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Induced freezing tolerance and free amino acids perturbation of spinach by exogenous proline
J Plant Biotechnol 2018;45:357-363
Published online December 31, 2018
© 2018 The Korean Society for Plant Biotechnology.

Hyunsuk Shin, Sewon Oh, Daeil Kim, Jeum Kyu Hong, Jae Gil Yun, Sang Woo Lee, Ki-Ho Son

Department of Horticulture, Gyeongnam National University of Science and Technology, Jinju, 52725, Korea
Department of Horticulture, Chungbuk National University, Cheongju 28644, Korea
Correspondence to: e-mail:
Received December 17, 2018; Revised December 17, 2018; Accepted December 17, 2018.
cc This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The objective of this study was to investigate whether exogenous proline (Pro) could confer freezing tolerance of spinach and determine fluctuations of free amino acids in spinach leaf tissues under freeze-induced stress. Treatment with Pro (10 mM) resulted in more accumulation of Pro (~2.6-fold) in Pro-treated spinaches compared to untreated ones. These Pro-pretreated spinaches were more freezing-tolerant, showing more turgid leaves and petioles compared to untreated controls. However, when spinaches pre-treated with or without Pro were subjected to freezing, there was no significant difference in overall amino acid contents, emphasizing the role of Pro as an osmoprotectant. Freezing stress prompted intensification of total amino acid contents irrespective of pretreatment with Pro. Asp, Glu, Ala, and Val were the most abundant free amino acids due to increased protein degradation and nitrogen mobilization for plant survival under freezing stress. Arg, a precursor for the synthesis of polyamines in plants, was profoundly enhanced under freezing stress. This implies that Arg plays an important role in modulating freezing tolerance. Gly, Leu, and Ile were maintained at relatively low levels in all treatments. However, Ser, Tyr, and Lys as primary constituents of dehydrins were accumulated under freezing stress, suggesting that they might play a role in increasing cryoprotective activity under freezing stress.
Keywords : Arginine, Aspartate, Freezing stress, Glutamate, Spinacia oleraceae, Valine

December 2018, 45 (4)
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