Physiological and molecular basis of leaf color variation and cold resistance in Platycladus orientalis cv. 'Mancheng No.1′

Platycladus orientalis cv. 'Mancheng No.1′ is a naturally occurring yellow-leaf variant selected from common green-leaved P. orientalis seedlings, exhibiting significant ornamental value. This study revealed seasonal patterns of leaf coloration and elucidated the mechanisms of cold adaptation in P. orientalis cv. 'Mancheng No.1′ through comprehensive physiological assessments and transcriptome analysis, using its green counterpart as a control. Comparative analysis revealed that while both plant types showed similar annual patterns in leaf color parameters and stress resistance indicators, P. orientalis cv. 'Mancheng No.1′ maintained consistently brighter yellow foliage characterized by significantly lower pigment content, higher L * and b * values, and increased reflectance in the blue, yellow, and red light spectra. During winter months, significant accumulation of soluble sugars and starch was observed in P. orientalis cv. 'Mancheng No.1′, along with peak activities of key stress indicators, including peroxidase, catalase, malondialdehyde, and relative electrolyte leakage. Transcriptome sequencing identified 28,431 differentially expressed genes in P. orientalis cv. 'Mancheng No.1′, with notable upregulation of carotenoid biosynthesis genes ( crtB , LcyB1 , Crtz , ZEP ) and flavonoid pathway genes ( CYP family members) during winter periods, suggesting their potential roles in mediating both leaf color maintenance and cold tolerance. Weighted gene co-expression network analysis pinpointed UGT92A1 as the central hub gene regulating coloration and NPF2.9 as the key role in cold adaptation. Additionally, four transcription factor families ( ERF , NAC , B-ARR , Trihelix ) were identified as appearing to coordinately regulate stress responses. This study provided a preliminary elucidation of the molecular mechanisms underlying leaf color formation and cold tolerance in P. orientalis cv. 'Mancheng No.1′, offering the theoretical basis for the utilization of its germplasm resources. • Platycladus orientalis cv. 'Mancheng No.1′ maintained bright yellow foliage with low pigment content year-round. • Transcriptome analysis revealed winter upregulation of carotenoid and flavonoid biosynthesis genes. • UGT92A1 and NPF2.9 were identified as hub genes for coloration and cold tolerance.