The role of strigolactones during plant interactions with the pathogenic fungus Fusarium oxysporum

Abstract

Strigolactones (SLs) do not influence spore germination or hyphal growth of Fusarium oxysporum. Mutant studies revealed no role for SLs but a role for ethylene signalling in defence against this pathogen in pea. Strigolactones (SLs) play important roles both inside the plant as a hormone and outside the plant as a rhizosphere signal in interactions with mycorrhizal fungi and parasitic weeds. What is less well understood is any potential role SLs may play in interactions with disease causing microbes such as pathogenic fungi. In this paper we investigate the influence of SLs on the hemibiotrophic pathogen Fusarium oxysporum f.sp. pisi both directly via their effects on fungal growth and inside the plant through the use of a mutant deficient in SL. Given that various stereoisomers of synthetic and naturally occuring SLs can display different biological activities, we used (+)-GR24, (-)-GR24 and the naturally occurring SL, (+)-strigol, as well as a racemic mixture of 5-deoxystrigol. As a positive control, we examined the influence of a plant mutant with altered ethylene signalling, ein2, on disease development. We found no evidence that SLs influence spore germination or hyphal growth of Fusarium oxysporum and that, while ethylene signalling influences pea susceptibility to this pathogen, SLs do not.

Recent progress in the chemistry and biochemistry of strigolactones

“…87) However, ccd8 mutants of pea and wild-type plants were equally susceptible to the soilborne pathogen Fusarium oxysporum. 137) Therefore, effects of SLs may vary with the pathosystem examined. 138) Additionally, SLs indirectly enhance plant resistance to pathogens by promoting AM symbiosis, which induces pathogen resistance.…”

Factors affecting expression of soybean sudden death syndrome: Flooding, oxygen level, and ethylene hormone

“…This increased resistance was probably due to accumulation of pathogenesis-related proteins and antimicrobial compounds such as phytoalexins . Furthermore, ethylene insensitivity in tobacco impaired resistance against soilborne fungi (Knoester et al 1998) and an ethylene insensitive pea mutant ein2 developed more severe symptoms when challenged by Fusarium oxysporum or Pythum irregulare compared to wild type peas (Foo et al 2016;Blake et al 2015). Similarly, our study showed that induction of ethylene signaling in soybean roots using ethephon enhanced resistance against SDS foliar symptoms and increased accumulation of key defense response genes such as CHS, and basic peroxidase IPER, compared to water treated control.…”

Changes at the Rhizosphere Microbiota of the Sunflower – Orobanche cumana Wallr Pathosystem

“…This class of compounds characterized by enormous structural diversity , which further strengthens the specifics of the various patho-systems. Besides clearly proven role in the formation of symbiosis between plants and arbuscular mycorrhizal fungi there are reports of an inhibitory effect on the growth of some phytopathogenic fungi from genus Botrytis and genus Cryphonectria (Ćavar et al, 2015), but on the growth of Fusarium oxisporum not found such (Foo et al, 2016), i.e. there is a divergence of action.…”