| As an important cash crop, tomato (Lycopersicon esculentum. moneymaker) is a world-wide distribution. Plants are continuously exposed to biotic and abiotic stress conditions during their whole life cycles. Salt stress is one of common abiotic stress factors, causing serious impact on crop growth and yield. Under salinity, drought and other stress environment, some compatibility substances usually accumulated in the plant cell, thereby reducing the damage caused by environmental stress on plants. Glycinebetaine(GB) is one of the organic compatible solutes that can accumulate rapidly in many plants under salinity stress, drought and low temperature, and enhanced the tolerance to adverse conditions.In this study, the WT and codA transgenic tomato were used to elucidate the affects of GB on tomato under salt stress during g seedling growth. In order to investigate the role of GB in the enhancement of the tolerance to salt stress, we determined the photosynthetic and chlorophyll fluorescence parameters, the production of reactive oxygen species (ROS) and activities of antioxidant enzyme and the flux of K+under salt stress. The main results are as follows:(1) Under salt stress, the growth of the tomato seedlings was restrained. Compared with WT, the growth (plant weight, root length, fresh weight) of transgenic seedlings decreased to a lesser extent during salt stress. Therefore, the transgenic plants increased the tolerance of salt stress.(2) Salt stress decreased the photosynthetic rate (Pn), actiual PSⅡ photochemical efficiency (ΦPSⅡ) and the maximal photochemical efficiency of PSⅡ (Fv/Fm). However, the Pn, ΦPSⅡ and Fv/Fm of the codA transgenic tomato plants decreased less than that of WT. The results showed that genetic engineering of the biosynthesis of glycinebetaine can stabilize the structure of photosynthetic apparatus, and alleviate the photoinhibition of PSII under salt stress. (3) Salt stress increased the accumulation of H2O2, O2-in the wild-type and transgenic tomato, but this accumulation was less in transgenic tomato. During salt stress, the codA transgenic tomato plants decreased the accumulation of ROS through maintain relatively higher antioxidant enzyme (SOD, CAT, APX) activities and antioxidants content.(4) The antioxidant enzyme activity of codA transgenic plants was improved higher than that of WT under salt stress.The contents of MDA and the relative electrical conductivity in WT were significantly higher than that in transgenic seedlings. The results suggest that the codA transgenic plants can better matained the plasma membrane integrity than the wild type under salt stress.(5) Under normal conditions, the content of K+was higher in transgenic tomato roots than that in WT roots. Similarly, the content of K+was also slightly higher in the wild-type tomato roots with the of5mM betaine incubated than the wild-type tomato. Salt stress after1day, potassium content was decreased, and the content of K+in the wild-type tomato root without betaine incubated decreased to the greatest extent.(6) The non-invasive micro-measurement results show that the potassium efflux is lower in the codA transgenic tomato roots than wild-type tomato, whether ender the instantaneous addition of NaCl or the long-term with one day of NaCl treatment, indicating that the transgenic tomato syntheytic glycine betaine alleviate the NaCl-induced potassium efflux. The various concentrations of exogenous glycine betaine also reduced NaCl-induced potassium efflux.These results suggested that the genetic engeering of the biosynthesis of glycine betaine can enhance the salt tolerance in tomato plants by improving the antioxidant enzyme activities and reactive oxygen species scavenging capacity and alleviating the NaCl-induced potassium efflux. |
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