Rice and heavy metals: A review of cadmium impact and potential remediation techniques

Metabolomic, biochemical, and cytological observations reveal β-Pinene's protective effects against cadmium toxicity in salt-tolerant rice

Sea rice (Haidao 86) is a vital cultivar that could be cultivated in saline soil but is sensitive to heavy metal stress, and cadmium (Cd) stress in eastern coastal parts of China is frequently a great hazard. Nevertheless, there is a scarcity of research on the metabolic pathways involved in the detoxification of Cd stress in sea rice. Here, we added a kind of monoterpene hormone, (1S)-(-)-β-Pinene (βP), in Cd (100 mg/kg) stressed experiment to study its interaction with sea rice. Multiple Morphological traits were significantly rescued after the application of βP. Similarly, Cd alleviation by βP was also demonstrated in physio-chemical indicators. Cd contents in roots, leaves, grains, H2O2, and MDA contents have decreased by 28.1 %, 50.9 %, 51.4 %, 18.2 %, and 18.0 %, respectively, with the presence of βP compared to Cd alone. SOD, POD, CAT, and GPX activities were elevated by 17.1 %, 40.0 %, 12.4 %, and 22.5 %, respectively, and contents of GSH and APX were also significantly modulated after the supplementation of βP. Transmission electron microscopy also indicated that the Cd+βP group had intact cellular structure compared to the Cd group. Through metabolomic analysis, 27 and 31 differentially expressed metabolites (DEMs) were identified from CKvsCd and CdvsCd+βP. According to the results, carbohydrate metabolism (e.g. I-inositol, Gluconapoleiferin), phenylpropanoid (lignan, flavonoids) biosynthesis (e.g. Cyanidin, Leucoside), terpenoids, and alkaloids biosynthesis, were all significantly regulated with the presence of βP. Our study provided a detailed understanding of the mechanism behind Cd-stress tolerance and will aid in developing Cd tolerance in sea rice.

Energy metabolism, antioxidant defense system, metal transport, and ion homeostasis are key contributors to Cd tolerance in SSSL derived from wild rice

Cadmium (Cd) toxicity poses major challenges to rice cultivation, affecting plant growth and development. Wild rice and nanoparticles offer promising strategies to enhance Cd tolerance, yet little is known about their combined effects. This study evaluates the single segment substitution line (SG004) from Oryza glumaepatula (wild rice) and its response to Cd stress compared to cultivated rice (HJX74). Both genotypes were also treated with calcium oxide nanoparticles (np-CaO). Results showed that Cd exposure disrupts reactive oxygen species (ROS) metabolism in both lines, such as malondialdehyde (MDA) increases by 57 % in HJX74 compared to SG004. Moreover, SG004 exhibited a 26 % reduction in shoot length compared to 41 % in HJX74 and a 42 % decline in chlorophyll ab content versus 53 % in HJX74. Antioxidant activity such as glutathione (GSH) decreased 25 % more in HJX74 than SG004 under Cd toxicity. Additionally, SG004 had lower Cd accumulation in roots (70 %) and shoots (85 %) than HJX74, indicating its enhanced tolerance to Cd toxicity. The root cell cytology reveals several deformations in different organelles of HJX74 but less in SG004. RNAseq analysis identifies key pathways, including energy metabolism, antioxidant defense, metal transport, and ion homeostasis, which may be critical for SG004 enhanced tolerance. Notably, two distinct metallothionein-like genes (BGIOSGA019338, BGIOSGA035982), a peroxidase (BGIOSGA019133), ammonium (BGIOSGA008640, BGIOSGA008641, and potassium transporters (BGIOSGA030867), NRAMP1 (BGIOSGA025476), and an aluminum-activated malate transporter (BGIOSGA014531), showed differential expressions in SG004 under Cd stress. Genes within the substituted fragment, including those for peroxidase 25 (BGIOSGA002866), metallothionein (BGIOSGA002389), and reductase (BGIOSGA002387), are also upregulated in SG004, reinforcing the role of antioxidant and ion homeostasis pathways. The utilization of np-CaO alleviates Cd-induced stress in both genotypes, hence reinforcing the application of wild rice and nanoparticles to improve Cd tolerance.

New insights into heavy metal cadmium-induced liver injury: Prominent role of programmed cell death mechanisms

The heavy metal cadmium (Cd) is an important environmental factor that induces liver injury and contributes to liver disease. Ongoing research aims to refine our understanding of the pathogenesis of cadmium-induced liver injury and the interactions between the various mechanisms. Oxidative stress, described as a pathophysiological basis of liver injury, is a process in which reactive oxygen species are generated, causing the destruction of hepatocyte structure and cellular dysfunction. Additionally, the activation of oxidative stress downstream signals regulates several forms of cell death, such as apoptosis, necroptosis, autophagy, ferroptosis, and pyroptosis, which significantly contributes to liver damage. Furthermore, the interplay between different types of programmed cell death highlights the complexity of liver injury mechanisms. This review summarizes the role of programmed cell death in Cd-induced liver injury and explores the relationships between different programmed cell death pathways, which is expected to provide new insights into the mechanisms of Cd-induced liver injury.

The Effect of [Glu][H2PO4] via Foliar Spraying on Cadmium and Arsenic Absorption and Translocation in Rice Plants

Rice is the main source of cadmium (Cd) and arsenic (As) in Chinese diet. The formulation of targeted agronomic interventions for mitigating Cd and As bioaccumulation in rice grains constitutes a critical pathway toward ensuring food safety and public health security. Foliar spraying technology with ionic liquids, effectively reduces Cd/As content in rice. In this study, an ionic liquid of amino acids ([Glu][H2PO4]) as a foliar conditioner was applied to two varieties of rice (X24 and Z35) to explore the mechanism of reducing the accumulation of Cd/As in rice. The results showed that [Glu][H2PO4] reduced Cd/As levels by up to 58.57% and 44.09%, respectively. [Glu][H2PO4] reduced the transfer factor from the root system to flag leaves, nodes, and other organs, thus reducing the Cd/As content in them. [Glu][H2PO4] promoted amino acid synthesis in seeds, increased Ca2+ level, increased OsGLR3.1-3.5 expression, and decreased OsLsi1-3 expression in flag leaves, thereby Cd/As was inhibited from being absorbed and transported by rice. The results demonstrated that the foliar application of [Glu][H2PO4] significantly mitigated the accumulation of Cd/As in rice. This study introduces a novel and effective strategy for reducing Cd/As accumulation in rice, hoping to enhance the safety and quality of rice crops.