Kundu Debangana, Dey Sankalan, Raychaudhuri Sarmistha Sen
Department of Biophysics, Molecular Biology, and Bioinformatics, University of Calcutta, 92, APC Road, Kolkata, 700009 India.
Genes Environ. 2018 Oct 15;40:21. doi: 10.1186/s41021-018-0109-0. eCollection 2018.
Plants experience severe physiological stress from heavy metal pollution caused by improper discarding of the industrial wastes. Hexavalent chromium [Cr (VI)] is one of the major heavy metal pollutants in India and is present particularly in some regions where grows to a great extent. This study was aimed at finding the effects of Cr (VI) on and manoeuvres of the plant to combat such heavy metal exposure in vitro.
Potassium dichromate was used as a source of Cr (VI) to induce the heavy metal stress. Range of Cr (VI) sublethal doses [0 mM (control), 0.1 mM, 0.3 mM, 0.5 mM, 1 mM, 1.5 mM and1.8 mM] was used to observe its effect on the plant. The seeds of the plant were grown on sucrose-agar media with different concentrations of potassium dichromate, and ten-day old seedlings were then harvested and examined.
The germination rate reduced below 50% at 1.9 mM Cr (VI) concentration and thus, 0 mM-1.8 mM concentration ranges were found to be suitable for sublethal dose. Morphological changes namely, reduction of the shoot-root length and multiple root development were caused by Cr (VI) in a dose-dependent manner. The plant showed elevated responses against Cr (VI), up to 1.5 mM (10 days treated) in terms of increasing accumulation of secondary metabolites like polyphenols, chlorophyll content (chlorophyll a, b and total chlorophyll), carotenoids and total antioxidant activity. DPPH radical scavenging activity along with malondialdehyde (MDA) content was not significantly elevated with the increase in Cr (VI) concentration indicating that the lipid peroxidation rate within the tissue was low. Phenylalanine ammonia lyase () and polyphenol oxidase () gene expressions were upregulated by 1 mM Cr (VI) concentration, which decreased at higher concentrations. The atomic absorption spectroscopy analysis also showed significant accumulation of Cr (VI) in the shoot and root with an increase in the potassium dichromate concentration.
Cr (VI) reduced the shoot-root length and seed germination in a dose-dependent manner. The plant system tried to combat the Cr (VI) stress by upregulating the stress response genes in the phenylpropanoid pathway along with an increase in polyphenol and antioxidant contents, which were evident from the lowering of lipid peroxidation rate and increase in and gene expressions.
由于工业废物的不当丢弃导致重金属污染，植物遭受严重的生理胁迫。六价铬[Cr(VI)]是印度主要的重金属污染物之一，尤其存在于某些该植物大量生长的地区。本研究旨在探究Cr(VI)对该植物的影响以及其在体外对抗这种重金属暴露的策略。
使用重铬酸钾作为Cr(VI)的来源以诱导重金属胁迫。采用一系列Cr(VI)亚致死剂量[0 mM(对照)、0.1 mM、0.3 mM、0.5 mM、1 mM、1.5 mM和1.8 mM]来观察其对植物的影响。将该植物的种子在含有不同浓度重铬酸钾的蔗糖 - 琼脂培养基上培养，然后收获并检查十天大的幼苗。
在Cr(VI)浓度为1.9 mM时，发芽率降至50%以下，因此，发现0 mM - 1.8 mM浓度范围适合作为亚致死剂量。形态学变化，即地上部 - 根长度的减少和多根发育，由Cr(VI)以剂量依赖的方式引起。就增加多酚、叶绿素含量(叶绿素a、b和总叶绿素)、类胡萝卜素和总抗氧化活性等次生代谢产物的积累而言，该植物对Cr(VI)表现出增强的响应，直至1.5 mM(处理10天)。随着Cr(VI)浓度的增加，DPPH自由基清除活性以及丙二醛(MDA)含量没有显著升高，表明组织内的脂质过氧化率较低。在1 mM Cr(VI)浓度下，苯丙氨酸解氨酶(PAL)和多酚氧化酶(PPO)基因表达上调，在更高浓度下则下降。原子吸收光谱分析还表明，随着重铬酸钾浓度的增加，Cr(VI)在地上部和根中显著积累。
Cr(VI)以剂量依赖的方式降低地上部 - 根长度和种子发芽率。植物系统试图通过上调苯丙烷途径中的应激反应基因以及增加多酚和抗氧化剂含量来对抗Cr(VI)胁迫，这从脂质过氧化率的降低以及PAL和PPO基因表达的增加中可以明显看出。
