Cheng Y, Zhou Y, Yang Y, Chi YJ, Zhou J, Chen JY, Wang F, Fan B, Shi K, Zhou YH, Yu JQ, Chen Z

WRKY transcription factors are encoded by a large gene superfamily with a broad range of roles in plants. Recently, several groups have reported that proteins containing a short VQ (FxxxVQxLTG) motif interact with WRKY proteins. We have recently discovered that two VQ proteins from Arabidopsis thaliana, SIB1 and SIB2, act ...

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as co-activators of WRKY33 in plant defense by specifically recognizing the C-terminal WRKY domain and stimulating the DNA-binding activity of WRKY33. In the present study, we have analyzed the entire family of 34 structurally divergent VQ proteins from Arabidopsis. Yeast two-hybrid assays showed that Arabidopsis VQ proteins interacted specifically with the C-terminal WRKY domains of Group I and the sole WRKY domains of Group IIc WRKY proteins. Using site-directed mutagenesis, we identified structural features of these two closely related groups of WRKY domains that are critical for interaction with VQ proteins. Quantitative RT-PCR revealed that expression of a majority ofArabidopsisVQ genes was responsive to pathogen infection and salicylic acid treatment. Functional analysis using both knockout mutants and overexpression lines revealed strong phenotypes in growth, development and susceptibility to pathogen infection. Altered phenotypes were substantially enhanced through co-overexpression of genes encoding interacting VQ and WRKY proteins. These findings indicate that VQ proteins play important role in plant growth, development and response to environmental conditions, most likely by acting as co-factors ofGroup I and IIc WRKY transcription factors.

Date: Apr. 24, 2012

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