SaMT3 in Sedum alfredii drives Cd detoxification by chelation and ROS-scavenging via Cys residues. (15th December 2022)

• Record Type: Journal Article
• Authors: Zhao, Jianqi; Xie, Ruohan; Lin, Jiayu; Xu, Lingling; Gao, Xiaoyu; Lin, Xianyong; Tian, Shengke; Lu, Lingli
• Is Part Of: Environmental pollution. Volume 315(2022)
• Publication Date: 2022-12-15
• Subjects: Metallothionein -- Cadmium -- Sedum alfredii -- Chelation -- Reactive oxygen species; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2022.120410
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Metallothioneins (MTs), a group of cysteine-rich proteins, are effective chelators of cadmium (Cd) and play a key role in plant Cd detoxification. However, little is known about the role of single cysteine (Cys) residues in the MTs involved in the adaptation of plants to Cd stress, especially, in hyperaccumulators. In the present study, we functionally characterised SaMT3 in S. alfredii, a Cd/Zn hyperaccumulator native to China. Our results showed that the C- and N- terminal regions of SaMT3 had differential functional natures in S. alfredii and determined its Cd hypertolerance and detoxification. Two CXC motifs within the C-terminal region were revealed to play a crucial role in Cd sensing and binding, whereas the four Cys-residues within the N-terminal region were involved in scavenging reactive oxygen species (ROS). An S. alfredii transgenic system based on callus transformation was developed to further investigate the in-planta gene function. The SaMT3 -overexpressing transgenic plant roots were more tolerant to Cd than those of wild-type plants. Knockout of SaMT3 resulted in significantly decreased Cd concentrations and increased ROS levels after exposure to Cd stress. We demonstrated the SaMT3 -mediated adaptation strategy in S. alfredii, which uses metal chelation and ROS scavenging in response to Cd stress. Our results further reveal the molecular mechanisms underlying Cd detoxification in hyperaccumulating plants, as well as the relation between Cys-related motifs and the metal binding properties of MTs. This research provides valuable insights into the functions of SaMT3 in S. alfredii, and improves our understanding of Cd hyperaccumulation in plants. Graphical abstract: Image 1 Highlights: Two CXC motifs in the C-terminal region of SaMT3 were important in Cd sensing and binding. Four Cys-residues in the N-terminal region of SaMT3 were involved in scavenging ROS. A reliable method for genetic transformation of S. alfredii were established. SaMT3 is involved in the detoxification of Cd in the shoot of S. alfredii.