A critical review on speciation, mobilization and toxicity of lead in soil-microbe-plant system and bioremediation strategies.

Diagnosis of soil contamination using microbiological indices: A review on heavy metal pollution.

Several species from the Brassica genus are very important agricultural crops in different parts of the world and are also known to be heavy metal accumulators. There have been a large number of studies regarding the tolerance, uptake and defense mechanism in several of these species, notably Brassica juncea and B. napus, against the stress induced by heavy metals. Numerous studies have also been published about the capacity of these species to be used for phytoremediation purposes but with mixed results. This review will focus on the latest developments in the study of the uptake capacity, oxidative damage and biochemical and physiological tolerance and defense mechanisms to heavy metal toxicity on six economically important species: B. juncea, B. napus, B. oleracea, B. carinata, B. rapa and B. nigra.

https://www.mdpi.com/1422-0067/16/8/17975/pdf

Effect of Heavy Metals in Plants of the Genus Brassica

Lead (Pb) is one of the most useful metals, and has contaminated most of the ecosystems. It has been known to influence various morphological, physiological and biochemical processes in plants. Higher plants have evolved sophisticated internal detoxification mechanisms, to deal with metal toxicity, that include selective metal uptake, excretion, chelation by specific ligands and compartmentalization. Despite these detoxification systems, Pb is able to induce the production of reactive oxygen species (ROS) which can cause harmful effects on vital constituents of plant cells: protein oxidation, lipid peroxidation, enzyme inactivation or DNA damages. Unlike other metals, little is known about the mechanisms involved in Pb uptake, toxicity, oxidative stress generation and detoxification in plants. This chapter reviews the recent understanding of physiological and biochemical mechanisms involved in Pb uptake and translocation into plants. It also provides a broad overview of the most important mechanisms of Pb toxicity and tolerance in plants.

Molecular Mechanisms Involved in Lead Uptake, Toxicity and Detoxification in Higher Plants

SnYSL3 encodes a plasma-localized transporter delivering various metal–nicotianamine complexes. The expression of
 SnYSL3 is up-regulated by excess Cd, suggesting an important role for SnYSL3 in response to Cd stress.
 The Yellow Stripe-Like (YSL) transporters have been proposed to participate in metal uptake and long-range transport in model plants. In this study, we isolated and characterized a novel member of the YSL gene family, SnYSL3, from the cadmium hyperaccumulator Solanum nigrum. SnYSL3 was constitutively expressed and encodes a plasma membrane-localized protein. In situ RNA hybridization localized the SnYSL3 transcripts predominantly in vascular tissues and epidermal cells of the roots and stems, while in leaves, the mRNA levels were high in the vasculature. The SnYSL3 expression level was up-regulated by excess Cd, excess Fe and Cu deficiency. Heterologous expression of SnYSL3 in yeast revealed that SnYSL3 transports nicotianamine complexes containing Fe(II), Cu, Zn and Cd. SnYSL3 overexpression in Arabidopsis thaliana decreased Fe and Mn concentrations in the roots and increased the root-to-shoot translocation ratios of Fe and Mn. Under Cd exposure, the transgenic plants showed increased translocation ratios of Fe and Cd, but no difference was observed in Mn translocation from roots to shoots between the transgenic and wild-type lines. Although the accurate function of SnYSL3 remains to be confirmed, these results suggest that SnYSL3 is a transporter delivering a broad range of metal–nicotianamine complexes and is potentially important for the response to heavy metal stress, especially due to Cd and Fe.

Isolation and characterization of a novel cadmium-regulated Yellow Stripe-Like transporter (SnYSL3) in Solanum nigrum

Heavy metal transporters play a key role in regulating metal accumulation and transport in plants. These are important candidate genes to study in metal tolerant and accumulator plants for their potential use in environmental clean up. We coupled a degenerate primer-based RT-PCR approach with a molecular fingerprinting technique based on amplified rDNA restriction analysis (ARDRA) to identify novel ESTs corresponding to heavy metal transporters from metal accumulator Brassica juncea. We utilized this technique to clone several family members of natural resistance-associated macrophage proteins (NRAMP) and yellow stripe-like proteins (YSL) in a high throughput manner to distinguish between closely related isoforms and/or allelic variants from the allopolyploid B. juncea. Partial clones of 23 Brassica juncea NRAMPs and 27 YSLs were obtained with similarity to known Arabidopsis thaliana and Noccaea (Thlaspi) caerulescens NRAMP and YSL genes. The cloned transporters showed Brassica-specific changes in domains, which can have important functional consequences. Semi-quantitative RT-PCR-based expression analysis of chosen members indicated that even closely related isoforms/allelic variants of BjNRAMP and BjYSL have distinct tissue-specific and metal-dependent expressions which might be essential for adaptive fitness and heavy metal tolerance. Consistent to this, BjYSL6.1 and BjYSL5.8 were found to show elevated expressions specifically in cadmium-treated shoots and lead-treated roots of B. juncea, respectively.

Isolation and expression analysis of partial sequences of heavy metal transporters from Brassica juncea by coupling high throughput cloning with a molecular fingerprinting technique.

Development of novel antivirals, which requires knowledge of the viral life cycle in molecular detail, is a daunting task, involving extensive investments, and frequently resulting in failure. As there exist significant commonalities among virus families in the manner of host interaction, identifying and targeting common rather than specific features may lead to the development of broadly useful antivirals. Here, we have targeted the 3C protease of Hepatitis A Virus (HAV), a feco-orally transmitted virus of the family Picornaviridae, for identification of potential antivirals. The 3C protease is a viable drug target as it is required by HAV, as well as by other picornaviruses, for post-translational proteolysis of viral polyproteins and for inhibiting host innate immune pathways. Computational screening, followed by chemical synthesis and experimental validation resulted in identification of a few compounds which, at low micromolar concentrations, could inhibit HAV 3C activity. These compounds were further tested experimentally against the 3C protease of Human Rhinovirus, another member of the Picornaviridae family, with comparable results. Computational studies on 3C proteases from other members of the picornavirus family have indicated that the compounds identified could potentially be generic inhibitors for picornavirus 3C proteases.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/febs.14707

Manidipa Banerjee

Papers

Isolation and expression analysis of partial sequences of heavy metal transporters from Brassica juncea by coupling high throughput cloning with a molecular fingerprinting technique.

Toward development of generic inhibitors against the 3C proteases of picornaviruses.