Transcriptional interplay between gibberellic acid and jasmonic acid modulates root growth in Arabidopsis thaliana

Abstract

Phytohormones integrate environmental cues to fine-tuning growth and developmental processes. Positive and negative feedbacks enable signal transduction responses to every signaling molecule and their interactions. For example, xylem formation in roots of Arabidopsis thaliana is promoted by jasmonic acid and antagonized by cytokinin. In contrast root meristem development is synergistically stimulated by auxins and cytokinins, which act as morphogens according to their local concentrations. Here, we report that gibberellin, a major regulator of stem elongation interplays with jasmonic acid, the canonical defense sentinel, at the transcriptional level, and leads to root growth inhibition. Gibberellin reduced root growth at high concentration of 300 µM without activation of the jasmonic acid response. Nonetheless, in treatment of 4 µM of jasmonic acid, gibberellin synergistically enhances root growth inhibition and upregulates the jasmonic acid response. Interestingly, there was a root growth reduction in coi1-1 mutant upon gibberellin and jasmonic acid supplementation. On the other hand, jasmonic acid upregulates gibberellin response, indicating a positive feedback loop between both hormones.