AUTHOR=Zhang Hongmei , Xu Zhaobin , Xu Junxiao , Wei Zhenlin , Shi Zhiyi 

TITLE=The differential expression and effects of Drosha on metamorphosis of Japanese flounder (paralichthys olivaceus)

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.957836

DOI=10.3389/fmars.2022.957836

ISSN=2296-7745

ABSTRACT=<p><italic>Drosha</italic> is critical for producing mature microRNAs (miRNAs) from their precursor molecules and small interfering RNAs (siRNAs). Although <italic>Drosha</italic> has been well characterized in most vertebrate species, identifying the Japanese flounder <italic>Drosha</italic> has remained elusive. In this study, we cloned the Japanese flounder <italic>Drosha</italic> gene, which has 4,122 nucleotides (nt), including a 5’-untranslated region (UTR) of 14 nt, a 3’-UTR of 230 nt, and a 3,879 nt open reading frame (ORF) encodes a 1,292 amino acid polypeptide. Then, we analyzed the conservation and phylogenetic evolution of <italic>Drosha</italic> in some species. Real-time quantitative PCR revealed that <italic>Drosha</italic> mRNA is highly expressed in the brain, and a lower amount of mRNA was also found in muscle than in other tissues. <italic>Drosha</italic> plays a vital role in controlling flounder development and metabolism, and its mRNA levels were relatively high at 36 dph (days post-hatching) in the period of metamorphosis and growth of the Japanese flounder. <italic>Drosha</italic> expression showed in advance with a peak at 23 dph following TH (thyroid hormone) treatment. To further investigate the role of <italic>Drosha</italic> in metamorphosis, we performed siRNA knockdown of <italic>Drosha</italic> in flounder embryonic cells (FEC) cells. The result shows that the <italic>Drosha</italic>-specific siRNA significantly down-regulated <italic>Drosha</italic> mRNA and miR-1,133,17,214,181a,181b levels, while primary miRNA (pri-miRNA) levels were not significantly different from negative control (NC). These results suggest that <italic>Drosha</italic> plays a vital role in Japanese flounder development and metamorphosis through processing to produce mature miRNAs, providing essential information for further studying of the part of the <italic>Drosha</italic> gene in the Japanese flounder development.</p>