Herbst Rebecca H, Bar-Zvi Dana, Reikhav Sharon, Soifer Ilya, Breker Michal, Jona Ghil, Shimoni Eyal, Schuldiner Maya, Levy Avraham A, Barkai Naama
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, 7610001, Israel.
Broad Institute of MIT and Harvard, Cambridge, MA, 02142, USA.
BMC Biol. 2017 May 11;15(1):38. doi: 10.1186/s12915-017-0373-7.
The merging of genomes in inter-specific hybrids can result in novel phenotypes, including increased growth rate and biomass yield, a phenomenon known as heterosis. Heterosis is typically viewed as the opposite of hybrid incompatibility. In this view, the superior performance of the hybrid is attributed to heterozygote combinations that compensate for deleterious mutations accumulating in each individual genome, or lead to new, over-dominating interactions with improved performance. Still, only fragmented knowledge is available on genes and processes contributing to heterosis.
We describe a budding yeast hybrid that grows faster than both its parents under different environments. Phenotypically, the hybrid progresses more rapidly through cell cycle checkpoints, relieves the repression of respiration in fast growing conditions, does not slow down its growth when presented with ethanol stress, and shows increased signs of DNA damage. A systematic genetic screen identified hundreds of S. cerevisiae alleles whose deletion reduced growth of the hybrid. These growth-affecting alleles were condition-dependent, and differed greatly from alleles that reduced the growth of the S. cerevisiae parent.
Our results define a budding yeast hybrid that is perturbed in multiple regulatory processes but still shows a clear growth heterosis. We propose that heterosis results from incompatibilities that perturb regulatory mechanisms, which evolved to protect cells against damage or prepare them for future challenges by limiting cell growth.
种间杂交中基因组的融合可导致新的表型，包括生长速率和生物量产量增加，这种现象称为杂种优势。杂种优势通常被视为杂种不亲和性的对立面。按照这种观点，杂种的优越性能归因于杂合子组合，这些组合补偿了每个个体基因组中积累的有害突变，或导致新的、具有优势的相互作用并提高性能。然而，关于导致杂种优势的基因和过程，目前仍只有零散的知识。
我们描述了一种出芽酵母杂种，它在不同环境下的生长速度都比其双亲快。从表型上看，该杂种在细胞周期检查点的进展更快，在快速生长条件下解除了对呼吸作用的抑制，在受到乙醇胁迫时生长速度不会减慢，并且显示出更多DNA损伤的迹象。一项系统的遗传筛选鉴定出数百个酿酒酵母等位基因，其缺失会降低杂种的生长。这些影响生长的等位基因是条件依赖性的，并且与那些降低酿酒酵母亲本生长的等位基因有很大差异。
我们的结果定义了一种出芽酵母杂种，它在多个调控过程中受到干扰，但仍表现出明显的生长杂种优势。我们提出，杂种优势源于干扰调控机制的不相容性，这些调控机制的进化是为了通过限制细胞生长来保护细胞免受损伤或为未来的挑战做好准备。
