Morpho-Physiological, Biochemical, and Genetic Responses to Salinity in Medicago truncatula.

Sabrine Hdira,Mohsen Hanana,Mounawer Badri,Maria Teresa Sanchez-Ballesta,Hatem Ben Jouira,Irene Romero,Chedly Abdelly,Asma Mahjoub,Loua Haddoudi,Ndiko Ludidi

doi:10.3390/plants10040808

Abstract

We used an integrated morpho-physiological, biochemical, and genetic approach to investigate the salt responses of four lines (TN1.11, TN6.18, JA17, and A10) of Medicago truncatula. Results showed that TN1.11 exhibited a high tolerance to salinity, compared with the other lines, recording a salinity induced an increase in soluble sugars and soluble proteins, a slight decrease in malondialdehyde (MDA) accumulation, and less reduction in plant biomass. TN6.18 was the most susceptible to salinity as it showed less plant weight, had elevated levels of MDA, and lower levels of soluble sugars and soluble proteins under salt stress. As transcription factors of the APETALA2/ethylene responsive factor (AP2/ERF) family play important roles in plant growth, development, and responses to biotic and abiotic stresses, we performed a functional characterization of MtERF1 gene. Real-time PCR analysis revealed that MtERF1 is mainly expressed in roots and is inducible by NaCl and low temperature. Additionally, under salt stress, a greater increase in the expression of MtERF1 was found in TN1.11 plants than that in TN6.18. Therefore, the MtERF1 pattern of expression may provide a useful marker for discriminating among lines of M. truncatula and can be used as a tool in breeding programs aiming at obtaining Medicago lines with improved salt tolerance.

Highlights

Due to the unpredictability of environmental conditions and the inability of plants to move in order to avoid unfavorable conditions, a number of abiotic stress factors threaten plant productivity and sustainability [1,2] Salinity is one of the main environmental stressors limiting crop production globally [3], it causes oxidative damages, ion toxicity, and nutrition imbalance [2,4,5,6]
The result indicates a rapid response of MtERF1 to salt stress because the accumulation decreases after 24 h of salt treatment. These results suggest that TN1.11 is a salt-tolerant line of Medicago truncatula and MtERF1 may play a role in regulating root growth and could be a marker gene for salt tolerance
Our results revealed that the 100 mM NaCl stress treatment has caused reduction of the biomass in all lines, but more pronounced reduction was found for the sensitive line TN6.18

Summary

Introduction

Due to the unpredictability of environmental conditions and the inability of plants to move in order to avoid unfavorable conditions, a number of abiotic stress factors threaten plant productivity and sustainability [1,2] Salinity is one of the main environmental stressors limiting crop production globally [3], it causes oxidative damages, ion toxicity, and nutrition imbalance [2,4,5,6]. According to the United Nations (UN) Environment Program (UNEP), worldwide, approximately 50% of agricultural lands are characterized as saline soils [6]. This area increases every day due to inadequate irrigation practices and it aggravates the salinity problem [7]. Survival under this stress requires the integration of adaptive metabolic, physiological, and molecular responses. Understanding the different adaption mechanisms to environmental stresses may lead to novel strategies for plant improvement

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