Jt. Wu et al., ROLE OF PROLINE ACCUMULATION IN RESPONSE TO TOXIC COPPER IN CHLORELLASP. (CHLOROPHYCEAE) CELLS, Journal of phycology, 34(1), 1998, pp. 113-117
The green alga Chlorella sp. (strain 2350) was found to accumulate pro
line, up to a maximum of 0.027 fmol . cell(-1), under stressful concen
trations of cupric ions. The function of the accumulated proline was s
tudied with respect to its effect on copper (Cu) uptake. By induction
with salt stress, cells with various levels of intracellular proline w
ere used for this study. It is shown that the amount of Cu taken zip b
y the cells was reduced when the intracellular proline levels were enh
anced. When proline was exogenously supplied prior to Cu treatment, th
e adsorption of Cu was markedly reduced. When exogenous proline was su
pplied after Cu treatment, it resulted in a remarkable desorption of t
he adsorbed Cu immediately after the addition of proline. The results
of the present study indicate that proline may exert some action on th
e cell surface and suggest that one function of accumulated proline is
to reduce the uptake of metal ions. The accumulation of proline may b
e related to a tolerance mechanism for dealing with Cu stress.