Responses of genes of DNA repair, alternative oxidase, and pro-/antioxidant state in Arabidopsis thaliana with altered expression of AOX1a to gamma irradiation

Abstract

Purpose

High doses of gamma (γ) irradiation cause oxidative stress and DNA damage. Alternative oxidase (AOX) catalyzes the energy-dissipating cyanide-resistant alternative pathway in plant mitochondria and is an important part of the cellular defense network under stress conditions. In this study, Arabidopsis thaliana plants with an altered expression of the AOX1a gene were exposed by high dose-rate ionizing radiation to assess the expression of genes of DNA repair and pro-/antioxidant states to elucidate the functional significance of AOX in plant stress response.

Materials and methods

Five-week-old A. thaliana plants, either with basal AOX1a gene expression (wild-type Colombia-0 (Col-0)), antisense silencing of AOX1a (AS-12), and overexpression of the gene (XX-2), were γ-irradiated at a dose of 200 Gy. Gene expression and biochemical analyses were performed 12 h after irradiation.

Results

Acute γ-irradiation caused different responses between the genotypes. XX-2 plants, either control or irradiated, showed the highest expression of AOX1a gene and AOX protein, and the lowest expression of DNA repair genes. Wild type and AS-12 plants exposed to γ-irradiation upregulated another stress-induced gene, AOX1d, and DNA repair genes. Furthermore, a higher activity of Mn-dependent superoxide dismutase (Mn-SOD) was observed in the irradiated AS-12 plants than in the untreated plants of this line. However, AS-12 plants were less effective than Col-0 plants in controlling the accumulation of the superoxide anion. XX-2 plants had the lowest reactive oxygen species (ROS) levels among the genotypes.

Conclusions

AS-12 plants display a compensatory mechanism by increasing the expression of AOX1d and the synthesis of the AOX protein, as well as by Mn-SOD activation. However, these were insufficient to maintain the background level of embryonic lethal mutations, and thereby the reproductive capacity. These results highlight the importance of AOX in the successful adaptation of plants to acute γ-irradiation, and indicate that AOX1a plays a key role in the regulation of the stress response.

Keywords:

• Arabidopsis thaliana
• alternative oxidase
• gamma radiation
• DNA repair
• oxidative stress
• embryonic lethal mutations

Acknowledgments

The authors would like to thank Vladislav Tarasenko and Olga Grabelnych for seeds of mutant A. thaliana lines, Siberian Institute of Plant Physiology and Biochemistry, Siberian Branch RAS. The work is done using the equipment of the Collective Usage Center (CUC) ‘Molecular Biology’, Institute of Biology, Komi Science Centre, Ural Branch RAS. We also would like to thank Maria V. Kyrnysheva and Elena E. Rasova for their technical assistance with biochemical analysis and embryonic lethal mutations assessment, Institute of Biology, Komi Science Centre, Ural Branch RAS.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by RFBR according to the research project No. 19-04-00476 А and partially supported by the grant from The Ministry of Science and Higher Education of the Russian Federation [AAAA-A17-117033010038-7, AAAAA18-118011190102-7].

Notes on contributors

Elena S. Belykh

Elena S. Belykh, Ph.D. in Biology, Radiobiologist, is a Researcher at the Department of Radiobiology, Institute of Biology, Komi Science Center, Russian Academy of Sciences, Syktyvkar, Russia.

Ilya O. Velegzhaninov

Ilya O. Velegzhaninov, Ph.D. in Biology, Radiobiologist, is a Senior Researcher at the Department of Radiobiology and a Senior Researcher of the CCU ‘Molecular Biology’, Institute of Biology, Komi Science Center, Russian Academy of Sciences, Syktyvkar, Russia.

Elena V. Garmash

Elena V. Garmash, D.Sc. in Biology, Plant Physiologist and Biochemist, is a Leader Researcher of the Laboratory of Ecological Plant Physiology, Institute of Biology, Komi Science Center, Russian Academy of Sciences, Syktyvkar, Russia.