Liu Shuai, Wang Qiaojun, Li Xinyu, Wang Guibin, Wan Yinglang
a College of Biological Sciences and Technology , Beijing Forestry University , Beijing , Haidian , PR China.
b Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, Institute of Tropical Agriculture and Forestry , Hainan University , Haikou , China.
Plant Signal Behav. 2019;14(8):1621088. doi: 10.1080/15592324.2019.1621088. Epub 2019 May 27.
Circular RNAs (circRNAs) are covalently closed single-strand RNA molecules identified in eukaryotes. Here we report 10 sequences of chloroplast genome (cpDNA) encoded circRNAs (cp-circRNA) from 3-day-old seedlings via next-generation sequencing. Their parental sequences were referred to as exonic, intronic, and intergenic gene sequences. Due to the very low level of cp-circRNA expression, we attempted to use a digital polymerase chain reaction technique to validate their existence. Four of these circRNAs were confirmed: , and . Their expression levels in etiolated and de-etiolated seedlings were quantified using digital PCR. Of the four, the exonic circRNA was highly expressed in etiolated seedlings. Its parental gene, (), has expression trends similar to . Given that is a single-exon gene, we propose that the circularization of occurs via an unknown process rather than via RNA-splicing-based mechanisms. Therefore, we provided a reliable method for detecting cp-circRNAs in low copies and implied an unknown circularisation mechanism of RNA in chloroplasts.
环状RNA（circRNAs）是在真核生物中发现的共价闭合单链RNA分子。在此，我们通过下一代测序报告了3日龄幼苗叶绿体基因组（cpDNA）编码的环状RNA（cp-circRNA）的10个序列。它们的亲本序列被称为外显子、内含子和基因间基因序列。由于cp-circRNA表达水平极低，我们尝试使用数字聚合酶链反应技术来验证它们的存在。其中4个环状RNA得到了证实： ，以及 。使用数字PCR对它们在黄化和去黄化幼苗中的表达水平进行了定量。在这4个中，外显子环状RNA 在黄化幼苗中高表达。其亲本基因 （ ）具有与 相似的表达趋势。鉴于 是一个单外显子基因，我们提出 的环化是通过未知过程发生的，而不是通过基于RNA剪接的机制。因此，我们提供了一种可靠的方法来检测低拷贝的cp-circRNAs，并暗示了叶绿体中RNA未知的环化机制。
