Mol. Cells 2017; 40(12): 966~975  https://doi.org/10.14348/molcells.2017.0229
Humic Acid Confers HIGH-AFFINITY K+ TRANSPORTER 1-Mediated Salinity Stress Tolerance in Arabidopsis
Laila Khaleda1, Hee Jin Park2,3, Dae-Jin Yun3, Jong-Rok Jeon4, Min Gab Kim5, Joon-Yung Cha1,*, and
Woe-Yeon Kim1,4,*
1Division of Applied Life Science (BK21Plus), Plant Molecular Biology and Biotechnology Research Center (PMBBRC), Research
Institute of Life Sciences (RILS), Gyeongsang National University, Jinju 52828, Korea, 2Institute of Glocal Disease Control, Konkuk
University, Seoul 05029, Korea, 3Department of Biomedical Science and Engineering, Konkuk University, Seoul 05029, Korea,
4Department of Agriculture Chemistry and Food Science & Technology, Institute of Agriculture and Life Science (IALS), Gyeongsang
National University, Jinju 52828, Korea, 5College of Pharmacy and Research Institute of Pharmaceutical Science, PMBBRC,
Gyeongsang National University, Jinju 52828, Korea
*Correspondence: kim1312@gnu.ac.kr (WYK); jycha@gnu.ac.kr (JYC)
Received September 25, 2017; Revised November 5, 2017; Accepted November 5, 2017.; Published online December 20, 2017.
© Korean Society for Molecular and Cellular Biology. All rights reserved.

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit (http://creativecommons.org/licenses/by-nc-sa/3.0/).
ABSTRACT
Excessive salt disrupts intracellular ion homeostasis and inhibits plant growth, which poses a serious threat to global food security. Plants have adapted various strategies to survive in unfavorable saline soil conditions. Here, we show that humic acid (HA) is a good soil amendment that can be used to help overcome salinity stress because it markedly reduces the adverse effects of salinity on Arabidopsis thaliana seedlings. To identify the molecular mechanisms of HA-induced salt stress tolerance in Arabidopsis, we examined possible roles of a sodium influx transporter HIGH-AFFINITY K+ TRANSPORTER 1 (HKT1). Salt-induced root growth inhibition in HKT1 overexpressor transgenic plants (HKT1-OX) was rescued by application of HA, but not in wild-type and other plants. Moreover, salt-induced degradation of HKT1 protein was blocked by HA treatment. In addition, the application of HA to HKT1-OX seedlings led to increased distribution of Na+ in roots up to the elongation zone and caused the reabsorption of Na+ by xylem and parenchyma cells. Both the influx of the secondary messenger calcium and its cytosolic release appear to function in the destabilization of HKT1 protein under salt stress. Taken together, these results suggest that HA could be applied to the field to enhance plant growth and salt stress tolerance via post-transcriptional control of the HKT1 transporter gene under saline conditions.
Keywords: Arabidopsis, calcium, HKT1, humic acid, salt stress


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31 December 2017 Volume 40,
Number 12, pp. 889~985

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