Gildor Tsvia, Malik Assaf, Sher Noa, Ben-Tabou de-Leon Smadar
Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa 31905, Israel.
Bioinformatics Core Unit, University of Haifa, Haifa 31905, Israel.
Dev Biol. 2016 Jun 1;414(1):121-31. doi: 10.1016/j.ydbio.2016.04.007. Epub 2016 Apr 13.
Early in embryogenesis, maternally deposited transcripts are degraded and new zygotic transcripts are generated during the maternal to zygotic transition. Recent works have shown that early zygotic transcripts are short compared to maternal transcripts, in zebrafish and Drosophila species. The reduced zygotic transcript length was attributed to the short cell cycle in these organisms that prevents the transcription of long primary transcripts (intron delay). Here we study the length of maternal mRNAs and their degradation kinetics in two sea urchin species to further the understanding of maternal gene usage and processing. Early zygotic primary transcripts and mRNAs are shorter than maternal ones in the sea urchin, Strongylocentrotus purpuratus. Yet, while primary transcripts length increases when cell cycle lengthens, typical for intron delay, the relatively short length of zygotic mRNAs is consistent. The enhanced mRNA length is due to significantly longer maternal open reading frames and 3'UTRs compared to the zygotic lengths, a ratio that does not change with developmental time. This implies unique usage of both coding sequences and regulatory information in the maternal stage compared to the zygotic stages. We extracted the half-lifetimes due to maternal and zygotic degradation mechanisms from high-density time course of a set of maternal mRNAs in Paracentrotus lividus. The degradation rates due to maternal and zygotic degradation mechanisms are not correlated, indicating that these mechanisms are independent and relay on different regulatory information. Our studies illuminate specific structural and kinetic properties of sea urchin maternal mRNAs that might be broadly shared by other organisms.
在胚胎发生早期，母源沉积的转录本会被降解，并且在母型向合子型转变过程中会产生新的合子转录本。最近的研究表明，与斑马鱼和果蝇物种中的母源转录本相比，早期合子转录本较短。合子转录本长度的缩短归因于这些生物中较短的细胞周期，这会阻止长初级转录本的转录（内含子延迟）。在这里，我们研究了两种海胆物种中母源mRNA的长度及其降解动力学，以进一步了解母源基因的使用和加工情况。在紫海胆中，早期合子初级转录本和mRNA比母源的短。然而，虽然当细胞周期延长时初级转录本长度会增加，这是内含子延迟的典型特征，但合子mRNA相对较短的长度却是一致的。mRNA长度的增加是由于母源开放阅读框和3'UTR与合子长度相比明显更长，这个比例不会随发育时间而变化。这意味着与合子阶段相比，母源阶段在编码序列和调控信息的使用上具有独特性。我们从地中海海胆一组母源mRNA的高密度时间进程中提取了母源和合子降解机制导致的半衰期。母源和合子降解机制导致的降解速率不相关，这表明这些机制是独立的，且依赖于不同的调控信息。我们的研究揭示了海胆母源mRNA的特定结构和动力学特性，这些特性可能在其他生物中广泛存在。
