Nicotiana benthamiana as a model plant host for Fusarium verticillioides to investigate RNA interference, cross-kingdom RNA exchange, and competitive endogenous RNA (ceRNA) network.

Abstract

Fusarium verticillioides is among the most devastating fungal pathogen of cereals. Therefore, it is crucial to employ effective and long-term strategies for managing F. verticillioides for sustainable agriculture. RNA interference (RNAi) being a natural defense mechanism of plants via regulation of gene expression, has emerged as a promising tool for eradicating pathogens. RNAi also operates between the host and pathogen through RNA exchange. RNAi interacts with competitive endogenous RNAs (ceRNAs) including long non-coding RNA (lncRNA), microRNA (miRNA), and mRNA. Due to the lack of an elaborate model to investigate all these mechanisms, this study aimed to establish a Nicotiana benthamiana (Nb)-F. verticillioides (Fv) phyto-pathosystem as an experimental model. Nb seedlings were inoculated with Fv, and the pathogenicity was monitored morphologically, microscopically, biochemically, and transcriptionally. To observe the role of RNAi and RNA-exchange in pathogenicity, Nb-miR172 and Nb-miR399 targeting Nb-lncRNA-IPS (Induced by Phosphate Starvation1) and Nb-AP2 (Apetala2) and Nb-PHO2 (phosphate over-accumulator) ceRNA network and Fv-V-ATPase (Vesicle-fusing ATPase) targeted by Nb-miR172 were investigated. As a result, epidermal cell density, leaf area, petiole length, and chlorophyll content were reduced while the density of stomata and trichome and phenolic content and the activity of ascorbate peroxidase (APX) and glutathione reductase (GR) were increased in response to Fv infection in Nb. The expression of AP2 and PHO2 were downregulated against Fv but no significant changes were detected in IPS, miR172, and miR399 expression. These findings suggested the Fv-Nb phyto-pathosystem as a useful experimental model to reveal genetic regulations.