Panax notoginseng WRKY Transcription Factor 9 Is a Positive Regulator in Responding to Root Rot Pathogen Fusarium solani

Abstract

Panax notoginseng (Burk) F.H. Chen is a rare and valuable Chinese herb, but root rot mainly caused by Fusarium solani severely affects the yield and quality of P. notoginseng herbal materials. In this study, we isolated 30 P. notoginseng WRKY transcription factors (TFs), which were divided into three groups (I, II, and III) on the basis of a phylogenetic analysis. The expression levels of 10 WRKY genes, including PnWRKY9, in P. notoginseng roots increased in response to a methyl jasmonate (MeJA) treatment and the following F. solani infection. Additionally, PnWRKY9 was functionally characterized. The PnWRKY9 protein was localized to the nucleus. The overexpression of PnWRKY9 in tobacco (Nicotiana tabacum) considerably increased the resistance to F. solani, whereas an RNAi-mediated decrease in the PnWRKY9 expression level in P. notoginseng leaves increased the susceptibility to F. solani. The RNA sequencing and hormone content analyses of PnWRKY9-overexpression tobacco revealed that PnWRKY9 and the jasmonic acid (JA) signaling pathway synergistically enhance disease resistance. The PnWRKY9 recombinant protein was observed to bind specifically to the W-box sequence in the promoter of a JA-responsive and F. solani resistance-related defensin gene (PnDEFL1). A yeast one-hybrid assay indicated that PnWRKY9 can activate the transcription of PnDEFL1. Furthermore, a co-expression assay in tobacco using β-glucuronidase (GUS) as a reporter further verified that PnWRKY9 positively regulates PnDEFL1 expression. Overall, in this study, we identified P. notoginseng WRKY TFs and demonstrated that PnWRKY9 positively affects plant defenses against the root rot pathogen. The data presented herein provide researchers with fundamental information regarding the regulatory mechanism mediating the coordinated activities of WRKY TFs and the JA signaling pathway in P. notoginseng responses to the root rot pathogen.

Plant–pathogen interaction with root rot of Panax notoginseng as a model: Insight into pathogen pathogenesis, plant defence response and biological control

“…WRKY TFs, a class of sequence-specific DNA-binding proteins found mainly in plants, play an important role in biotic stress (Jiang et al, 2017). (Zheng et al, 2022). In addition to WRKY TFs, MYB, AP2/ERF and NAC TFs are involved in P. notoginseng resistance against pathogens.…”

Molecular regulation of the key specialized metabolism pathways in medicinal plants

“…Overexpression of PnWRKY9 increased the tolerance to F. solani in tobacco, while its suppression using RNAi in P. notoginseng leaves increased susceptibility to F. solani . Biochemical experiments proved that PnWRKY9 directly trans‐activated PnDEFL1 , an F. solani resistance‐related gene (Zheng et al, 2022). Likewise, P. notoginseng leaves with PnWRKY15 suppression mediated by RNAi were more sensitive to F. solani accompanying with decease of an osmotin‐like protein PnOLP1 , while PnWRKY15‐ overexpressed tobacco evidently were more resistant to F. solani (Su et al, 2023).…”

Advances in the Research on Plant WRKY Transcription Factors Responsive to External Stresses

“…The overexpression of PnWRKY9 in transgenic tobacco plants results in a significant increase in the resistance to F. solani , while the RNAi-mediated decrease in PnWRKY9 expression increases the susceptibility of P. notoginseng leaves to F. solani . Furthermore, PnWRKY9 and the JA signaling pathway synergistically affect the disease resistance of transgenic tobacco [ 32 ]. The overexpression of the rice ( Oryza sativa ) OsWRKY45 transcription factor gene results in increased resistance to Magnaporthe oryzae [ 33 ].…”

“…They may have roles upstream and downstream of hormones; contribute to the antagonism among the SA, JA, and ET pathways; and control development-related processes through auxin, cytokinin, and brassinosteroids. The SA-mediated signaling pathway is generally associated with the resistance to biotrophic and semi-biotrophic pathogens, whereas JA/ET signaling pathways are associated with the resistance to necrotrophic pathogens [ 32 , 33 , 34 ]. For example, WRKY70 activates the expression of SA-responsive genes but has the opposite effect on JA-responsive genes.…”

“…The PnWRKY9 recombinant protein overexpressed in tobacco ( Nicotiana tabacum ) was observed to bind specifically to the W-box sequence in the promoter of a JA-responsive and fungal-resistance-related defensin gene ( PnDEFL1 ) in eggplant. According to yeast one-hybrid assays, PnWRKY9 can activate PnDEFL1 transcription; a tobacco co-expression experiment involving β-glucosidase as a reporter verified these findings [ 32 ].…”