High-Throughput Sequencing And Degradome Analysis Of Salt Stress-Responsive MicroRNAs In Paulownia Fortunei

Salt is a major abiotic stress that limits tree growth and timber yield. Micro RNAs(mi RNAs) have been found to play important roles in nearly all of the biological, metabolic, and stress-response processes of woody plants. To identify and investigate salt-related mi RNAs in Paulownia fortunei(P. fortunei), we constructed and sequenced two small RNA libraries(PF2 and PF2-S4). A total of 33 conserved and 80 novel mi RNAs were identified in the two libraries by High-Throughput Sequencing. Among these mi RNAs, 27 mi RNAs(3 conserved and 24 novel) were differentially expressed and 45 mi RNAs(13 conserved and 32 novel) were significantly differentially expressed in response to salt stress in P. fortunei, respectively. Degradome analysis identified 61 target genes of 34 mi RNAs in PF2 degradome library and 64 target genes of 35 mi RNAs in PF2-S4 degradome library, respectively. Subsequently, the mi RNA targets were assigned Gene Ontology(GO) terms under the three GO categories. Of these, 56 target genes were involved in molecular function, 52 target genes were involved in cellular component, and 52 target genes were involved in biological process. Finally, six of the differentially expressed mi RNAs and eight target genes were confirmed by quantitative real-time polymerase chain reaction.In this study, some mi RNA targets in P. fortunei may be involved in salt stress-responses were discussion. For example, the annotation of Dof zinc finger protein and F-box protein were mapped to pfo-mi R5021a/5021 b targets, E3 ubiquitin-protein ligase RGLG2 was mapped to pfo-mi R157a/157 b, THO complex subunit 3-like was mapped to pfo-mir843, and histone H2/H2 A was mapped to pfo-mir580. These mi RNAs and their target genes may participate in the salt stress-responses in P. fortunei.In summary, we detected P. fortunei mi RNAs and their target genes with expression profiles that changed under salt stress. These results may help increase the understanding of how mi RNAs respond to salt stress in P. fortunei and provided a reference for salt-resistance breeding of paulownia.