Polyamines and flavonoids: key compounds in mycorrhizal colonization of improved and unimproved soybean genotypes

SALLOUM MS; BENAVIDES MP; LARRAURI M; SILVENTE S; MENDUNI MF; LUNA CM

SYMBIOSIS

SPRINGER

Lugar: Berlin; Año: 2018 vol. 76 p. 265 - 275

0334-5114

Modern breeding programs might have caused a reduction in plant responsiveness to arbuscular mycorrhizal fungi (AMF). Flavonoidsandpolyamines(PAs)arehypothesizedtoplayaroleinthissymbiosis.WetestedtheeffectsoftheminAMFrootsof improved(I-1)andunimproved(UI-4)soybeangenotypes,underthehypothesisthatdomesticationdecreasedtheirconcentration in roots, affecting AMF colonization, particularly arbuscule formation. After 20 days of treatment, AMF roots of UI-4 genotype had greater amount of total flavonoids/phenols and PAs while in I-1 genotype no differences were observed between roots of mycorrhizal (M) and non mycorrhizal(NM)plants. Exogenousapplication offlavonoidsled toanincreaseinarbusculesinboth genotypes.Improved-1genotypeneededhigherlevelsofflavonoidstoreachthepercentageofmycorrhizationachievedbyUI-4 control. In regard to PAs, mycorrhizal plants of both genotypes had higher endogenous concentration than NM plants, however, the highest concentration, especially of putrescine (put) was in UI-4 M genotype. To check the participation of put in symbiosis we used RNAi silencing methodology. Down regulation of the GmADC transcript, involved in put formation, had a profound negativeeffectonmycorrhizal colonizationandalsoaffectedthenormaldevelopment ofthe plant.Bycontrast, downregulation of GmDAO, in which ADC transcript was expressed, arbuscule formation was similar to control plant. Our results suggest that mycorrhizal colonization is affected by soybean domestication particularly arbuscule formation and this effect seems to be mediated by the endogenous roots levels of flavonoids and PAs, especially put.