Abstract
Arabidopsis VQ motif-containing proteins have recently been demonstrated to interact with several WRKY transcription factors; however, their specific biological functions and the molecular mechanisms underlying their involvement in defense responses remain largely unclear. Here, we showed that two VQ genes, VQ12 and VQ29, were highly responsive to the necrotrophic fungal pathogen Botrytis cinerea. To characterize their roles in plant defense, we generated amiR-vq12 transgenic plants by using an artificial miRNA approach to suppress the expression of VQ12, and isolated a loss-of-function mutant of VQ29. Phenotypic analysis showed that decreasing the expression of VQ12 and VQ29 simultaneously rendered the amiR-vq12 vq29 double mutant plants resistant against B. cinerea. Consistently, the B. cinerea-induced expression of defense-related PLANT DEFENSIN1.2 (PDF1.2) was increased in amiR-vq12 vq29. In contrast, constitutively-expressing VQ12 or VQ29 confered transgenic plants susceptible to B. cinerea. Further investigation revealed that VQ12 and VQ29 physically interacted with themselves and each other to form homodimers and heterodimer. Moreover, expression analysis of VQ12 and VQ29 in defense-signaling mutants suggested that they were partially involved in jasmonate (JA)-signaling pathway. Taken together, our study indicates that VQ12 and VQ29 negatively regulate plant basal resistance against B. cinerea.
Highlights
In nature, plants are constantly threatened by various microbial pathogens
VQ29 (AT4G37710) encode two VQ motif-containing proteins with 114 and 123 amino acids, respectively[27]. To characterize their biological functions, we generated homozygous T3 lines of promoterVQ12:GUS and promoterVQ29:GUS transgenic plants. β -Glucuronidase (GUS) staining showed that VQ12 was mainly expressed in the root, leaf, hypocotyl, and silique base (Fig. 1A), which is similar to the basic expression pattern of VQ2937
The expression level of VQ29 was upregulated by methyl jasmonate (MeJA) treatment (Fig. 1C)
Summary
Plants are constantly threatened by various microbial pathogens. To protect themselves against pathogen infection, resisant plants have evolved an effective innate immune system. Accumulating evidence has indicated that WRKY proteins act as both positive and negative regulators in modulating plant defense responses[17,18,19]. WRKY33 positively regulates plant resistance to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola[20]. Several WRKY family members negatively modulate plant pathogen resistance. The evolutionarily related WRKY18, WRKY40 and WRKY60 function as negative regulators of plant resistance against P. syringae[22]. Increasing studies have demonstrated that VQ proteins play crucial roles in modulating plant defense responses. The structurally related VQ16 and VQ23, previously identified as sigma factor binding proteins, redundantly regulate plant defense response against B. cinerea[26,30,33]. Our results provide evidence that VQ12 and VQ29 negatively regulate plant basal resistance against B. cinerea
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