Effects of Si on the expression of miRNA398 and miRNA408 and its target gene, superoxide dismutase (CuSOD) in Fe deficient cucumber plants

Abstract

Silicon (Si) is a beneficial element in several crops enhancing growth and alleviating different biotic and abiotic stresses. Iron (Fe) deficiency stress in plants includes changes in the expression and the activity of certain antioxidative enzymes. Our previous study suggested the role of Si in alleviation of Fe deficiency stress by an increased root Fe acquisition (Pavlovic et al., 2013). MicroRNAs (miRNAs) are a class of endogenous small RNAs (21 to 24 nucleotides) playing a crucial role in the development of both plant and animals by down regulating gene expression at the post-transcriptional level. Here we studied the expression of miRNA398 and miRNA408 and its target gene superoxide dismutase (SOD) in Fe deficient cucumber (Cucumis sativus L.) plants grown with or without addition of Si. The expression of miRNAs and target gene was measured in roots, stems and leaves as well as in the leaves of different ages. lntercostal chlorosis in the young leaves was markedly decreased in the Si treatment. Plants treated with Si also showed increased expression of miRNA398 and miRNA408 in all organs, and consequently lower level of CuSOD transcripts. The expression of particular miRNAs followed this pattern; the highest level in the old fully developed leaves and the lowest level in young chlorotic leaves. Our results indicate that Si reduces (or at least respond on) the oxidative stress in Fe deficient cucumber plants on the posttranscriptional level mediated by miRNAs398 and 408.