Jasmonate inhibits adventitious root initiation through transcriptional repression of CKX1 and activation of RAP2.6L transcription factor in Arabidopsis

Abstract

Adventitious rooting is a de novo organogenesis process that enables plants to propagate clonally and cope with environmental stresses. Adventitious root initiation (ARI) is controlled by interconnected transcriptional and hormonal networks, but there is little knowledge of the genetic and molecular programs orchestrating these networks. Thus, we have applied genome-wide transcriptome profiling to elucidate the profound transcriptional reprogramming events preceding ARI. These reprogramming events are associated with downregulation of cytokinin (CK) signaling and response genes, which could be triggers for ARI. Interestingly, we found that CK free-base content declined during ARI, due to downregulation of de novo CK biosynthesis and upregulation of CK inactivation pathways. We also found that MYC2-dependent jasmonate (JA) signaling inhibits ARI by downregulating expression of the CYTOKININ OXIDASE/DEHYDROGENASE1 gene. We also demonstrated that JA and CK synergistically activate expression of RELATED to APETALA2.6 LIKE (RAP2.6L) transcription factor, and constitutive expression of this transcription factor strongly inhibits ARI. Collectively, our findings reveal that previously unknown genetic interactions between JA and CK play key roles in ARI