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

<i>Liriodendron</i> 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 <i>Liriodendron chinense</i> (Hemsl.) Sargent, an orange-yellow basal band in <i>Liriodendron tulipifera</i> 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 <i>PORA1</i> and <i>PORA2</i> showed a strong positive correlation with chlorophyll content, and their downregulation led to disrupted chloroplast structure and reduced chlorophyll levels. Concurrently, carotenoid biosynthesis genes <i>CRTISO</i> and <i>LCYE</i> 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 <i>Liriodendron</i>, providing a genetic basis for the targeted breeding of ornamental traits.