Cell Reselection Research Articles

Restoration of the Regeneration Potential of Long-term Cell Culture in Rice ( Oryza sativa L.) by Salt Pretreatment

Summary Cell suspension, initiated with seed-derived embryogenic callus and maintained for 2 years, produced morphogenically different cell types. No plant was regenerated from fine and friable cells. Low and sporadic regeneration frequency (0.0-0.3 %) was observed in compact cell clusters. Friable cells (20-21 months old) were exposed to salt stress; 0.75 % NaCI mainly inhibited cell growth and induced cells to become compact, whereas 1.5 % NaCI expressed a selective effect of killing all but embryogenic cells of friable cultures. A 3 month pretreatment with 1.5 % NaCl resulted in a reselection of embryogenic cells, restoring the high regeneration capacity of 2-year-old cultures of Oryzella by 60 % and Karolina by 37 % on salt-free medium. NaCl used at a suitable concentration appeared to be an efficient factor for re-establishment of the regeneration capacity of embryogenic calli derived from cell culture in rice.

The reversion of D-arabinose positive strains of coliform bacteria.

Bacterium lactis aerogenes adapted to d-arabinose (A + ) rather rapidly suffers a very slight reversion on subculture in glucose, and further reversion only after long periods. In media containing acetate or succinate the effect is more marked. Comparative tests with artificial mixtures of A + and A - cells show that it is not due to the re-selection of a few unadapted cells in the trained strain, but is an actual loss of A + character. Escherichia coli loses its adaptation much more readily, and the reversion is accompanied by the appearance of types intermediate in character between the A + and the A - forms.