The CmDOF6 Transcription Factor Controls Chrysanthemum Plant Height by Repressing CmGA20ox1 via CmTCP8

Plant height is a crucial index for evaluating plant architecture, which affects plant adaptability and ecological niche. The plant hormone gibberellic acid (GA) greatly influences plant height. The DNA binding with one finger (DOF) transcription factor family members play an important role in plant growth, development and response to plant hormones. However, the regulatory network mediating the DOF–GA interplay remains unclear. Here, we identified CmDOF6, a member of the group Ⅲ DOF transcription factor family, as a regulator of chrysanthemum plant height. CmDOF6 overexpression reduced plant height and the content of bioactive GAs (GA1, GA3, GA4, GA7) as well as upstream GAs (GA9, GA15, GA20). In addition, CmDOF6 overexpression repressed the GA biosynthesis gene CmGA20ox1, although CmDOF6 does not directly regulate CmGA20ox1. Notably, RNA-seq and DAP-seq analyses revealed CmTCP8 as a candidate CmDOF6 target. We present several lines of evidence suggesting that CmDOF6 binds the CmTCP8 promoter and represses its expression. Furthermore, our study also verified the ability of CmTCP8 to bind the CmGA20ox1 promoter and promote its expression. Due to the overexpression of CmDOF6, the promotion effect of CmTCP8 on CmGA20ox1 was weakened, ultimately leading to reduced GA levels. Taken together, our data demonstrate that the CmDOF6–CmTCP8–CmGA20ox1 pathway regulates chrysanthemum plant architecture.