Abstract
BackgroundMicroRNAs (miRNAs) represent a class of small ncRNAs that repress gene expression on the post-transcriptional level by the degradation or translation inhibition of target mRNA.MethodologyThree small RNA libraries from oyster haemocytes were sequenced on the Illumina platform to investigate the latent immunomodulation of miRNAs after bacteria challenge and heat stress. Totally, 10,498,663, 8,588,606 and 9,679,663 high-quality reads were obtained in the control, bacteria and bacteria+heat library, respectively, from which 199 oyster miRNAs including 71 known and 128 novel ones were identified. Among these miRNAs, 6 known and 23 novel ones were predicted to possess more than one precursor-coding region, and cgi-miR-10a, cgi-miR-184b, cgi-miR-100, cgi-miR-1984 and cgi-miR-67a were observed to be the most abundant miRNAs in the control library. The expression levels of 22 miRNAs in the bacteria library were significantly higher than those in the control library, while there were another 33 miRNAs whose expression levels were significantly lower than that in the control library. Meanwhile, the expression levels of 65 miRNAs in the bacteria+heat library changed significantly compared to those in the bacteria library. The target genes of these differentially expressed miRNAs were annotated, and they fell in immune and stress-related GO terms including antioxidant, cell killing, death, immune system process, and response to stimulus. Furthermore, there were 42 differentially expressed miRNAs detected in both control/bacteria and bacteria/bacteria+heat comparisons, among which 9 miRNAs displayed the identical pattern in the two comparisons, and the expression alterations of 8 miRNAs were confirmed using quantitative RT-PCR.ConclusionsThese results indicated collectively that immune challenge could induce the expression of immune-related miRNAs, which might modulate the immune response such as redox reaction, phagocytosis and apoptosis, and the expression of some immune-related miRNAs could be also regulated by heat stress to improve the environmental adaption of oyster.
Highlights
MicroRNAs are endogenously encoded singlestranded non-coding RNAs of about 22 nt in length [1]
These results indicated collectively that immune challenge could induce the expression of immune-related miRNAs, which might modulate the immune response such as redox reaction, phagocytosis and apoptosis, and the expression of some immune-related miRNAs could be regulated by heat stress to improve the environmental adaption of oyster
After transferring into the cytoplasm, the precursor miRNA is further cleaved by Dicer into the functional double-stranded RNA, which is incorporated into the RNA-induced silencing complex (RISC) and forms the mature miRNA [2,3]
Summary
MicroRNAs (miRNAs) are endogenously encoded singlestranded non-coding RNAs of about 22 nt in length [1]. They are initially transcribed by RNA polymerase II in the nucleus as primary miRNAs, which are cleaved by the nuclear RNase III type enzyme Drosha to produce a short hairpin precursor miRNA. Mature miRNAs have the ability to regulate the stability and/or translational efficiency of their mRNA targets in metazoa through the imperfect base-pairing between target transcript and the 59 seed region of the miRNA [5]. MicroRNAs (miRNAs) represent a class of small ncRNAs that repress gene expression on the posttranscriptional level by the degradation or translation inhibition of target mRNA
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