Two cDNA clones, pcMY21 and pBFLO, coding for glutelin polypeptides were isolated from a cDNA library of polyA-RNA of endosperm polysomes.
Nucleotide sequence comparison of pcMY21 and pBFLO shows a difference of about 10% in the 3' coding region. The clones code for polypeptides rich in proline and cysteine and also share a high degree of homology to the glutelin clones recently isolated by Prat et al. (Gene , 52:41, 1987). In hybrid-selected translation experiments pcMY21 selects a mRNA coding for a 16Kd (apparent molecular weight) polypeptide, while pBFLO selects a mRNA coding for a 28Kd polypeptide. However, both cDNA clones also select a mRNA coding for a polypeptide of about 21Kd.
In order to clarify the genomic organization of these glutelin sequences, Southern blot experiments and copy number evaluation were carried out. DNAs from different inbred maize lines ( A69Y, W64A and W22) were digested with different restriction enzymes (XbaI, BamHI, EcoRI, HindIII) and then hybridized with the pcMY21 fragment or pBFLO fragment. The resulting hybridization patterns indicate restriction fragment polymorphism among the lines and about 8-12 copies per haploid complement. These results are quite different from those reported by Gallardo et al. (Plant Sci. 54:211, 1988) who evaluated one or two copies per haploid genome.
By in situ hybridization experiments on different maize cytogenetic
stocks carrying heterologous translocations, the pcMY21 sequence was localized
only on the short arm of chromosome seven close to the cluster of the zein
genes previously localized in the same chromosomal region (Viotti et al.,
EMBO J. 1:53, 1982).
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