Early evolution of land plants

我们对陆生植物早期进化的研究主要有以下几个方面的结果：1.根据rbeL、psaA、psaB、psbD和rpoC 2的部分核苷酸序列（共456.3bp），构建了3个brandites纲和维管植物的系统发育树。说明金鱼藻是陆地植物多样性的基础，藓类和地钱是一个单系类群，与维管植物形成姊妹类群.对从Ceratopteris richardii（蕨类）和Physcomitrella patens（苔藓）中分离的MADS、HD-ZIP和KNOX基因家族的cDNA进行了核苷酸序列测定。基因家族被认为是重要的。在有花植物器官形成中的作用。分子系统树表明。基因复制发生在陆生植物多样化之前。组基因表达分析表明，这些基因可能具有器官特异性或世代特异性。显示出这样的特异性。构建了一个标记转化子文库，建立了一个从立碗藓转化子中分离基因的实验系统.细胞谱系的顶端进行了分析，以确定现存的地下根茎的同源性。原始维管植物裸盖蕨地下根状茎的顶端细胞以不规则的方式产生子顶端细胞，导致不规则的分枝模式。这种不规则性是裸盖蕨地下根茎所特有的。

Our studies on (he early evolution of land plants had the following results :1. A phylogenetic tree among three bryophyte classes and vascular plants was deduced based on partial nucleotide sequences of rbeL, psaA, psaB, psbD, and rpoC2 (456.3 bp in total). It was suggested that the hornworts are basal in land plant diversification and the mosses and liverworts are a monophyletic group which form sister groups with vascular Plants.2. The nucleotide sequences were letermined of eDNA of MADS, HD-ZIP AND KNOX gene families isolated from Ceratopteris richardii (fern) and Physcomitrella pa tens (moss). The gene families are understood to play significant. roles in organ formation in flowering plants. A molecular phylogenetic tree suggested that. gene duplication took place prior to diversification of the land plant. groups. Analyses of gene expression showed that the genes may be organ-specific or generation-specific or not. show such specificity.3. A library of tagged transforms was formed to establish an experimental system for isolating genes from transforms in Physcomitrella pa tens.4. Cell lineages of apices were analyzed to determine the homology of the subterranean rhizome of the extant. primitive vascular plant. Psilotum nudum. The apical cell of the subterranean rhizome produces daughter apical cells in an irregular manner, resulting in the irregular branching pattern. Such irregularities are unique to the Psilotum nudum subterranean rhizome.