PORA1/2-dependent chlorophyll biosynthesis coordinates with carotenoid accumulation to drive petal color patterning in Liriodendron

Liriodendron is a highly valued ornamental genus renowned for its distinctive tulip-shaped flowers. Despite its horticultural importance, the molecular mechanisms underlying interspecific variation in petal coloration, namely green petals in Liriodendron chinense (Hemsl.) Sargent, an orange-yellow basal band in Liriodendron tulipifera Linn., and an extended orange-yellow band in their hybrid, remain poorly understood. By integrating morphological, transcriptomic, and metabolomic analyses, we found that orange-yellow pigmentation during petal development is closely associated with chlorophyll degradation and carotenoid biosynthesis. The expression of chlorophyll synthesis genes PORA1 and PORA2 showed a strong positive correlation with chlorophyll content, and their downregulation led to disrupted chloroplast structure and reduced chlorophyll levels. Concurrently, carotenoid biosynthesis genes CRTISO and LCYE were markedly upregulated during the formation of the colored petal band. These results highlight the synergistic roles of chlorophyll and carotenoid metabolism in determining petal color patterning in Liriodendron, providing a genetic basis for the targeted breeding of ornamental traits.