MicroRNAs (miRNAs) are important for plant growth and responses to environmental stresses via post-transcriptional regulation of gene expression. Tea, which is primarily produced from one bud and two tender leaves of the tea plant (Camellia sinensis), is one of the most popular non-alcoholic beverages worldwide owing to its abundance of secondary metabolites. A large number of miRNAs have been identified in various plants, including non-model species. However, due to the lack of reference genome sequences and/or information of tea plant genome survey scaffold sequences, discovery of miRNAs has been limited in C. sinensis.

Using small RNA sequencing, combined with their recently obtained genome survey data, scientists have identified and analyzed 175 conserved and 83 novel miRNAs mainly in one bud and two tender leaves of the tea plant. Among these, 93 conserved and 18 novel miRNAs were validated using miRNA microarray hybridization. In addition, the expression pattern of 11 conserved and 8 novel miRNAs were validated by stem-loop-qRT-PCR. A total of 716 potential target genes of identified miRNAs were predicted. Further, Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that most of the target genes were primarily involved in stress response and enzymes related to phenylpropanoid biosynthesis. The predicted targets of 4 conserved miRNAs were further validated by 5’RLM-RACE. A negative correlation between expression profiles of 3 out of 4 conserved miRNAs (csn-miR160a-5p, csn-miR164a, csn-miR828 and csn-miR858a) and their targets (ARF17, NAC100, WER and MYB12 transcription factor) were observed.

Number of paralogs per conserved miRNA family in six plant species

 

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Camellia sinensis (red), Populus trichocarpa (orange), Oryza sativa (black), Vitis vinifera (blue), Arabidopsis thaliana (purple) and Medicago truncatula (green). The number of members of the miRNA family in the five plant species from miRBase and in Camellia sinensis obtained in the present study are listed

In summary, the present study is one of few such studies on miRNA detection and identification in the tea plant. The predicted target genes of miRNAs encoded enzymes, transcription factors, and functional proteins. The miRNA–target transcription factor gene interactions may provide important clues about the regulatory mechanism of these miRNAs in the tea plant. The data reported in this study will make a huge contribution to knowledge on the potential miRNA regulators of the secondary metabolism pathway and other important biological processes in C. sinensis.

 

Reference
A. Jeyaraj, X. Zhang, Y. Hou, M. Shangguan, P. Gajjeraman, Y. Li, C. Wei (2017) Genome-wide identification of conserved and novel microRNAs in one bud and two tender leaves of tea plant (Camellia sinensis) by small RNA sequencing, microarray-based hybridization and genome survey scaffold sequences BMC Plant Biology doi: 10.1186/s12870-017-1169-1 [article]

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