Wheat Elongator subunit 4 is required for epigenetic regulation of host immune response to Rhizoctonia cerealis

Wheat (Triticum aestivum) is necessary for global food security. The necrotrophic fungus Rhizoctonia cerealis is the causal agent of sharp eyespot, a devastating disease of wheat. Although the Elongator complex, composed of six subunits, has been implicated in growth, development, and innate immunity in Arabidopsis, little is known about its functions in wheat or the involvement of Elongator subunit 4 in histone acetylation. In this study, we identified the Elongator subunit 4-encoding gene TaELP4 in wheat resistance response to R. cerealis, and verified that TaELP4 increased histone acetylation in regions of defense-associated genes and regulated immune response to R. cerealis. TaELP4 was more highly expressed in resistant than in susceptible wheat cultivars and was induced in resistant wheat after infection by R. cerealis. Silencing of TaELP4 in wheat not only impaired resistance to R. cerealis, but also repressed both histone acetylation levels and the expression of a subset of defense-associated genes, including TaAGC1, TaCPK7-D, TaPAL5, Defensin, and Chitinase2. Ectopic expression of TaELP4 in Arabidopsis increased histone acetylation levels in coding and promoter regions of defense genes and increased their transcription, leading to increased resistance to infection by the pathogen Botrytis cinerea. These results suggest that TaELP4 positively regulates innate immune responses of wheat and Arabidopsis to R. cerealis and B. cinerea by increasing histone acetylation levels of defense-associated genes and increasing their transcription. This study has shed light on the involvement of TaELP4 in histone acetylation and resistance response against R. cerealis. TaELP4 may potentially be used to improve wheat resistance against sharp eyespot.