BoSKU5-BoARF8 complex modulates leaf margin development via the BoUIF1-BoCUC2 cascade in kale

Leaves are the primary source of photosynthesis in plants. Elucidating the mechanism of leaf shape variation is essential for plant development. In previous studies, we demonstrated that BoALG10, a member of the glycosyltransferase family, is responsible for the smooth-leaved trait in kale (Brassica oleracea var. acephala), but the underlying molecular mechanism remains unclear. Here, we performed quantitative N-glycoproteomics with the BoALG10 overexpression line and the corresponding wild type. A cupredoxin domain-containing protein Skewed5 (SKU5) specifically underwent N-glycosylation in the BoALG10 overexpression line. Site-directed mutagenesis of the N-glycosylation site Asn-444 affected BoSKU5 nuclear localization and protein function in maintaining smooth leaf margins. Transcriptome sequencing showed that the BoSKU5 mutation altered the expression of auxin signaling and cell wall modification-related genes. We then identified a transcription factor BoARF8, which interacted with the protein BoSKU5, through yeast two-hybrid library screening. BoARF8 promoted smooth leaf margin formation and positively regulated its target gene BoUIF1. The BoSKU5-BoARF8 complex further enhanced the activation of the BoARF8-BoUIF1 cascade. Moreover, BoUIF1 directly repressed the expression of BoCUC2, a leaf margin regulator. The BoSKU5/BoARF8-BoUIF1-BoCUC2 module illustrated the novel function of Skewed5 in leaf margin development. This will provide deeper insights into the genetic improvement in plants.