Jiancheng Zhang

Background: Fruit skin color is a key determinant of grape quality and market value, primarily governed by anthocyanin biosynthesis. Methods: In this study, we explored the molecular basis of skin color variation in the grape cultivar Zaoheibao and its bud mutant, which displays a striking shift from purple-black to yellow-green. Integrated metabolomic and transcriptomic analyses revealed extensive reprogramming of the flavonoid pathway in the mutant. Results: Metabolite profiling identified 233 differentially accumulated metabolites (DAMs), with a drastic reduction in anthocyanins, particularly cyanidin- and peonidin-derivatives, together with altered levels of flavonols and flavonoid glycosides. Transcriptome analysis detected 4036 differentially expressed genes (DEGs), with key anthocyanin biosynthetic genes (DFR, ANS, UFGT, GST) and MYB significantly downregulated. Multi-omics integration confirmed consistent enrichment of flavonoid-related pathways, while correlation network analysis highlighted strong associations between MYB regulators, structural genes, and anthocyanin-type metabolites. Conclusions: Collectively, these findings demonstrate that suppression of a MYB-centered regulatory module underlies the loss of pigmentation in the bud mutant, providing new insights into the molecular regulation of grape skin coloration and a theoretical basis for grape breeding and quality improvement.

Piriformospora indica is a beneficial endophytic fungus that promotes plant growth and root development by colonizing plant roots. In order to investigate whether P. indica could promote the growth of tissue-cultured Cerasus humilis seedlings, in this study, we co-cultivated P. indica colony segments (P+) and P. indica spore suspensions (P++) in the rooting medium, and plant biomass as well as chlorophyll and root hormone contents of ‘3-19-3’ tissue-cultured C. humilis seedlings were determined under P+, P++, and CK (without fungus inoculation) treatments. The results showed that above-ground biomass and chlorophyll content of P+-and P++-treated tissue-cultured seedlings were significantly increased, and root peroxidase (POD), indole-3-acetic-acid (IAA) content, and root activities were significantly enhanced, while jasmonic acid (JA) and 1-aminocyclopropane-1-carboxylic acid (ACC) contents were reduced. Moreover, the growth-promoting effects of P++ treatment were found to be stronger than those of P+ treatment. Our results confirmed that P. indica was able to promote the growth of tissue-cultured C. humilis seedlings and effectively promoted root development by regulating hormone content. Therefore, the application of P. indica in the production of C. humilis is promising, especially in the cultivation of elite varieties.

Numerous studies have shown that the endophytic fungus Piriformospora indica has a broad range of promoting effects on root development and plant growth in host plants. However, there are currently no reports on the application of this fungus on Cerasus humilis. This study first compared the colonization ability of P. indica on 11 C. humilis varieties and found that the colonization rate of this fungus on these varieties ranged from 90% to 100%, with the colonization rate of the varieties ‘09-01’ and ‘Nongda 7’ being as high as 100%. Subsequently, the effect of P. indica on root development and plant growth of C. humilis was investigated using cuttings of ‘09-01’ and ‘Nongda 7’ as materials. P. indica colonization was found to increase the biomass of ‘09-01’ and ‘Nongda 7’ plants; root activity, POD enzymes, and chlorophyll content were also significantly increased. In addition, indole-3-acetic acid (IAA) content in the roots of C. humilis plants increased after colonization, while jasmonic acid (JA) and 1-aminocyclopropane-1-car- boxylic acid (ACC) content decreased. In conclusion, it has been demonstrated that P. indica can promote the growth of C. humilis plants by accelerating biomass accumulation, promoting rooting, and enhancing the production of photosynthetic pigments, as well as regulating hormone synthesis.

Chinese dwarf cherry (Cerasus humilis) is a wild fruit tree and medicinal plant endemic to China. Its fruits are rich in various bioactive compounds, such as flavonoids and carotenoids, which contribute greatly to their high antioxidant capacity. In this study, the contents of bioactive substances (chlorophyll, carotenoids, ascorbic acid, anthocyanin, total flavonoids, and total phenols), antioxidant capacities, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonicacid) (ABTS⁺) scavenging ability, and ferric-reducing antioxidant power (FRAP)) in differentially pigmented C. humilis fruits of four varieties were determined and compared. The results revealed that anthocyanin, total flavonoids and total phenols were the three main components responsible for the antioxidant activity of C. humilis fruits. ‘Jinou No.1’ fruits with dark red peel and red flesh had the highest contents of anthocyanin, total flavonoids, and total phenols, as well as the highest antioxidant capacities; ‘Nongda No.5’ fruits with yellow-green peel and yellow flesh had the highest contents of carotenoids and chlorophyll, while ‘Nongda No.6’ fruit had the highest ascorbic acid content. To further reveal the molecular mechanism underlying differences in the accumulation of carotenoids and flavonoids among differentially pigmented C. humilis fruits, the expression patterns of structural genes involved in the biosynthesis of the two compounds were investigated. Correlation analysis results revealed that the content of carotenoids in C. humilis fruits was very significantly positively correlated with the expression of the ChCHYB, ChZEP, ChVDE, ChNSY, ChCCD1, ChCCD4, ChNCED1, and ChNCED5 genes (p < 0.01) and significantly negatively correlated with the expression of ChZDS (p < 0.05). The anthocyanin content was very significantly positively correlated with ChCHS, ChFLS, and ChUFGT expression (p < 0.01). The total flavonoid content was very significantly positively correlated with the expression of ChCHS, ChUFGT, and ChC4H (p < 0.01) and significantly positively correlated with ChFLS expression (p < 0.05). This study can provide a basis for understanding the differences in the accumulation of bioactive substances, and is helpful for clarifying the mechanisms underlying the accumulation of various carotenoids and flavonoids among differentially pigmented C. humilis fruits.

Carotenoid cleavage oxygenases (CCOs) are key enzymes that function in degrading carotenoids into a variety of apocarotenoids and some other compounds. In this study, we performed genome-wide identification and characterization analysis of CCO genes in Cerasus humilis. Totally, nine CCO genes could be classified into six subfamilies, including carotenoid cleavage dioxygenase 1 (CCD1), CCD4, CCD7, CCD8, CCD-like and nine-cis-epoxycarotenoid dioxygenase (NCED), were identified. Results of gene expression analysis showed that ChCCOs exhibited diverse expression patterns in different organs and in fruits at different ripening stages. To investigate the roles of ChCCOs in carotenoids degradation, enzyme assays of the ChCCD1 and ChCCD4 were performed in Escerichia coli BL21(DE3) that can accumulate lycopene, β-carotene and zeaxanthin. The prokaryotic expressed ChCCD1 resulted in obvious degradation of lycopene, β-carotene and zeaxanthin, but ChCCD4 did not show similar functions. To further determine the cleaved volatile apocarotenoids of these two proteins, headspace gas chromatography/mass spectrometer analysis was performed. Results showed that ChCCD1 could cleave lycopene at 5, 6 and 5′, 6′ positions to produce 6-methy-5-hepten-2-one and could catalyze β-carotene at 9, 10 and 9′, 10′ positions to generate β-ionone. Our study will be helpful for clarifying the roles of CCO genes especially ChCCD1 in regulating carotenoid degradation and apocarotenoid production in C. humilis.