Characterization of the <Emphasis Type="Italic">Selaginella remotifolia</Emphasis> MADS-box gene

Recent progress in plant molecular genetics has revealed that floral organ development is regulated by several homeotic selector genes, most of which belong to the MADS-box gene family. Here we report on SrMADS1, a MIKC^c-type MADS-box gene from Selaginella, a spikemoss belonging to the lycophytes. SrMADS1 phylogenetically forms a monophyletic clade with genes of the LAMB2 group, which are MIKC^c genes of the clubmoss Lycopodium, and is expressed in whole sporophytic tissues except roots and rhizophores. Our results and the previous report on Lycopodium MIKC^c genes suggest that the ancestral MIKC^c gene of primitive dichotomous plants in the early Devonian was involved in the development of basic sporophytic tissues such as shoot, stem, and sporangium. Electronic Publication     

Ancestry of plant MADS-box genes revealed by bryophyte (Physcomitrella patens) homologues

Three MADS-box cDNA clones and two corresponding genomic sequences (gDNAs) have been isolated from the bryophyte Physcomitrella patens and sequenced. Our findings indicate that the genes may be expressed in a tissue- or age-specific manner, and that expression of one of them is regulated by an alternative splicing mechanism. Conceptual translation of the clones reveals that the encoded MADS-domain proteins have the typical plant-domain pattern (MIKC). Additionally, there is a high degree of conservation of intron number and positions between angiosperm MADS-box genes and the moss loci. These observations confirm the homology of moss and higher plant MADS-box genes. We conclude that the MIKC pattern evolved in MADS-box genes after the separation of the plant lineage from that of fungi and animals, and that it must have been present in the common ancestor of mosses, ferns and seed plants. Therefore it evolved at least 400 million yr ago. Phylogenetic analysis of a large subset of the sequenced plant MADS-box genes, incorporating those from P. patens , indicates that the bryophyte genes are not orthologues of spermatophyte genes belonging to any of the well recognized higher plant gene subfamilies. This conclusion accords well with reports that the known fern MADS-box genes also comprise subfamilies distinct from those of higher plants. Therefore we tentatively propose that the gene duplication and diversification events that created the MADS-box gene subfamilies, discernible in extant angiosperm and other spermatophyte groups, occurred after separation of the moss and fern lineages from the lineage which produced the higher plants.     

AGAMOUS like 6亚家族基因研究进展

开花是植物由营养生长向生殖生长转变的重要过程,许多开花相关基因参与这一过程,AGAMOUS like 6(AGL6)亚家族是其中的重要一类,AGL6亚家族基因编码MIKC-type MADS box转录因子,含有MADS-box保守结构域,通过多条途径参与花时的调节及花器官发育。该文对AGL6及其同源基因的结构、功能、进化以及与其它相关基因之间的调控关系进行综述,并对该基因研究中存在的一些问题及今后的研究方向进行了讨论。     

甘蓝型油菜MADS-box基因家族的鉴定与系统进化分析

MADS-box基因家族参与调控开花时间、花器官分化、根系生长、分生组织分化、子房和配子发育、果实膨大及衰老等植物生长发育的重要过程。基于甘蓝型油菜(Brassica napus)基因组测序数据,利用生物信息学方法对甘蓝型油菜MADS-box基因家族进行鉴定和注释及基因结构与系统进化分析。结果显示,在甘蓝型油菜中鉴定出307个MADS-box基因家族成员,根据进化关系可将其分为两大类型,I型(M-type)包含α、β、γ三个亚家族,II型(MIKC-type)包括MIKCC和MIKC*两个亚家族,MIKCC可进一步分为13个小类;甘蓝型油菜A基因组染色体上分布的MADS-box基因多于C基因组。在基因结构上,MIKC-type亚家族基因序列普遍比M-type长且含有较多的外显子;M-type亚家族蛋白序列中的motif数量为2–5个,MIKC-type亚家族蛋白序列中平均含有7个motif。拟南芥(Arabidopsis thaliana)与甘蓝型油菜MADS-box基因共线性分析结果显示,全基因组复制事件对MADS-box基因家族尤其是MIKC亚家族的扩张起重要作用;MIKC亚家族基因在进化过程中受到的选择压力约为M-type的2倍,这表明MIKC-type亚家族在进化过程中被选择性保留。