Heavy metal stress in rice: Uptake, transport, signaling, and tolerance mechanisms

Abstract

Heavy metal contamination of agricultural fields has become a global concern as it causes a direct impact on human health. Rice is the major food crop for almost half of the world population and is grown under diverse environmental conditions, including heavy metal‐contaminated soil. In recent years, the impact of heavy metal contamination on rice yield and grain quality has been shown through multiple approaches. In this review article, different aspects of heavy metal stress, that is uptake, transport, signaling and tolerance mechanisms, are comprehensively discussed with special emphasis on rice. For uptake, some of the transporters have specificity to one or two metal ions, whereas many other transporters are able to transport many different ions. After uptake, the intercellular signaling is mediated through different signaling pathways involving the regulation of various hormones, alteration of calcium levels, and the activation of mitogen‐activated protein kinases. Heavy metal stress signals from various intermediate molecules activate various transcription factors, which triggers the expression of various antioxidant enzymes. Activated antioxidant enzymes then scavenge various reactive oxygen species, which eventually leads to stress tolerance in plants. Non‐enzymatic antioxidants, such as ascorbate, metalloids, and even metal‐binding peptides (metallothionein and phytochelatin) can also help to reduce metal toxicity in plants. Genetic engineering has been successfully used in rice and many other crops to increase metal tolerance and reduce heavy metals accumulation. A comprehensive understanding of uptake, transport, signaling, and tolerance mechanisms will help to grow rice plants in agricultural fields with less heavy metal accumulation in grains.

Plant E3 Ligases and Their Role in Abiotic Stress Response

“…Some are considered essential, in minimal amounts, for normal plant growth, (e.g., Cu 2+ , Mo 4+ , Ni 2+ , Se 2+ , Co 2+ , Zn 2+ and Mn 2+ ), while others have no known benefits to plants (e.g., Cd 2+ , Sb 3+ , Cr 3+ , As 3+ , Pb 2+ , Ag 1+ and Hg 2+ ) [ 209 , 210 ]. The high-level uptake of heavy metals in general is harmful [ 211 ], and in crops it can cause a reduction in yield [ 212 , 213 ]. There are several E3 ligases that have been described to be involved in the regulation of HMs stress tolerance ( Table 1 ).…”

Combine Effect of ZnO NPs and Bacteria on Protein and Gene’s Expression Profile of Rice (Oryza sativa L.) Plant

“…A recent study by Akhtar [3] revealed that the water samples that were obtained from Hayatabad industrial estate (HIE), Peshawar and Gadoon industrial estate (GIE), Sawabi, Pakistan, contain large amounts of HMs that are further used to irrigate local vegetable crops. Since plants are sessile, they are often subjected to a wide range of biotic or abiotic stresses, including HM stress [4].…”

CRISPR/Cas genome editing improves abiotic and biotic stress tolerance of crops

“…It has adverse effects on plant physiology and biochemistry through osmotic stress, ion imbalance, oxidative stress, membrane tissue disorder, cytotoxicity and metabolic homeostasis (Hoque et al, 2021). Heavy metals accumulated in plants will cause serious harm to human health after ingestion (Kaur et al, 2021). Knockdown of OsNramp5 and OsLCT1 by CRISPR/Cas9 reduces cadmium (Cd) accumulation in rice (Songmei et al, 2019).…”