Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2008
Publication Date: 8/17/2008
Citation: Friesen, T.L., Liu, Z.H., Zhang, Z., Faris, J.D., Solomon, P.S., Tan, K.C., Ferguson, H.M., Oliver, R.P. 2008. Identification, cloning, and characterization of sntox3 using heterologous expression transformation, and site directed gene disruption. Meeting Abstract. 7th Mycosphaerella Stagonospora Symposium, Ascona, Switzerland, August 18-22, 2008
Technical Abstract: Stagonospora nodorum blotch (SNB) of wheat caused by Stagonospora nodorum (teleomorph Phaeosphaeria nodorum) has been shown to be at least partially controlled by multiple host selective toxins (HSTs) that interact directly or indirectly with dominant host sensitivity gene products in wheat leading to disease development. Presently four HST-host gene interactions and their significance in disease development have been described. These include SnToxA-Tsn1, SnTox1-Snn1, SnTox2-Snn2, and SnTox3-Snn3. Here we describe the characterization of SnTox3, the HST shown to be involved in the SnTox3-Snn3 interaction as well as the fungal gene responsible for its production. SnTox3 is a proteinaceous HST shown to account for as much as 17% of the disease in a host population segregating for Snn3, the host gene conferring sensitivity to SnTox3. The gene responsible for production of SnTox3 is 693 nucleotides in length and no introns with the first 60 bp accounting for a predicted signal sequence. Preliminary results show that SnTox3 is present in the majority of North American isolates but may be less prevalent in other areas of the world. The SnTox3 protein has a predicted size of 25.8 kDa and based on the predicted 20 amino acid signal sequence the mature protein would have a predicted size of approximately 23.7 kDa. The protein has been expressed in Pichia pastoris and an active protein has been produced which causes necrosis on wheat lines containing Snn3 but not on lines deficient in Snn3 (e.g. containing snn3). An avirulent S. nodorum isolate has been transformed with SnTox3 making the transformed strains virulent on host lines containing Snn3, as well as producing culture filtrates that induce necrosis on these same lines but not on lines harboring snn3. Site directed gene disruption mutants have also been generated and preliminary evidence has shown that these mutants are deficient in producing SnTox3 as well as being deficient in causing disease associated with Snn3 sensitivity. This work indicates that the addition of SnTox3 is sufficient to cause disease on wheat lines containing Snn3 and is an important virulence factor in the SNB system.