Abstract
Coordination of the maintenance of the undifferentiated fate in the shoot meristem and the promotion of cellular differentiation in organs is essential for the development of plant shoots. CINCINNATA-like (CIN-like) TCP transcription factors are involved in this coordination via the negative regulation of CUP-SHAPED COTYLEDON (CUC) genes, which regulate the formation of shoot meristems and the specification of organ boundaries. However, the mechanism of this negative regulation is poorly understood. We show here that TCP3, a model of CIN-like TCPs of Arabidopsis, directly activates the expression of genes for miR164, ASYMMETRIC LEAVES1 (AS1), IAA3/SHY2, and SAUR proteins. Gain of function of these genes resulted in the fusion of cotyledons and the defect of shoot meristems, whereas their loss of function induced ectopic CUC expression in leaves. Our results indicate that miR164, AS1, IAA3/SHY2, and SAUR partially but cooperatively suppress the CUC expression. Since CIN-like TCP genes act dose-dependently in the leaf differentiation, we propose that CIN-like TCPs have important roles to generate different leaf forms, without having any lethal effects on shoots.
