Department of Biology and Institute for Genome Sciences and Policy, Duke University, USA.
Mol Biol Evol. 2011 Jan;28(1):803-12. doi: 10.1093/molbev/msq254. Epub 2010 Sep 20.
The evolution of land plants is tightly linked to the evolution of the alternation of generations. Because alternating ploidal generations share their genomes, investigating generation-biased gene expression can give insight into the evolution of life cycles in land plants. Toward this end, we describe gene expression differences associated with the alternation of isogenic sporophyte and gametophyte generations in bryophytes, extant representatives of early diverging land plants, using a moss model system (Funaria hygrometrica). We found that differentiation in gene expression between the sporophyte and gametophyte generations is weaker in the bryophyte model system than in Arabidopsis thaliana. This is in line with the basal phylogenetic position of bryophytes and with the origin of alternating generations from a purely haplontic life cycle. Comparative analysis of F. hygrometrica and A. thaliana gene expression data shows that there is limited conservation of generation-biased gene expression across land plants. However, genes showing shared sporophyte-biased expression in both F. hygrometrica and A. thaliana appear to be enriched for biological pathways representing critical molecular adaptations to terrestrial life. Comparative analyses of the expression of F. hygrometrica and A. thaliana regulatory genes suggest that conserved regulatory networks may be involved in growth and reproductive tissue development of the angiosperm and bryophyte sporophyte generations despite their morphological divergence. This study represents the first attempt to describe generation-biased gene expression in a plant with a well-developed sporophyte and gametophyte generations, and as such it lays the foundation for future targeted research on the developmental mechanisms underlying evolutionary diversification of plant sporophytes.
陆地植物的进化与世代交替的进化密切相关。由于交替的倍性世代共享其基因组，因此研究世代偏向的基因表达可以深入了解陆地植物生活史的进化。为此，我们使用苔藓模型系统（Funaria hygrometrica）描述了与苔藓植物（早期分化的陆地植物的现存代表）的同型世代和配子世代交替相关的基因表达差异。我们发现，与拟南芥相比，苔藓模式系统中孢子体和配子体世代之间基因表达的分化较弱。这与苔藓植物的基础系统发育位置以及世代交替从纯粹的单倍体生活史起源是一致的。对 F. hygrometrica 和 A. thaliana 基因表达数据的比较分析表明，世代偏向的基因表达在陆地植物中没有得到很好的保守。然而，在 F. hygrometrica 和 A. thaliana 中都表现出共享的孢子体偏向表达的基因似乎富集了代表对陆地生活的关键分子适应的生物学途径。对 F. hygrometrica 和 A. thaliana 调控基因表达的比较分析表明，尽管被子植物和苔藓植物的孢子体在形态上存在分化，但保守的调控网络可能参与了它们的生长和生殖组织发育。本研究首次尝试描述具有发达孢子体和配子体世代的植物中的世代偏向基因表达，为未来针对植物孢子体进化多样性的发育机制的靶向研究奠定了基础。
