Glutathione S-transferase related detoxification processes are correlated with receptor-mediated vacuolar sorting mechanisms

Triticum durum Glutathione S-transferase Z1 is specifically responsive to glyphosate. Its expression influences the receptor-mediated vacuolar sorting mechanisms involved in tolerance mechanisms. A zeta subfamily glutathione S-transferase gene from Triticum durum (cv Cappelli) (TdGSTZ1) was characterized as part of a complex detoxification mechanism. The effect of different abiotic stresses on TdGSTZ1 revealed that the gene is unexpectedly responsive to glyphosate (GLY) herbicide despite it should not be part of tolerance mechanisms. Its role in the non-target-site mechanism of GLY resistance was then investigated. To analyze the GLY and the TdGSTZ1 overexpression effects on vacuolar sorting mechanisms, we performed transient transformation experiments in Nicotiana tabacum protoplasts using two vacuolar markers, AleuGFPgl133 and GFPgl133Chi, labeling the Sar1 dependent or independent sorting, respectively. We observed that the adaptive reaction of tobacco protoplasts vacuolar system to the treatment with GLY could be partially mimicked by the overexpression of TdGSTZ1 gene. To confirm the influence of GLY on the two vacuolar markers accumulation and the potential involvement of the secretion pathway activity in detoxification events, Arabidopsis thaliana transgenic plants overexpressing the non-glycosylated versions of the two markers were analyzed. The results suggested that GLY treatment specifically altered different vacuolar sorting characteristics, suggesting an involvement of the receptor-mediated AleuGFP sorting mechanism in GLY resistance. Finally, the expression analysis of selected genes confirmed that the non-target-site GLY resistance mechanisms are related to vacuolar sorting.