Bioinformatic analysis based genome-wide identification, characterization, diversification and regulatory transcription components of RNA silencing machinery genes in wheat (Triticum aestivum L.)

Dicer-Like (DCL), Argonaute (AGO), and RNA-dependent RNA polymerase (RDR) gene families are known as RNA silencing machinery genes or RNAi genes. They have important activities at post-transcriptional and chromatin modification levels. They regulate gene expression relating to different stresses, growth, and development in eukaryotes. A complete cycle of gene silencing is occurred by the collaboration of these three families. However, these gene families are not yet rigorously studied in the economically important wheat genome. Our bioinformatic analysis based genome-wide identification, characterization, diversification and regulatory components of these gene families identified 7 TaDCL, 39 TaAGO and 16 TaRDR genes from wheat genome against RNAi genes of Arabidopsis thaliana. Phylogenetic analysis of wheat genome with Arabidopsis and rice RNAi genes showed that TaDCL, TaAGO and TaRDR proteins are clustered into four, eight and four subgroups respectively. Domain, motif and exon-intron structure analyses showed that the TaDCL, TaAGO and TaRDR proteins conserve identical characteristics within groups while retain diverse differences between groups. GO annotations implied that a number of biological and molecular pathways are linked to RNAi mechanism in wheat. Gene networking between transcription factors and RNAi proteins indicates that ERF is the leading family linked to maximum RNAi genes followed by MIKC-MADS, C2H2, BBR-BPC, MYB, and Dof. Cis-regulatory elements associated to RNAi genes are predicted to act as regulatory components against various environmental conditions. Expressed sequence tag analysis showed that larger numbers of RNAi genes are expressed in different tissues and organs predicted to play roles for healthy plants and grains. Expression analysis of 7 TaDCL genes using qRT-PCR showed that only TaDCL3a and TaDCL3b had root specific significant expression (p-value<0.05) with no expression in leaf validated EST results. Besides, TaDCL3b and TaDCL4 significantly prompted in drought condition indicating their potential role in drought stress tolerance. Overall results would however help researchers for in-depth biological investigation of these RNAi genes in wheat crop improvement.