Cytokinin regulates vegetative phase change in Arabidopsis thaliana through the miR172/TOE1-TOE2 module

During vegetative growth plants pass from a juvenile to an adult phase causing changes in shoot morphology. This vegetative phase change is primarily regulated by the opposite actions of two microRNAs, the inhibitory miR156 and the promoting miR172 as well as their respective target genes, constituting the age pathway. Here we show that the phytohormone cytokinin promotes the juvenile-to-adult phase transition through regulating components of the age pathway. Reduction of cytokinin signalling substantially delayed the transition to the adult stage. tZ-type cytokinin was particularly important as compared to iP- and the inactive cZ-type cytokinin, and root-derived tZ influenced the phase transition significantly. Genetic and transcriptional analyses indicated the requirement of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors and miR172 for cytokinin activity. Two miR172 targets, TARGET OF EAT1 (TOE1) and TOE2 encoding transcriptional repressors were necessary and sufficient to mediate the influence of cytokinin on vegetative phase change. This cytokinin pathway regulating plant aging adds to the complexity of the regulatory network controlling the juvenile-to-adult phase transition and links cytokinin to miRNA action. The antagonistic activities of miR156 and miR172 regulate juvenile-to-adult phase transition during plant shoot growth. Here the authors show that cytokinin promotes this transition by increasing miR172 abundance which in turn represses the activity of the transcriptional regulators TOE1 and TOE2.

Automated summary

Cytokinin regulates the transition from juvenile to adult phase in plants by promoting the abundance of miR172, which then represses the activity of transcriptional regulators TOE1 and TOE2. The antagonistic activities of miR156 and miR172 play a crucial role in the juvenile-to-adult phase transition during plant growth.