Barley ADH-1 modulates susceptibility to Bgh and is involved in chitin-induced systemic resistance

The plant primary energy metabolism is profoundly reorganized under biotic stress conditions and there is increasing evidence for a role of the fermentative pathway in biotic interactions. Previously we showed via transient gene silencing or overexpression a function of barley alcohol dehydrogenase 1 (HvADH-1) in the interaction of barley with the parasitic fungus Blumeria graminis f.sp. hordei (Bgh). Here we extend our studies on stable transgenic barley events over- or under-expressing HvADH-1 to analyse ADH-1 functions at the level of whole plants. Knock-down (KD) of HvADH-1 by dsRNA interference resulted in reduced and overexpression of HvADH-1 in strongly increased HvADH-1 enzyme activity in leaves of stable transgenic barley plants. The KD of HvADH-1 coincided with a reduced susceptibility to Bgh of both excised leaves and leaves of intact plants. Overexpression (OE) of HvADH-1 results in increased susceptibility to Bgh when excised leaves but not when whole seedlings were inoculated. When first leaves of 10-day-old barley plants were treated with a chitin elicitor, we observed a reduced enzyme activity of ADH-1/-1 homodimers at 48 h after treatment in the second, systemic leaf for empty vector controls and HvADH-1 KD events, but not for the HvADH-1 OE events. Reduced ADH-1 activity in the systemic leaf of empty vector controls and HvADH-1 KD events coincided with chitin-induced resistance to Bgh. Taken together, stable HvADH-1 (KD) or systemic down-regulation of ADH-1/-1 activity by chitin treatment modulated the pathogen response of barley to the biotrophic fungal parasite Bgh and resulted in less successful infections by Bgh.