Studies on Evolution of Mutator transposable element in Grass Family

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Rice homolog to maize Mutator transposable element was cloned, which has similarity to transposase (TNP) domain of the Mutator element in maize. The exact domain consisting of 426bp is capable to translate into142 amino acids. and share 69% homology at DNA level and 80% at amino acids level. Rice cultlvars carry at least three copies in their genomes and wild relatives carry different number of copies and RFLP patterns. Expression of the domain was confirmed by RT-PCR with Japonica strains but not in lndica strains at seedling and mature leaf stage. Mutable strains were generated through self pollination from a famous Hokkaido's local cultivar, which showed some mutants such as albino, chimera and twin embryo. They also presented RFLPs probed with rice TNP-like domain. There is no reason to believe pollen and other contamination sources for the RFLPs because the progeny was self-pollinated through several generations and stil carried recessive dwarf-1 gene as homozygous condition. And we also obtalned albino, chlorina and twin embryo mutants from the progeny. Other progenies from Akage are also known to carry several mutant genes generated spontaneously through self-pollination such as awnless-1, awnless-2, dwarf-2 and Undulated rachis-1 for one century. Such mutabllity affected to plant breeding, which enlarge their cultivated area up to more north region. Other sources as mutable populations will be discussed. The populations generated from subspecies level-crosses like a hybrid dysgenesis system in Drosophila. At least 0.5% mutants were generated in their progenies. The ratio would be 1/20 genes related to those chlorosis phenomena per generation.