Nishiyama Tomoaki, Fujita Tomomichi, Shin-I Tadasu, Seki Motoaki, Nishide Hiroyo, Uchiyama Ikuo, Kamiya Asako, Carninci Piero, Hayashizaki Yoshihide, Shinozaki Kazuo, Kohara Yuji, Hasebe Mitsuyasu
Division of Speciation Mechanisms 2 and Computer Laboratory, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Proc Natl Acad Sci U S A. 2003 Jun 24;100(13):8007-12. doi: 10.1073/pnas.0932694100. Epub 2003 Jun 13.
The mosses and flowering plants diverged >400 million years ago. The mosses have haploid-dominant life cycles, whereas the flowering plants are diploid-dominant. The common ancestors of land plants have been inferred to be haploid-dominant, suggesting that genes used in the diploid body of flowering plants were recruited from the genes used in the haploid body of the ancestors during the evolution of land plants. To assess this evolutionary hypothesis, we constructed an EST library of the moss Physcomitrella patens, and compared the moss transcriptome to the genome of Arabidopsis thaliana. We constructed full-length enriched cDNA libraries from auxin-treated, cytokinin-treated, and untreated gametophytes of P. patens, and sequenced both ends of >40,000 clones. These data, together with the mRNA sequences in the public databases, were assembled into 15,883 putative transcripts. Sequence comparisons of A. thaliana and P. patens showed that at least 66% of the A. thaliana genes had homologues in P. patens. Comparison of the P. patens putative transcripts with all known proteins, revealed 9,907 putative transcripts with high levels of similarity to vascular plant genes, and 850 putative transcripts with high levels of similarity to other organisms. The haploid transcriptome of P. patens appears to be quite similar to the A. thaliana genome, supporting the evolutionary hypothesis. Our study also revealed that a number of genes are moss specific and were lost in the flowering plant lineage.
苔藓植物和开花植物在4亿多年前就分化了。苔藓植物具有单倍体主导的生命周期，而开花植物则是二倍体主导。陆地植物的共同祖先被推断为单倍体主导，这表明开花植物二倍体中使用的基因是在陆地植物进化过程中从祖先单倍体中使用的基因招募而来的。为了评估这一进化假说，我们构建了小立碗藓的EST文库，并将苔藓转录组与拟南芥基因组进行了比较。我们从小立碗藓经生长素处理、细胞分裂素处理和未处理的配子体中构建了全长富集cDNA文库，并对40000多个克隆的两端进行了测序。这些数据与公共数据库中的mRNA序列一起被组装成15883个推定转录本。拟南芥和小立碗藓的序列比较表明，拟南芥中至少66%的基因在小立碗藓中有同源物。将小立碗藓的推定转录本与所有已知蛋白质进行比较，发现9907个推定转录本与维管植物基因具有高度相似性，850个推定转录本与其他生物具有高度相似性。小立碗藓的单倍体转录组似乎与拟南芥基因组非常相似，支持了这一进化假说。我们的研究还表明，许多基因是苔藓特有的，并且在开花植物谱系中丢失了。
