Jasmonic Acid coordinates with Light, Glucose and Auxin signalling in Regulating Branching Angle ofArabidopsisLateral Roots

AbstractThe role of jasmonates (JAs) in primary root growth and development and in plant response to external stimuli is already known. However, its role in lateral root (LR) development remains to be explored. Our work identified methyl jasmonate (MeJA) as a key phytohormone in determining the branching angle ofArabidopsisLRs. MeJA inclines the LRs to a more vertical orientation, which was dependent on the canonicalJAR1-COI1-MYC2, 3, 4signalling. Our work also highlights the dual roles of light in governing LR angle. Light signalling enhances JA biosynthesis, leading to erect root architecture; whereas, glucose (Glc) induces wider branching angles. Combining physiological and molecular assays, we revealed that Glc antagonizes the MeJA response via TARGET OF RAPAMYCIN (TOR) signalling. Moreover, physiological assays using auxin mutants, MYC2-mediated transcriptional activation ofLAZY2, LAZY4and auxin biosynthetic geneCYP79B2, and asymmetric distribution ofDR5::GFPandPIN2::GFPpinpointed the role of an intact auxin mechanism required by MeJA for vertical growth of LRs. We also demonstrated that light perception and signalling are indispensable for inducing vertical angles by MeJA. Thus, our investigation highlights antagonism between light and Glc signalling and how they interact with JA-auxin signals to optimize the branching angle of LRs.