Characterization of leaf transcriptome in grafted tomato seedlings inoculated with beneficial rhizobacteria Azospirillum brasiliensis and Paraburkholderia graminis

Abstract Aims: Characterization of the transcriptomic responses of grafted tomato seedlings inoculated with two beneficial microorganisms.Methods: mRNA sequencing analyses were performed from leaves of grafted tomato seedlings at flowering stage, 35 days after inoculations. The differential expression analysis results were validated by carrying out a quantitative reverse transcription PCR on nine selected genes.Results and Conclusions: Root inoculations with the two beneficial bacteria can influence the genes activity also in organs distant from roots. Interactions between grafted tomato seedlings and microorganisms suggest that the interactions between tomato and microorganisms are species-specific, and affect the activity of specific sets of genes, that in turn activate and/or involve similar pathways and mechanisms. This study provides novel knowledge on the effects of inoculation of Azospirillum brasiliensis (AB) and Paraburkholderia graminis (PG)on grafted tomato seedling metabolism, and on the molecular mechanisms underlying the improved performance of tomato plants after these treatments as far as yield and stress responses are regarded. AB induced genes coding for different MYB trascrption factors known to be involved in response to biotic and abiotic stresses, PG upregulated 5 genes coding for putative late blight resistance protein homolog. Auxine responsive molecules and giberellins involved in the fruit-set and early fruit growth in tomato were mainly induced by AB.