Shutov A D, Braun H, Chesnokov Y V, Horstmann C, Kakhovskaya I A, Bäumlein H
Institut für Pflanzengenetik und Kulturpflanzenforschung, Corrensstrasse 3, D-06466 Gatersleben, Germany.
J Mol Evol. 1998 Oct;47(4):486-92. doi: 10.1007/pl00006405.
The development of seeds as a specialized organ for the nutrition, protection, and dispersal of the next generation was an important step in the evolution of land plants. Seed maturation is accompanied by massive synthesis of storage compounds such as proteins, starch, and lipids. To study the processes of seed storage protein evolution we have partially sequenced storage proteins from maturing seeds of representatives from the gymnosperm genera Gnetum, Ephedra, and Welwitschia-morphologically diverse and unusual taxa that are grouped in most formal systems into the common order Gnetales. Based on partial N-terminal amino acid sequences, oligonucleotide primers were derived and used for PCR amplification and cloning of the corresponding cDNAs. We also describe the structure of the nuclear gene for legumin of Welwitschia mirabilis. This first gnetalean nuclear gene structure contains introns in only two of the four conserved positions previously characterized in other spermatophyte legumin genes. The distinct phylogenetic status of the gnetalean taxa is also reflected in a sequence peculiarity of their legumin genes. A comparative analysis of exon/intron sequences leads to the hypothesis that legumin genes from Gnetales belong to a monophyletic evolutionary branch clearly distinct from that of legumin genes of extant Ginkgoales and Coniferales as well as from all angiosperms.
种子作为为下一代提供营养、保护和传播的特殊器官的发育，是陆地植物进化中的重要一步。种子成熟伴随着大量贮藏化合物的合成，如蛋白质、淀粉和脂质。为了研究种子贮藏蛋白的进化过程，我们对裸子植物买麻藤属、麻黄属和百岁兰属（在大多数分类系统中，这些形态多样且独特的类群被归为买麻藤目）成熟种子中的贮藏蛋白进行了部分测序。根据部分N端氨基酸序列设计了寡核苷酸引物，并用于相应cDNA的PCR扩增和克隆。我们还描述了百岁兰豆球蛋白核基因的结构。这个首个买麻藤目核基因结构仅在先前在其他种子植物豆球蛋白基因中确定的四个保守位置中的两个位置含有内含子。买麻藤目类群独特的系统发育地位也反映在它们豆球蛋白基因的序列特性上。外显子/内含子序列的比较分析得出一个假设，即买麻藤目的豆球蛋白基因属于一个单系进化分支，与现存银杏目和松柏目以及所有被子植物的豆球蛋白基因的进化分支明显不同。
