芸薹属蔬菜三基因组杂交与多倍化过程中的表观遗传机制研究

Variations were obtained in the process of heterologous genomic hybridization and polyploidization, however, the studies on the relation between phenotype and epigenetic regulation during the hybridization and polyploidization is still very weak. In this study, Brassica trigenomic haploid( ABC) and allohexaploid( AABBCC), which have been synthesized by distant hybridization previously, are used as plant materials. The epigenetic mechanism during distant hybridization and polyploidization are expected to be revealed from the relationship among phenotype, DNA methylation and small RNA. Difference of small RNA and DNA methylation among the allotriploid, allohexaploid and their parents can be analyzed through high throughput sequencing and MSAP, based on which change of their patterns during hybridization and polyploidization and their effect on phenotype will be explored. As well as analysis of DNA methylation patterns, gene expression level and functional verification, ralationship among DNA methylation, gene and phenotype can be revealed. The study will illuminate the epigenetic mechanism during distant hybridization and polyploidization, which will make a significant contribution to the study of mechanism in germplasm innovation by hybridization and the efficient utilization of heterosis.

异源基因组杂交和多倍化过程中可以产生大量的性状遗传变异，目前关于杂交及多倍化过程中性状表现与其表观调控的研究还很薄弱。本项目以前期通过远缘杂交获得的芸薹属蔬菜三基因组单倍体(ABC)与六倍体(AABBCC)为研究材料，从small RNA、DNA甲基化变化以及杂种性状之间的关系着手，研究远缘杂交与多倍化过程中的表观遗传调控机制。利用高通量测序、MSAP技术，分析small RNA、DNA甲基化在亲本、单倍体及多倍体杂种中的异同，结合杂种的性状表现，探究其在杂交、多倍化过程中的模式及在性状表现中的作用；通过DNA甲基化模式差异、基因表达水平以及功能验证，解析DNA甲基化-基因-性状之间的关系。研究结果有望阐明远缘杂交及多倍化过程中表观遗传调控机制，对于杂交创制新种质的机制以及杂种优势高效利用等方面具有重要的意义。

异源基因组杂交和多倍化过程中可以产生大量的性状遗传变异，项目针对以下科学问题即small RNA、DNA甲基化在杂交与多倍化过程中如何变化、以及其与杂种性状表现之间的关系开展了研究。以榨菜与紫甘蓝远缘杂交产生的杂种三倍体H0、异源六倍体S0 及其亲本为实验材料，对杂交及多倍化过程中的基因组行为、small RNA表达、基因表达以及DNA甲基化模式进行分析。主要结果为：（1）在基因组水平上，杂交过程导致大量亲本条带丢失（19.5%），且多数为紫甘蓝特有条带，而在加倍后，染色体组趋于稳定，说明杂交比加倍对基因组的影响更大。（2）杂交造成大量的miRNA和基因表达发生变化，且后代miRNA与基因的表达与父本紫甘蓝的差异更多，与杂交过程相比较，多倍化过程造成的miRNA与基因表达差异较少。（3）与亲本相比较，2类杂种后代的DNA甲基化水平显著下降；与H0相比较，S0的DNA甲基化水平略有下降。杂种后代中，其DNA甲基化模式更多的遗传于母本榨菜，与两亲本相比较，H0及S0后代中DNA甲基化模式发生改变的频率为2.33%。（4）利用S0分别与榨菜、白菜杂交获得了基因组为AABBC和AABC的新材料。经田间观察发现，AABBC在抗病性上有明显优势，而AABC在口感上辣味减少，具有成为鲜食蔬菜的潜力。本项目的研究明确了杂交和多倍化进程中的遗传和表观遗传变化，探究其变化与杂种后代优势性状的相关性，为杂种优势性状的产生研究提供理论依据。