Comparative transcriptome analysis reveals candidate genes for leaf color formation in a thermo-sensitive leaf-color mutant generated by carbon-ion beam in green wandering Jew (Tradescantia fluminensis)

Leaf color is considered a valuable trait when breeding ornamental plants. In this study, a novel thermo-sensitive leaf-color mutant (mt) of green wandering Jew was obtained through carbon-ion beam irradiation. Young leaves of the mt plant exhibited pink coloration under low temperature (mt_7 degrees C) and green coloration under normal temperature (mt_25 degrees C). However, young leaves of the wild type (WT) remained green under low and normal temperatures. Here, we compared the mt and WT in terms of their anatomical, physiological, transcriptomic, and metabolomic characteristics at 7 degrees C and 25 degrees C. Histological analyses showed that the upper epidermis and palisade parenchyma of mt were fewer and smaller. Chloroplasts of mt_25 degrees C were abnormally inflated, and leucoplasts were present instead of chloroplasts in mt_7 degrees C leaves. Physiological experiments also showed that mt_7 degrees C had lower chlorophyll and carotenoid contents, and higher anthocyanin contents; however, the chlorophyll content in mt_25 degrees C leaves were higher than that in the WT. Transcriptome profiling revealed that 99 differentially expressed genes (DEGs) and 1597 transcription factors (TFs) are involved in photosynthesis, chlorophyll biosynthesis, and flavonoid and anthocyanin biosyntheses. This study identified 8 candidate genes associated with the PS II reaction center, 13 genes related to PS I, 15 genes for LHC, 4 genes for PET/Cyt b6/f, and 2 genes for ATP synthase; these genes were differentially expressed at 7 degrees C. DEGs related to photosynthesis and chlorophyll biosynthesis were down-regulated in the pink leaves of mt_7 degrees C, whereas DEGs involved in flavonoid and anthocyanin biosyntheses were up-regulated in mt_7 degrees C and mt_25 degrees C leaves. Differential expression levels were further confirmed by qRT-PCR, Chlorophyll fluorescence signals, and previous HPLC results the. The anthocyanin content of mt_7 degrees C was 20-fold higher than that of the other pigments resulting in pink coloration at low temperature. This study provides a systematic evaluation of thermo-sensitive color variation in the mt. Based on these results, we identified key pathways related to thermo-sensitive leaf-color change in green wandering Jew.

Automated summary

Leaf color is an important trait in breeding ornamental plants. A study on a novel thermo-sensitive leaf-color mutant of green wandering Jew revealed differences in anatomical, physiological, transcriptomic, and metabolomic characteristics compared to the wild type under different temperatures. Differential gene expression related to photosynthesis and pigmentation pathways were identified, providing insights into the underlying mechanisms of thermo-sensitive color change in plants.