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Abstract

Medicago truncatula is a widely studied legume and its compound leaves provide a sensitive model system to explore the mechanisms regulating leaf complexity. Activation or repression of indeterminacy in developing leaves can change the patterning of compound leaves. In this issue, Wang et al. (pages 2279-2291) report that MtKNOX4 plays a major role in the regulation of compound leaf formation by integrating the cytokinin pathway and boundary regulators. This work provides new insight into the roles of Class II KNOX proteins in regulating the elaboration of compound leaves.