Abstract
BackgroundChromium (Cr) being multifarious industrial used element, is considered a potential environmental threat. Cr found to be a prospective water and soil pollutant, and thus it is a current area of concern. Oilseed rape (Brassica napus L.) is well known as a major source of edible oil around the globe. Due to its higher growth, larger biomass and capability to uptake toxic materials B. napus is considered a potential candidate plant against unfavorable conditions. To date, no study has been done that described the Cr and GSH mechanism at RNA-Seq level.ResultsBoth digital gene expression (DGE) and transcriptome profile analysis (TPA) approaches had opened new insights to uncover the several number of genes related to Cr stress and GSH alleviating mechanism in two leading cultivars (ZS 758 and Zheda 622) of B. napus plants. Data showed that Cr inhibited KEGG pathways i.e. stilbenoid, diarlyheptanoid and gingerol biosynthesis; limonene and pentose degradation and glutathione metabolism in ZS 758; and ribosome and glucosinolate biosynthesis in Zheda-622. On the other hand, vitamin B6, tryptophan, sulfur, nitrogen and fructose and manose metabolisms were induced in ZS 758, and zeatin biosynthesis, linoleic acid metabolism, arginine and proline metabolism, and alanine, asparate and glutamate metabolism pathways in Zheda 622. Cr increased the TFs that were related to hydralase activity, antioxidant activity, catalytic activity phosphatase and pyrophosphatase activity in ZS 758, and vitamin binding and oxidoreductase activity in Zheda 622. Cr also up-regulated the promising proteins related to intracellular membrane bounded organelles, nitrile hyrdatase activity, cytoskeleton protein binding and stress response. It also uncovered, a novel Cr-responsive protein (CL2535.Contig1_All) that was statistically increased as compared to control and GSH treated plants. Exogenously applied GSH successfully not only recovered the changes in metabolic pathways but also induced cysteine and methionine metabolism in ZS 758 and ubiquinone and other terpenoid-quinone biosynthesis pathways in Zheda 622. Furthermore, GSH increased the level of TFs i.e. the gene expression of antioxidant and catalytic activities, iron ion binding and hydrolase activity as compared with Cr. Moreover, results pointed out a novel GSH responsive protein (CL827.Contig3_All) whose expression was found to be significantly increased when compared than Cr stress. Results further delineated that GSH induced TFs such as glutathione disulphide oxidoreducatse and aminoacyl-tRNA ligase activity, and beta glucosidase activity in ZS 758. Similarly in Zheda 622, GSH induced the TFs for instance DNA binding and protein dimerization activity. GSH also highlighted the proteins that were involved in transportation, photosynthesis process, RNA polymerase activity, and against the metal toxicity. These results indicated that cultivar ZS 758 had better metabolism and showed higher tolerance against Cr toxicity.ConclusionThe responses of ZS 758 and Zheda 622 differed considerably at both physiological and transcriptional level. Moreover, RNA-Seq method explored the hazardous behavior of Cr as well as GSH up-regulating mechanism by activating plant metabolism, stress responsive genes, TFs and protein encyclopedia.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3200-6) contains supplementary material, which is available to authorized users.
Highlights
Chromium (Cr) being multifarious industrial used element, is considered a potential environmental threat
RNA-Seq method explored the hazardous behavior of Cr as well as Reduced glutathione (GSH) up-regulating mechanism by activating plant metabolism, stress responsive genes, transcription factors (TFs) and protein encyclopedia
Plant material and growth conditions For this study, seeds of two leading cultivars of B. napus named as black seeded (ZS 758) and yellow seeded (Zheda 622) were selected on the basis of previous findings [10], in which we found that these two cultivars showed different tolerance response to Cr stress
Summary
Chromium (Cr) being multifarious industrial used element, is considered a potential environmental threat. Cr being 22nd ranked element on the world’s soil, is available in various concentrations ranges from 1 to 300 mg/kg with an average of 100 mg/kg [1, 2]. It is available in different reactive forms, but promising species are monovalent (Cr 0), trivalent (Cr III), and the hexavalent (Cr VI) [3]. It comes into the plant body passively [4] and through the sulphate anions as a carrier [5]. Enhanced level of ROS in different plant parts might be the imbalance between its production and inactivation by antioxidants that known as superoxide dismutase, peroxidase, catalase and ascorbate peroxidase, and non enzymatic defense machinery called glutathione and carotenoids [13, 14]
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