Partial cytological diploidization of neoautotetraploid meiosis by induced cross-over rate reduction.
Partial cytological diploidization of neoautotetraploid meiosis by induced cross-over rate reduction.
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DOI：
10.1073/pnas.2305002120
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发表时间：
2023-08-15
影响因子：
11.1
通讯作者：
Bomblies, Kirsten
中科院分区：
文献类型：
--
作者：
Gonzalo, Adrian;Parra-Nunez, Pablo;Bachmann, Andreas L.;Sanchez-Moran, Eugenio;Bomblies, Kirsten
多倍性，或全基因组复制，已经发生在整个真核生物，特别是植物。多倍体通常表现出较大的果实，种子或叶子，以及对干旱等气候压力的适应性等优势，这可能解释了为什么多倍体在植物中的比例过高。不幸的是，新形成的新多倍体在作物改良中的使用往往受到其低生育力的阻碍--这一特征通常与减数分裂缺陷相关。基于对自然多倍体如何进化出减数分裂挑战的解决方案的先前理解，在这里，我们测试了降低减数分裂重组率可能是解决这个问题的有用的工程解决方案的假设。我们表明，确实减少了交换率确实减轻了一些减数分裂缺陷，但这并不是问题的全部。多倍体是由全基因组复制事件引起的，它对整个真核生物的基因组进化做出了贡献。在植物中，新多倍体的新特征包括可以在进化上或农业上有益的性状，例如增加的非生物胁迫耐受性。因此，除了从进化的角度来看是有趣的，基因组复制也越来越被认为是一个有前途的作物改良工具。然而，新形成的（neo）多倍体通常遭受生育问题，这归因于减数分裂期间多个同源染色体拷贝之间的异常关联（多价体）。在这里，我们测试了长期存在的假设，减少减数分裂的交换数可能足以限制多价体的形成，有利于二倍体样二价体协会（细胞学二倍体化）。为此，我们通过组合HEI 10和TAF 4 b的突变开发了具有低交换率的拟南芥品系。双突变体在不影响减数分裂稳定性的情况下，二倍体的交换数减少了约33%。来自双突变体的新多倍体显示出相对于野生型新四倍体约40%的交换率降低，并且四个同源物的组确实形成了更少的多价体和更多的二价体。然而，我们也表明，多价体的减少伴随着单价体频率略有增加的代价，并且它并不能挽救新多倍体的生育能力。因此，虽然我们的研究结果确实表明，降低交换率可以降低新多倍体中的多价频率，但它们也强调，在解决新多倍体育性挑战时，需要考虑影响减数分裂稳定性和新多倍体育性的其他因素。
Polyploidy, or whole-genome duplication, has occurred throughout eukaryotes, especially plants. Polyploids often exhibit advantages such as larger fruits, seeds, or leaves, and resilience to climate-stressors like drought, likely explaining why polyploids are overrepresented especially among plants. Unfortunately, the use of newly formed neopolyploids in crop improvement is often hampered by their low fertility—a trait often correlated with meiotic defects. Based on prior understanding of how natural polyploids evolved solutions to meiotic challenges, here we test the hypothesis that reducing meiotic recombination rates could be a useful engineered solution for this problem. We show that indeed a cross-over rate reduction does mitigate some meiotic defects, but also that this is not the whole problem. Polyploids, which arise from whole-genome duplication events, have contributed to genome evolution throughout eukaryotes. Among plants, novel features of neopolyploids include traits that can be evolutionarily or agriculturally beneficial, such as increased abiotic stress tolerance. Thus, in addition to being interesting from an evolutionary perspective, genome duplication is also increasingly recognized as a promising crop improvement tool. However, newly formed (neo)polyploids commonly suffer from fertility problems, which have been attributed to abnormal associations among the multiple homologous chromosome copies during meiosis (multivalents). Here, we test the long-standing hypothesis that reducing meiotic cross-over number may be sufficient to limit multivalent formation, favoring diploid-like bivalent associations (cytological diploidization). To do so, we developed Arabidopsis thaliana lines with low cross-over rates by combining mutations for HEI10 and TAF4b. Double mutants showed a reduction of ~33% in cross-over numbers in diploids without compromising meiotic stability. Neopolyploids derived from the double mutant show a cross-over rate reduction of about 40% relative to wild-type neotetraploids, and groups of four homologs indeed formed fewer multivalents and more bivalents. However, we also show that the reduction in multivalents comes with the cost of a slightly increased frequency of univalents and that it does not rescue neopolyploid fertility. Thus, while our results do show that reducing cross-over rates can reduce multivalent frequency in neopolyploids, they also emphasize that there are additional factors affecting both meiotic stability and neopolyploid fertility that will need to be considered in solving the neopolyploid fertility challenge.
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