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Calcium (Ca) plays important role in plant development and response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effect of Ca (50 mM) in controlling cadmium (Cd) uptake in mustard (Brassica juncea L.) plants exposed to toxic levels of Cd (200 mg L−1 and 300 mg L−1). The Cd treatment showed substantial decrease in plant height, root length, dry weight, pigments and protein content. Application of Ca improved the growth and biomass yield of the Cd-stressed mustard seedlings. More importantly, the oil content of mustard seeds of Cd-stressed plants was also enhanced with Ca treatment. Proline was significantly increased in mustard plants under Cd stress, and exogenously sprayed Ca was found to have a positive impact on proline content in Cd-stressed plants. Different concentrations of Cd increased lipid peroxidation but the application of Ca minimized it to appreciable level in Cd-treated plants. Excessive Cd treatment enhanced the activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase and glutathione reductase, which were further enhanced by the addition of Ca. Additionally, Cd stress caused reduced uptake of essential elements and increased Cd accumulation in roots and shoots. However, application of Ca enhanced the concentration of essential elements and decreased Cd accumulation in Cd-stressed plants. Our results indicated that application of Ca enables mustard plant to withstand the deleterious effect of Cd, resulting in improved growth and seed quality of mustard plants.

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Jasmonates (JAs) [Jasmonic acid (JA) and methyl jasmonates (MeJAs)] are known to take part in various physiological processes. Exogenous application of JAs so far tested on different plants under abiotic stresses particularly salinity, drought, and temperature (low/high) conditions have proved effective in improving plant stress tolerance. However, its extent of effectiveness entirely depends on the type of plant species tested or its concentration. The effects of introgression or silencing of different JA- and Me-JA-related genes have been summarized in this review, which have shown a substantial role in improving crop yield and quality in different plants under stress or non-stress conditions. Regulation of JAs synthesis is impaired in stressed as well as unstressed plant cells/tissues, which is believed to be associated with a variety of metabolic events including signal transduction. Although, mitogen activated protein kinases (MAPKs) are important components of JA signaling and biosynthesis pathways, nitric oxide, ROS, calcium, ABA, ethylene, and salicylic acid are also important mediators of plant growth and development during JA signal transduction and synthesis. The exploration of other signaling molecules can be beneficial to examine the details of underlying molecular mechanisms of JA signal transduction. Much work is to be done in near future to find the proper answers of the questions like action of JA related metabolites, and identification of universal JA receptors etc. Complete signaling pathways involving MAPKs, CDPK, TGA, SIPK, WIPK, and WRKY transcription factors are yet to be investigated to understand the complete mechanism of action of JAs.

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Artemisia L. is among the most diverse and medicinally important genera of the plant family Asteraceae. Discrepancies arise in the taxonomic classification of Artemisia due to the occurrence of multiple polyploidy events in separate lineages and its complex morphology. The discrepancies could be resolved by increasing the genomic resources. A. scoparia is one of the most medicinally important species in Artemisia. In this paper, we report the complete chloroplast genome sequence of Artemisia scoparia. The genome was 151,060 bp (base pairs), comprising a large single copy (82,834 bp) and small single copy (18,282 bp), separated by a pair of long inverted repeats (IRa and IRb: 24,972 bp each). We identified 114 unique genes, including four ribosomal RNAs, 30 transfer RNAs, and 80 protein-coding genes. We analysed the chloroplast genome features, including oligonucleotide repeats, microsatellites, amino acid frequencies, RNA editing sites, and codon usage. Transversion substitutions were twice as frequent as transition substitutions. Mutational hotspot loci included ccsA-ndhD, trnH-psbA, ndhG-ndhI, rps18-rpl20, and rps15-ycf1. These loci can be used to develop cost-effective and robust molecular markers for resolving the taxonomic discrepancies. The reconstructed phylogenetic tree supported previous findings of Artemisia as a monophyletic genus, sister to the genus Chrysanthemum, whereby A. scoparia appeared as sister to A. capillaris.

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