A role of hexokinases in plant resistance to oxidative stress and pathogen infection

Previously, we reported that mitochondria-associated hexokinases are active in controlling programmed cell death in plants (Plant Cell 18, 2341-2355). Here, we investigated their role under abiotic- and biotic-stress conditions. Expression ofNbHxk1, aNicotiana benthamiana hexokinase gene, was stimulated by treatment with salicylic acid or methyl viologen (MV), and was also up-regulated by pathogen infection. In response to MV-induced oxidative stress, NbHxk1-silenced plants exhibited increased susceptibility, while the HXK1— and HXK2-overexpressingArabidopsis plants had enhanced tolerance. Moreover, those overexpressing plants showed greater resistance to the necrotrophic fungal pathogenAlternaria brassicicola. HXK-over-expression also mildly protected plants against the bacterial pathogenPseudomonas syringae pv.tomato DC3000, a response that was accompanied by increased H₂O₂ production and elevatedPR1 gene expression. These results demonstrate that higher levels of hexokinase confer improved resistance to MV-induced oxidative stress and pathogen infection.