Conserved MicroRNA Act Boldly During Sprout Development and Quality Formation in Pingyang Tezaocha (Camellia sinensis)

Lei Zhao,Changsong Chen,Jiazhi Shen,Zhaotang Ding,Yu Wang

doi:10.3389/fgene.2019.00237

Abstract

Tea tree [Camellia sinensis (L.) O. Kuntze] is an important leaf (sometimes tender stem)-using commercial plant with many medicinal uses. The development of newly sprouts would directly affect the yield and quality of tea product, especially significant for Pingyang Tezaocha (PYTZ) which takes up a large percent in the early spring tea market. MicroRNA (miRNA), particularly the conserved miRNAs, often position in the center of subtle and complex gene regulatory systems, precisely control the biological processes together with other factors in a spatio-temporal pattern. Here, quality-determined metabolites catechins, theanine and caffeine in PYTZ sprouts including buds (sBud), different development stages of leaves (sL1, sL2) and stems (sS1, sS2) were quantified. A total of 15 miRNA libraries of the same tissue with three repetitions for each were constructed to explore vital miRNAs during the biological processes of development and quality formation. We analyzed the whole miRNA profiles during the sprout development and defined conserved miRNA families in the tea plant. The differentially expressed miRNAs related to the expression profiles buds, leaves, and stems development stages were described. Twenty one miRNAs and eight miRNA-TF pairs that most likely to participate in regulating development, and at least two miRNA-TF-metabolite triplets that participate in both development and quality formation had been filtered. Our results indicated that conserved miRNA act boldly during important biological processes, they are (i) more likely to be linked with morphological function in primary metabolism during sprout development, and (ii) hold an important position in secondary metabolism during quality formation in tea plant, also (iii) coordinate with transcription factors in forming networks of complex multicellular organism regulation.

Highlights

Produced in China, green tea nowadays is the star among the top list beverages, attribute to its good taste, health benefits, and mysterious process, which brings considerable economic benefit in planting and exporting countries such as China, India, Kenya, and Sri Lanka
Kuntze “Pingyang Tezaocha” (PYTZ) were planted in the Germplasm of Qingdao Tea Repository at the Tea Research Institute located in Qingdao (35◦N119◦E, Qingdao city, China) under natural light condition
Among the three kinds of characteristic metabolites, the content of total catechin accounts for the most majority proportion, while distributing significantly different among tender leaves and stems (Figure 1B). The galloylated catechins such like epigallocatechin gallate (EGCG) (Figure 1F) and epicatechin gallate (ECG) (Figure 1H), take up 67.4% in total catechin concentration obtained by summation of the individual components ranged from 37.3 to 119.2 mg/g (Figure 1B)

Summary

Introduction

Produced in China, green tea nowadays is the star among the top list beverages, attribute to its good taste, health benefits, and mysterious process, which brings considerable economic benefit in planting and exporting countries such as China, India, Kenya, and Sri Lanka. As young leaves and tender stems from the tea tree are processed to prepare “tea”, the developmental characters are supposed to have a direct and significant bearing on the yield and the quality of tea product. The plant miRNA families were placed to be at the central position within gene expression programs, always with small numbers per cell and large amounts of transcripts (Voinnet, 2009), yet have powerful effect in developmental regulation, morphogenesis, stress responses (Axtell and Bowman, 2008; De Lima et al, 2012; Jones-Rhoades, 2012; Yang et al, 2013). Seldom gene regulation could be completed without consideration of the transcription factors. Hypothesis demonstrated that the miRNA binding sites evolve faster than the transcription factor binding sites, as the ways to repress a gene is relatively much more than to activate one (Chen and Rajewsky, 2007)

Methods

Results

Conclusion