Functional evaluation of a homologue of plant rapid alkalinisation factor (RALF) peptides in Fusarium graminearum

Abstract

The cereal infecting fungus Fusarium graminearum is predicted to possess a single homologue of plant RALF (rapid alkalinisation factor) peptides. Fusarium mutant strains lacking FgRALF were generated and found to exhibit wildtype virulence on wheat and Arabidopsis floral tissue. Arabidopsis lines constitutively overexpressing FgRALF exhibited no obvious change in susceptibility to F. graminearum leaf infection. In contrast transient virus-mediated over-expression (VOX) of FgRALF in wheat prior to F. graminearum infection, slightly increased the rate of fungal colonisation of floral tissue. Ten putative Feronia (FER) receptors of RALF peptide were identified bioinformatically in hexaploid wheat ( Triticum aestivum ). Transient silencing of two wheat FER homoeologous genes prior to F. graminearum inoculation did not alter the subsequent interaction outcome. Collectively, our VOX results show that the fungal RALF peptide may be a minor contributor in F. graminearum virulence but results from fungal gene deletion experiments indicate potential functional redundancy within the F. graminearum genome. We demonstrate that virus-mediated over-expression is a useful tool to provide novel information about gene/protein function when results from gene deletion/disruption experimentation were uninformative.

Proteomics-Based Data Integration of Wheat Cultivars Facing Fusarium graminearum Strains Revealed a Core-Responsive Pattern Controlling Fusarium Head Blight

“…Two of these proteins encoded by wheat genes homologous to AtFER from Arabidopsis thaliana were identified in this work (i.e., TraesCS1B01G241400.1 and TraesCS4B01G171100.1). While the role of these genes is not yet fully understood in wheat (Wood et al, 2020), it was shown that an A. thaliana defective mutant in FERONIA displayed enhanced resistance to Fusarium oxysporum and to powdery mildew infection (Kessler et al, 2010;Masachis et al, 2016;Fernandes et al, 2017). A similar increase in protein abundance was also identified for five other proteins harboring a high degree of homology with the proteins encoded by susceptibility genes known to be involved in the inhibition of the salicylic acid biosynthesis pathway (Supplementary Table 9).…”

Cell wall integrity regulation across plant species

“…Os FLR1 has a crucial role in parasitism of Meloidogyne incognita where it interacts with parasite-derived RALFs and manipulates plant cell expansion and cell wall modification to facilitate parasitism (Zhang et al 2020a ). This is in contrast to the situation in Triticum aestivum ( Ta ), where transient silencing of Ta FER1 and Ta FER2 had no obvious impact on Fusarium graminearum infection (Wood et al 2020 ).…”

Phytocytokines function as immunological modulators of plant immunity

“…Sequence alignments indicate that RALF homologs are not only widely distributed in plants but also across phylogenetically distant phytopathogens, such as pathogenic Fusarium fungi and Actinobacteria (Masachis et al 2016;Thynne et al 2017;Wood et al 2020). The RALF-like proteins are also present in multiple species of root-knot nematodes (Masachis et al 2016;Thynne et al 2017;Zhang et al 2020b).…”