Maize is one of the most important crops worldwide, but it suffers from salt stress when grown in saline-alkaline soil. There is therefore an urgent need to improve maize salt tolerance and crop yield. In this study, the SsNHX1 gene of Suaeda salsa, which encodes a vacuolar membrane Na⁺/H⁺ antiporter, was transformed into the maize inbred line 18-599 by Agrobacterium-mediated transformation. Transgenic maize plants overexpressing the SsNHX1 gene showed less growth retardation when treated with an increasing NaCl gradient of up to 1%, indicating enhanced salt tolerance. The improved salt tolerance of transgenic plants was also demonstrated by a significantly elevated seed germination rate (79%) and a reduction in seminal root length inhibition. Moreover, transgenic plants under salt stress exhibited less physiological damage. SsNHX1-overexpressing transgenic maize accumulated more Na⁺ and K⁺ than wild-type (WT) plants particularly in the leaves, resulting in a higher ratio of K+/Na+ in the leaves under salt stress. This result revealed that the improved salt tolerance of SsNHX1-overexpressing transgenic maize plants was likely attributed to SsNHX1-mediated localization of Na⁺ to vacuoles and subsequent maintenance of the cytosolic ionic balance. In addition, SsNHX1 overexpression also improved the drought tolerance of the transgenic maize plants, as rehydrated transgenic plants were restored to normal growth while WT plants did not grow normally after dehydration treatment. Therefore, based on our engineering approach, SsNHX1 represents a promising candidate gene for improving the salt and drought tolerance of maize and other crops.

Heat shock protein 70 (HSP70) is one of the most important members in the heat shock protein family, and plays important roles in the thermotolerance of insect.  To explore the molecular mechanism of thermotolerance of Frankliniella occidentalis adults, the difference in the expression of HSP70s in F. occidentalis male or female adults under the thermal stress was studied under the laboratory conditions.  Two full length cDNAs of HSP70s gene (Fohsc704 and Fohsc705) were cloned from F. occidentalis by using RT-PCR and RACE.  The genomic sequence was demonstrated by genomic validation, and the position and size of the intron were analyzed by sequence analysis of cDNA.  Real-time PCR was used to analyze the HSP70 expression patterns.  The cDNA of Fohsc704 and Fohsc705 possessed 2 073 and 1 476 bp which encoded 690 and 491 amino acids (aa) with a calculated molecular weight of 75 and 54 kDa, respectively.  Four introns in Fohsc704 and six introns in Fohsc705 protein were found.  However, the HSP70 protein sequences in our study were ended with EKKN and GIFL, which were different from the reported FoHSP70s.  Various expression patterns of Fohsc704 and Fohsc705 were found in both genders of F. occidentalis under thermal stress.  The expression of Fohsc704 and Fohsc705 reached to the highest level at –12 and –8°C in male adults, respectively, and Fohsc705 expressed the highest level at 33°C in female adults.  In conclusion, HSP70s of F. occidentalis in our study are novel heat shock proteins.  There were difference in expression patterns of the two hsc70s in genders of F. occidentalis, and the two HSP70s play important roles in the thermotolerance of F. occidentalis.