ISSN:
1573-5028
Keywords:
Nms-25 (nodulin-25) DNA sequence
;
nodule-specific gene
;
symbiotic nitrogen fixation
;
evolution by exon-shuffling
;
retrotransposon
;
Medicago sativa (alfalfa)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract We present the primary structure of a nudule-specific gene, Nms-25 from Medicago sativa L. cultivar Nagyszénási. Analysis of the nucleotide sequence of Nms-25 revealed that this gene shows all the characteristics of an interrupted plant gene consisting of 13 exons and 12 introns. The promoter region of Nms-25 contains the common promoter elements of plant genes as well as motifs which are supposed to be involved in nodule-specific expression. There are two exon-like sequences in the gene named PE1 and PE2 which are not present in the cDNA clones of Medicago sativa cultivar Cardinal. Intron 9 carries a retrotransposon-like element, Tms1, which might be responsible for downstream deletion events in which a heptanucleotide, ATTAGCT, might have been involved. Most of the exons, exept 1, 12 and 13, are similar to each other both in length (54 bp) and sequence (up to 94% sequence similarity). All exons are interrupted by introns in the same phase (type I). It is suggested that exon-shuffling based on illegitimate recombination in which the ATTAGCT motif might have played an active role, and retrotransposon-mediated DNA rearrangements were the primary events in the molecular evolution of the Nms-25 gene. The nucleotide sequence of the genomic clone of Nms-25 from Medicago sativa is available from the EMBL/GenBank/DDBJ Nucleotide Sequence Databases under the accession number X13287.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00036915
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