Numerous studies have demonstrated that WRKY transcription factors function as important components in complex signaling processes during various stress responses, especially in biotic stresses. However, far less information is available about the functions of WRKY proteins in antiviral defense than about their functions in defense against bacterial or fungal pathogens.
Prof. YU Diqiu and his team of Xishuangbanna Tropical Botanical Garden (XTBG) have been engaged in studying the functions of Arabidopsis thaliana WRKY DNA-binding protein 8 (WRKY8) for many years.In previous studies, they found that WRKY8 was involved in regulating plant basal defense responses to both the necrotrophic fungal pathogen B. cinerea and the biotrophic bacterial pathogen P. syringae and also played a role in plant response to salt stress. In a recent study, they reported that WRKY8 also functions as a positive regulator during TMV-cg’s (tobacco mosaic virus)systemic infection.
In the study, they monitored the transcriptional reprogramming induced by TMV-cg defense and explained how it regulated its downstream target genes to respond to TMV-cg infection. They demonstrated that mutation of WRKY8 made plants more susceptible to TMV-cg infection. WRKY8 positively regulated ABI4 expression and negatively modulated ACS6 and ERF104 expression by directly binding to the W-box consensus motifs within their promoters. Thus, WRKY8 participated in plant–TMV-cg interaction by regulating both the ABA- and ET-signaling pathways.
The results suggested that WRKY8 might mediate crosstalk between ET and ABA signaling when plants are infected by TMV-cg. The researchers deduced that ET and ABA have opposite roles in the anti–TMV-cg defense response and may interact antagonistically during plant–virus interaction.
The study was supported by the Science Foundation of the Ministry of Agriculture of the Peoples’ Republic of China Grant 2009ZX08009-066B, Natural
Science Foundation of China Grants 90817003 and 31200915, and the Science Foundation of the Chinese Academy of Sciences 135 program XTBG-F04.
The study entitled “WRKY8 transcription factor functions in the TMV-cg defense response by mediating both abscisic acid and ethylene signaling in Arabidopsis” has been published in Proceedings of the National Academy of Sciences of the United States of America, DOI: 10.1073/pnas.1221347110