ABSTRACT
Seed germination is highly sensitive to changes in the surrounding environment. This work examined the impact of imbibition with copper solution on the germination rate and behavior of some enzyme capacities involved in stress response. Chickpea (Cicer arietinum L.) seeds were germinated at 25°C in the dark for 7 days of imbibition with distilled water or an aqueous solution of chloride salt of 100 or 500µM CuCl2. The exposure of seeds to copper (Cu(2+)) induced changes in the antioxidant status. In Cu-treated seeds, the non-protein thiols (SHNP) pool and ferredoxin:thioredoxin reductase (FTR) expression and activity increased. Cysteinyl sulfurs in the thioredoxin (Trx) function as ligands for metal ions. The accumulation of Cu(2+) inhibited seed germination and embryo growth. It appears that the FTR system mediates a novel form of redox signaling in plants under copper excess.
Subject(s)
Chloroplast Thioredoxins/metabolism , Cicer/enzymology , Copper/toxicity , Iron-Sulfur Proteins/metabolism , Oxidoreductases/metabolism , Antioxidants/metabolism , Biomass , Cicer/drug effects , Cicer/genetics , Cicer/growth & development , Cicer/physiology , Ferredoxins/metabolism , Germination , Iron-Sulfur Proteins/genetics , Oxidation-Reduction , Oxidoreductases/genetics , Plant Proteins/genetics , Plant Proteins/metabolism , Seeds/drug effects , Seeds/enzymology , Seeds/genetics , Seeds/growth & development , Seeds/physiology , Signal TransductionABSTRACT
Thioredoxin (TRX) proteins perform important biological functions in cells by changing the redox state of proteins via dithiol disulfide exchange. Several systems are able to control the activity, stability, and correct folding of enzymes through dithiol/disulfide isomerization reactions including the enzyme protein disulfide-isomerase, the glutathione-dependent glutaredoxin system, and the thioredoxin systems. Plants have devised sophisticated mechanisms to cope with biotic and abiotic stresses imposed by their environment. Among these mechanisms, those collectively referred to as redox reactions induced by endogenous systems. This is of agronomical importance since a better knowledge of the involved mechanisms can offer novel means for crop protection. In the plant life cycle, the seed and seedling stages are key developmental stages conditioning the final yield of crops. Both are very sensitive to heavy metal stress. Plant redox reactions are principally studied on adult plant organs and there is only very scarce informations about the onset of redox regulation at the level of seed germination. In the here presented study, we discussed the importance of redox proteins in plant cell metabolism and defence. Special focus is given to TRX, which are involved in detoxification of ROS and also to their targets.
