Salinity tolerance of tomato plants: the role of jasmonic acid and root ammonium transporters
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Date
2016
Authors
Abouelsaad, Ibrahim
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Abstract
Plant hormones and ion transporters are key elements for plant salt tolerance. To investigate the potential involvement of jasmonic acid (JA) and root ammonium transporters (AMTs) in salt tolerance, salt stress responses of tomato (Solanum lycopersicon) JA-deficient mutant def-1 (defenseless-1) and two tomato species (S. lycopersicon and S. pennellii) varying in salt tolerance were analyzed, respectively. The physiological and biochemical analyses of def-1 under salt stress showed a reduction in nitrogen (N) content and an increase in hydrogen peroxide and malondialdehyde compared to the wild type (WT) plants. The ROS (reactive oxygen species)-associated injury phenotype for def-1 was associated with lower activity of both enzymatic antioxidants and non-enzymatic antioxidants. These findings suggest that JA plays a role in maintaining N and ROS homeostasis under salt stress. The results of the bioinformatics analysis for tomato AMTs indicated that the three known genes belong to the plant AMT1 subfamily (electreogenic NH4+ transport system) and five new genes were found in the plant AMT2 subfamily (electroneutral NH3 transport system). Gene expression analysis revealed that tomato roots expressed two members of the AMT1 subfamily (involved in NH4+ uptake) and one member of the AMT2 subfamily (potentially involved in the efflux of the gaseous NH3 species). The comparative analysis between S. lycopersicon and the wild species S. pennellii under salt stress, indicated that the latter is more salt tolerant. In root tissues of both species, the expression of key genes for NO3− uptake and assimilation were reduced under salt stress. However, salt tolerance of S. pennellii was coupled with higher relative mRNA levels of NH4+ uptake genes (AMT1-type transporters, AMT1.1 and AMT1.2) and assimilation genes. These findings suggest that AMTs are involved in salt tolerance by facilitating the NH4+ uptake and reducing the energy requirements for growth. Overall, the results of my research improve our understanding of salinity tolerance and will be beneficial to improve tomato growth in saline soil.
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Keywords
Salinity, Stress, Tomato