R. Ishikawa1 T. Konno1, M. Senda2, S. AKADA2, T. HARADA’ and M. NIIZEKI1

     Akihikari was a leading variety in Aomori Prefecture in the past, Japan. We examined inheritance of DNA mediated transposable element, Rice Mutator (Ishikawa and Freeling, preparation) and RNA mediated retro-transposable element Tos 17 (Hirochika et a!. 1996) and also tried to activate these transposable elements by successive tissue culturing.

     Calli induced from Akihikari were cultured during three to eight months and used to regenerate plants from calli. Genomic DNA of R0 plants was extracted and digested with Sac I restriction enzyme that is known not to cut inside of RMu elements ever cloned. RFLPs were observed among R0 plants when probed only with Tosi 7. Copy number of TosI 7 in the original strain is two (data not shown), and that in regenerated plants was drastically changed (Fig. 1). The same blot was washed and re-hybridized with TIR probe containing RMu termini. There was no difference for banding pattern in regenerated plants. Other RMu probe also represented no difference (data not shown). It suggests that the culture condition would affect the RMu transposable elements (Fig. 2).

     Under usual cultivation condition in Aomori, several varieties showed RFLPs as a result of transposition of RMu transposable elements. The transposition events were recognized as RFLPs between siblings. Dwarf mutant was originated from Fujiminori by gamma irradiation. Reimei and Fujiminori revealed RFLPs between sibling plants with TIR probe. Toyonishiki and Reimei are the parents of Akihikari. These parental strains also showed RFLPs between sibling plants. Akihikari also showed RFLPs in sibling plants. The mutability of Rice Mutator found in the local varieties would be due to the cultivation condition in Aomori or the genetic information of these varieties.
 

 

 

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