Plant-specific Dof transcription factors VASCULAR-RELATED DOF1 and VASCULAR-RELATED DOF2 regulate vascular cell differentiation and lignin biosynthesis in Arabidopsis

Key message Plant-specific Dof transcription factors VDOF1 and VDOF2 are novel regulators of vascular cell differentiation through the course of a lifetime in Arabidopsis, with shifting their transcriptional target genes. Vascular system is one of critical tissues for vascular plants to transport low-molecular compounds, such as water, minerals, and the photosynthetic product, sucrose. Here, we report the involvement of two Dof transcription factors, named VASCULAR-RELATED DOF1 (VDOF1)/VDOF4.6 and VDOF2/VDOF1.8, in vascular cell differentiation and lignin biosynthesis in Arabidopsis.VDOFgenes were expressed in vascular tissues, but the detailed expression sites were partly different betweenVDOF1andVDOF2. Vein patterning and lignin analysis ofVDOFoverexpressors and double mutantvdof1 vdof2suggested that VDOF1 and VDOF2 would function as negative regulators of vein formation in seedlings, and lignin deposition in inflorescence stems. Interestingly, effects ofVDOFoverexpression in lignin deposition were different by developmental stages of inflorescence stems, and total lignin contents were increased and decreased inVDOF1andVDOF2overexpressors, respectively. RNA-seq analysis of inducibleVDOFoverexpressors demonstrated that the genes for cell wall biosynthesis, including lignin biosynthetic genes, and the transcription factor genes related to stress response and brassinosteroid signaling were commonly affected byVDOF1andVDOF2overexpression. Taken together, we concluded that VDOF1 and VDOF2 are novel regulators of vascular cell differentiation through the course of a lifetime, with shifting their transcriptional target genes: in seedlings, theVDOFgenes negatively regulate vein formation, while at reproductive stages, the VDOF proteins target lignin biosynthesis.