(A) CsIVP regulates organ morphogenesis via 2 pathways, one by directly promoting the expression of vascular-related genes—including CsYAB5 and CsBP—to regulate vascular development, and the other by directly binding to the E-box of CsAUX4 to mediate auxin signaling. Grey arrow indicates the putative positive role of auxin in vascular development. (B) CsIVP may act as a repressor for SA production and physically interacts with CsNIMIN1 to compromise downy mildew resistance in cucumber. Black arrows, positive regulation; black crosses, inhibition regulation; red arrows, transcription start; black dotted crosses, putative inhibition regulation. AUX4, AUXIN/INDOLEACETIC ACIDS4; BP, BREVIPEDICELLUS; Cs, Cucumis sativus; CsIVP, Cucumis sativus Irregular Vasculature Patterning; NIMIN1, NIM1-INTERACTING1; SA, salicylic acid; YAB5, YABBY5.