Investigation of the Fusarium virguliforme Transcriptomes Induced during Infection of Soybean Roots Suggests that Enzymes with Hydrolytic Activities Could Play a Major Role in Root Necrosis

Abstract

Sudden death syndrome (SDS) is caused by the fungal pathogen, Fusarium virguliforme, and is a major threat to soybean production in North America. There are two major components of this disease: (i) root necrosis and (ii) foliar SDS. Root symptoms consist of root necrosis with vascular discoloration. Foliar SDS is characterized by interveinal chlorosis and leaf necrosis, and in severe cases by flower and pod abscission. A major toxin involved in initiating foliar SDS has been identified. Nothing is known about how root necrosis develops. In order to unravel the mechanisms used by the pathogen to cause root necrosis, the transcriptome of the pathogen in infected soybean root tissues of a susceptible cultivar, ‘Essex’, was investigated. The transcriptomes of the germinating conidia and mycelia were also examined. Of the 14,845 predicted F. virguliforme genes, we observed that 12,017 (81%) were expressed in germinating conidia and 12,208 (82%) in mycelia and 10,626 (72%) in infected soybean roots. Of the 10,626 genes induced in infected roots, 224 were transcribed only following infection. Expression of several infection-induced genes encoding enzymes with oxidation-reduction properties suggests that degradation of antimicrobial compounds such as the phytoalexin, glyceollin, could be important in early stages of the root tissue infection. Enzymes with hydrolytic and catalytic activities could play an important role in establishing the necrotrophic phase. The expression of a large number of genes encoding enzymes with catalytic and hydrolytic activities during the late infection stages suggests that cell wall degradation could be involved in root necrosis and the establishment of the necrotrophic phase in this pathogen.

Fusarium virguliforme Transcriptional Plasticity Is Revealed by Host Colonization of Maize versus Soybean

“…By the time F. virguliforme had penetrated maize roots (;7 DAI), infection on soybean had already begun to transition from a biotrophic lifestyle to a necrotrophic infection. Upregulation of small protein secretion and fungal-derived toxin production demonstrates host cell modification by F. virguliforme in soybean roots, key events associated with, and required for, nutrient access (Sahu et al, 2017). Throughout the remainder of the time course of infection, we observed a general increase in the gene expression associated with cell death and pathogenicity in F. virguliformeinfected soybean.…”

“…P6685). The F. virguliforme Mont-1 isolate has been extensively used as a model for the advancement of our understanding of soybean (Glycine max) SDS, including serving as a model for genomics and transcriptomics (Srivastava et al, 2014;Ngaki et al, 2016;Sahu et al, 2017) for the analysis of pathogen effector biology (Chang et al, 2016a;Chang et al, 2016b). DNA was extracted using a modified cetyl trimethylammonium bromide procedure, with 1% polyvinylpyrrolidone (Lade et al, 2014).…”

Transcriptome analysis of mycorrhizal and nonmycorrhizal soybean plantlets upon infection with Fusarium virguliforme, one causal agent of sudden death syndrome

“…phenylpropanoid pathway, signal transduction, transcription factors and programmed cell death) in response to SDS (Gallou et al, 2012). A number of genes encoding enzymes involved in production of antimicrobial compounds and in cell wall degradation have also been identified as putative virulence factors of F. virguliforme (Sahu et al, 2017). These studies have increased understanding of the virulence mechanisms of F. virguliforme and the molecular mechanisms deployed by the soybean plant to combat the pathogen.…”

Transcriptome analysis of mycorrhizal and non-mycorrhizal soybean plantlets upon infection withFusarium virguliforme, one causal agent of sudden death syndrome

“…Using the same system, Marquez et al (2018), investigated transcriptional changes in mycorrhizal and non-mycorrhizal soybean plants upon infection with the fungal pathogen Macrophomina phaseolina revealing the complex underlying mechanisms involved in AMF-mediated biocontrol. Transcriptional changes during interaction between soybean plants and F. virguliforme have already been analysed and contributed to increasing our understanding of the virulence mechanisms of F. virguliforme to produce SDS (Chang et al , 2016; Sahu et al , 2017) and the molecular response of the plant to combat the pathogen (Radwan et al , 2011; Ngaki et al , 2016). Likewise, several studies have focused on the transcriptome profiles of AMF-colonized plants with the aim of analysing wide-scale gene reprogramming during the establishment and development of arbuscular mycorrhizal symbioses (Liu et al , 2007; Gallou et al , 2012) or during interaction of AMF-colonized plants with below-(e.g.…”

“…phenylpropanoid pathway, signal transduction, transcription factors, and programmed cell death) in response to SDS (Iqbal et al , 2005; Yuan et al , 2008; Radwan et al , 2011). A number of genes encoding enzymes involved in antimicrobial compounds and cell wall degradation have also been identified as putative virulence factors of F. virguliforme (Sahu et al , 2017). These studies contributed to expand our understanding of the virulence mechanisms of F. virguliforme and the molecular mechanisms deployed by the soybean plant to combat the pathogen.…”