Sequence Peculiarity of Gnetalean Legumin-Like Seed Storage Proteins |
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Authors: | AD Shutov H Braun YuV Chesnokov Ch Horstmann IA Kakhovskaya H Bäumlein |
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Institution: | Institut für Pflanzengenetik und Kulturpflanzenforschung, Corrensstra?e 3, D-06466 Gatersleben, Germany, DE Laboratory of Protein Chemistry, State University of Moldova, MD-2009 Kishinev, Moldova, MD
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Abstract: | 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.
Received: 5 June 1997 / Accepted: 31 March 1998 |
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Keywords: | : Gene evolution — Seed storage proteins — Legumin genes — Intron/exon structure — Gnetales |
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