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Induced Expression of Sarcotoxin IA Enhanced Host Resistance Against Both Bacterial and Fungal Pathogens in Transgenic Tobacco

¹National Institute of Agrobiological Resources, 2-1-2 Kannondai, Tsukuba City, Ibaraki 305-8602, Japan; ²Core Research of Science and Technology (CREST), Japan Science and Technology, 2--3 Surugadai, Kannda, Chiyoda-ku, Tokyo 101-0062, Japan; ³Hokuriku National Agricultural Research Station, 1-2-1 Inada, Niigata 943-0154, Japan; ⁴Louisiana State University and LSU Agricultural Center, Baton Rouge 70803-1720, U. S. A.; ⁵Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198, Japan

We demonstrate here that induced expression of sarcotoxin IA, a bactericidal peptide from Sarcophaga peregrina, enhanced the resistance of transgenic tobacco plants to both bacterial and fungal pathogens. The peptide was produced with a modified PR1a promoter, which is further activated by salicylic acid treatment and necrotic lesion formation by pathogen infection. Host resistance to infection of bacteria Erwinia carotovora subsp. carotovora and Pseudomonas syringae pv. tabaci was shown to be dependent on the amounts of sarcotoxin IA expressed. Since we found antifungal activity of the peptide in vitro, transgenic seedlings were also inoculated with fungal pathogens Rhizoctonia solani and Pythium aphanidermatum. Transgenic plants expressing higher levels of sarcotoxin were able to withstand fungal infection and remained healthy even after 4 weeks, while control plants were dead by fungal infection after 2 weeks.