Genetic variation in pea (Pisum) dehydrins: sequence elements responsible for length differences between dehydrin alleles and between dehydrin loci in Pisum sativum L. |
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Authors: | E Grosselindemann M Robertson J A Wilmer P M Chandler |
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Institution: | (1) CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia Fax: 61 2 6246 5000 E-mail: masumi.robertson@pi.csiro.au, AU |
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Abstract: | The electrophoretic patterns of dehydrins extracted from mature seeds of a range of pea (Pisum) species revealed extensive variation in dehydrin polypeptide mobility. Variation was also observed among lines of P. sativum. Crosses between lines with different dehydrin electrophoretic patterns produced F1 seeds with additive patterns, and segregation in the F2 generation was consistent with a 1 : 2 : 1 ratio, indicating allelic variation at each of two dehydrin loci (Dhn2, Dhn3). Genetic linkage was observed between Dhn2 and Dhn3, and the segregation ratios indicated preferential transmission of one allele at the Dhn3 locus. Dehydrin cDNA clones were characterised that encoded the allelic variants at Dhn2 and Dhn3. Their deduced amino-acid sequences were very similar to each other as well as to the product of the Dhn1 locus reported previously. Comparisons were made between the sequences of allelic variants at a single locus, and between
the products of different loci. Differences in the electrophoretic mobilities between allelic variants at Dhn2 and Dhn3 were associated with differences in polypeptide length resulting principally from tandem duplications of 21 (Dhn2) or 24 (Dhn3) amino-acid residues. These duplications accounted for much of the difference in length between dehydrins encoded by the
different loci. The conserved core of one of the duplicated regions varied in copy number, and small insertions/deletions
of amino acids near this core also contributed to length variation both between allelic forms and between loci. Dehydrins
possess characteristic highly conserved amino-acid sequence motifs, yet vary considerably in length. Mechanisms involving
sequence duplication appear to be responsible for generating the length differences observed between allelic variants as well
as between the products of different loci.
Received: 12 June 1997 / Accepted: 29 October 1997 |
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Keywords: | Allelic variation Genetic variation Dehydrin Pea (Pisum sativum L ) |
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