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Plant cells accumulate osmotic substances (e.g., sugar) to protect cell components and maintain osmotic balance under drought stress conditions. Previous studies found that pOsHAK1:OsFLN2 promotes sugar metabolism and improves the drought tolerance of rice plants under drought stress. This study further evaluated the effect of the ectopic expression of the OsSUT1 gene driven by the OsHAK1 promoter on the sugar transport and drought tolerance of rice. The results showed that the net photosynthetic rate and sucrose phosphate synthase activity of plants expressing the OsSUT1 gene were not significantly different from those of wild-type (WT) rice plants under drought conditions. However, the sucrose transport rate in the phloem increased in the transgenic plants, and the sucrose contents were significantly lower in the leaves but significantly higher in the roots of transgenic plants than those in WT plants. The pOsHAK1:OsSUT1 and pOsHAK1:OsFLN2 transgenic lines had similar rates of long-distance sucrose transport and drought tolerance, which were higher than those of the WT plants. The relative water content of the transgenic plants was higher, while their water loss rate, hydrogen peroxide (H2O2), and malondialdehyde (MDA) contents were lower than those of the WT plants. The stress-responsive gene OsbZIP23 and the antioxidant-related gene OsCATB were significantly upregulated in the drought-treated transgenic lines, while the senescence indicator gene SGR and the stress-responsive gene OsNAC2 were down-regulated compared to WT plants. These results showed that promoting the long-distance sugar transport through the expression of pOsHAK1:OsSUT1 could produce an improved drought tolerance effect similar to that of pOsHAK1:OsFLN2, providing an effective way to improve the drought tolerance of cereal crops at the seedling stage. [ABSTRACT FROM AUTHOR]

In order to study the role of nitrate transporter (NRT) in the uptake and transport of nitrate in tobacco, a nitrate transporter gene encoding 612 amino acids with a total length of 1 839 bp was cloned using the cDNA of tobacco cultivar K326 as a template and named as NtNRT1.7. Bioinformatics analysis indicated that NtNRT1.7 had typical transmembrane domains. The homology analysis showed that the homology of NtNRT1.7 and Arabidopsis thaliana AtNRT1.7 was 57.23%. Subcellular localization results showed that this protein was located on the cell membrane and was a typical membrane protein. Promoter analysis and QRT-PCR results of different stress treatments indicated that NtNRT1.7 gene was highly expressed in mature leaves, its expression was suppressed by low nitrogen and enhanced by drought, low temperature, high salt and other stresses, which suggested that NtNRT1.7 gene might be involved in nitrate recycle under abiotic stresses. [ABSTRACT FROM AUTHOR]