Annals of Botany

Gliadin gene control – comfort comes closer for celiac sufferers

There is little doubt that the incidence of diagnosis of celiac (cœliac) disease – mainly caused by allergy to wheat α-gliadins – is increasing. Whether this increase arises, as some suggest, from the way that bread is manufactured on a large scale or whether detection of the condition has improved is not clear. Van Herpen et al. (a joint UK–Netherlands research team; pp. 331–342) cite previous results showing that the allergic reactions exhibited by sufferers are elicited by particular epitopes in the α-gliadins encoded in the D-genome and, to a lesser extent, in the A-genome of wheat. Gliadins encoded by the B-genome are much less allergenic. Further, there is evidence that the timings of deposition during grain development of the α-gliadins encoded by the three genomes are subtly different. With this knowledge comes the possibility that the allergenicity of wheat α-gliadins could be much reduced by altering the proportions of the total α-gliadin content encoded by the three genomes. The authors used a 592-bp fragment of the promoter of an α-gliadin gene in wheat’s B-genome to drive the synthesis of a marker protein, β-glucuronidase (GUS) in transgenic plants. As expected, GUS was deposited in the starchy endosperm and in the subaleurone but, unexpectedly, also in the aleurone itself. Since α-gliadins were not detected in the aleurone this suggests that other controls operate in addition to those based on this promoter fragment, possibly mediated by sequences further upstream. There are also sequence differences between α-gliadin promoters from the A- and B-genomes. Unfortunately the databases do not yet contain sequences from any D-genome α-gliadin promoters. Nevertheless, the differences in temporal patterns of deposition, coupled with the already known differences in promoter sequences raise the possibility of using GM techniques to modify the proportions of the different α-gliadins to the benefit of celiac disease sufferers. The hope is that this can be done without affecting adversely the physico-chemical properties of wheat flour.