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First author: Simon C. Groen; Affiliations: New York University (纽约大学): New York, USA
Corresponding author: Michael D. Purugganan
Levels of gene expression underpin organismal phenotypes, but the nature of selection that acts on gene expression and its role in adaptive evolution remain unknown. Here we assayed gene expression in rice (Oryza sativa), and used phenotypic selection analysis to estimate the type and strength of selection on the levels of more than 15,000 transcripts. Variation in most transcripts appears (nearly) neutral or under very weak stabilizing selection in wet paddy conditions (with median standardized selection differentials near zero), but selection is stronger under drought conditions. Overall, more transcripts are conditionally neutral (2.83%) than are antagonistically pleiotropic (0.04%), and transcripts that display lower levels of expression and stochastic noise and higher levels of plasticity are under stronger selection. Selection strength was further weakly negatively associated with levels of cis-regulation and network connectivity. Our multivariate analysis suggests that selection acts on the expression of photosynthesis genes, but that the efficacy of selection is genetically constrained under drought conditions. Drought selected for earlier flowering and a higher expression of OsMADS18 (Os07g0605200), which encodes a MADS-box transcription factor and is a known regulator of early flowering—marking this gene as a drought-escape gene. The ability to estimate selection strengths provides insights into how selection can shape molecular traits at the core of gene action.
基因的表达水平是生物表型的基础,但对于基因表达的自然选择及其在适应性演化方面的作用还不清楚。本文中,作者分析了水稻中的基因表达,并利用表型选择分析对超过15000个转录本估计了选择的类型与强度。在湿润稻田环境下,大多数转录本上的变异几乎都是中性或者具有非常弱的稳定选择,但是在干旱条件下,选择的强度会增强。总体来说,条件性中性的转录本占了2.83%,要比拮抗性多效性转录本(占0.04%)多,并且那些基因表达和随机噪音水平更低、可塑性更高的转录本往往受到更强的选择。选择强度与顺式调控和网络连接性水平具有弱的负相关性。多元分析显示在干旱条件下,选择作用于光合基因的表达,但是选择的效果会受到遗传限制。干旱条件选择早花表型以及OsMADS18基因的高表达,该基因编码一个MADS-box转录因子,作用于早花调控,因此被认为是一个“干旱逃逸”基因。本文对于选择强度的估计为选择如何塑造核心基因功能的分子性状提供了新的见解。
p.s. 稳定选择(stabilizing selection):针对某个特征的选择,处于中间型的性状被自然选择保留,而处于两端的性状被淘汰。
拮抗的基因多效性(Antagonistic pleiotropy):1953年,美国演化生物学家George C. Williams提出的一个理论,用来解释衰老问题。该理论认为自然选择虽然富集了促有效生殖的基因,但忽略了对寿命的不利影响。然而,如果一个基因突变虽然缩短寿命,但能导致更多后代出生,就能够短时间内产生更多携带父母基因的后代,从而补偿父母寿命的损失。因此,随着时间的推移,亲本中有利生殖的“健康突变”和减少寿命的“衰老突变”都积极地被保留了下来。
通讯:Michael D. Purugganan (https://www.york.ac.uk/biology/research/plant-biology/ian-a-graham/)
个人简介:1985年,菲律宾大学,学士;1986年,哥伦比亚大学,硕士;1993年,佐治亚大学,博士。
研究方向:植物适应的演化基因组学与生态基因组学;植物驯化遗传学;生物的多细胞性演化与社会性行为研究。
doi: https://doi.org/10.1038/s41586-020-1997-2
Journal: Nature
Published date: February 12, 2020
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