Characterization of conserved and novel microRNAs and their targets, including a TuMV‐induced TIR–NBS–LRR class R gene‐derived novel miRNA in Brassica

Nine conserved miRNA families and three potential novel miRNAs in Brassica rapa were identified from a small RNA library. The expression patterns of some conserved miRNAs had different tissue specificity in Brassica and Arabidopsis. One of the three potential miRNAs, named bra‐miR1885, was verified as a true functional miRNA. It could be induced specifically by Turnip mosaic virus (TuMV) infection, and target TIR–NBS–LRR class disease‐resistant transcripts for cleavage. Based on the hypothesis for de novo generation of new miRNA genes and the sequence similarity between bra‐MIR1885 precursor loci and target transcript sequences, we suggest that bra‐MIR1885 is a new miRNA gene that originated through inverted duplication events from TIR–NBS–LRR class disease‐resistant protein‐coding gene sequences, which became bra‐miR1885 targets.

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