732 / 2019-05-11 00:20:42

The molecular mechanism of vegetative phase change

miR156, SPL, phase change, shoot apical meristem

Growth and Development > Growth and Development

Plants transition from a juvenile to an adult phase of vegetative development prior to producing reproductive structures. This transition is regulated by miR156/miR157 and miR172, which act by repressing the expression of, respectively, SPL and AP2-like transcription factors. miR156 promotes juvenile identity by repressing the translation of its targets. The mechanism by which it does this is acutely sensitive to the dose of miR156, such that small changes in the abundance of miR156 result in disproportionately large changes in the abundance of SPL proteins. Variation in the robustness of leaf identity is attributable to variation in amount of miR156: leaves with very high levels of miR156 are developmentally robust whereas those with low levels of miR156 are quite plastic. In Arabidopsis, the shoot apical meristem contributes to the identity of leaves produced very early in shoot development, but plays a relatively small role in the specification of leaf identity later in shoot growth. The juvenile-to-adult transition is regulated by diffusible factors produced by leaves, which act on newly-formed leaf primordia to repress the expression of miR156.