Indigenous Tocopherol Improves Tolerance of Oilseed Rape to Cadmium Stress.

Essa Ali,Ahmad Naeem Shahzad,Muhammad Irfan,Saad Alkahtani,Murtaza Ali,Syed Asad Hussain Bukhari,Haseeb-Ur- Rehman,Jawad Munawar Shah,Shabir Hussain,Zeshan Hassan,Shafaqat Ali,Mohamed M Abdel-Daim

doi:10.3389/fpls.2020.547133

Abstract

Two oilseed rape genotypes (Jiu-Er-13XI and Zheyou-50), differing in seed oil content, were subjected to cadmium (Cd) stress in hydroponic experiment. Genotypic differences were observed in terms of tolerance to Cd exposure. Cd treatment negatively affected both genotypes, but the effects were more devastating in Jiu-Er-13XI (low seed oil content) than in Zheyou-50 (high seed oil content). Jiu-Er-13XI accumulated more reactive oxygen species (ROS), which destroyed chloroplast structure and decreased photosynthetic pigments, than Zheyou-50. Total fatty acids, especially 18:2 and 18:3, severely decreased as suggested by increase in MDA content. Roots and shoots of Jiu-Er-13XI plants accumulated more Cd content, while less amount of tocopherol (Toc) was observed under Cd stress, than Zheyou-50. Conversely, Zheyou-50 was less affected by Cd stress than its counterpart. It accumulated comparatively less amount of Cd in roots and shoots, along with reduced accumulation of malondialdehyde (MDA) and ROS under Cd stress, than Jiu-Er-13XI. Further, the level of Toc, especially α-Tocopherol, was much higher in Zheyou-50 than in Jiu-Er-13XI, which was also supported by high expression of Toc biosynthesis genes in Zheyou-50 during early hours. Toc not only restricted the absorption of Cd by roots and its translocation to shoot but also scavenged the ROS generated during oxidative stresses. The low level of MDA shows that polyunsaturated fatty acids in chloroplast membranes remained intact. In the present study the tolerance of Zheyou-50 to Cd stress, over Jiu-Er-13XI, is attributed to the activities of Toc. This study shows that plants with high seed oil content are tolerant to Cd stress due to high production of Toc.

Highlights

Heavy metals are major environmental pollutants due to their detrimental effects on life
Comprehensive study on tolerance of plants to Cd stress is of utmost importance to elucidate the underlying mechanisms to develop Cd-tolerant genotypes
Tocopherols are regarded as the non-enzymatic component of the plant defense system and play major roles in protecting plants against stresses at cellular and subcellular level (Collakova and DellaPenna, 2003; Li et al, 2010)

Summary

Introduction

Heavy metals are major environmental pollutants due to their detrimental effects on life. Heavy metals enter the food chain through plants grown on polluted soil or irrigated with contaminated water (Bukhari et al, 2016). Cadmium becomes a part of the soil–plant environment as plants absorb water and nutrients from the soil. Cadmium can affect plants in many ways, especially by damaging their photosynthetic apparatus (Ali et al, 2015), reducing gas exchange ability (Jia et al, 2011), causing nutrient imbalance (Feng et al, 2013), subcellular changes like chloroplast, mitochondrial, and nuclear membrane disintegration (Liu et al, 1995; Wang et al, 2011; Ali et al, 2018), and destroying antioxidant defense systems (Ahmad et al, 2011). Tocopherols are considered as an important component of non-enzymatic protection against stresses

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Results

Conclusion