背景回顾：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. 

主要发现：Here we show that the phytohormone cytokinin promotes the juvenile-to-adult phase transition through regulating components of the age pathway. 

结果1-CK信号减弱，转变延迟：Reduction of cytokinin signalling substantially delayed the transition to the adult stage.

结果2-tZ细胞分裂素： 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. 

结果3-SPL和miR172：Genetic and transcriptional analyses indicated the requirement of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors and miR172 for cytokinin activity. 

结果4-miR172靶基因：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. 

结论：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.

 摘 要