Submitted to: National Fusarium Head Blight Forum Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 12/31/2005
Publication Date: 1/1/2006
Citation: Blechl, A.E., Somleva, M.N. Accumulation of transgene-encoded defense-associated enzymes in tissues vulnerable to initial fusarium infection. National Fusarium Head Blight Forum Proceedings. pp. 102 Interpretive Summary:
Technical Abstract: Our goal is to achieve Fusarium Head Blight resistance by employing genetic transformation to introduce new genes into wheat. Of particular interest are anti-Fusarium genes that could provide protection in the early stages of infection, thus improving Type I resistance. To achieve this, we have employed an expression vector carrying the barley Lem1 promoter, which we had previously shown to be active in the outer organs of transgenic wheat florets from anthesis to the soft dough stage of kernel development. Into this vector, we inserted coding regions from three candidate anti-Fusarium genes that have been associated with naturally occurring plant defense mechanisms: Aspergillus glucose oxidase (GO) and barley peroxidases Prx7 and Prx8. GO is an apoplastic enzyme that catalyzes oxidation of '-D-glucose, generating H2O2, a compound with multiple functions in plant defense. Induction of the peroxidases Prx7 and Prx8 has been correlated with the appearance of antifungal compounds and papillae structures, respectively, in barley leaves exposed to powdery mildew. We have analyzed several transformed wheat plants for inheritance and expression of the Lem1::PRX and/or Lem1::GO transgenes. Peroxidase and glucose oxidase enzymes were detected in situ in the outer tissues of the floret, where they accumulated either in the extracellular space (GO and Prx8) or inside the cells (Prx7). In some of the lines, lignin content was increased in the outer floret tissues. The potential for synergistic effects of the transgene-encoded enzymes in improving host resistance to initial fungal infection and pathogen spread will be discussed.