Novel Micro-RNAs Targeting to Genes Associated with Drought Stress in a Oil Crop Camelina sativa

Camelina (Camelina sativa L.) belonging to the Brassicaceae has been cultivated for seed oil containing high unsaturated fatty acids. Small non-coding and single stranded miRNAs that regulate gene expression at posttranscriptional level were explored from the Camelina cDNA library under drought stress. A total of the predicted 145 miRNAs (61 conserved and 84 putative novel miRNAs) were found to be 28 and 72 different miRNA families, respectively. Most of the miRNAs were 21 nt long (54.4%), but their precursor sequences extended to 66 to 305 long. Fifty percentage of predicted novel miRNAs possessed uracil/thymine at first base position of their sequences, suggesting that they play a vital role in miRNA-mediated gene regulation. In silico prediction indicated that the 45 putative novel miRNAs have higher complimentary with gene coding sequences targeting 70 genes involved in stress resistance, lipid metabolism, and transcription factors. Some of the newly identified miRNA targets may be unique to the Camelina species. All target genes were highly up-regulated in well-watered control leaves where miRNAs showed relatively low expression. In contrast, target genes were down-regulated upon drought treatment at 10 kPa and 100 kPa, whereas miRNAs showed up-regulated expression. Coordinated expression changes between validated miRNAs and their counterpart target genes varied under drought conditions, suggesting that the predicted miRNAs in this study could be stress responsive and contribute to gene regulatory frameworks in response to drought stress in the Camelina.