**6. Conclusion**

Both heavy metals and pesticides significantly arrest plant growth and development. The co-contamination of soils by both heavy metals and pesticides has raised concerns regarding crop safety and productivity, and is therefore crucial to remediate. Phytoremediation presents the advantages of high efficiency, low cost, and sustainability. Thus, it has been one of the most common strategies for the remediation of polluted soils. This chapter summarizes the critical role of PCS in heavy metal detoxification and the involvement of PCS in GS-conjugate degradation. In the presence of heavy metals, PCS catalyzes the synthesis of PCs and the initiation of GS-conjugate metabolism. Despite a large body of literature illustrating the function of PCS in heavy metal resistance, there has been less emphasis on the participation of PCS in the detoxification of xenobiotic compounds and its potential application in biodegradation. Given that PCS has diverse functions in different types of stress, this chapter discusses the potential inclusion of PCS to achieve phytoremediation for combined pollutions.

The key question related to PCS overexpression in plant materials for phytoremediation is how GSH homeostasis can be balanced. Although pathway engineering enhancing GSH metabolism and PCS activity seems a promising approach, the consequences of manipulating these pathways may not directly lead to improving the performance of plants exposed to stress, due to the complexity of the cellular GSH network. Thus, the challenge for the future is not only to characterize the involvement of PCS in stress responses but also to broaden our knowledge in PCS as a factor that regulates GSH status and cellular redox homeostasis.
