Identification of miRNAs Responsive to Botrytis cinerea in Herbaceous Peony (Paeonia lactiflora Pall.) by High-Throughput Sequencing.

Herbaceous peony (Paeonia lactiflora Pall.), one of the world's most important ornamental plants, is highly susceptible to Botrytis cinerea, and improving resistance to this pathogenic fungus is a problem yet to be solved. MicroRNAs (miRNAs) play an essential role in resistance to B. cinerea, but until now, no studies have been reported concerning miRNAs induction in P. lactiflora. Here, we constructed and sequenced two small RNA (sRNA) libraries from two B. cinerea-infected P. lactiflora cultivars ("Zifengyu" and "Dafugui") with significantly different levels of resistance to B. cinerea, using the Illumina HiSeq 2000 platform. From the raw reads generated, 4,592,881 and 5,809,796 sRNAs were obtained, and 280 and 306 miRNAs were identified from "Zifengyu" and "Dafugui", respectively. A total of 237 conserved and 7 novel sequences of miRNAs were differentially expressed between the two cultivars, and we predicted and annotated their potential target genes. Subsequently, 7 differentially expressed candidate miRNAs were screened according to their target genes annotated in KEGG pathways, and the expression patterns of miRNAs and corresponding target genes were elucidated. We found that miR5254, miR165a-3p, miR3897-3p and miR6450a might be involved in the P. lactiflora response to B. cinerea infection. These results provide insight into the molecular mechanisms responsible for resistance to B. cinerea in P. lactiflora.