Scientists reveal how petunias fight off viral infections
image: A proposed model for the role of PhWRKY30 in antiviral defense response. The infection with TRV or TMV induces the transcription of PhWRKY30. PhWRKY30 specifically regulates the downstream gene PhPAL2b by binding to its promoter, resulting in promoted SA biosynthesis. SA contributes to virus resistance by modulating ROS production and RNA silencing pathways. Solid line ending with an arrow or a short perpendicular line indicates a positive or a negative regulation, respectively.
Credit: Horticulture Research
Virus infections severely threaten the ornamental quality and yield of petunia, but the genetic and biochemical mechanisms underlying antiviral defense in this species have remained unclear. This study identifies PhWRKY30, a transcription factor that dramatically enhances petunia’s resistance to multiple plant viruses. The gene works by increasing the production of salicylic acid (SA), a major immune hormone in plants, and by activating downstream genes involved in antiviral defense. When PhWRKY30 expression is reduced, plants become more vulnerable to viral invasion, whereas overexpression leads to stronger resistance and milder disease symptoms. These findings highlight PhWRKY30 as a promising genetic target for breeding virus-resistant ornamental plants.
Petunia is one of the most commercially important ornamental flowers worldwide, but it is highly susceptible to infection by a wide range of plant viruses, including Tobacco rattle virus (TRV) and Tobacco mosaic virus (TMV). These infections often result in chlorosis, mottling, stunted growth, and severe yield and quality loss. Although salicylic acid (SA) is known to activate plant immune defenses, the key molecular regulators that connect SA biosynthesis with antiviral response in petunia have remained poorly understood. Based on these challenges, it is necessary to conduct in-depth research on the specific genes that mediate SA-associated antiviral defense mechanisms.
Researchers from Northwest A&F University and collaborators reported new findings (DOI: 10.1093/hr/uhaf013) on May 1, 2025, in the journal Horticulture Research, uncovering how the transcription factor PhWRKY30 regulates petunia's defense against viral infection. The team demonstrated that PhWRKY30 activates SA biosynthesis and enhances antiviral immunity against both TRV and TMV. The discovery provides molecular evidence for how SA-driven signaling contributes to petunia’s systemic resistance responses.
The study demonstrated that PhWRKY30 expression is strongly induced upon virus infection and SA treatment. Plants in which PhWRKY30 was silenced showed significantly increased virus accumulation, severe leaf chlorosis, and reduced chlorophyll content. In contrast, overexpression of PhWRKY30 led to enhanced viral resistance and normal plant growth, indicating its role as a positive regulator of antiviral defense. Through biochemical analysis, the team found that PhWRKY30 increases the synthesis of SA, a central immune hormone. Specifically, PhWRKY30 directly binds to and activates the promoter of PhPAL2b, a key gene involved in SA biosynthesis. Loss and gain of PhPAL2b function further confirmed that it is required for SA accumulation and antiviral defense. The results also revealed how PhWRKY30 enhances two critical defense mechanisms: reactive oxygen species (ROS) signaling and RNA silencing pathways. Genes responsible for ROS production and antiviral RNA degradation were upregulated when PhWRKY30 or PhPAL2b were overexpressed, supporting a coordinated immune response against viral invasion.
The authors emphasized the significance of linking transcription factor activity with hormone-mediated defense. They noted that PhWRKY30 acts as a molecular switch that boosts salicylic-acid-dependent immunity and broad-spectrum antiviral resistance in petunia. By identifying the direct regulatory relationship between PhWRKY30 and PhPAL2b, the study provides a mechanistic framework for understanding how transcription factors orchestrate hormone biosynthesis to enhance plant immunity.
This research offers important implications for molecular breeding of virus-resistant ornamental crops. Because PhWRKY30 activates a core immune signaling pathway, its use as a breeding target could improve antiviral defense without relying on chemical treatments or intensive disease management. The findings may extend beyond petunia, as WRKY transcription factors are conserved across plant species, suggesting potential applications in resistance breeding for vegetables, fruits, and other ornamentals. Future work may explore how PhWRKY30 interacts with additional hormone signaling networks and environmental stress responses.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf013
Funding information
This work was funded by National Natural Science Foundation of China (Grant nos. 32271953 and 31801895), Key Research and Development Plan Project in Shaanxi Province (grant no. 2023-YBNY-081), Basic Scientific Research Project in Northwest A&F University (grant nos Z1090323002 and Z1090322159).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.