NGATHA-LIKEs Control Leaf Margin Development by Repressing Transcription.

The leaf margin is a fascinating feature of leaf morphology, contributing to the incredible diversity of leaf shapes and forms. As a central regulator of plant organ separation and margin development, CUP-SHAPED COTYLEDON2 (CUC2), a NAM, ATAF1, 2, CUC2 (NAC)-family transcription factor, governs the extent of serrations along the leaf margin. CUC2 activity is tightly regulated at transcriptional and posttranscriptional levels. However, the molecular mechanism that controls transcription during leaf development has not been fully elucidated. Here we report that Arabidopsis () NGATHA-LIKE1 (NGAL1) to NGAL3, which are three related B3 family transcription factors, act as negative regulators of leaf margin serration formation. Over-expression of led to "cup-shaped" cotyledons and smooth leaf margins, whereas the triple loss-of-function mutant exhibited more serrated leaves than the wild type. RNA-sequencing analyses revealed that the expression levels of a number of transcription factor genes involved in leaf development are regulated by NGALs, including Comparative transcriptome analyses further uncovered a significant overlap between NGAL- and CUC2-regulated genes. Moreover, genetic analyses using various combinations of gain- and loss-of-function mutants of and confirmed that CUC2 acts downstream of NGALs in promoting the formation of leaf-margin serrations. Finally, we demonstrate that NGAL1 directly binds to the promoter causing repressed expression. In summary, direct transcriptional repression by NGAL1 characterizes a further regulatory module controlling leaf margin development.