development of the nematode-feeding sites, i.e. to deepen into the molecular bases of the plant-nematode interaction, are required to identify alternative approaches for nematode control. Here, we summarize recent advances specifically in the role of the small RNAs during the compatible interactions between RKNs and Arabidopsis and tomato hosts. Most of the studies describe the deregulation in the galls and/or GCs of gene regulatory modules composed by miRNAs and transcription factors which have already an assigned function during development and/or organogenesis processes in the plant. This may point to a role for these miRNAs as molecular hubs of pathways triggered either by developmental plant cues or by a biotic stress as the nematode infection.