Genome-Wide Identification and Characterization of RNA/DNA Differences Associated with Drought Response in Wheat

The emerging role of epitranscriptome in shaping stress responses in plants

KEY MESSAGE

RNA modifications and editing changes constitute 'epitranscriptome' and are crucial in regulating the development and stress response in plants. Exploration of the epitranscriptome and associated machinery would facilitate the engineering of stress tolerance in crops. RNA editing and modifications post-transcriptionally decorate almost all classes of cellular RNAs, including tRNAs, rRNAs, snRNAs, lncRNAs and mRNAs, with more than 170 known modifications, among which m6A, Ψ, m5C, 8-OHG and C-to-U editing are the most abundant. Together, these modifications constitute the "epitranscriptome", and contribute to changes in several RNA attributes, thus providing an additional structural and functional diversification to the "cellular messages" and adding another layer of gene regulation in organisms, including plants. Numerous evidences suggest that RNA modifications have a widespread impact on plant development as well as in regulating the response of plants to abiotic and biotic stresses. High-throughput sequencing studies demonstrate that the landscapes of m6A, m5C, Am, Cm, C-to-U, U-to-G, and A-to-I editing are remarkably dynamic during stress conditions in plants. GO analysis of transcripts enriched in Ψ, m6A and m5C modifications have identified bonafide components of stress regulatory pathways. Furthermore, significant alterations in the expression pattern of genes encoding writers, readers, and erasers of certain modifications have been documented when plants are grown in challenging environments. Notably, manipulating the expression levels of a few components of RNA editing machinery markedly influenced the stress tolerance in plants. We provide updated information on the current understanding on the contribution of RNA modifications in shaping the stress responses in plants. Unraveling of the epitranscriptome has opened new avenues for designing crops with enhanced productivity and stress resilience in view of global climate change.

Genome-Wide Identification of Potential mRNAs in Drought Response in Wheat (Triticum aestivum L.)

Plant cell metabolism inevitably forms an important drought-responsive mechanism, which halts crop productivity. Globally, more than 30% of the total harvested area was affected by dehydration. RNA-seq technology has enabled biologists to identify stress-responsive genes in relatively quick times. However, one shortcoming of this technology is the inconsistent data generation compared to other parts of the world. So, we have tried, here, to generate a consensus by analyzing meta-transcriptomic data available in the public microarray database GEO NCBI. In this way, the aim was set, here, to identify stress genes commonly identified as differentially expressed (p < 0.05) then followed by downstream analyses. The search term “Drought in wheat” resulted in 233 microarray experiments from the GEO NCBI database. After discarding empty datasets containing no expression data, the large-scale meta-transcriptome analytics and one sample proportional test were carried out (Bonferroni adjusted p < 0.05) to reveal a set of 11 drought-responsive genes on a global scale. The annotation of these genes revealed that the transcription factor activity of RNA polymerase II and sequence-specific DNA-binding mechanism had a significant role during the drought response in wheat. Similarly, the primary root differentiation zone annotations, controlled by TraesCS5A02G456300 and TraesCS7B02G243600 genes, were found as top-enriched terms (p < 0.05 and Q < 0.05). The resultant standard drought genes, glycosyltransferase; Arabidopsis thaliana KNOTTED-like; bHLH family protein; Probable helicase MAGATAMA 3; SBP family protein; Cytochrome c oxidase subunit 2; Trihelix family protein; Mic1 domain-containing protein; ERF family protein; HD-ZIP I protein; and ERF family protein, are important in terms of their worldwide proved link with stress. From a future perspective, this study could be important in a breeding program contributing to increased crop yield. Moreover, the wheat varieties could be identified as drought-resistant/sensitive based on the nature of gene expression levels.

Roles of microRNAs in abiotic stress response and characteristics regulation of plant

MicroRNAs (miRNAs) are a class of non-coding endogenous small RNAs (long 20-24 nucleotides) that negatively regulate eukaryotes gene expression at post-transcriptional level via cleavage or/and translational inhibition of targeting mRNA. Based on the diverse roles of miRNA in regulating eukaryotes gene expression, research on the identification of miRNA target genes has been carried out, and a growing body of research has demonstrated that miRNAs act on target genes and are involved in various biological functions of plants. It has an important influence on plant growth and development, morphogenesis, and stress response. Recent case studies indicate that miRNA-mediated regulation pattern may improve agronomic properties and confer abiotic stress resistance of plants, so as to ensure sustainable agricultural production. In this regard, we focus on the recent updates on miRNAs and their targets involved in responding to abiotic stress including low temperature, high temperature, drought, soil salinity, and heavy metals, as well as plant-growing development. In particular, this review highlights the diverse functions of miRNAs on achieving the desirable agronomic traits in important crops. Herein, the main research strategies of miRNAs involved in abiotic stress resistance and crop traits improvement were summarized. Furthermore, the miRNA-related challenges and future perspectives of plants have been discussed. miRNA-based research lays the foundation for exploring miRNA regulatory mechanism, which aims to provide insights into a potential form of crop improvement and stress resistance breeding.