YELLOW, SERRATED LEAF is essential for cotyledon vein patterning in Arabidopsis.

Venation develops complex patterns within the leaves of angiosperms, and the mechanism of leaf vein patterning remains poorly understood. Here, we report a spontaneous mutant that exhibits yellow serrated leaves and defective cotyledon vein patterning. We mapped and cloned the relevant gene YELLOW, SERRATED LEAF (YSL), a previously unreported gene in plants. YSL interacts with VH1-interacting kinase (VIK), a protein that functions in cotyledon venation development. VIK is a vascular-specific adaptor protein kinase that interacts with another vascular developmental protein, VASCULAR HIGHWAY1 (VH1)/BRASSINOSTEROID INSENSITIVE 1-LIKE 2 (BRL2), which is a receptor-like kinase of the BRASSINOSTEROID INSENSITIVE 1 (BRI1) family. Mutation of YSL affects the auxin response and the expression of auxin-related genes in Arabidopsis (Arabidopsis thaliana). Our results reveal that YSL affects cotyledon vein patterning by interacting with VIK in Arabidopsis.