Transcription Factor TeMADS6 Coregulates Carotenoid Biosynthesis and Chlorophyll Degradation Resulting in Yellow-Green Petal Color of Marigold (Tagetes erecta)

Marigold (Tagetes erecta) is an important ornamental and industrial crop valued for its high lutein content. Although petal pigmentation during inflorescence development involves coordinated chlorophyll degradation and carotenoid biosynthesis, the transcriptional mechanisms regulating these processes remain poorly understood. Here, we identified a MADS-box transcription factor, TeMADS6, that coordinately regulates chlorophyll and carotenoid metabolism in marigold. Constitutive overexpression of TeMADS6 resulted in yellow-green petals. HPLC analysis revealed that lycopene, antheraxanthin, violaxanthin, zeaxanthin, and lutein levels were substantially reduced in TeMADS6-overexpression lines, while chlorophyll content was significantly increased compared with wild-type plants. Transcriptome profiling revealed strong repressions of the carotenoid biosynthetic genes TePSY1 and TeHYDB in transgenic florets. Moreover, the chlorophyll degradation gene TeNYC1 and TePPH2 were significantly downregulated, whereas TeSGR2 was upregulated. Together, these findings demonstrate that TeMADS6 acts as a dual-function transcriptional regulator controlling both chlorophyll degradation and carotenoid biosynthesis. This study provides new genetic resources for manipulating petal color and enhancing lutein accumulation in marigold, and advance understanding of the transcriptional networks orchestrating pigment metabolism during flower development.