Metalloprotein-Specific or Critical Amino Acid Residues: Perspectives on Plant-Precise Detoxification and Recognition Mechanisms under Cadmium Stress

Abstract

Cadmium (Cd) pollution in cultivated land is caused by irresistible geological factors and human activities; intense diffusion and migration have seriously affected the safety of food crops. Plants have evolved mechanisms to control excessive influx of Cd in the environment, such as directional transport, chelation and detoxification. This is done by some specific metalloproteins, whose key amino acid motifs have been investigated by scientists one by one. The application of powerful cell biology, crystal structure science, and molecular probe targeted labeling technology has identified a series of protein families involved in the influx, transport and detoxification of the heavy metal Cd. This review summarizes them as influx proteins (NRAMP, ZIP), chelating proteins (MT, PDF), vacuolar proteins (CAX, ABCC, MTP), long-distance transport proteins (OPT, HMA) and efflux proteins (PCR, ABCG). We selected representative proteins from each family, and compared their amino acid sequence, motif structure, subcellular location, tissue specific distribution and other characteristics of differences and common points, so as to summarize the key residues of the Cd binding target. Then, we explain its special mechanism of action from the molecular structure. In conclusion, this review is expected to provide a reference for the exploration of key amino acid targets of Cd, and lay a foundation for the intelligent design and breeding of crops with high/low Cd accumulation.

Transcriptomics, proteomics, and metabolomics interventions prompt crop improvement against metal(loid) toxicity

“…Oxidative-stress-mediated metal(loid) toxicity primarily affects various intracellular organelles and components, including cell membranes, mitochondria, chloroplasts, and some proteins involved in detoxification and metabolism (Kumar et al 2016 ; Hasan et al 2017 ). Four main mechanisms have been proposed to explain metal(loid) toxicity: (1) competition with other essential micro- and macro-elements, disrupting mineral nutrition (Amari et al 2017 ; Vasile et al 2021 ); (2) metal(loid) interactions with thiol and carboxyl groups in biomolecules, inhibiting protein and antioxidant enzyme activities (Gulcin and Alwasel 2022 ); (3) occupation of specific ion-binding sites in proteins, rendering them inactive (Mishra et al 2017 ; Li et al 2022a ); and (4) overproduction of ROS, leading to progressive oxidative stress, DNA damage, and ultimately cell death (Georgiadou et al 2018 ; Zainab et al 2021 ; Ghuge et al 2023 ).…”

“…Defective PC synthesis can change metal ion accumulation patterns and the appearance of sensitive and resistant plants (Zhu et al 2021 ). MTs, a superfamily of cys-rich proteins, play an important role in ionomic homeostasis, detoxification, and metal(loid) tolerance (Pan et al 2018 ; Li et al 2022a ). Class II MTs, found in plants, can be grouped into four types (MT1–MT4) and have been associated with improved tolerance to metal(loid) toxicity.…”

UVB-Pretreatment-Enhanced Cadmium Absorption and Enrichment in Poplar Plants

“…Under different treatments, the expression differences of these detoxification-related genes in roots and leaves led to the difference in Cd tolerance. The NRAMP, ZIP, MTP, CAX, and YSL protein families are responsible for the uptake and transport of Cd in plants [57][58][59]. On the whole, the expression levels of most genes were induced to a higher degree in the roots than in the leaves after treatment, which also resulted in the retention of most Cd ions in the roots.…”

Chemical forms of cadmium in soil and its distribution in French marigold sub-cells in response to chelator GLDA

“…The latter can bind heavy metals to reduce their effectiveness and to decrease their transportation to the organelle 29,30 , thus reducing the stress of cadmium on plants. A significant increase occurred in the percentage of cellular soluble Cd content with increasing GLDA application, likely due to the high content of sulfur-rich states and organic acids in the vesicles that chelate and segregate Cd, thus eliminating Cd damage to the organelles 31 . The increase of Cd content in soluble fraction was flatten followed by a reduction, similar to Floodgate's principle 32 .…”