Xu Jihua, Tanino Karen K, Robinson Stephen J
Department of Plant Sciences, University of Saskatchewan Saskatoon, SK, Canada.
Department of Plant Sciences, University of SaskatchewanSaskatoon, SK, Canada; Agriculture and Agri-Food Canada, Saskatoon Research CentreSaskatoon, SK, Canada.
Front Plant Sci. 2016 Nov 29;7:1768. doi: 10.3389/fpls.2016.01768. eCollection 2016.
Epigenetic inheritance was transmitted through selection over five generations of extreme early, but not late flowering time phenotypic lines in . Epigenetic variation was initially artificially induced using the DNA demethylation reagent 5-azacytidine (5-azaC). It is the first report to explore epigenetic variant selection and phenotypic trait inheritance in strawberry. Transmission frequency of these traits was determined across generations. The early flowering (EF4) and late stolon (LS) phenotypic traits were successfully transmitted across five and three generations through meiosis, respectively. Stable mitotic transmission of the early flowering phenotype was also demonstrated using clonal daughters derived from the 4th Generation (S4) mother plant. In order to further explore the DNA methylation patterns underlying the early flowering trait, the standard MSAP method using isoschizomers Hpa II/Msp I, and newly modified MSAP method using isoschizomers Tfi I/Pfe I which detected DNA methylation at CG, CHG, CHH sites were used in two early flowering lines, EF lines 1 (P2) and EF lines 2 (P3), and control lines (P1). A significant reduction in the number of fully-methylated bands was detected in P2 and P3 when compared to P1 using the novel MSAP method. In the standard MSAP, the symmetric CG and CHG methylation was maintained over generations in the early flowering lines based on the clustering in P2 and P3, the novel MSAP approach revealed the asymmetric CHH methylation pattern was not maintained over generations. This study provides evidence of stable selection of phenotypic traits, particularly early flowering through both meiosis and mitosis, which is meaningful to both breeding programs and commercial horticulture. The maintenance in CG and CHG methylation over generations suggests the early flowering phenotype might be related to DNA methylation alterations at the CG or CHG sites. Finally, this work provides a new approach for studying the role of epigenetics on complex quantitative trait improvement in strawberry, as well as providing a tool to expand phenotypic diversity and expedite potential new horticulture cultivar releases through either seed or vegetative propagation.
表观遗传通过对五代极端早花但非晚花表型株系的选择进行传递。表观遗传变异最初是使用DNA去甲基化试剂5-氮杂胞苷（5-azaC）人工诱导产生的。这是首次探索草莓表观遗传变异选择和表型性状遗传的报告。这些性状的传递频率在多代中进行了测定。早花（EF4）和晚匍匐茎（LS）表型性状分别通过减数分裂成功传递了五代和三代。使用来自第4代（S4）母株的克隆子代也证明了早花表型的稳定有丝分裂传递。为了进一步探究早花性状背后的DNA甲基化模式，在两个早花株系EF株系1（P2）和EF株系2（P3）以及对照株系（P1）中使用了标准的使用同裂酶Hpa II/Msp I的MSAP方法，以及新改良的使用同裂酶Tfi I/Pfe I的MSAP方法，后者可检测CG、CHG、CHH位点的DNA甲基化。与P1相比，使用新型MSAP方法在P2和P3中检测到完全甲基化条带数量显著减少。在标准MSAP中，基于P2和P3中的聚类，早花株系中对称的CG和CHG甲基化在多代中得以维持，而新型MSAP方法显示不对称的CHH甲基化模式在多代中未得以维持。本研究提供了表型性状稳定选择的证据，特别是通过减数分裂和有丝分裂实现的早花，这对育种计划和商业园艺都具有重要意义。CG和CHG甲基化在多代中的维持表明早花表型可能与CG或CHG位点的DNA甲基化改变有关。最后，这项工作为研究表观遗传学在草莓复杂数量性状改良中的作用提供了一种新方法，同时也提供了一种工具，可通过种子或营养繁殖来扩大表型多样性并加速潜在新园艺品种的发布。
