Absolute quantification of microRNAs in green tea (Camellia sinensis) by stem-loop quantitative real-time PCR

Functional role of microRNA in the regulation of biotic and abiotic stress in agronomic plants

The increasing demand for food is the result of an increasing population. It is crucial to enhance crop yield for sustainable production. Recently, microRNAs (miRNAs) have gained importance because of their involvement in crop productivity by regulating gene transcription in numerous biological processes, such as growth, development and abiotic and biotic stresses. miRNAs are small, non-coding RNA involved in numerous other biological functions in a plant that range from genomic integrity, metabolism, growth, and development to environmental stress response, which collectively influence the agronomic traits of the crop species. Additionally, miRNA families associated with various agronomic properties are conserved across diverse plant species. The miRNA adaptive responses enhance the plants to survive environmental stresses, such as drought, salinity, cold, and heat conditions, as well as biotic stresses, such as pathogens and insect pests. Thus, understanding the detailed mechanism of the potential response of miRNAs during stress response is necessary to promote the agronomic traits of crops. In this review, we updated the details of the functional aspects of miRNAs as potential regulators of various stress-related responses in agronomic plants.

Recent trends in miRNA therapeutics and the application of plant miRNA for prevention and treatment of human diseases

Background

Researchers now have a new avenue to investigate when it comes to miRNA-based therapeutics. miRNAs have the potential to be valuable biomarkers for disease detection. Variations in miRNA levels may be able to predict changes in normal physiological processes. At the epigenetic level, miRNA has been identified as a promising candidate for distinguishing and treating various diseases and defects.

Main body

In recent pharmacology, plants miRNA-based drugs have demonstrated a potential role in drug therapeutics. The purpose of this review paper is to discuss miRNA-based therapeutics, the role of miRNA in pharmacoepigenetics modulations, plant miRNA inter-kingdom regulation, and the therapeutic value and application of plant miRNA for cross-kingdom approaches. Target prediction and complementarity with host genes, as well as cross-kingdom gene interactions with plant miRNAs, are also revealed by bioinformatics research. We also show how plant miRNA can be transmitted from one species to another by crossing kingdom boundaries in this review. Despite several unidentified barriers to plant miRNA cross-transfer, plant miRNA-based gene regulation in trans-kingdom gene regulation may soon be valued as a possible approach in plant-based drug therapeutics.

Conclusion

This review summarised the biochemical synthesis of miRNAs, pharmacoepigenetics, drug therapeutics and miRNA transkingdom transfer.

Environmental risk assessment of the DvSSJ1 dsRNA and the IPD072Aa protein to non-target organisms

Event DP-Ø23211-2 (hereafter referred to as DP23211) maize expresses the DvSSJ1 double-stranded RNA (DvSSJ1 dsRNA) and the IPD072Aa protein, encoded by the ipd072Aa gene. DvSSJ1 dsRNA and the IPD072Aa protein each provide control of corn rootworms (Diabrotica spp.) when expressed in plants. As part of the environmental risk assessment (ERA), the potential hazard to non-target organisms (NTOs) exposed to the DvSSJ1 dsRNA and the IPD072Aa protein expressed in DP23211 maize was assessed. Worst-case estimated environmental concentrations (EECs) for different NTO functional groups (pollinators and pollen feeders, soil dwelling detritivores, predators and parasitoids, aquatic detritivores, insectivorous birds, and wild mammals) were calculated using worst-case assumptions. Several factors that reduce exposure to NTOs under more realistic environmental conditions were applied, when needed to provide more environmentally relevant EECs. Laboratory bioassays were conducted to assess the activity of DvSSJ1 dsRNA or the IPD072Aa protein against selected surrogate species, and margins of exposure (MOEs) were calculated by comparing the Tier I hazard study results to worst-case or refined EECs. Based on specificity and MOE values, DvSSJ1 dsRNA and the IPD072Aa protein expressed in DP23211 maize are not expected to be harmful to NTO populations at environmentally relevant concentrations.

Utilization of microRNAs and their regulatory functions for improving biotic stress tolerance in tea plant [Camellia sinensis (L.) O. Kuntze]

MicroRNAs play a central role in responses to biotic stressors through their interactions with their target mRNAs. Tea plant (Camellia sinensis L.), an important beverage crop, is vulnerable to tea geometrid and anthracnose disease that causes considerable crop loss and tea production worldwide. Sustainable production of tea in the current scenario to biotic factors is major challenges. To overcome the problem of biotic stresses, high-throughput sequencing (HTS) with bioinformatics analyses has been used as an effective approach for the identification of stress-responsive miRNAs and their regulatory functions in tea plant. These stress-responsive miRNAs can be utilized for miRNA-mediated gene silencing to enhance stress tolerance in tea plant. Therefore, this review summarizes the current understanding of miRNAs regulatory functions in tea plant responding to Ectropis oblique and Colletotrichum gloeosporioides attacks for future miRNA research. Also, it highlights the utilization of miRNA-mediated gene silencing strategies for developing biotic stress-tolerant tea plant.

Expression of mouse small interfering RNAs in lettuce using artificial microRNA technology

Artificial miRNA technology enables the generation of siRNAs to regulate the expression of targeted genes. However, the application of siRNAs to alter gene expression is challenging due to their instability and requires a means to efficiently deliver siRNAs into the host. Here, we report that the siRNAs targeted to animal mRNAs can be heterologously expressed and stably produced in lettuce. We have modified rice miRNA precursors to produce siRNAs in lettuce with the potential to target mRNAs of mouse complement 3 (C3) and coagulation factor 7 (CF7). Expression of primary and mature siRNAs in the transgenic lettuce lines was confirmed via Sanger sequencing. Our study demonstrates an applicable tool to alter gene expression in the targeted host and has potential utility in siRNA-based oral therapeutics.

Plant MIR156 regulates intestinal growth in mammals by targeting the Wnt/β-catenin pathway

MicroRNAs (miRNAs) are important negative regulators of genes involved in physiological and pathological processes in plants and animals. Recent studies have shown that miRNAs might regulate gene expression among different species in a cross-kingdom manner. However, the specific roles of plant miRNAs in animals remain poorly understood and somewhat. Herein, we found that plant MIR156 regulates proliferation of intestinal cells both in vitro and in vivo. Continuous administration of a high plant miRNA diet or synthetic MIR156 elevated MIR156 levels and inhibited the Wnt/β-catenin signaling pathway in mouse intestine. Bioinformatics predictions and luciferase reporter assays indicated that MIR156 targets Wnt10b. In vitro, MIR156 suppressed proliferation by downregulating the Wnt10b protein and upregulating β-catenin phosphorylation in the porcine jejunum epithelial (IPEC-J2) cell line. Lithium chloride and an MIR156 inhibitor relieved this inhibition. This research is the first to demonstrate that plant MIR156 inhibits intestinal cell proliferation by targeting Wnt10b. More importantly, plant miRNAs may represent a new class of bioactive molecules that act as epigenetic regulators in humans and other animals.

Circular RNA architecture and differentiation during leaf bud to young leaf development in tea (Camellia sinensis)

Circular RNA (circRNA) discovery, expression patterns and experimental validation in developing tea leaves indicates its correlation with circRNA-parental genes and potential roles in ceRNA interaction network. Circular RNAs (circRNAs) have recently emerged as a novel class of abundant endogenous stable RNAs produced by circularization with regulatory potential. However, identification of circRNAs in plants, especially in non-model plants with large genomes, is challenging. In this study, we undertook a systematic identification of circRNAs from different stage tissues of tea plant (Camellia sinensis) leaf development using rRNA-depleted circular RNA-seq. By combining two state-of-the-art detecting tools, we characterized 3174 circRNAs, of which 342 were shared by each approach, and thus considered high-confidence circRNAs. A few predicted circRNAs were randomly chosen, and 20 out of 24 were experimental confirmed by PCR and Sanger sequencing. Similar in other plants, tissue-specific expression was also observed for many C. sinensis circRNAs. In addition, we found that circRNA abundances were positively correlated with the mRNA transcript abundances of their parental genes. qRT-PCR validated the differential expression patterns of circRNAs between leaf bud and young leaf, which also indicated the low expression abundance of circRNAs compared to the standard mRNAs from the parental genes. We predicted the circRNA-microRNA interaction networks, and 54 of the differentially expressed circRNAs were found to have potential tea plant miRNA binding sites. The gene sets encoding circRNAs were significantly enriched in chloroplasts related GO terms and photosynthesis/metabolites biosynthesis related KEGG pathways, suggesting the candidate roles of circRNAs in photosynthetic machinery and metabolites biosynthesis during leaf development.