Metabolic responses to arbuscular mycorrhizal fungi are shifted in roots of contrasting soybean genotypes

Abstract

Modern breeding programs have reduced genetic variability and might have caused a reduction in plant colonization byarbuscular mycorrhizal fungi (AM). In our previous studies, mycorrhizal colonization was affected in improved soybean geno-types, mainly arbuscule formation. Despite substantial knowledge of the symbiosis-related changes of the transcriptome andproteome, only sparse clues regarding metabolite alterations are available. Here, we evaluated metabolite changes betweenimproved (I-1) and unimproved (UI-4) soybean genotypes and also compare their metabolic responses after AM root coloniza-tion. Soybean genotypes inoculated or not with AM were grown in a chamber under controlled light and temperature conditions.At 20 days after inoculation, we evaluated soluble metabolites of each genotype and treatment measured by GC-MS. In thisanalysis, when comparing non-AM roots between genotypes, I-1 had a lower amount of 31 and higher amount of only 4metabolites than the UI-4 genotype. When comparing AM roots, I-1 had a lower amount of 36 and higher amount of 4metabolites than UI-4 (different to those found altered in non-AM treated plants). Lastly, comparing the AM vs non-AMtreatments, I-1 had increased levels of three and reduced levels of 24 metabolites, while UI-4 only had levels of 12 metabolitesreduced by the effect of mycorrhizas. We found the major changes in sugars, polyols, amino acids, and carboxylic acids. In atargeted analysis, we found lower levels of isoflavonoids and alpha-tocopherol and higher levels of malondialdehyde in the I-1genotype that can affect soybean-AM symbiosis. Our studies have the potential to support improving soybean with a greatercapacity to be colonized and responsive to AM interaction.