mRNA/microRNA Profile at the Metamorphic Stage of Olive Flounder (Paralichthys olivaceus)

Flatfish is famous for the asymmetric transformation during metamorphosis. The molecular mechanism behind the asymmetric development has been speculated over a century and is still not well understood. To date, none of the metamorphosis-related genes has been identified in flatfish. As the first step to screen metamorphosis-related gene, we constructed a whole-body cDNA library and a whole-body miRNA library in this study and identified 1051 unique ESTs, 23 unique miRNAs, and 4 snoRNAs in premetamorphosing and prometamorphosing Paralichthys olivaceus. 1005 of the ESTs were novel, suggesting that there was a special gene expression profile at metamorphic stage. Four miRNAs (pol-miR-20c, pol-miR-23c, pol-miR-130d, and pol-miR-181e) were novel to P. olivaceus; they were characterized as highly preserved homologies of published miRNAs but with at least one nucleotide differed. Representative 24 mRNAs and 23 miRNAs were quantified during metamorphosis of P. olivaceus by using quantitative RT PCR or stem-loop qRT PCR. Our results showed that 20 of mRNAs might be associated with early metamorphic events, 10 of mRNAs might be related with later metamorphic events, and 16 of miRNAs might be involved in the regulation of metamorphosis. The data provided in this study would be helpful for further identifying metamorphosis-related gene in P. olivaceus

The genome and transcriptome of Japanese flounder provide insights into flatfish asymmetry

Flatfish have the most extreme asymmetric body morphology of vertebrates. During metamorphosis, one eye migrates to the contralateral side of the skull, and this migration is accompanied by extensive craniofacial transformations and simultaneous development of lopsided body pigmentation(1-5). The evolution of this developmental and physiological innovation remains enigmatic. Comparative genomics of two flatfish and transcriptomic analyses during metamorphosis point to a role for thyroid hormone and retinoic acid signaling, as well as phototransduction pathways. We demonstrate that retinoic acid is critical in establishing asymmetric pigmentation and, via cross-talk with thyroid hormones, in modulating eye migration. The unexpected expression of the visual opsins from the phototransduction pathway in the skin translates illumination differences and generates retinoic acid gradients that underlie the generation of asymmetry. Identifying the genetic underpinning of this unique developmental process answers long-standing questions about the evolutionary origin of asymmetry, but it also provides insight into the mechanisms that control body shape in vertebrates.National Natural Science Foundation of China [31130057, 31461163005, 31530078, 31472269, 31472262, 31472273]; State 863 High Technology R&D Project of China [2012AA092203, 2012AA10A408, 2012AA10A403-2]; Education and Research of Guangdong Province [2013B090800017]; Taishan Scholar Climb Project Fund of Shandong of China; Taishan Scholar Project Fund of Shandong of China for Young Scientists; Shanghai Universities First-class Disciplines Project of Fisheries; Program for Professor of Special Appointment (Eastern Scholar) at the Shanghai Institutions of Higher Learning; Shanghai Municipal Science, Special Project on the Integration of Industryinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/publishedVersio