Coordinating the morphogenesis-differentiation balance by tweaking the cytokinin-gibberellin equilibrium

Abstract

Morphogenesis and differentiation are important stages in organ development and shape determination. However, how they are balanced and tuned during development is not fully understood. In the compound leaved tomato, an extended morphogenesis phase allows for the initiation of leaflets, resulting in the compound form. Maintaining a prolonged morphogenetic phase in early stages of compound-leaf development is dependent on delayed activity of several factors that promote differentiation, including CIN-TCP transcription factor (TF) LA, the MYB TF CLAU and the plant hormone Gibberellin (GA). Here, we investigated the genetic regulation of the morphogenesis-differentiation balance by studying the relationship between LA, CLAU and GA. Our genetic and molecular examination suggest that LA is expressed more broadly than CLAU and determines the spatio-temporal context of CLAU activity. We demonstrate that both LA and CLAU affect the Cytokinin/Gibberellin (CK/GA) balance. LA reduces the sensitivity of the leaf margin to CK, shown before to be also affected by CLAU. CLAU affects leaf active GA content and sensitivity, shown previously to be also influenced by LA. Therefore, LA and CLAU likely function in parallel pathways to promote leaf differentiation by converging on common downstream processes, including the CK/GA balance.