Summary The ever‐red leaf trait, which is important for breeding ornamental and higher anthocyanin plants, rarely appears in Malus families, but little is known about the regulation of anthocyanin biosynthesis involved in the red leaves. In our study, HPLC analysis showed that the anthocyanin concentration in ever‐red leaves, especially cyanidin, was significantly higher than that in evergreen leaves. The transcript level of McMYB10 was significantly correlated with anthocyanin synthesis between the ‘Royalty’ and evergreen leaf ‘Flame’ cultivars during leaf development. We also found the ever‐red leaf colour cultivar ‘Royalty’ contained the known R6: McMYB10 sequence, but was not in the evergreen leaf colour cultivar ‘Flame’, which have been reported in apple fruit. The distinction in promoter region maybe is the main reason why higher expression level of McMYB10 in red foliage crabapple cultivar. Furthermore, McMYB10 promoted anthocyanin biosynthesis in crabapple leaves and callus at low temperatures and during long‐day treatments. Both heterologous expression in tobacco (Nicotiana tabacum) and Arabidopsis pap1 mutant, and homologous expression in crabapple and apple suggested that McMYB10 could promote anthocyanins synthesis and enhanced anthocyanin accumulation in plants. Interestingly, electrophoretic mobility shift assays, coupled with yeast one‐hybrid analysis, revealed that McMYB10 positively regulates McF3′H via directly binding to AACCTAAC and TATCCAACC motifs in the promoter. To sum up, our results demonstrated that McMYB10 plays an important role in ever‐red leaf coloration, by positively regulating McF3′H in crabapple. Therefore, our work provides new perspectives for ornamental fruit tree breeding.

The developmental process that produces the ornate petals of the China rose (Rosa chinensis) is complex and is thought to depend on the balanced expression of a functionally diverse array of genes; however, the molecular basis of rose petal development is largely unknown. Here, petal growth of the R. chinensis cultivar ‘Old Blush’ was divided into four developmental stages, and RNA-seq technology was used to analyse the dynamic changes in transcription that occur as development progresses. In total, 598 million clean reads and 61,456 successfully annotated unigenes were obtained. Differentially expressed gene (DEG) analysis comparing the transcriptomes of the developmental stages resulted in the identification of several potential candidate genes involved in petal development. DEGs involved in anthocyanin biosynthesis, petal expansion, and phytohormone pathways were considered in depth, in addition to several candidate transcription factors. These results lay a foundation for future studies on the regulatory mechanisms underlying rose petal development and may be used in molecular breeding programs aimed at generating ornamental rose lines with desirable traits.

Rose is one of the most valuable ornamental crops worldwide. In this study, the composition of hydrophilic and lipophilic pigments in petals of six rose cultivars at seven developing stages was investigated using high performance liquid chromatography and mass spectrometry. Four anthocyanins, 20 flavonols, and 10 carotenoids were detected in petals of tested cultivars. Major individual anthocyanin, flavonol, and carotenoid were cyanidin/pelargonidin 3,5-diglucoside, kaempferol 3- O -rhamnoside, and (9 Z )-violaxanthin, respectively. Significant differences were observed in pigments content in petals of different rose cultivars. The yellow petals of YI and GC exhibited no to very small amounts of anthocyanins, moderate amount of total flavonols, and highest content of total carotenoids. Similarly, pink petals of PF, WQ, and YX showed average concentration of total anthocyanins, highest concentration of total flavonols, and small amount of carotenoids. Further, orange petals of CH showed highest content of total anthocyanins, lowest content of total flavonols, and average content of total carotenoids. Correlation analysis demonstrated that there were many pigments influencing petal colors. Moreover, multiple linear regression indicated that pelargonidin 3,5-diglucoside, total anthocyanins and (9 Z )-violaxanthin were the major factors. In addition, this study showed that orange cultivar CH, pink cultivar PF and yellow cultivar YI can have great potential as a natural source for the extraction of pelargonidin 3- O -glucoside, kaempferol 3- O -rhamnoside, and (9 Z )-violaxanthin, respectively. These investigations would contribute toward understanding the mechanism on the development of flower colors and provide a theoretical basis for the breeding of rose with specific color.

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Flavonoids are secondary metabolites that play important roles in plant physiology. Despite numerous studies examined the effects of available carbon (C) or nitrogen (N) on flavonoid biosynthesis, the mechanism of C/N interactive effects on flavonoid metabolism is still unclear. In this study, we analyzed the composition of flavonoids and the expression levels of flavonoid-related genes in leaves and calli of crabapple (Malus sp.) cultivars with different leaf colors grown on media with different C/N ratios. Our results show that high C/N ratios induce anthocyanin pigmentation in leaves of the ever-red cultivar ‘Royalty’ and the spring-red cultivar ‘Prairifire,’ as well as in three types of calli derived from the ever-green cultivar ‘Spring Snow,’ but not in the leaves of the ever-green cultivar ‘Flame.’ This phenomenon therefore correlated with anthocyanin content in these different samples. In addition, high C/N ratios in the growth media resulted in an increase in the concentration of flavones and flavonols in the leaves of the three crabapple cultivars. The transcript levels of the general flavonoid pathway genes [from chalcone synthase (CHS) to uridine diphosphat-glucose: flavonoid 3-O-glycosyltransferase (UFGT) and flavonol synthase (FLS)] increased in response to high C/N ratios, and this in turn was correlated with the concentration of anthocyanins, flavones and flavonols in the leaves and calli. Expression of the late flavonoid/anthocyanin biosynthetic genes, anthocyanidin synthase (ANS), UFGT and FLS in particular, was more strongly influenced by C/N ratios than other structural genes, and the increased expression of the structural genes under high C/N ratios coincided with a coordinated increase in transcript levels of a MYB transcription factor, MYB10. These results are likely to be useful for future generation of plants with an optimized flavonoid/anthocyanin content or desirable organ coloration.