Indolic glucosinolate pathway provides resistance to mycorrhizal fungal colonization in a non‐host Brassicaceae

Using BLAST to identify indolic glucosinolates orthologs across 29 Brassicales, we show that non-mycorrhizal species possess orthologous proteins for IG biosynthesis to Arabidopsis which arbuscular mycorrhizal fungi -associated Brassicales lack

M. A. Anthony; J. L. Celenza; A. Armstrong; S. D. Frey

2020

Scholarcy highlights

  • Few angiosperms do not form symbiotic relationships with arbuscular mycorrhizal fungi
  • Since Arabidopsis produces aliphatic glucosinolates, we quantified the abundant AG 4MSOB to assess whether its production was altered by the genotypes used. 4MSOB was less concentrated in wild-type and indolic glucosinolates-enhanced plants compared to IG-removed plants levels with 1 Æ 0.3 and 0.8 Æ 0.2 nmol/mg dry tissue, respectively
  • These results support our general hypothesis that IGs are involved in suppressing AMF colonization on the root systems of Arabidopsis. We suggest that these results extend beyond the Arabidopsis–Rhizophagus system since AMF can colonize other species in the Brassicaceae, other AMF taxa besides R. irregularis can colonize non-host Brassicaceae, and because IG orthologs are found across non-mycorrhizal species within the Brassicaceae
  • There is strong evidence that the loss of conserved symbiosis related genes is responsible for non-functional arbuscular mycorrhizas in Arabidopsis, but mechanisms by which Arabidopsis can defend itself against AMFinduced growth suppression are poorly understood
  • We hypothesized that AMF inoculation would suppress the growth, activate induced plant defenses, and promote AMF colonization on the root systems of IG-removed > wild-type > IGenhanced plants
  • Since small concentrations of glucosinolates can suppress AMF germination, the impact of AMF on Arabidopsis may not scale with IG production capacity within the range we detected
  • To assess whether these results may be applicable beyond Arabidopsis, we determined whether arbuscular mycorrhizal fungi host plants and non-mycorrhizal species within the Brassicales produce similar proteins for indolic glucosinolates production

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