H2Bub1 Regulates RbohD-Dependent Hydrogen Peroxide Signal Pathway in the Defense Responses to Verticillium dahliae Toxins

Histone H2B monoubiquitination (H2Bub1) plays critical roles in regulating growth and development as well as stress responses in Arabidopsis ( Arabidopsis thaliana ). In this study, we used wild-type and HUB1 and HUB2 loss-of-function Arabidopsis plants to elucidate the mechanisms involved in the regulation of the plant's defense responses to Verticillium dahliae toxins (Vd-toxins). We demonstrated that HUB-mediated H2Bub1 regulates the expression of the NADPH oxidase RbohD by enhancing the enrichment of histone H3 trimethylated on Lys-4 in response to Vd-toxins. RbohD -dependent hydrogen peroxide (H 2 O 2 ) signaling is a critical modulator in the defense response against Vd-toxins. Moreover, H2Bub1 also affects posttranscriptional mitogen-activated protein kinase (or MPK) signaling. H2Bub1 was required for the activation of MPK3 and MPK6. MPK3 and MPK6 are involved in regulating RbohD -mediated H 2 O 2 production. MPK3 and MPK6 are associated with protein tyrosine phosphatases (PTPs), such as Tyr-specific phosphatase1 and mitogen-activated protein kinases phosphatase1, which negatively regulated H 2 O 2 production. In addition, H2Bub1 is involved in regulating the expression of WRKY33 WRKY33 directly binds to RbohD promoter and functions as a transcription factor to regulate the expression of RbohD Collectively, our results indicate that H2Bub1 regulates the NADPH oxidase RbohD -dependent H 2 O 2 production and that the PTP-MPK3/6-WRKY pathway plays an important role in the regulation of RbohD -dependent H 2 O 2 signaling in defense responses to Vd-toxins in Arabidopsis.