OsSUV3 functions in cadmium and zinc stress tolerance in rice (Oryza sativa L. cv IR64)

Cadmium in Cereal Crops: Uptake and Transport Mechanisms and Minimizing Strategies

Cadmium (Cd) contamination in soils and accumulation in cereal grains have posed food security risks and serious health concerns worldwide. Understanding the Cd transport process and its management for minimizing Cd accumulation in cereals may help to improve crop growth and grain quality. In this review, we summarize Cd uptake, translocation, and accumulation mechanisms in cereal crops and discuss efficient measures to reduce Cd uptake as well as potential remediation strategies, including the applications of plant growth regulators, microbes, nanoparticles, and cropping systems and developing low-Cd grain cultivars by CRISPR/Cas9. In addition, miRNAs modulate Cd translocation, and accumulation in crops through the regulation of their target genes was revealed. Combined use of multiple remediation methods may successfully decrease Cd concentrations in cereals. The findings in this review provide some insights into innovative and applicable approaches for reducing Cd accumulation in cereal grains and sustainable management of Cd-contaminated paddy fields.

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

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.

Linking the plant stress responses with RNA helicases

RNA helicases are omnipresent plant proteins across all kingdoms and have been demonstrated to play an essential role in all cellular processes involving nucleic acids. Currently, these proteins emerged as a new tool for plant molecular biologists to modulate plant stress responses. Here, we review the crucial role of RNA helicases triggered by biotic, abiotic, and multiple stress conditions. In this review, the emphasis has been given on the role of these proteins upon viral stress. Further, we have explored RNA helicase mediated regulation of RNA metabolism, starting from ribosome biogenesis to its decay upon stress induction. We also highlighted the cross-talk between RNA helicase, phytohormones, and ROS. Different overexpression and transgenic studies have been provided in the text to indicate the stress tolerance abilities of these proteins.

OsSUV3 transgenic rice maintains higher endogenous levels of plant hormones that mitigates adverse effects of salinity and sustains crop productivity

BACKGROUND

The SUV3 (suppressor of Var 3) gene encodes a DNA and RNA helicase, which is localized in the mitochondria. Plant SUV3 has not yet been characterized in detail. However, the Arabidopsis ortholog of SUV3 (AT4G14790) has been shown to be involved in embryo sac development. Previously, we have reported that rice SUV3 functions as DNA and RNA helicase and provides salinity stress tolerance by maintaining photosynthesis and antioxidant machinery. Here, we report further analysis of the transgenic OsSUV3 rice plants under salt stress.

FINDINGS

The transgenic OsSUV3 overexpressing rice T1 lines showed significantly higher endogenous content of plant hormones viz., gibberellic acid (GA3), zeatin (Z) and indole-3-acetic acid (IAA) in leaf, stem and root as compared to wild-type (WT), vector control (VC) and antisense (AS) plants under salt (200 mM NaCl) stress condition. A similar trend of endogenous plant hormones profile was also reflected in the T2 generation of OsSUV3 transgenic rice under defined parameters and stress condition.

CONCLUSIONS

In response to stress, OsSUV3 rice plants maintained plant hormone levels that regulate the expression of several stress-induced genes and reduce adverse effects of salt on plant growth and development and therefore sustains crop productivity.