Production of salt stress tolerant rice by overexpression of the catalase gene, katE, derived from Escherichia coli

Saline stress is one of the major factors limiting crop production in the world. Production of salt tolerant crops is, there- fore, a significant subject in agribiotechnology. We transformed a Japonica rice ( Oryza sativa cv. Nipponbare) and Indica rices (O. sativa cvs. Kasalath and BR5) with a gene encoding catalase, katE, derived from Escherichia coli which decomposes H2O2, one of reactive oxygen species produced by saline stress, and acts as a quencher of damage by H 2 O 2 . Rice plants were transformed using Agrobacterium tumefaciens EHA101 carrying pIG121/Hm/katE. The presence of katE gene in transgenic plants was confirmed by PCR, Southern blot and the expression of katE gene was detected by RT-PCR. Catalase activities of katE transgenic T1 plants are about 1.5 to 2.5 fold higher level than those of non transgenic plants. Transgenic plants (T 0 , T 1 ) of Nipponbare could grow even in 250mM NaCl solution for 14 days and seeds could be obtained when T1 transgenic plants were cultured throughout in 100mM NaCl solution. The transgenic plants of Kasalath and BR5 could grow in 100mM NaCl solution. Non-transformed plants of all cultivars did not grow in 50mM and higher concentrations of NaCl. Production of marker-free transgenic plants is required to get public acceptance. We used MAT Vector to produce marker-free salt tolerant Nipponbare. In MAT Vector System, selection markers are removed by recombinase and only katE remains. We succeeded to produce marker-free transgenic plants which could grow in 200mM NaCl solution. These findings reported here indicate the feasibility of producing salt tolerant transgenic plants to expand available lands for cultivation of crops on earth.