AUTHOR=Zhang He , Liu Shuai , Li Xinyu , Yao Lijuan , Wu Hongyang , Baluška František , Wan Yinglang 

TITLE=An Antisense Circular RNA Regulates Expression of RuBisCO Small Subunit Genes in Arabidopsis

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.665014

DOI=10.3389/fpls.2021.665014

ISSN=1664-462X

ABSTRACT=<p>Circular RNA (circRNA) is a novel class of endogenous long non-coding RNA (lncRNA) and participates in diverse physiological process in plants. From the dataset obtained by high-throughput RNA sequencing, we identified a circRNA encoded by the sense strand of the exon regions spanning two RuBisCO small subunit genes, <italic>RBCS2B</italic> and <italic>RBCS3B</italic>, in <italic>Arabidopsis thaliana</italic>. We further applied the single specific primer-polymerase chain reaction (PCR) and Sanger sequencing techniques to verify this circRNA and named it <italic>ag-circRBCS</italic> (<italic>antisense and across genic-circular</italic> RNA <italic>RBCS</italic>). Using quantitative real-time PCR (qRT-PCR), we found that <italic>ag-circRBCS</italic> shares a similar rhythmic expression pattern with other <italic>RBCS</italic> genes. The expression level of <italic>ag-circRBCS</italic> is 10–40 times lower than the expression levels of <italic>RBCS</italic> genes in the photosynthetic organs in <italic>Arabidopsis</italic>, whereas the <italic>Arabidopsis</italic> root lacked <italic>ag-circRBCS</italic> expression. Furthermore, we used the delaminated layered double hydroxide lactate nanosheets (LDH-lactate-NS) to deliver <italic>in vitro</italic> synthesized <italic>ag-circRBCS</italic> into <italic>Arabidopsis</italic> seedlings. Our results indicate that <italic>ag-circRBCS</italic> could significantly depress the expression of <italic>RBCS</italic>. Given that <italic>ag-circRBCS</italic> was expressed at low concentration <italic>in vivo</italic>, we suggest that <italic>ag-circRBCS</italic> may represent a fine-tuning mechanism to regulating the expression of <italic>RBCS</italic> genes and protein content in <italic>Arabidopsis</italic>.</p>