VQ motif-containing proteins (VQ proteins)have been shown to act in partnership with WRKY transcription factors to modulate various physiological processes in Arabidopsis. Nevertheless, the exact interactions between WRKY transcription factors and VQ proteins in specific physiological conditions remain largely unknown.
Prof. YU Diqiu and his team of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to investigate the relationships between WRKY and VQ. They aimed to understand the biological roles of VQ proteins.
To investigate the mechanisms of WRKY34-mediated processes, they used a yeast two-hybrid assay to identify its potential interacting partners. They found that the GST-fused WRKY34 or WRKY2 could retain VQ20-His, whereas GST alone could not.
To further verify the interactions of WRKY34 and WRKY2 with VQ20 in vivo, the researchers examined their interactions in plant cells by bimolecular fluorescence complementation (BiFC) assay. They found that WRKY34 and WRKY2 interact with VQ20 in the nuclei of plant cells.
They further found that VQ20 is localized in the nucleus and specifically expressed in pollen. The VQ20 gene expressed strongly in male gametophytic tissues but barely in seedlings, leaves, petioles, stems, and roots. Mutations of WRKY2, WRKY34 and VQ20 simultaneously lead to male fertility defects. The wrky2-1 wrky34-1 vq20-1 (w2-1 w34-1 vq20-1) triple mutant displayed defects in pollen development, germination, and tube growth.VQ20 interferes with the transcriptional functions of its interacting WRKY partners.
Moreover, the VQ motif of VQ20 is important for pollen development, as a mutant form of VQ20 in which LVQK residues in the VQ motif were replaced by EDLE didn’t rescue the phenotype of the w2-1 w34-1 vq20-1.
The results demonstrate that VQ20 assists WRKY2 and WKRY34 in plant male gametogenesis.