ANNOUNCEMENTS
MIR408 family is one of the most conserved family in plant kingdom as its annotated in 97 plant species based on pmiREN database. miR408 is a conserved microRNA which was reported to play important roles in plant development and also involved in regulation of stress response via suppressing genes encoding copper requiring proteins. Further also plays role in regulating drought stress in rice plant. Here we contributed towards the understanding of MIR408 evolution in plants with in-planta validation of its targets in rice thought degradome and comparative expression analysis of targets in N22 under drought and MIR408 overexpression seedlings. miR408 mature sequences were found to be highly conserved while precursor sequences showed diversity. In phylogeny analysis, it was found that only 3 different clades were being formed in case of mature sequences. However, diversity in clade formation was seen among precursor sequences, separating monocots, dicots, gymnosperms and angiosperms.The major class of targets cleaved by miR408 include copper-binding plantacyanins while several other diverse classes of targets were also identified through degradome of rice. A total of 121 targets were identified for miR408-3p including 9, 10 and 94 for 0, 1, 2 category respectively. Expression correlation analysis of miR408-3p targets in N22 in flag leaf, infloresence and root highlighted tissue specific regulation of miR408-target module. In flag leaf tissue, 11 targets had shown anticorrelation with miR408 expression. In the inflorescence tissue, 29 targets had shown opposite regulation (upregulation) with respect to miR408 which showed negative regulation here. Finally, in root tissue, most of the targets (36) showed anticorrelation with miR408 expression. Further the RNA seq expression analysis of MIR408 overexpressing seedlings showed the downregulation of 53 targets in Ox- MIR408 seedlings. 5 targets with root specific and harboring opposite expression to that of miR408-3p were validated though qRT-PCR. The results similar drought regulated downregulation for all genes.
The snp-seek analysis of MIR408 and its promoter region showed wide range of SNPs in promoter while precursor was highly conserved.
Keywords: miRNAs, conserved, miRNA targets, post-transcriptional gene regulation, degradome.
