Abstract
MicroRNAs (miRNAs) are a class of small, 21-24 nucleotides long, non-coding RNAs involved in the post-transcriptional regulation of gene expression. Using the array analysis on Arabidopsis thaliana infected with the Oil-seed Rape Mosaic Virus (ORMV), we have found 28 up-regulated miRNAs. From them, six were selected for further validation by Northern blot analysis: miRNA172a, miRNA161, miRNA167a&b, miRNA168a&b, miRNA171a, and miRNA159. In addition, 29 miRNAs were detected in plants exposed to drought stress, 13 of those detected miRNAs were up-regulated and 16 down-regulated miRNAs. Out of 29 differentially expressed miRNAs during the abiotic stress, six miRNAs (167a&b, 168a&b, 173, 171b&c, 399d and 447c) were chosen for Northern blot and RT-PCR analysis to confirm the array results. Interestingly, four out of these six miRNAs, 171b&c, 168a&b, 399d, and 447c, showed very high abundance of pri-miRNAs and pre-miRNAs. Furthermore, mature forms of miRNAs171b&c, 399d, and 447c, were not detectable in the rosette leaves, indicating that miRNA processing is tissue specific. In conclusion, using the array analysis we show that 28 miRNAs are involved in the plant response to viral infection and 29 miRNAs are involved in the regulation of drought stress. We also demonstrate that at least some miRNAs involved in the stress response in Arabidopsis thaliana are regulated at the maturation level. One such example is miRNA 171b&c. This miRNA is transcribed in all tissues, evidenced by its detected pri and pre-miRNA forms; however, its mature form is constitutively or transiently expressed depending on the tissue type.
Highlights
MicroRNAs are non-coding RNAs that negatively regulate gene expression at the post-transcriptional level by binding to the target mRNAs [ ]
We demonstrate that at least some miRNAs involved in the stress response in Arabidopsis thaliana are regulated at the maturation level
We demonstrate how miRNA expression during the Oil-seed Rape Mosaic Virus (ORMV) infection causes uniform up-regulation of all detected miRNAs involved in the stress regulation
Summary
MicroRNAs (miRNAs) are non-coding RNAs that negatively regulate gene expression at the post-transcriptional level by binding to the target mRNAs [ ]. There are two post-transcriptional mechanisms of gene expression regulation by miRNAs [ , ]. When expressed in Arabidopsis thaliana, the Beet yellows virus p and the Tomato bushy stunt virus p silencing suppressors bind the duplex but not singlestranded miRNAs leading to increased abundance of miRNA* and reduced miRNA-mediated cleavage of target mRNAs [ - ]. One important miRNA family heavily involved in RNA silencing during viral infection is the miRNA [ ]. This miRNA has been reported to target AGO protein, an
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