Submitted to: International Gluten Workshop
Publication Type: Proceedings
Publication Acceptance Date: September 16, 2007
Publication Date: January 1, 2007
Citation: Altenbach, S.B., Kothari, K.M. 2007. Post-anthesis fertilizer influences expression of genes encoding allergenic proteins. In: G. L. Lookhart and P.K.W. Ng, editors. Ninth International Gluten Workshop, Gluten Proteins 2006, September 14-16, 2006, San Francisco, CA. p. 330-334 Interpretive Summary: Among the complex mixture of proteins in wheat flour are certain gluten proteins, the omega gliadins, shown to be responsible for several important food allergies. DNA sequences for omega gliadins found in a US wheat variety were identified in public databases. Based on these sequences, quantitative methods were developed to measure the expression of two omega gliadin genes. These methods were used to evaluate the effects of fertilizer applications during grain development. The study revealed that omega gliadin gene expression was enhanced by fertilizer, resulting in higher levels of omega gliadin proteins in grains that received fertilizer than in those that did not. The data suggest that an agricultural practice used to improve grain protein content may also preferentially increase the levels of certain allergenic proteins in the grain.
Technical Abstract: Omega-gliadins comprise between 5-10% of the wheat flour protein and have been implicated in food allergies. In particular, omega-gliadins encoded by the 1B chromosome have been associated with wheat-dependent exercise-induced anaphalaxis (WDEIA) and urticaria. Because the omega-gliadins consist almost entirely of repetitive sequences, the genes encoding these proteins have proved difficult to clone. Therefore, the complement of omega-gliadin genes expressed in the US spring wheat ‘Butte 86’ was surveyed by examining expressed sequence tags (ESTs) available from the TIGR Wheat Gene Index (http://www.tigr.org/). Based on these sequences, primers specific for two types of omega-gliadin genes were designed and quantitative real time RT-PCR was used to investigate the accumulation of transcripts in developing wheat grains produced with or without post-anthesis fertilizer supplied as NPK 20-20-20. Transcripts for both types of omega-gliadin proteins were detected at 8 days post-anthesis (DPA). The levels of transcript changed little between 8 and 32 DPA in the absence of NPK. When plants were supplied with NPK, transcript levels increased gradually between 8 and 32 DPA so that levels of omega-gliadin transcripts were significantly higher in grains that received NPK than in those that did not. Transcripts for a gamma-gliadin showed a different profile and levels of gamma-gliadin transcripts changed little in response to NPK. The data suggest that the application of nitrogen to improve grain protein content may also lead to increased levels of one type of allergenic protein.