Intracellular and extracellular thiol-peptides modulate the response of <i>Marchantia polymorpha</i> to physiological needs, excess, and starvation of zinc, copper, and iron

Thiol-peptides, such as glutathione and phytochelatins, are believed to play a crucial role in regulating metal micronutrient needs (in particular, copper, iron, and zinc), and in detoxifying their excessive amounts. This study provides insight into the mechanisms involved in detoxification, starvation, and physiological control of the aforesaid metals in the liverwort <i>Marchantia polymorpha</i>. The results show that the phytochelatin synthase activity in gametophytes of <i>M. polymorpha</i> is induced mainly by zinc, followed by copper, and iron. Interestingly, the amount of phytochelatins produced seems to be controlled by the enzyme activity, rather than by the expression level of its gene. Moreover, when gametophytes are deprived of zinc, copper, and iron, phytochelatin levels decrease, compared with normal nutrient supply. Phytochelatins and glutathione, on the other hand, appear to play a key role in detoxification of excess zinc, copper, and iron, particularly when these thiol-peptides are released extracellularly. This suggests a potential novel function for phytochelatins and glutathione as detoxifying compounds also in the extracellular environment.