Evaluation of mature miR398 family, expression analysis and the post-transcriptional regulation evidence in gamma-irradiated and nitrogen-stressed Medicago sativa seedlings

Background: The miR398 (microRNA398) posttranscriptionally regulates the superoxide dismutase (Cu/Zn-SOD). Materials and methods: The miR398 level was quantitated in gamma-irradiated (20Gy and 200Gy) and nitrogen-stressed seedlings by stem-loop RT-PCR (Real Time-Polymerase chain reaction). The positional preference of nucleotide (nt) for miR398 families and new targets was done. The SOD enzyme was assayed in native PAGE (Polyacrylamide gel electrophoresis). Results: A relative increase in miR398-3p expression in the roots, and reduction in shoots for gamma-irradiated tissue and downregulation in miR398-5p in shoots is noted. The nitrogen stress shows upregulation of miR398-3p in roots and shoots, whereas the expression of miR398-5p is upregulated in roots and downregulated in shoots. Positional preference in miR398-3p for 1-14 nt is 90% conserved unlike miR398-5p where no nucleotide positional preference is seen. Targets obtained were functionally characterized. Conclusions: The mature miR398-5p and miR398-3p levels estimated in gamma-irradiated (20 and 200Gy) and nitrogen-stressed Medicago sativa seedlings show differential levels in roots and shoots. Native PAGE of Cu/Zn-SOD suggests its negative correlation with miR398 in shoots of irradiated and nitrogen-stressed samples. The nucleotide preferences for the nucleotide for a given position and functional characterization of targets are reported herein.