Plant hormone crosstalk mediated by humic acids

Abstract

BackgroundThe reliance on chemical inputs to support high yields is the Achilles’ heel of modern crop production. The soil organic matter management is as old as agriculture itself. Recently, the use of soluble humic substances as plant growth promoters has been brought to attention due to their effects on nutrient uptake and water use efficiency. Humic substances applied directly at low concentrations can trigger different molecular, biochemical, and physiological processes in plants. However, how humic substances exert this plethoric regulatory action remains unclear. The objective of this study was to evaluate changes in the transcription level of genes coding cell receptors, phosphatases, synthesis, and function of different plant hormones and transcription factors.Materials and methodsAfter seven days of humic acid treatment, we used RNAseq in maize root seedlings. The level of gene transcription was compared with control plants.ResultsPlant kinase receptors and different phosphatases were regulated by humic acids. Likewise, genes related to plant hormones (auxin, gibberellin, ethylene, cytokinin, abscisic acid, brassinosteroids, jasmonic and salicylic acids) were transcript in differential levels in maize root seedlings as well as the expression of a hundred of transcription factors modifying the signal transduction pathway via alterations of the subsequent gene response.ConclusionWe showed a general mechanism for simultaneously regulating the activity of several hormones where humic acids act as a key regulatory hub in plant responses integrating hormonal signalling and response pathways.