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The molecular mechanisms of signal transduction of plants in response to Verticillium dahliae (VD) are not known. Here, we show that Arabidopsis reacts to VD-toxins with a rapid burst of nitric oxide (NO) and cortical microtubule destabilization. VD-toxins treatment triggered a disruption of cortical microtubules network. This disruption can be influenced by NO production. However, cortical microtubule disruptions were not involved in regulating the NO production. The results indicated that NO may act as an upstream signalling molecule to trigger the depolymerization of cortical microtubule. Cortical microtubules may act as a target of NO signal and as a sensor to mediate the activation of PR-1 gene expression. These results suggested that NO production and cortical microtubule dynamics appeared to be parts of the important signalling system and are involved in the defence mechanisms to VD-toxins in Arabidopsis. [ABSTRACT FROM AUTHOR]

Although hydrogen peroxide (H₂O₂) and nitric oxide (NO) can act as an upstream signaling molecule to modulate the dynamic microtubule cytoskeleton during the defense responses to Verticillium dahliae (VD) toxins in Arabidopsis, it is not known the relationship between these two signaling molecules. Here, we show that VD-toxin-induced NO accumulation was dependent on prior H₂O₂ production, NO is downstream of H₂O₂ in the signaling process, and that H₂O₂ acted synergistically with NO to modulate the dynamic microtubule cytoskeleton responses to VD-toxins in Arabidopsis.