Characterization of miRNA160/164 and Their Targets Expression of Beet (Beta vulgaris) Seedlings Under the Salt Tolerance

MicroRNAs (miRNAs) are non-coding endogenous small RNAs that play important roles in plant growth, development, and stress response. Soil salinization leads to environmental and ecological problems, which greatly restricts agricultural production. MiRNAs are activated in various plants in response to salinity stress, although data from beet (Beta vulgaris) is still lacking. We addressed this in the present study by investigating the mechanisms of salt tolerance in the seedlings of two different varieties of beet. We examined the involvement of the miR160 and miR164 and their targets auxin response factor (ARF) and no apical meristem (NAM)–Arabidopsis transcription activation factor (ATAF)–cup-shaped cotyledon (CUC) (collectively referred to as NAC), respectively. Seedlings from different leaf stages were treated with 300 mM NaCl for 0, 12, 24, 48, or 72 h, and miR160-ARF17/18 and miR164-NAC(21/22)/100 expression in roots and leaves was analyzed by quantitative real-time PCR. MiR160/164 expression differed markedly between the two varieties of beet and according to stress duration, organ, and growth stage. Meanwhile, changes in the expression of ARF17/18 and NAC(21/22)/100 were the opposite of those observed for their regulatory miRNAs. These results provide insight into the mechanisms of salt tolerance in this economically valuable crop. The signal pathways of miR160/164 and its target genes ARF17/18 and NAC(21/22)/100 were analyzed by bioinformatics technique using KEGG pathway and Interpro. The results showed that miR160 and its target genes were involved in plant hormone signaling (map04075) and mitogen-activated protein kinase (MAPK) signaling (map04016), through the indirect regulation of the two metabolic pathways, to deal with salt stress.