In the previous studies, Prof. Yu Diqiu and his team of Xishuangbanna Tropical Botanical Garden (XTBG) demonstrated the importance of the transcription factor WRKY8 in basal resistance against pathogen infections. However, the regulatory mechanisms of the involvement of WRKY factors in stress responses are still not fully understood.
To further clarify the potential functions of WRKY8, they further investigated its expression patterns. The WRKY8 gene was predominantly expressed in roots and was highly up-regulated by NaCl treatment. However, expression of WRKY8 was not up-regulated by osmotic stress, dehydration, cold, or heat. The results suggested that the WRKY8 gene mainly responds to high-salinity during certain abiotic stress treatments.
Phenotype analyses showed that the wrky8 mutants germinated later than wild type in the presence of salt, particularly on high-salt medium. Both mutants were also hypersensitive to salt stress during post-germination development and vegetative growth stages. Thus, the NaCl-responsive WRKY8 factor functioned as a positive modulator of salt stress tolerance.
Further investigation showed that WRKY8 interacted in the nucleus with VQ9, a VQ motif-containing protein. Experimental results suggested that VQ9 decreased the DNA binding activity of WRKY8, thereby negatively regulating salinity stress responses.
The functional antagonism between WRKY8 and VQ9 may be a specific mechanism to maintain an appropriate balance of WRKY8-mediated signaling pathways to establish salt stress.
The study entitled “Arabidopsis transcription factor WRKY8 functions antagonistically with its interacting partner VQ9 to modulate salinity stress tolerance” has been accepted by The Plant Journal, DOI: 10.1111/tpj.12159