Integrated physiological and genomic analysis reveals structural variations and expression patterns of candidate genes for colored- and green-leaf poplar.

Colored-leaf plants are increasingly popular and have been attracting more and more attentions. However, the molecular mechanism of leaf coloration in plants has not been fully understood. In this study, a colored-leaf cultivar of Populus deltoides (Caihong poplar, CHP) and green-leaf cultivar of Populus deltoides L2025 were used to explore the mechanism of leaf coloration through physiological and the whole genome resequencing analysis. The content of anthocyanins, total Chl, and carotenoids in the leaves of CHP and L2025 were evaluated. The ratio of anthocyanins to total Chl in CHP was 25.0 times higher than that in L2025; this could be attributed to the red leaf color of CHP. Based on the whole genome resequencing analysis, 951,421 polymorphic SNPs and 221,907 indels were screened between CHP and L2025. Using qRT-PCR analysis, three structural genes (flavonol synthase 1 family protein, UDP-glucose flavonoid 3-O-glucosyltransferase 3' and flavonoid 3-O-galactosyl transferase family protein) and six transcription factors (MYB-related protein Myb4, transcription factor GAMYB, PtrMYB179, transcription factor bHLH53, transcription factor bHLH3, VARICOSE family protein) may be involved in the anthocyanin synthesis pathway, which could be used as candidate genes to explore the molecular regulation mechanism of leaf coloration in Populus deltoids, and could be used in molecular breeding in the future.