Detection of siRNA-Directed DNA Methylation and Gene Silencing in Response to Salinity Stress

Small RNAs are able to organise a lot of biological machineries in organisms. Different types of sRNAs play divergent roles in the regulation of gene expression in plants, including RNAdirected DNA methylation (RDDM), which results from double-stranded RNAs and is often capable of directing DNA cytosine methylation at target sequences. Cytosine methylation forms the basis of an epigenetic regulatory system that has been shown to be involved in abiotic and biotic stress responses of plants. In this study applied a direct delivery method to introduce SOS1-siRNA (small interfering RNA) and HKT1-siRNA into Arabidopsis thaliana to test their ability to direct DNA methylation within promoters of the AtSOSI and AtHKTI genes in response to salt stress during the growth period. There was clear evidence of the siRNAs uptake and that the AtSOS1 promoter was methylated in the presence of HKT1-siRNA when treated with salt. In addition, lethal effects were observed on the phenotype, which suggested that AtSOSI and AtHKT1 genes expressions had been affected. Direct siRNA delivery was therefore used successfully and it caused significant effects on the phenotype of plants. This method has the potential to allow targeted regulation of gene expression in response to stress.