ABSTRACT
Histone H2B monoubiquitination (H2Bub) is being recognized as a regulatory mechanism that controls a range of cellular processes in plants, but the molecular mechanisms of H2Bub that are involved in responses to biotic stress are largely unknown. In this study, we used wild-type and H2Bub loss-of-function mutations of Arabidopsis (Arabidopsis thaliana) to elucidate which of its mechanisms are involved in the regulation of the plant's defense response to Verticillium dahliae (Vd) toxins. We demonstrate that the depolymerization of the cortical microtubules (MTs) was different in the wild type and the mutants in the response to Vd toxins. The loss-of-function alleles of HISTONE MONOUBIQUITINATION1 and HISTONE MONOUBIQUITINATION2 mutations present a weaker depolymerization of the MTs, and protein tyrosine phosphorylation plays a critical role in the regulation of the dynamics of MTs. Moreover, H2Bub is a positive regulator of the gene expression of protein tyrosine phosphatases. These findings provide direct evidence for H2Bub as an important modification with regulatory roles in the defense against Vd toxins and demonstrate that H2Bub is involved in modulating the dynamics of MTs, likely through the protein tyrosine phosphatase-mediated signaling pathway.
Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/immunology , Arabidopsis/microbiology , Microtubules/metabolism , Mycotoxins/toxicity , Ubiquitin-Protein Ligases/metabolism , Ubiquitination/drug effects , Verticillium/metabolism , Arabidopsis/drug effects , Arabidopsis/genetics , Arsenicals/pharmacology , Gene Expression Regulation, Plant/drug effects , Genistein/pharmacology , Histones/metabolism , Microtubules/drug effects , Phosphorylation/drug effects , Phosphotyrosine/metabolismABSTRACT
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.
Subject(s)
Arabidopsis/drug effects , Cytoskeleton/drug effects , Hydrogen Peroxide/metabolism , Mycotoxins/pharmacology , Nitric Oxide/metabolism , Plant Immunity/physiology , Verticillium/metabolism , Arabidopsis/metabolism , Arabidopsis/microbiology , Cytoskeleton/metabolism , Microtubules/drug effects , Microtubules/metabolism , Plant Diseases/microbiology , Signal TransductionABSTRACT
The molecular mechanisms of signal transduction of plants in response to infection by Verticillium dahliae (VD) are not well understood. We previously showed that NO may act as an upstream signalling molecule to trigger the depolymerization of cortical microtubules in Arabidopsis. In the present study, we used the wild-type, and atrbohD and atrbohF mutants of Arabidopsis to explore the mechanisms of action of H(2)O(2) signals and the dynamic microtubule cytoskeleton in defence responses. We demonstrated that H(2)O(2) may also act as an upstream signalling molecule to regulate cortical microtubule depolymerization. The depolymerization of the cortical microtubules played a functional role in the signalling pathway to mediate the expression of defence genes. The results indicate that H(2)O(2) modulates the dynamic microtubule cytoskeleton to trigger the expression of defence genes against V. dahliae toxins (VD-toxins) in Arabidopsis.
Subject(s)
Arabidopsis/physiology , Cytoskeleton/drug effects , Gene Expression Regulation, Plant/drug effects , Hydrogen Peroxide/pharmacology , Mycotoxins/pharmacology , Verticillium/chemistry , Arabidopsis/drug effects , Arabidopsis/genetics , Arabidopsis/ultrastructure , Arabidopsis Proteins/genetics , Cytoskeleton/metabolism , Hydrogen Peroxide/metabolism , Microtubules/drug effects , Microtubules/metabolism , Mycotoxins/isolation & purification , Plant Diseases/microbiology , Plant Immunity , Plant Leaves/genetics , Plant Leaves/physiology , Plant Leaves/ultrastructure , Plants, Genetically Modified/genetics , Plants, Genetically Modified/physiology , Plants, Genetically Modified/ultrastructure , RNA, Plant/genetics , Seedlings/genetics , Seedlings/physiology , Seedlings/ultrastructure , Sequence Deletion , Signal Transduction/drug effectsABSTRACT
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.
