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Cloning of the wheat sterol C-24 methyltransferase gene.
In Southern blot analyses of wheat genomic DNA digested with different restriction enzymes, the 32P-labelled insert of pWMT hybridized to two BamHI (15.0 and 7.0 kb), a single EcoRI (3.5 kb), and three each of HindIII (15 .0, 9.0 and 4.0 kb) and SacI (10.0, 7.0 and 5.1 kb) fragments (Fig. 3). Based on the Southern blot results, a sub-genomic library was constructed using the 5.0-3.0 kb fraction of the EcoRI-digest. This library was screened using pWMT insert as the probe. The genomic sequence of TA-MT, when compared with the pWMT cDNA clone, revealed the presence of 11 exons and 10 introns within the coding region.

Chromosomal localization of TA-MT.
We used the mapping system developed for wheat (Sharp et al. 1989) to assign the chromosomal location of TA- MT gene. Southern hybridization of the insert of pWMT to HindIII-digested DNA from 20 nullisomic-tetrasomic and 2 ditelocentric lines showed that the TA-MT gene is located on chromosomes 5A, 4B and 4D (Fig. 4). The localization on the 5A chromosome could be explained by the fact that, during the course of evolution of modern-day chromosome 4A, there had been a translocation event involving the distal regions of the long arm of chromosomes 4A and 5A (Devos et al. 1995). This implicates a relatively distal location on the long arm of group 4 chromosomes for TA-MT gene.

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