Arbuscular Mycorrhizal Symbiosis Mitigates Iron (Fe)-Deficiency Retardation in Alfalfa (Medicago sativa L.) Through the Enhancement of Fe Accumulation and Sulfur-Assisted Antioxidant Defense

Int J Mol Sci. 2020 Mar 23;21(6):2219. doi: 10.3390/ijms21062219.

Abstract

Iron (Fe)-deficiency is one of the major constraints affecting growth, yield and nutritional quality in plants. This study was performed to elucidate how arbuscular mycorrhizal fungi (AMF) alleviate Fe-deficiency retardation in alfalfa (Medicago sativa L.). AMF supplementation improved plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), and reduced cell death, electrolyte leakage, and hydrogen peroxide accumulation in alfalfa. Moreover, AMF enhanced ferric chelate reductase activity as well as Fe, Zn, S and P in alfalfa under Fe-deficiency. Although Fe-transporters (MsIRT1 and MsNramp1) did not induce in root but MsFRO1 significantly induced by AMF under Fe deficiency in roots, suggesting that AMF-mediated Fe enhancement is related to the bioavailability of Fe at rhizosphere/root apoplast rather than the upregulation of Fe transporters under Fe deficiency in alfalfa. Several S-transporters (MsSULTR1;1, MsSULTR1;2, MsSULTR1;3, and MsSULTR3;1) markedly increased following AMF supplementation with or without Fe-deficiency alfalfa. Our study further suggests that Fe uptake system is independently influenced by AMF regardless of the S status in alfalfa. However, the increase of S in alfalfa is correlated with the elevation of GR and S-metabolites (glutathione and cysteine) associated with antioxidant defense under Fe deficiency.

Keywords: Fe-chelate reductase; Fe-deficiency; Fe-mobilization; Medicago sativa; alfalfa; arbuscular mycorrhizal fungi; symbiosis.

MeSH terms

  • Antioxidants / metabolism*
  • Iron / metabolism*
  • Iron Deficiencies*
  • Medicago sativa / growth & development
  • Medicago sativa / metabolism*
  • Medicago sativa / microbiology*
  • Minerals / metabolism
  • Mycorrhizae / physiology*
  • Oxidative Stress
  • Phenotype
  • Sulfur / metabolism*
  • Symbiosis*

Substances

  • Antioxidants
  • Minerals
  • Sulfur
  • Iron