Carotenoid Accumulation and Distinct Transcript Profiling of Structural Genes Involved in Carotenoid Biosynthesis in Celery

Carotenoids, a diverse group of pigments, participate in various biological processes in plants and contribute to an important quality trait for many plants. Celery is an important leafy vegetable crop, and the leaf is the main edible organ. However, the molecular mechanism of carotenoid biosynthetic pathway in celery has yet to be characterized. Here, two celery varieties with obviously different appearances, ‘Liuhe yellow heart celery’ and ‘Ventura’, were selected to study the carotenoid accumulation and distinct transcript profiling of structural genes involved in carotenoid biosynthesis. The contents of lutein, β-carotene, and α-carotene of leaf blades and petioles of celery were determined by UPLC at 30, 45, and 60 days after germination (DAG). In the two celery varieties, the highest lutein content was 14.56 mg/g DW (dry weight) in leaf blades of ‘Ventura’ at 45 DAG. The lowest lutein content was 1.56 mg/g DW in petioles of ‘Liuhe yellow heart celery’ at 60 DAG. The highest β-carotene content was 0.42 mg/g DW in leaf blades of ‘Ventura’ at 45 DAG. The lowest β-carotene content was 0.07 mg/g DW in petioles of ‘Liuhe yellow heart celery’ at 45 DAG. Lutein and β-carotene contents in leaf blades were higher than that in petioles. The contents of lutein and β-carotene in ‘Ventura’ were higher than that in ‘Liuhe yellow heart celery’. The relative expression levels of structural genes involved in carotenoid biosynthesis were also detected. The contents of lutein and β-carotene were correlated with the transcription level of genes involved in carotenoid biosynthesis. The relative expression of AgPSY1 and AgLCYE in ‘Ventura’ was significantly higher than that in ‘Liuhe yellow heart celery’ at three growth stages. The content of α-carotene could not detected in leaves of the two celery cultivars. These results provide potential insights into carotenoid biosynthetic pathway in celery during growth and development.