Abstract
Salinity is an important abiotic stressor that negatively affects plant growth. In this study, we investigated the physiological and molecular mechanisms underlying moderate and high salt tolerance in diploid (2×) and tetraploid (4×) Robinia pseudoacacia L. Our results showed greater H2O2 accumulation and higher levels of important antioxidative enzymes and non-enzymatic antioxidants in 4× plants compared with 2× plants under salt stress. In addition, 4× leaves maintained a relatively intact structure compared to 2× leaves under a corresponding condition. NaCl treatment didn’t significantly affect the photosynthetic rate, stomatal conductance or leaf intercellular CO2 concentrations in 4× leaves. Moreover, proteins from control and salt treated 2× and 4× leaf chloroplast samples were extracted and separated by two-dimensional gel electrophoresis. A total of 61 spots in 2× (24) and 4× (27) leaves exhibited reproducible and significant changes under salt stress. In addition, 10 proteins overlapped between 2× and 4× plants under salt stress. These identified proteins were grouped into the following 7 functional categories: photosynthetic Calvin-Benson Cycle (26), photosynthetic electron transfer (7), regulation/defense (5), chaperone (3), energy and metabolism (12), redox homeostasis (1) and unknown function (8). This study provides important information of use in the improvement of salt tolerance in plants.
Highlights
Salinity is an important abiotic stressor that negatively affects plant growth
We investigated the response of chloroplasts in tetraploid black locust and its corresponding diploid in response to salt stress
Tetraploid R. pseudoacacia (4× ) leaves did not show any obvious etiolation under the same conditions (Fig. 1)
Summary
Salinity is an important abiotic stressor that negatively affects plant growth. In this study, we investigated the physiological and molecular mechanisms underlying moderate and high salt tolerance in diploid (2×) and tetraploid (4×) Robinia pseudoacacia L. Some polyploids are superior to their corresponding diploids in terms of tolerance to environmental stresses, such as drought[3], heat[4], nutrient-poor soils[1] and salinity[5]. This increased tolerance may be attributable to duplicate gene expression or related to evolutionary time. Physiological, ultrastructural and proteomic analyses have been used to detect changes in chloroplasts in response to high salinity in many plant species such as wheat[10], maize[11], Nicotiana benthamiana[12] and rice[13]. Knowledge regarding chloroplasts in woody species, especially polyploids, under salt stress conditions is still scarce
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