Identification of salt tolerance genes from the mangrove plant Bruguiera gymnorhiza using Agrobacterium functional screening

To identify key genes in the regulation of salt tolerance in the mangrove plant Bruguiera gymnorhiza, cDNA expression libraries were constructed from salt-treated roots and leaves using the host organism Agrobacterium tumefaciens. Functional screening of the Agrobacterium libraries identified 44 putative salt tolerance genes in B.gymnorhiza. A cDNA clone which is homologous to an unknown cDNA from the mangrove plant K. candel and the cyc02 gene from Catharanthus roseus conferred the highest level of salt tolerance (450 mM NaCl) to A. tumefaciens, indicating that it plays a major role in the regulation of salt tolerance in mangrove plants. Several of the genes that we identified have not previously been implicated in plant salt tolerance. Transgenic Arabidopsis plants expressing Bg70 and cyc02 homologue exhibited increased tolerance to NaCl. These results demonstrate that Agrobacterium functional screening is an effective supplemental method to pre-screen genes involved in abiotic stress tolerance.