The impaired virulence of <i>cks1</i> correlates with an enhanced induction of the oxidative burst and can be partially restored by inhibiting NAD(P)H oxidase activity.

Abstract

<p>The relationship between virulence and reactive oxygen species accumulation was evaluated in the <i>cks1-</i>infected leaves. (A) The oxidative burst was detected 48 h after inoculation using DAB stain that turns brown upon reaction with H₂O₂. Brown spots correspond to sites where the wild-type blast fungus penetrated (see inlet), whereas a global browning was visible with infection with <i>cks1</i> mutant. This experiment was repeated two times and gave similar results. (B, C) DPI, an NAD(P)H oxidase inhibitor partially restores the virulence of the <i>cks1</i> mutant. One day after inoculation (once appressorium formation was initiated), plants were treated with DPI (0.5μM diluted in DMSO as previously described [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1005457#ppat.1005457.ref054" target="_blank">54</a>]. The symptoms were observed 6 dpi (B) and the number of lesions per leaf was measured (C). The letters indicate significantly different values according to a generalized linear model and ANOVA analysis (p-value < 0.04), see <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1005457#sec019" target="_blank">Materials and Methods</a>.</p