Unraveling the KNOTTED1 regulatory network in maize meristems

By providing a global chromatin immunoprecipitation (ChIP) analysis of binding targets of KNOTTED1 (KN1), this paper offers new insight into how this well-studied transcription factor contributes to cell fate determination in plants. Since its characterisation more than 20 years ago in maize, KN1 and its counterparts in other plant species have emerged as key players in the regulation of growth in the shoot apical meristem. Expression of KN1 is a key requirement for cell proliferation in pluripotent tissues, while its down-regulation is a prerequisite to the normal differentiation of shoot-derived organs, such as leaves. Although a number of studies have identified genes whose expression is sensitive to KN1 activity, for only a handful has it been shown responses are direct. The global analysis offered by this ChIP study suggests a variety of genes encoding transcription factors, including those involved in auxin responses, are well represented among those genes that both bind to and that are responsive to KN1. Though the complexity of these interactions within the shoot apical meristem remains largely unexplained, the work described in this paper provides an important basis for future modelling and experimental work.