Phenotypic and transcriptome analysis on red leaf and green leaf Eucommia ulmoides Oliver

Eucommia ulmoides Oliver. (E. ulmoides) is an important medicinal and economic tree species, and "Huazhong No.12" (HZ12) is the only existing red leaf genotype of E. ulmoides. In this study, phenotype/anatomic observation and photosynthetic pigment content detection were performed on "Huazhong No.11" (HZ11, green leaf E. ulmoides) and HZ12. Additionally, the transcriptome sequencing data of HZ11 and HZ12 leaves were also analyzed and compared. The results showed that the palisade tissue of HZ12 leaf was red, while the palisade tissue of HZ11 leaf was green. Chlorophyll a, b, a+b, and carotenoid contents of HZ12 leaf were significantly lower than that of HZ11 leaf. While the total flavonoids and anthocyanin contents in HZ12 leaf were significantly higher than that in HZ11 leaf. Transcriptome analysis indicated that, compared with HZ12, there were 26 MYB and 49 bHLH TF genes, and some structural genes were differentially expressed in HZ11, and among these differentially expressed genes (DEGs), 2 MYB, 1 bHLH, 1 F3 ' H, 1 F3 ' 5 ' H, 5 DFR and 9 GT genes were involved with flavonoid biosynthesis and anthocyanin biosynthesis pathways. Taken together, the results that achieved in the present study not only provide valuable clues for the excavation on anthocyanin biosynthesis related genes and the corresponding gene regulation networks in E. ulmoides, but also provide reference for the leaf coloration mechanism research in other woody plant species.