| Abstract |
Occurrence of the midget chromosome in a common wheat with rye cytoplasm [(cereale)-Chinese Spring (CS)] indicates that the chromosome carries the essential gene(s) for maintaining the function of rye cytoplasm. To elucidate the interaction between the midget chromosome and rye cytoplasm, in this study, an attempt was made to isolate rye-type cDNAs from a cDNA library of (cereale)-CS by differential screening. Two replica filters from each plate were hybridized with digoxigenin (DIG)-labeled wheat CS cDNAs and with DIG-labeled rye cDNAs,respectively. Out of ca. 20,000 plaques, 27 were hybridized more strongly with rye cDNAs than with CS cDNAs. These clones were classified into six classes (Ⅰ-Ⅵ) by blot hybridization. The majority of the clones (21 out of 27) was belonged to the same class (1), showing rye-type RFLP (restriction fragment length polymorphism). The DNA sequence of clone CrClA in class Ⅰ, was very similar to that of wheat ribulose 1,5-bisphosphate carboxylase,large subnit gene, rbcL(94.5% homology). However, the 3' end of CrClA was shorter than that of wheat rbcL, and terminated at TAA instead of TAG, like the rbcL of Aegilops crassa. In the clone CrC5.4, the first half of the sequence was similar to that of one rice EST clone, the functions of which are not known, and the latter was similar to the reverse sequence of maize 4.5S-23S ribosomal RNA. This suggests that CrC5.4 had been derived from two defferent cDNAs of (cereale)-CS. Three other clones had homology to the chlorophyll a/b binding protein genes (cab) of wheat, maize and tomato, and one to wheat rbcS (ribulose1,5-bisphosphate carboxylase small subnit gene). However, no clear polymorphisms were detected between wheat and rye by using those clones as probes.
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