Abstract
Trehalose plays a critical role in plant response to salinity but the involved regulatory mechanisms remain obscure. Here, this study explored the mechanism of exogenous trehalose-induced salt tolerance in tomato plants by the hydroponic test method. Our results indicated that 10 mM trehalose displayed remarkable plant biomass by improving growth physiology, which were supported by the results of chlorophyll fluorescence and rapid light–response curve. In the salinity environment, trehalose + NaCl treatment could greatly inhibit the decrease of malondialdehyde level, and it increases the contents of other osmotic substances, carbohydrates, K+, and K+/Na+ ratio. Meanwhile, trehalose still had similar effects after recovery from salt stress. Furthermore, trehalose pretreatment promoted trehalose metabolism; significantly increased the enzymatic activity of the trehalose metabolic pathway, including trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP), and trehalase (TRE); and upregulated the expression of SlTPS1, SlTPS5, SlTPS7, SlTPPJ, SlTPPH, and SlTRE under saline conditions. However, the transcriptional levels of SlTPS1, SlTPS5, and SlTPS7 genes and the activity of TPS enzyme were reversed after recovery. In addition, we found that hydrogen peroxide (H2O2) and superoxide anion (O2−) were accumulated in tomato leaves because of salt stress, but these parameters were all recovered by foliar-applied trehalose, and its visualization degree was correspondingly reduced. Antioxidant enzyme activities (SOD, POD, and CAT) and related gene expression (SlCu/Zn-SOD, SlFe-SOD, SlMn-SOD, SlPOD, and SlCAT) in salt-stressed tomato leaves were also elevated by trehalose to counteract salt stress. Collectively, exogenous trehalose appeared to be the effective treatment in counteracting the negative effects of salt stress.
Highlights
Salt stress is a severe environmental pressure affecting crop yields worldwide (Yu et al, 2020)
Compared with CK, no significant discrepancies were observed in plant height, stem diameter, plant weight, relative electrical conductivity (REC), and cell damage rate in S1; plant height, stem diameter, shoot fresh weight, root fresh weight, and shoot dry weight in plants fed with S2 were significantly decreased by 10.85%, 4.59%, 25.86%, 42.34%, and 15.60%, respectively, but the difference in root dry weight was not significant, which was classified as mild stress
We found that SlTPS1, SlTPS5, SlTPS7, SlTPPJ and SlTPPH genes were induced to express under saline conditions (X5d), and the upregulation trend was higher after the exogenous supply of trehalose
Summary
Salt stress is a severe environmental pressure affecting crop yields worldwide (Yu et al, 2020). It is regarded as a contemporary agricultural issue restricting land use and a major problem limiting the increase in demand for food crops (Abbasi et al, 2016; Isayenkov and Maathuis, 2019). Nowadays, adopting grafting (Penella et al, 2017; Singh et al, 2020), crop rotation (Ahmad et al, 2013; Neves et al, 2015) and other agricultural operations, selecting salttolerant varieties (Tran et al, 2021), and applying exogenous substances (Zheng et al, 2016; Ali et al, 2020) are the most simple and common methods to improve the salt tolerance of plants and overcome the problem of soil salinization in production
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