Resistance to Hemi-Biotrophic F. graminearum Infection Is Associated with Coordinated and Ordered Expression of Diverse Defense Signaling Pathways

Abstract

Fusarium species cause serious diseases in cereal staple food crops such as wheat and maize. Currently, the mechanisms underlying resistance to Fusarium-caused diseases are still largely unknown. In the present study, we employed a combined proteomic and transcriptomic approach to investigate wheat genes responding to F. graminearum infection that causes Fusarium head blight (FHB). We found a total of 163 genes and 37 proteins that were induced by infection. These genes and proteins were associated with signaling pathways mediated by salicylic acid (SA), jasmonic acid (JA), ethylene (ET), calcium ions, phosphatidic acid (PA), as well as with reactive oxygen species (ROS) production and scavenging, antimicrobial compound synthesis, detoxification, and cell wall fortification. We compared the time-course expression profiles between FHB-resistant Wangshuibai plants and susceptible Meh0106 mutant plants of a selected set of genes that are critical to the plants' resistance and defense reactions. A biphasic phenomenon was observed during the first 24 h after inoculation (hai) in the resistant plants. The SA and Ca2+ signaling pathways were activated within 6 hai followed by the JA mediated defense signaling activated around 12 hai. ET signaling was activated between these two phases. Genes for PA and ROS synthesis were induced during the SA and JA phases, respectively. The delayed activation of the SA defense pathway in the mutant was associated with its susceptibility. After F. graminearum infection, the endogenous contents of SA and JA in Wangshuibai and the mutant changed in a manner similar to the investigated genes corresponding to the individual pathways. A few genes for resistance-related cell modification and phytoalexin production were also identified. This study provided important clues for designing strategies to curb diseases caused by Fusarium.

Priming of Wheat with the Green Leaf Volatile Z-3-Hexenyl Acetate Enhances Defense against Fusarium graminearum But Boosts Deoxynivalenol Production

“…Because of the hemibiotrophic lifestyle of F. graminearum, it can be expected that SA and JA will play a sequential role in the plant defense against F. graminearum. This biphasic defense response has already been shown by Ding et al (2011), who reported a peak in SA content followed by a peak in JA content. At the gene level, this was confirmed in our study.…”

“…Plant defense against the biotrophic and necrotrophic phases generally has been linked to SA-and JArelated pathways, respectively (Glazebrook, 2005). This was also found in the study by Ding et al (2011). They reported higher endogenous SA concentrations during the first hours of infection, followed by a rise in JA concentrations later on.…”

“…We selected PHENYLALANINE AMMONIA LYASE (PAL) and ISOCHORISMATE SYNTHASE (ICS) as marker genes for the biosynthesis of salicylate (Ding et al, 2011) and LIPOXYGENASE1 (LOX1) and LOX2 as marker genes for the biosynthesis of JA (Feng et al, 2010). Using the leaf sheath bioassay, we infected Figure 1.…”

“…We selected PAL and ICS as marker genes for the salicylate pathway (Ding et al, 2011) and LOX1 and LOX2 for the jasmonate pathway (Feng et al, 2010). Additionally, we selected different plant defense genes encoding pathogenesis-related proteins, which are known to play a role in the defense against infection with F. graminearum, namely, the pathogenesis-related proteins PR1 (Makandar et al, 2012), PR2, b-1,3-glucanase (Gao et al, 2013), PR4, shown to possess antifungal properties against Fusarium spp.…”

Enhanced Secondary- and Hormone Metabolism in Leaves of Arbuscular Mycorrhizal Medicago truncatula

“…The lower concentrations of hormones (100 mM MeJA and 10 mM ABA) were not sufficient in our conditions to significantly alter the expression of the above AM-regulated genes (Supplemental Table S11). The insignificant expression change of MYC2 by the lower concentration of MeJA could be explained by the fact that this is an early JA-induced gene (Ding et al, 2011;An et al, 2016), so that its expression levels may be down again at 24 h after the application of MeJA. Taken together, these data suggest that the treatment of leaves from nonmycorrhized plants with 1 mM MeJA can induce a similar pattern of alterations in JA biosynthesis and signaling pathways as well as flavonoid and terpenoid biosynthesis to that in AM plants, most likely via MYC2-regulated pathways.…”