Menzel Mandy, Sletvold Nina, Ågren Jon, Hansson Bengt
Molecular Ecology and Evolution Laboratory, Department of Biology, Lund University, Lund, Sweden Unit of Respiratory Immunopharmacology, Department of Experimental Medical Science, Lund University, Lund, Sweden.
Plant Ecology and Evolution, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
Mol Biol Evol. 2015 Aug;32(8):2036-47. doi: 10.1093/molbev/msv086. Epub 2015 Apr 7.
Knowledge of which genes and pathways are affected by inbreeding may help understanding the genetic basis of inbreeding depression, the potential for purging (selection against deleterious recessive alleles), and the transition from outcrossing to selfing. Arabidopsis lyrata is a predominantly self-incompatible perennial plant, closely related to the selfing model species A. thaliana. To examine how inbreeding affects gene expression, we compared the transcriptome of experimentally selfed and outcrossed A. lyrata originating from two Scandinavian populations that express similar inbreeding depression for fitness (∂ ≈ 0.80). The number of genes significantly differentially expressed between selfed and outcrossed individuals were 2.5 times higher in the Norwegian population (≈ 500 genes) than in the Swedish population (≈ 200 genes). In both populations, a majority of genes were upregulated on selfing (≈ 80%). Functional annotation analysis of the differentially expressed genes showed that selfed offspring were characterized by 1) upregulation of stress-related genes in both populations and 2) upregulation of photosynthesis-related genes in Sweden but downregulation in Norway. Moreover, we found that reproduction- and pollination-related genes were affected by inbreeding only in Norway. We conclude that inbreeding causes both general and population-specific effects. The observed common effects suggest that inbreeding generally upregulates rather than downregulates gene expression and affects genes associated with stress response and general metabolic activity. Population differences in the number of affected genes and in effects on the expression of photosynthesis-related genes show that the genetic basis of inbreeding depression can differ between populations with very similar levels of inbreeding depression.
了解哪些基因和通路受近亲繁殖影响，可能有助于理解近亲繁殖衰退的遗传基础、清除有害隐性等位基因的潜力，以及从异交向自交的转变。琴叶拟南芥是一种主要自交不亲和的多年生植物，与自交模式物种拟南芥亲缘关系密切。为了研究近亲繁殖如何影响基因表达，我们比较了来自两个斯堪的纳维亚种群的实验自交和异交琴叶拟南芥的转录组，这两个种群在适合度上表现出相似的近亲繁殖衰退（∂≈0.80）。自交和异交个体之间显著差异表达的基因数量，在挪威种群（约500个基因）中比在瑞典种群（约200个基因）中高2.5倍。在两个种群中，大多数基因在自交时上调（约80%）。对差异表达基因的功能注释分析表明，自交后代的特征是：1）两个种群中与应激相关的基因均上调；2）瑞典种群中与光合作用相关的基因上调，而挪威种群中则下调。此外，我们发现与繁殖和授粉相关的基因仅在挪威受近亲繁殖影响。我们得出结论，近亲繁殖会产生普遍效应和种群特异性效应。观察到的共同效应表明，近亲繁殖通常会上调而非下调基因表达，并影响与应激反应和一般代谢活动相关的基因。受影响基因数量以及对光合作用相关基因表达影响的种群差异表明，近亲繁殖衰退的遗传基础在近亲繁殖衰退水平非常相似的种群之间可能有所不同。
