Identification of microRNA associated with flower organ development in Rosa chinensis ‘Viridiflora’

In this study, two independent microRNA (miRNA) libraries of Rosa chinensis ‘Viridiflora’and ‘Old Blush’ at the flower bud development stage were constructed and sequenced with Illumina sequencing. In total, 39 known miRNAs and 42 known pre-miRNAs were discovered, and 56 novel miRNAs and 57 novel pre-miRNAs were predicted in the ‘Viridiflora’library. In total, 39 known miRNAs and 40 known pre-miRNAs were identified, and 53 novel miRNAs and 57 novel pre-miRNAs were predicted in the ‘Old Blush’ library. Compared with ‘Old Blush’, there were 31 differentially expressed miRNAs in ‘Viridiflora’, with 17 up-regulated and 14 down-regulated. The RT-qPCR results showed that the expressions of miR156, miR398, and miR535 were up-regulated, whereas those of miR167, miR172, and miR396 were down-regulated in ‘Viridiflora’, identical to those obtained by sequencing. The expressions of miR172 and miR156 in different floral organs of the two rose species were detected by RT-qPCR. We found that miR172 was down-regulated in the petals, pistils, and stamens of ‘Viridiflora’. Furthermore, RcAP2 was previously reported to be up-regulated in relative flower organs, suggesting that miR172 may negatively regulate the expression of its target gene RcAP2. Thus, miR172 may play an important role in the development of floral organs of ‘Viridiflora’.