Expression of Y-Tocopherol Methyltransferase in Chloroplasts Results in Massive Proliferation of the Inner Envelope Membrane and Decreases Susceptibility to Salt and Metal-Induced Oxidative Stress by Reducing Reactive Oxygen Species
Date of this Version
Plant Biotechnology Journal
The γ-tocopherol methyltransferase (γ-TMT) is an important enzyme regulating synthesis of four tocopherols (α, γ, β and δ). In this report, we investigated the role of γ-TMT in regulating abiotic stress within chloroplasts. The At γ-tmt overexpressed via the tobacco chloroplast genome accumulated up to 7.7% of the total leaf protein, resulting in massive proliferation of the inner envelope membrane (IEM, up to 8 layers). Such high level expression of γ-TMT converted most of γ-tocopherol to α-tocopherol in transplastomic seeds (~10 fold higher) in the absence of abiotic stress. When grown in 400 mM NaCl, α-tocopherol content in transplastomic TMT leaves increased up to 8.2-fold and 2.4-fold higher than wild-type leaves. Likewise, under heavy metal stress α-tocopherol content in the TMT leaves increased up to 7.5-fold, twice higher than in the wild-type. Under extreme salt stress, the wild-type accumulated higher starch and total soluble sugars but TMT plants were able to regulate sugar transport. Hydrogen peroxide and superoxide content in wild-type increased up to 3-fold within 48 hours of NaCl stress when compared to TMT plants. The ion leakage from TMT leaves was significantly less than wild-type plants under abiotic stress and with less malondialdehyde, indicating lower lipid peroxidation. Taken together, these studies show that α-tocopherol plays a crucial role in the alleviation of salt and heavy metal stresses by decreasing ROS, lipid peroxidation and ion leakage, in addition to enhancing vitamin E conversion. Increased proliferation of the IEM should facilitate studies on retrograde signaling from chloroplast to the nucleus.
This is the peer reviewed version of the following article:Jin, S., & Daniell, H. (2014). Expression of γ‐tocopherol methyltransferase in chloroplasts results in massive proliferation of the inner envelope membrane and decreases susceptibility to salt and metal‐induced oxidative stresses by reducing reactive oxygen species. Plant Biotechnology Journal, 12(9), 1274-1285. doi:10.1111/pbi.12224, which has been published in final form at https://doi.org/10.1111/pbi.12224. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving [link to http://olabout.wiley.com/WileyCDA/Section/id-820227.html#terms].
chloroplast transformation, abiotic stress tolerance, γ-tocopherol methyltransferase
Jin, S., & Daniell, H. (2014). Expression of Y-Tocopherol Methyltransferase in Chloroplasts Results in Massive Proliferation of the Inner Envelope Membrane and Decreases Susceptibility to Salt and Metal-Induced Oxidative Stress by Reducing Reactive Oxygen Species. Plant Biotechnology Journal, 12 (9), 1274-1285. http://dx.doi.org/10.1111/pbi.12224
Date Posted: 01 March 2022
This document has been peer reviewed.