Recovery of growth capacity and of chloroplast transglutaminase activity induced by polyamines in a polyamine-deficient variant strain of Dunaliella salina

The variant strain of Dunaliella salina is characterised by: a) a very low growth capacity; b) a deficiency in polyamines, transglutaminase chlorophyl l, and protein content; and c) an unbalanced putrescine/spermidine ratio. A supply of 100 mu mol/L putrescine or 1 mmol/L ornithine induces the resump tion of growth. Putrescine has several additional effects: endogenous putre scine and spermidine levels increase and their ratio reaches 1.6, a value t ypical of the growing wild type; chlorophyll a and b also increase and thei r ratio (3.6) becomes close to that of the wild type (3.0); protein content increases, especially in the chloroplast. Transglutaminase(s) in chloropla sts of putrescine-treated algae is stimulated and increases its conjugating activity by 9-fold in the light and less than 3-fold in the dark when comp ared to untreated controls. The role of polyamines in improving the physiol ogical condition of the chloroplast and their effect on growth are discusse d.