BackgroundBeneficial microorganisms modify root architecture through different mechanisms mostly related to plant hormones synthesis. Less information is available regarding the emission of microbial volatile organic compounds (VOCs) and their effects on root architecture. Numerous studies describe the release of VOCs by bacteria and filamentous fungi, but little information is available regarding soil yeasts.MethodsThe VOCs released by the soil yeast Solicoccozyma terrea were evaluated in an experiment with tomato seedlings. Four treatments (tomato seedlings, T; S. terrea inoculum without tomato seedlings, St; tomato seedlings exposed to the volatiles of S. terrea inoculum, TSt; and a control without tomato seedlings or yeast inoculum, C) were assessed in terms of root morphology. VOCs were analyzed by GC-MS, and in a second experiment, the response of tomato seedlings and root nitrate uptake transporters to specific compounds identified in the first experiment was evaluated under low and high N supply.ResultsA mixture with 57 VOCs was identified which promoted lateral roots formation in tomato plants. Three compounds (isopropyl alcohol, 2-pentylfuran and trans-1,3-pentadiene) were exclusively present in the TSt treatment. All three compounds stimulated lateral roots formation and increased root volume. These compounds showed a stimulatory effect on the expression of NRT1.2, NRT2.1 and NRT2.3 nitrate transporters under N deficiency conditions.ConclusionsThis study provides, for the first time, information on a soil yeast capable of promoting lateral roots formation in tomato through VOCs and that isopropyl alcohol, 2-pentylfuran and trans-1,3-pentadiene modulate root nitrate transporters expression under N deficiency conditions.