Transcriptome Profiling of the Mangrove PlantBruguiera gymnorhizaand Identification of Salt Tolerance Genes byAgrobacteriumFunctional Screening

To identify key genes in the regulation of salt tolerance in the mangrove plant Bruguiera gymnorhiza, transcriptome profiling in the lateral and main roots under conditions of salt stress was performed. Statistical analysis revealed that 175 and 403 of 11,997 genes shoewd significantly increased high expression in the lateral and main roots respectively. One hundred and sixty genes were up-regulated in both types of roots in the early time period, 1 to 12 h after salt treatment. Expression vectors for 28 selected salt responsive genes were constructed and transformed in Agrobacterium tumefaciens, and then screened for salt tolerance. A. tumefaciens transformed with genes for lipid transfer, zinc finger, and ankyrin repeat proteins showed enhanced salt tolerance. Transgenic Arabidopsis plants expressing these three genes also exhibited increased tolerance to NaCl. These results indicate that Agrobacterium functional screening is an effective supplemental method of pre-screening genes involved in abiotic stress tolerance.