Wheat Chromatin Remodeling Protein TaSWP73 Contributes to Compatible Wheat–Powdery Mildew Interaction

Wheat powdery mildew disease caused by the obligate biotrophic fungal pathogen <i>Blumeria graminis forma specialis tritici</i> (<i>B.g. tritici</i>) seriously threatens global wheat production. Although improved powdery mildew resistance is an aim in wheat breeding, the regulatory mechanism underlying the wheat-<i>B.g. tritici</i> interaction remains poorly understood. In this study, the wheat chromatin remodeling protein TaSWP73 was identified as a negative regulator of post-penetration resistance against <i>B.g. tritici.</i> The transient overexpression of <i>TaSWP73</i> attenuates wheat post-penetration resistance against <i>B.g. tritici</i>, while the silencing of <i>TaSWP73</i> potentiates salicylic acid (SA) biosynthesis and activates post-penetration resistance against <i>B.g. tritici.</i> Importantly, chromatin in the promoter regions of <i>TaSARD1,</i> an activator gene of SA biosynthesis, is marked by high nucleosome occupancy in the <i>TaSWP73</i>-silenced wheat leaves. The silencing of <i>TaSARD1</i> could suppress SA biosynthesis and attenuate post-penetration resistance against <i>B.g. tritici</i> with a lack of <i>TaSWP73.</i> In addition, TaICS1 was characterized as an essential component of wheat SA biosynthetic machinery. Potentiated SA biosynthesis and increased post-penetration resistance against <i>B.g. tritici</i> with a lack of <i>TaSWP73</i> could be suppressed by the silencing of <i>TaICS1</i> expression. These results collectively support the hypothesis that the wheat chromatin remodeling protein TaSWP73 contributes to the compatible wheat-powdery mildew interaction presumably via the suppression of the TaSARD1-TaICS1-SA pathway.