Tanabe Yoichi, Hasebe Mitsuyasu, Sekimoto Hiroyuki, Nishiyama Tomoaki, Kitani Masakazu, Henschel Katrin, Münster Thomas, Theissen Günter, Nozaki Hisayoshi, Ito Motomi
Department of Multi-Disciplinary Sciences, Graduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan.
Proc Natl Acad Sci U S A. 2005 Feb 15;102(7):2436-41. doi: 10.1073/pnas.0409860102. Epub 2005 Feb 7.
The MADS-box genes of land plants are extensively diverged to form a superfamily and are important in various aspects of development including the specification of floral organs as homeotic selector genes. The closest relatives of land plants are the freshwater green algae charophyceans. To study the origin and evolution of land plant MADS-box genes, we characterized these genes in three charophycean green algae: the stonewort Chara globularis, the coleochaete Coleochaete scutata, and the desmid Closterium peracerosum-strigosum-littorale complex. Phylogenetic analyses suggested that MADS-box genes diverged extensively in the land plant lineage after the separation of charophyceans from land plants. The stonewort C. globularis mRNA was specifically detected in the oogonium and antheridium together with the egg and spermatozoid during their differentiation. The expression of the C. peracerosum-strigosum-littorale-complex gene increased when vegetative cells began to differentiate into gametangial cells and decreased after fertilization. These expression patterns suggest that the precursors of land plant MADS-box genes originally functioned in haploid reproductive cell differentiation and that the haploid MADS-box genes were recruited into a diploid generation during the evolution of land plants.
陆地植物的MADS-box基因广泛分化形成一个超家族，并且在包括作为同源异型选择基因决定花器官特征在内的发育的各个方面都很重要。陆地植物的近亲是淡水绿藻轮藻纲植物。为了研究陆地植物MADS-box基因的起源和进化，我们对三种轮藻纲绿藻中的这些基因进行了表征：轮藻属的球状轮藻、鞘毛藻属的盾状鞘毛藻以及新月藻属的近头状新月藻-条纹新月藻-沿岸新月藻复合体。系统发育分析表明，在轮藻纲植物与陆地植物分离后，MADS-box基因在陆地植物谱系中广泛分化。在球状轮藻的卵囊和精子囊以及卵和游动精子分化过程中，特异性检测到了球状轮藻的mRNA。当营养细胞开始分化为配子囊细胞时，近头状新月藻-条纹新月藻-沿岸新月藻复合体基因的表达增加，而在受精后表达下降。这些表达模式表明，陆地植物MADS-box基因的前体最初在单倍体生殖细胞分化中起作用，并且在陆地植物进化过程中，单倍体MADS-box基因被纳入了二倍体世代。
