Abstract
Bread wheat (Triticum aestivum L.) is an agronomically significant cereal cultivated worldwide. Wheat breeding is limited by numerous abiotic and biotic stresses. One of the most deleterious factors is biotic stress provoked by the Fusarium culmorum fungus. This pathogen is a causative agent of Fusarium root rot and Fusarium head blight. Beneficial fungi Trichoderma atroviride and T. cremeum are strong antagonists of mycotoxigenic Fusarium spp. These fungi promote plant growth and enhance their tolerance of negative environmental conditions. The aim of the study was to determine and compare the spatial (in above- and underground organs) and temporal (early: 6 and 22 hpi; and late: 5 and 7 dpi reactions) expression profiles of three mature miRNAs (miR398, miR167, and miR159) in wheat plants inoculated with two strains of F. culmorum (KF846 and EW49). Moreover, the spatial expression patterns in wheat response between plants inoculated with beneficial T. atroviride (AN35) and T. cremeum (AN392) were assessed. Understanding the sophisticated role of miRNAs in wheat–fungal interactions may initiate a discussion concerning the use of this knowledge to protect wheat plants from the harmful effects of fungal pathogens. With the use of droplet digital PCR (ddPCR), the absolute quantification of the selected miRNAs in the tested material was carried out. The differential accumulation of miR398, miR167, and miR159 in the studied groups was observed. The abundance of all analyzed miRNAs in the roots demonstrated an increase in the early and reduction in late wheat response to F. culmorum inoculation, suggesting the role of these particles in the initial wheat reaction to the studied fungal pathogen. The diverse expression patterns of the studied miRNAs between Trichoderma–inoculated or F. culmorum–inoculated plants and control wheat, as well as between Trichoderma–inoculated and F. culmorum–inoculated plants, were noticed, indicating the need for further analysis.
Highlights
Plants under attack from pathogens are able to manage and mediate the expression cascade of genes that activate and facilitate the host immune response
The results of our research suggest that miR398 is involved in wheat responses to infections with pathogenic F. culmorum strains, as well as inoculation with symbiotic Trichoderma fungi
Our research showed that miR398, miR167, and miR159 participate in the wheat–F. culmorum interaction and demonstrate time, organ, and fungal strain-specific expression patterns
Summary
Plants under attack from pathogens are able to manage and mediate the expression cascade of genes that activate and facilitate the host immune response. MiRNAs are defined as non-coding single-stranded RNAs, 20–24 nt in length, and have a pivotal role in gene expression regulation at the posttranscriptional level [1,2]. During plant–pathogenic fungi interactions, miRNAs participate in two important defense mechanisms: PAMP-triggered immunity (PTI) triggered by pathogen-associated molecular patterns (PAMP) as a preliminary defense, and effector-triggered immunity (ETI) as a secondary defense, thereby regulating plant gene expression [8]. MiRNA molecules can be transmitted across kingdoms and can trigger gene silencing as trans-regulators in interacting, even evolutionary distant, organisms [9,10]. Knowledge regarding miRNAs’ participation, regulation, and function in wheat–fungi interactions is still scarce
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