Department of Evolution and Ecology, University of California, Davis, CA, 95616, USA.
BMC Genomics. 2022 Sep 8;23(1):641. doi: 10.1186/s12864-022-08839-4.
Maternal gene products supplied to the egg during oogenesis drive the earliest events of development in all metazoans. After the initial stages of embryogenesis, maternal transcripts are degraded as zygotic transcription is activated; this is known as the maternal to zygotic transition (MZT). Recently, it has been shown that the expression of maternal and zygotic transcripts have evolved in the Drosophila genus over the course of 50 million years. However, the extent of natural variation of maternal and zygotic transcripts within a species has yet to be determined. We asked how the maternal and zygotic pools of mRNA vary within and between populations of D. melanogaster. In order to maximize sampling of genetic diversity, African lines of D. melanogaster originating from Zambia as well as DGRP lines originating from North America were chosen for transcriptomic analysis.
Generally, we find that maternal transcripts are more highly conserved, and zygotic transcripts evolve at a higher rate. We find that there is more within-population variation in transcript abundance than between populations and that expression variation is highest post- MZT between African lines.
Determining the natural variation of gene expression surrounding the MZT in natural populations of D. melanogaster gives insight into the extent of how a tightly regulated process may vary within a species, the extent of developmental constraint at both stages and on both the maternal and zygotic genomes, and reveals expression changes allowing this species to adapt as it spread across the world.
在所有后生动物中，卵子在卵母细胞发生过程中提供的母体基因产物驱动着早期发育事件。在胚胎发生的初始阶段之后，母体转录本被降解，因为合子转录被激活；这被称为母体到合子过渡（MZT）。最近，已经表明，在 5000 万年的过程中，果蝇属中的母体和合子转录本的表达已经进化。然而，在一个物种内，母体和合子转录本的自然变异程度尚未确定。我们询问了母体和合子 mRNA 库在黑腹果蝇的种群内和种群之间的变化情况。为了最大限度地增加遗传多样性的采样，选择了来自赞比亚的非洲黑腹果蝇系以及来自北美的 DGRP 系进行转录组分析。
一般来说，我们发现母体转录本更保守，而合子转录本进化速度更快。我们发现，转录本丰度的种群内变异比种群间变异更大，并且在 MZT 后非洲系之间的表达变异最高。
在黑腹果蝇自然种群中围绕 MZT 的基因表达的自然变异为深入了解在一个物种内，一个受严格调控的过程可能在多大程度上发生变化，在两个阶段以及母体和合子基因组上的发育约束的程度，以及揭示使该物种在其分布于全球时能够适应的表达变化提供了见解。
