ABC Transporters and Heavy Metals

Abstract

The first evidence showing that ABC transporters are involved in heavy metal resistance in eukaryotic cells has been obtained from experiments in Schizosaccharomyces pombe and Saccharomyces cerevisae, where a half-size transporter of the ABCB subclass and an ABCC-type transporter, respectively, have been shown to confer heavy metal tolerance. Biochemical studies have indicated that vacuolar ABC transporters should also play an important role in heavy metal detoxification in plants. But it was only recently that two ABCC-type transporters, AtABCC1 and AtABCC2, have been identified as major apo-phytochelatin and phytochelatin-heavy metal(oid) complex transporters. Several plasma membrane transporters have also been shown to confer heavy metal resistance. However, with the exception of STAR1, an UDP glucose exporter, which-by altering cell wall composition-confers aluminum tolerance, the substrates required to be transported to confer heavy metal resistance by these plasma membrane-localized ABC proteins are still not elucidated. A mitochondrial ABC transporter AtATM3 was shown to be required for plant growth and development. The different studies indicate that this transporter is important for the production of cytosolic iron sulfur complexes and molybdenum cofactors, prosthetic groups required for several enzymes. However, the final proof as to which substrate is transported by AtATM3 is still missing. Several laboratories took advantage of the fact that ABC transporters are involved in heavy metal tolerance to generate transgenic plants suitable for phytoremediation. The results show that overexpression of ABC proteins alone is not sufficient to produce plants that can efficiently decontaminate soils, but they indicate that this class of transporters, when combined with other transporters and enzymes involved in heavy metal transport and detoxification, may prove a good solution to produce plants that can stabilize, and in the long term clean up, soils contaminated with heavy metals.

Evolution of Abscisic Acid Signaling for Stress Responses to Toxic Metals and Metalloids

“…Membrane transporters play critical roles in loading minerals toward root vascular tissues and subsequent accumulation in plants ( Song et al, 2014a ; Clemens and Ma, 2016 ; Deng et al, 2019 ; Zhao and Wang, 2020 ). For example, the plasma membrane-localized heavy metal ATPases (HMAs), such as AtHMA2, AtHMA4, and OsHMA2, confer to loading Cd into the stele and subsequent accumulation in shoot ( Hussain et al, 2004 ; Mills et al, 2005 ; Yamaji et al, 2013 ), while the tonoplast-localized AtHMA3 and OsHMA3 limit Cd allocation to the stem, leaves, and grain through sequestration Cd into the vacuole of root cells ( Morel et al, 2009 ; Ueno et al, 2010 ).…”

“…For instance, ABCB25 has a role in Cd and Pb resistance in Arabidopsis and C-type ABC transporters are involved in sequestration of GSH- and PC-conjugated heavy metals and metalloids in various angiosperms. G-type ABC transporters contribute to ABA transport as well as Cd and Pb efflux ( Song et al, 2014a ; Hwang et al, 2016 ). We found that ABC transporters are ubiquitous in all 41 genomes used for comparative genetic analysis ( Figure 4 ).…”

N-Terminal Extension and C-Terminal Domains Are Required for ABCB6/HMT-1 Protein Interactions, Function in Cadmium Detoxification, and Localization to the Endosomal-Recycling System in Caenorhabditis elegans

“…Members of the highly conserved family of ATP-binding cassette (ABC) transporters are recognized for their contribution to heavy metal detoxification in different species ( Ortiz et al, 1992 ; Broeks et al, 1996 ; Jalil et al, 2008 ; Preveral et al, 2009 ; Sooksa-Nguan et al, 2009 ; Kim et al, 2010 ; Song et al, 2014 ). For example, plasma membrane-localized ABCC1/MRP1 and ABCC2/MRP2 of humans confer cellular efflux of arsenic-glutathione (GSH) conjugates ( Leslie et al, 2004 ; Leslie, 2012 ).…”

Transcriptome Analysis of Wheat Roots Reveals a Differential Regulation of Stress Responses Related to Arbuscular Mycorrhizal Fungi and Soil Disturbance

“…GO enrichment analysis showed that "ATP binding", "ATPase activity", and "manganese ion binding" were up-regulated in the L. rigidum Undisturbed treatment as compared with O. compressus. ATP binding cassette (ABC) proteins were found amongst the most up-regulated genes in L. rigidum system; ABC transporters family members are known to be engaged in numerous functions, including secondary metabolite transport [56], heavy metal detoxification [57], and phytohormone transport [58], thus being important for tolerance to different kinds of abiotic and biotic stresses. The up-regulation of these transporters in the L. rigidum treatment agrees with the Mn stress-induced changes that were later observed in the plants' growth.…”