Evolution of Morphological Characters based on genes in Uasculan plants

花是陆地植物中最复杂的生殖器官，由萼片、花瓣、雄蕊和雌蕊群组成(S)。单倍体细胞，即大孢子和小孢子，在雄蕊和雌蕊群中减数分裂形成。小孢子被包裹在一个多细胞的孢子囊中。大孢子在覆盖着内外珠被的珠心中发育。裸子植物和蕨类植物的生殖器官比裸子植物更简单，没有隔片和隔膜。裸子植物的珠心只有一个珠被，花器官的发育主要受MADS基因家族成员的调控，MADS基因家族的成员是含有保守的MADS和K结构域的转录因子。根据基因树，被子植物的MADS基因分为10多个组，而蕨类植物的MADS基因则分为3组，它们与被子植物的MADS基因的关系不明确，…在被子植物中，MADS基因的数量增加可能与植物复杂生殖器官的进化有关。在被子植物中，一些MADS基因作为同源选择基因在特定的花器官原基中表达，而另一些MADS基因在生殖器官和营养器官中都表达。在裸子植物中，MADS基因的生殖器官特异性表达已被报道。与后一类被子植物MADS基因一样，MADS基因也是在特定的花器官原基中表达的。大多数蕨类植物MADS基因在生殖器官和营养器官中都有表达。普遍表达的MADS基因可能比生殖器官特异的MADS基因更原始。如果是这样的话，很可能是一些MADS基因被选作特殊生殖器官的同源选择基因，它们的表达仅限于特定的花器官原基，即蕨类植物和种子植物分化后发生的事件。MADS基因表达的限制可能是由于调节MADS基因的其他基因的进化造成的。这些最新的结果可能表明：(1)MADS基因的增加是通过基因复制而产生的，(2)某些MADS基因在特定生殖器官中的表达受到限制；(3)MADS基因在被子植物谱系中作为同源异型选择基因的专化性在维管植物花器官进化中起着重要作用。较少

A flower is the most complex reproductive organ in land plants and composed of sepals, petals, stamens, and gynoecium (s).Haploid cells, mega and microspores, for syngamy are formed by meiosis in a stamen and a gynoecium.Microspores are enclosed in a multicellular sporangium.Megaspores develop in a nucellus covered with inner and outer integuments.Gymnosperms and ferns have simpler reproductive organs than anigiosperms and lack sepals and sepals.A nucellus of a gymnosperm is covered with only one integument, while sporangiums of ferns have no integuments and are naked on the abaxial side of a leaf.The development of floral organs is mainly regulated by the members of the MADS gene family whose members are transcription factors containing conserved MADS and K domains.MADS genes of angiosperms are divided into more than 10 groups based on thegene tree, while MADS genes of the fern Ceratopteris richardii are classified into 3 groups whose relationships to angiosperm MADS genes are ambiguo … More us with low bootstrap values.Based on the studies of three gymnosperms, Pinus, Ginkgo and Gnetum, almost all groups of angiosperm MADS genes have been differenciated, suggesting that increase of MADS gene number is likely to be related to the evolution of complexed reproductive organs in plants.In angiosperms, some MADS genes are expressed in specific floral organ primordia as homeotic selector genes, while other MADS genes are expressed in both reproductive and vegetative organs.In gymnosperms, reproductive-organ-specific expression of MADS genes have been reported.Like the latter type of angiosperm MADS genes, most of the fern MADS genes are expressed in both the reproductive and vegetative organs.The generally-expressed MADS genes may be more primitive than the reproductive organ-specific MADS genes.If so, it is likely that some of the MADS genes were co-opted as homeotic selector genes of specialized reproductive organs and their expression restricted to specific floral organ primordia, events that occurred after the divergence of ferns and seed plants.The restriction of MADS gene expression may have been caused by the evolution of other genes that regulate the MADS genes.These recent results may indicate that (1) the increase of MADS genes via gene duplication, (2) the restriction of expression of some MADS genes to specific reproductive organs, and (3) the specialization of MADS gene functions as homeotic selector genes in the angiosperm lineage were important in the floral organ evolution of vascular plants. Less