Identification of miRNAs associated with dark-induced senescence in Arabidopsis

Background: microRNAs (miRNAs) are endogenous small (similar to 21 nucleotide) single-stranded non-coding RNAs that typically function by guiding cleavage of target genes. To find the miRNAs that may be involved in dark-induced leaf senescence, we identified miRNAs by microarray platform using Arabidopsis thaliana leaves from both whole darkened plants (DPs) and individually darkened leaves (IDLs). Results: We found that the expressions of 137 miRNAs (P < 0.01, signal intensity >0) were significantly changed both in DP and IDL leaves. Among them, the expression levels of 44 miRNAs were relative higher than others (P < 0.01, signal intensity >500). Of these differentially expressed miRNAs, 6 miRNAs (miR319a, 319c, miR159, miR164a, miR164c and miR390a) have been previously reported to be involved in dark-induced leaf senescence, and the remaining 38 miRNAs have not been implicated in leaf senescence before. Target genes of all 44 miRNAs were predicted, and some of them, such as NAC1, At3g28690, At2g17640 and At2g45160, were found in the Leaf Senescence Database (LSD). GO and KEGG analysis of 137 miRNAs showed that the predicted target genes were significantly enriched in transcription regulation, development-related biological processes and metabolic pathways. Expression levels of some of the corresponding miRNA targets (At1g73440, At2g03220 and At5g54810) were analysed and found to be significantly different in DP/IDL than that in WT. Conclusions: A microarray analysis about dark-induced miRNAs involved in leaf senescence are present here. Further expression analysis revealed that some new founding miRNAs maybe regulate leaf senescence in Arabidopsis, and the findings highlight the important role of miRNAs in dark-induced leaf senescence.