Abstract
MicroRNAs play an important role in plant development and plant responses to various biotic and abiotic stimuli. As one of the most important ornamental crops, rose (Rosa hybrida) possesses several specific morphological and physiological features, including recurrent flowering, highly divergent flower shapes, colors and volatiles. Ethylene plays an important role in regulating petal cell expansion during rose flower opening. Here, we report the population and expression profiles of miRNAs in rose petals during flower opening and in response to ethylene based on high throughput sequencing. We identified a total of 33 conserved miRNAs, as well as 47 putative novel miRNAs were identified from rose petals. The conserved and novel targets to those miRNAs were predicted using the rose floral transcriptome database. Expression profiling revealed that expression of 28 known (84.8% of known miRNAs) and 39 novel (83.0% of novel miRNAs) miRNAs was substantially changed in rose petals during the earlier opening period. We also found that 28 known and 22 novel miRNAs showed expression changes in response to ethylene treatment. Furthermore, we performed integrative analysis of expression profiles of miRNAs and their targets. We found that ethylene-caused expression changes of five miRNAs (miR156, miR164, miR166, miR5139 and rhy-miRC1) were inversely correlated to those of their seven target genes. These results indicate that these miRNA/target modules might be regulated by ethylene and were involved in ethylene-regulated petal growth.
Highlights
MicroRNAs are 20–24 nucleotide-long noncoding RNA species that play profound roles in plant development and in plant responses to abiotic and biotic stimuli by regulating expression of their target genes, mainly at the post-transcriptional level
To obtain a comprehensive survey of miRNAs in rose petals in the rapid growth (RG) period and in response to ethylene treatment, we constructed and sequenced small RNA libraries from petals of unopened buds, opened buds, partially opened flowers, and ethylene-treated flowers
21-nt, 23-nt and 24-nt small RNAs were the major population, consistent with the size of Dicer-like protein cleavage products, and 24-nt was the most dominant, similar to the results obtained from most tested plants, such as Arabidopsis thaliana, rice, tomato, cucumber, apple and peach [7,9,10,11,16,17,31,32]
Summary
MicroRNAs (miRNAs) are 20–24 nucleotide (nt)-long noncoding RNA species that play profound roles in plant development and in plant responses to abiotic and biotic stimuli by regulating expression of their target genes, mainly at the post-transcriptional level. The pri-miRNAs are processed to generate precursor miRNAs (pre-miRNAs) by a protein complex consisting of the Dicer-like 1 (DCL1), the C2H2-zinc finger protein SERRATE 11 (SE), and the double-stranded RNA-binding protein HYPONASTIC LEAVES1 (HYL1) [1]. Mature miRNA duplex (miRNA/ miRNA*) is excised from pre-miRNAs by DCL1 and each strand is methylated by HEN1 protein. The miRNA strand is loaded into the Argonaute (AGO) protein of RNA-induced silencing complex (RISC) to carry out its function [1,2]. Translational repression of targets is the most important way for miRNAmediated regulation in animals, in plants cleavage of the targets is predominant [1,3]
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