Synergistic exposure of rice seeds to different doses of γ-ray and salinity stress resulted in increased antioxidant enzyme activities and gene-specific modulation of TC-NER pathway.

Anca Macovei,Daniela Carbonera,Armando Buttafava,Narendra Tuteja,Sarvajeet Singh Gill,Alma Balestrazzi,Shailendra Raikwar,Juan Francisco Jiménez Bremont,Bharti Garg

doi:10.1155/2014/676934

Abstract

Recent reports have underlined the potential of gamma (γ)-rays as tools for seed priming, a process used in seed industry to increase seed vigor and to enhance plant tolerance to biotic/abiotic stresses. However, the impact of γ-rays on key aspects of plant metabolism still needs to be carefully evaluated. In the present study, rice seeds were challenged with different doses of γ-rays and grown in absence/presence of NaCl to assess the impact of these treatments on the early stages of plant life. Enhanced germination efficiency associated with increase in radicle and hypocotyl length was observed, while at later stages no increase in plant tolerance to salinity stress was evident. APX, CAT, and GR were enhanced at transcriptional level and in terms of enzyme activity, indicating the activation of antioxidant defence. The profiles of DNA damage accumulation were obtained using SCGE and the implication of TC-NER pathway in DNA damage sensing and repair mechanisms is discussed. OsXPB2, OsXPD, OsTFIIS, and OsTFIIS-like genes showed differential modulation in seedlings and plantlets in response to γ-irradiation and salinity stress. Altogether, the synergistic exposure to γ-rays and NaCl resulted in enhanced oxidative stress and proper activation of antioxidant mechanisms, thus being compatible with plant survival.

Highlights

Rice is one of the leading food crops worldwide and increasing the rice production is expected to play a significant role in upgrading the economic status of developing countries in Asia and Africa
Dry seeds were exposed to different γ-ray total doses using a 60Cobalt source as follows: 25 and 50 Gy delivered at low dose rate (LDR; 0.28 Gy min−1); 100 and 200 Gy delivered at high dose rate (HDR; 5.15 Gy min−1)
Rice seeds irradiated with 25 and 50 Gy delivered at a low dose rate, and 100 and 200 Gy delivered at a high dose rate, were rehydrated under physiological conditions and imbibed in a solution containing 100 mM NaCl

Summary

Introduction

Rice is highly sensitive to salt stress, especially at the early stages of plant development, and excess salt adversely affects all the plant’s major metabolic activities causing yield losses [1]. Recent studies reported that plant exposure to different doses of gamma (γ)-irradiation may improve the tolerance to abiotic stress conditions, for example, salt and drought [3, 4]. Gamma radiation, composed of high energy photons, is a type of ionizing radiation, able to penetrate and interact with living tissues. It causes decreased growth rate and reproduction capacity along with DNA damage and morphological changes [5, 6]. Irradiation with low doses is known to have stimulatory effects on plant growth, a concept referred to as hormesis [7]

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Conclusion