College of Horticulture, Northeast Agricultural University, Harbin 150030, PR China.
Annoroad Gene Technology (Beijing) Co., Ltd, Beijing 100176, PR China.
Gene. 2018 Jul 30;665:119-126. doi: 10.1016/j.gene.2018.04.047. Epub 2018 Apr 27.
Inbreeding depression is the reduction in fitness observed in inbred populations. In plants, it leads to disease, weaker resistance to adverse environmental conditions, inhibition of growth, and decrease of yield. To elucidate molecular mechanisms behind inbreeding depression, we compared global DNA methylation and transcriptome profiles of a normal and a highly inbred heading degenerated variety of the Chinese cabbage (Brassica rapa L. ssp. pekinensis). DNA methylation was reduced in inbred plants, suggesting a change in the epigenetic landscape. Transcriptome analysis by RNA-Seq revealed that genes in auxin-response and synthesis pathways were differentially expressed in the inbreeding depression lines. Interestingly, methylation levels of some of those genes were also changed. Furthermore, endogenous IAA content was decreased in inbred plants, in agreement with expression and methylation data. Chemical inhibition of auxin also replicated the degenerated phenotype in normal plants, while exogenous IAA application had no effect in inbred depression plants, suggesting a more complex mechanism. These data indicate DNA methylation-regulated auxin pathways play a role in establishing inbred depression phenotypes in plants. Our findings reveal new insights into inbreeding depression and leafy head development in Chinese cabbage.
自交衰退是指在自交群体中观察到的适合度降低。在植物中，它会导致疾病、对不利环境条件的抗性减弱、生长抑制和产量下降。为了阐明自交衰退背后的分子机制，我们比较了正常和高度自交的大白菜（Brassica rapa L. ssp. pekinensis）抽薹退化品种的全基因组 DNA 甲基化和转录组谱。自交植物中的 DNA 甲基化减少，表明表观遗传景观发生了变化。通过 RNA-Seq 的转录组分析表明，生长素响应和合成途径中的基因在自交衰退系中差异表达。有趣的是，这些基因中的一些基因的甲基化水平也发生了变化。此外，自交植物中的内源 IAA 含量降低，与表达和甲基化数据一致。生长素的化学抑制也在正常植物中复制了退化表型，而外源 IAA 的应用对自交衰退植物没有影响，表明存在更复杂的机制。这些数据表明，DNA 甲基化调控的生长素途径在植物中自交衰退表型的建立中起作用。我们的研究结果为大白菜自交衰退和叶球发育提供了新的见解。
