Heterologous Expression of the Phytochelatin Synthase CaPCS2 from Chlamydomonas acidophila and Its Effect on Different Stress Factors in Escherichia coli

Phytochelatins (PCs) are cysteine-rich small peptides, enzymatically synthesized from reduced glutathione (GSH) by cytosolic enzyme phytochelatin synthase (PCS). The open reading frame (ORF) of the phytochelatin synthase CaPCS2 gene from the microalgae Chlamydomonas acidophila was heterologously expressed in Escherichia coli strain DH5 alpha, to analyze its role in protection against various abiotic agents that cause cellular stress. The transformed E. coli strain showed increased tolerance to exposure to different heavy metals (HMs) and arsenic (As), as well as to acidic pH and exposure to UVB, salt, or perchlorate. In addition to metal detoxification activity, new functions have also been reported for PCS and PCs. According to the results obtained in this work, the heterologous expression of CaPCS2 in E. coli provides protection against oxidative stress produced by metals and exposure to different ROS-inducing agents. However, the function of this PCS is not related to HM bioaccumulation.