CERZOS-CONICET, CCT-Bahía Blanca, Bahía Blanca, Argentina.
Departamento de Agronomía, Universidad Nacional del Sur, Bahía Blanca, Argentina.
PLoS One. 2017 Apr 18;12(4):e0175852. doi: 10.1371/journal.pone.0175852. eCollection 2017.
To overcome environmental stress, plants develop physiological responses that are triggered by genetic or epigenetic changes, some of which involve DNA methylation. It has been proposed that apomixis, the formation of asexual seeds without meiosis, occurs through the temporal or spatial deregulation of the sexual process mediated by genetic and epigenetic factors influenced by the environment. Here, we explored whether there was a link between the occurrence of apomixis and various factors that generate stress, including drought stress, in vitro culture, and intraspecific hybridization. For this purpose, we monitored the embryo sacs of different weeping lovegrass (Eragrostis curvula [Schrad.] Nees) genotypes after the plants were subjected to these stress conditions. Progeny tests based on molecular markers and genome methylation status were analyzed following the stress treatment. When grown in the greenhouse, the cultivar Tanganyika INTA generated less than 2% of its progeny by sexual reproduction. Plants of this cultivar subjected to different stresses showed an increase of sexual embryo sacs, demonstrating an increased expression of sexuality compared to control plants. Plants of the cv. Tanganyika USDA did not demonstrate the ability to generate sexual embryo sacs under any conditions and is therefore classified as a fully apomictic cultivar. We found that this change in the prevalence of sexuality was correlated with genetic and epigenetic changes analyzed by MSAP and AFLPs profiles. Our results demonstrate that different stress conditions can alter the expression of sexual reproduction in facultative tetraploid apomictic cultivars and when the stress stops the reproductive mode shift back to the apomixis original level. These data together with previous observations allow us to generate a hypothetical model of the regulation of apomixis in weeping lovegrass in which the genetic/s region/s that condition apomixis, is/are affected by ploidy, and is/are subjected to epigenetic control.
为了克服环境压力，植物会产生生理反应，这些反应是由遗传或表观遗传变化触发的，其中一些涉及 DNA 甲基化。有人提出，无融合生殖（即不经减数分裂形成无性种子的过程）是通过遗传和表观遗传因素介导的有性过程的时间或空间失调而发生的，这些因素受环境影响。在这里，我们探讨了无融合生殖的发生是否与各种产生应激的因素有关，包括干旱应激、体外培养和种内杂交。为此，我们在对这些应激条件下的植物进行监测后，观察了不同垂穗披碱草（Eragrostis curvula [Schrad.] Nees）基因型的胚囊。在应激处理后，我们基于分子标记和基因组甲基化状态对后代进行了测试分析。当在温室中生长时，坦噶尼喀 INTA 品种的后代中通过有性繁殖产生的比例不到 2%。该品种的植物在受到不同应激后，表现出有性胚囊的增加，与对照植物相比，表现出更高的有性表达。坦噶尼喀 USDA 品种的植物在任何条件下都没有表现出产生有性胚囊的能力，因此被归类为完全无融合生殖的品种。我们发现，这种有性生殖出现频率的变化与通过 MSAP 和 AFLP 分析的遗传和表观遗传变化有关。我们的结果表明，不同的应激条件可以改变兼性四倍体无融合生殖品种有性繁殖的表达，当应激停止时，繁殖模式又回到无融合生殖的原始水平。这些数据与以前的观察结果一起，使我们能够生成垂穗披碱草无融合生殖调控的假设模型，其中决定无融合生殖的遗传/区域受倍性影响，并受到表观遗传控制。
