Sequence complexity of messenger RNA in cotyledons of developing pea (Pisum sativum) seeds |
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Authors: | Heather Morton IMarta Evans John A Gatehouse Donald Boulter |
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Institution: | Department of Botany, University of Durham, South Road, Durham, DH1 3LE, U.K. |
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Abstract: | The hybridization kinetics of poly(A)+-RNA preparations from the cotyledons of developing pea (Pisum sativum seeds to complementary DNAs have shown that the number of distinct sequences in poly(A)+ -RNA decreases from ca 20 000 at the early stage of cotyledon development to ca 200 at a late stage of cotyledon development. The decrease in sequences is accounted for entirely by the disappearance of ‘rare’ poly(A)+ -RNAs (< 103 copies/cell) as seed development proceeds. There is an increase (1–6) in very abundant poly(A)+-RNA sequences (? 5 × 105 copies/cell) from early- to mid-developmental stages, concomitantly with the increase in the synthesis of seed-specific storage protein polypeptides. In agreement with the continuing synthesis of most of these polypeptides to the end of seed development, the number of very abundant poly(A)+-RNAs is maintained to the late cotyledon development stage. Abundant poly(A)+-RNA sequences (ca 104 sequences/cell) increase from 80 to 180 during development, possibly corresponding to the polypeptides which are not storage proteins but are known to be accumulated in pea seeds. Hybridization of single-copy pea genomic DNA sequences to poly(A)+-RNA from developing seeds showed that ca 5 % of the single-copy sequences were present in mRNA from mid-development cotyledons. In addition, hybridization of cDNA prepared against poly(A)+-RNA from nuclei of early development cotyledons to the corresponding cytoplasmic polysomal poly(A)+-RNA showed that the cytoplasmic poly(A)+-RNA contained ca 50 % of the sequences present in the nuclei. These results are discussed and interpreted in the light of existing results from similar systems. |
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Keywords: | Leguminosae poly(A)-containing mRNA single-copy DNA hybridization kinetics storage proteins |
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