Molecular and functional comparisons of the vacuolar Na^+/H^+ exchangers originated from glycophytic and halophytic species

A novel vacuolar Na+/H+ exchanger, CgNHX1, was cloned from a halophytic species Chenopodium glaucum by using reverse transcriptase-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) technique. Sequence alignment and phylogenetic analysis of 22 NHX genes from GenBank as well as the new CgNHX1 gene indicate that NHX genes shared a great degree of similarity, regardless of their glycophytic or halophytic origin. Expression of the CgNHX1 gene was induced by NaCl and peaked at 400 mmol/L NaCl. Overexpression of NHX1 genes in rice enhanced their tolerance to salt stress. However, there is no significant difference in salt tolerance among the transgenic rice plants overexpressing the NHX1 genes from either glycophytic or halophytic species. The Na+ content of both the wild type (WT) and transgenic plants increased when exposed to 50 and 100 mmol/L NaCl, and the Na+ concentration in transgenic plants was marginally higher than that of WT. Our data demonstrate that the overexpression of the NHX1 gene from either glycophytic or halophytic species resulted in the enhanced tolerance to salt stress at a similar level, suggesting that NHX gene per se might not be the reason accounting for the difference in salt tolerance between glycophytes and halophytes.

Screening Chinese soybean genotypes for Agrobacterium-mediated genetic transformation suitability

The Agrobacterium-mediated transformation system is the most commonly used method in soybean transformation.Screening of soybean genotypes favorable for Agrobacterium-infection and tissue regeneration is the most important step to establish an efficient genetic transformation system.In this study,twenty soybean genotypes that originated from different soybean production regions in China were screened for transient infection,regeneration capacity,and stable transgenic efficiency.Three genotypes,Yuechun 04-5,Yuechun 03-3,and Tianlong 1,showed comparable stable transgenic efficiencies with that of the previously reported American genotypes Williams 82 and Jack in our experimental system.For the Tianlong 1,the average stable transformation efficiency is 4.59%,higher than that of control genotypes(Jack and Williams 82),which is enough for further genomic research and genetic engineering.While polymerase chain reaction(PCR),LibertyLink strips,and β-glucuronidase(GUS) staining assays were used to detect the insertion and expression of the transgene,leaves painted with 135 mg/L Basta could efficiently identify the transformants.

Expression of the Arabidopsis thaliana Histone Gene AtHTA1 Enhances Rice Transformation Efficiency

We expressed the Arabidopsis thaliana histone AtHTA1 in rice under the control of the maize ubiquitin promoter. Transformation efficiencies of rice plants that constitutively expressed AtHTA 1 were 28-44% higher than calli containing an empty vector control. Furthermore, co-infection of rice calli with a vector containing AtHTA 1 and another vector with the target gene increased transformation by 27-50%. Thus, expression of AtHTA 1 either transiently or in stably transformed cells improved rice transformation efficiency.