ATP-binding cassette (ABC) transporters comprise a transport system superfamily which is ubiquitous in eukaryotic and prokaryotic cells. In plants, ABC transporters play important roles in hormone transport and stress tolerance. In this study, 15 BhABC transporters encoded by genes identified from the transcriptome of Betula halophila were categorized into four subfamilies (ABCB, ABCF, ABCG, and ABCI) using structural domain and phylogenetic analyses. Upon B. halophila exposure to exogenous phytohormones and abiotic stressors, gene expression patterns and transcriptional responses for each subfamily of genes were obtained using semi-quantitative RT-PCR analysis. The results demonstrated that expression of most genes belonging to ABCB and ABCG subfamilies changed in response to exogenous phytohormone exposures and abiotic stress. These results suggest that BhABC genes may participate in hormone transport and that their expression may be influenced by ABA-dependent signaling pathways involved in abiotic stress responses to various stressors.

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Salt stress inhibits normal plant growth and development by disrupting cellular water absorption and metabolism. Therefore, understanding plant salt tolerance mechanisms should provide a theoretical basis for developing salt-resistant varieties. Here, we cloned ThTrx5 from Tamarix hispida, a salt-resistant woody shrub, and generated ThTrx5-overexpressing transgenic Arabidopsis thaliana lines. Under NaCl stress, the germination rate of overexpressing ThTrx5 lines was significantly increased relative to that of the nontransgenic line; under salt stress, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione levels and root length and fresh weight values of transgenic ThTrx5 plants were significantly greater than corresponding values for wild-type plants. Moreover, with regard to the transcriptome, comparison of differential gene expression of transgenic versus nontransgenic lines at 0 h and 3 h of salt stress exposure revealed 500 and 194 differentially expressed genes (DEGs), respectively, that were mainly functionally linked to catalytic activity and binding process. Pull-down experiments showed that ThTrx bound 2-Cys peroxiredoxin BAS1-like protein that influences stress response-associated redox, hormone signal transduction, and transcription factor functions. Therefore, this work provides important insights into ThTrx5 mechanisms that promote salt tolerance in plants.were significantly higher than WT control levels after NaCl stress exposure. Moreover, root lengths and fresh weights of OE1 and OE2 plants were greater than respective values for WT plants (Figure 1). When SOD (superoxide dismutase), POD (peroxidase), CAT (catalase), and glutathione (GSSG) levels in transgenic and WT plants were measured at 0 h and 48 h of stress exposure, the results revealed that expression levels of enzymes and glutathione in transgenic line plants were significantly greater than respective levels in WT plants (Figure 2). Int. J. Mol. Sci. 2020, 21, 1165 3 of 19 while most plants of OE1/OE2 lines grew normally (Figure 2A). Chlorophyll measurement results showed significantly reduced chlorophyll content levels for both WT and transgenic lines, but chlorophyll levels in transgenic lines were significantly higher than WT control levels after NaCl stress exposure. Moreover, root lengths and fresh weights of OE1 and OE2 plants were greater than respective values for WT plants (Figure 1). When SOD (superoxide dismutase), POD (peroxidase), CAT (catalase), and glutathione (GSSG) levels in transgenic and WT plants were measured at 0 h and 48 h of stress exposure, the results revealed that expression levels of enzymes and glutathione in transgenic line plants were significantly greater than respective levels in WT plants (Figure 2).Int. J. Mol. Sci. 2020, 21, 1165 5 of 19 the prolongation of NaCl treatment time, the ThTrx5 expression level decreased to its lowest at 12 h and 24 h (<2-fold) and then increased, and then the expression quantity increased to nearly two times than the value of 24h at 48 h. Int. J. Mol....