Integrated miRNA-mRNA analysis reveals the roles of miRNAs in the replanting benefit of Achyranthes bidentata roots

The yield and quality of the medicinal plant Achyranthes bidentata can be increased when it is replanted into a field cultivated previously with the same crop, however, fundamental aspects of its biology (so-called "replanting benefit") still remain to be elucidated. miRNAs are sRNA molecules involved in the post-transcriptional regulation of gene expression in plant biological processes. Here, 267 conserved and 36 novel miRNAs were identified in A. bidentata roots. We compared the miRNA content of the roots (R1) from first-year planting with that of the roots (R2) of second-year replanting, and screened 21 differentially expressed (DE) miRNAs. Based on in silico functional analysis, integrated miRNA-mRNA datasets allowed the identification of 10 miRNA-target family modules, which might participate in the benefit. The expression profiles of the miRNA-target modules were potentially correlated with the presence of the replanting benefit. The indication was that the miRNA-responsive continuous monoculture could reprogram miRNA-mRNA expression patterns, which possibly promote the root growth and development, enhance its transport activity and strengthen its tolerance to various stresses, thereby improving A. bidentata productivity as observed in the replanting benefit. Our study provides basic data for further research on the molecular mechanisms of the benefit in A. bidentata.