Increase of chromium tolerance in Scenedesmus acutus after sulfur starvation: Chromium uptake and compartmentalization in two strains with different sensitivities to Cr(VI).

摘要: In photosynthetic organisms sulfate constitutes the main sulfur source for biosynthesis of GSH and its precursor Cys. Hence, availability can modulate capacity to cope with environmental stresses, a phenomenon known as SIR/SED (Sulfur Induced Resistance or Sulfur Enhanced Defence). Since chromate may compete transport into cells, in this study chromium accumulation tolerance were investigated relation two strains unicellular green alga Scenedesmus acutus different Cr-sensitivities. Paradoxically, deprivation has been demonstrated induce transient increase Cr-tolerance both strains. is enhance uptake/assimilation pathway leading important consequences on Cr-tolerance: (i) reduced uptake due induction high affinity transporters (ii) higher production cysteine which play role through formation unsoluble complexes their sequestration inert compartments. To investigate above mentioned mechanisms, Cr total cells cell compartments (cell wall, membranes, soluble miscellaneous fractions) was analyzed sulfur-starved unstarved cells. Both mainly accumulated fraction, but wild-type. type short period starvation before Cr(VI) treatment lowered level observed Cr-tolerant strain, seems instead less influenced by S-starvation, since no significant decrease observed. The following S-starvation thus rely mechanisms strains, suggesting mechanism constitutively active maybe transporter also Changes wall membrane fractions suggest strong involvement these S-starvation.