Genetic manipulation of genes to upregulate specific branches of metabolic pathways is a method that is commonly used to improve fruit quality. However, the use of a single gene to impact several metabolic pathways is difficult. Here, we show that overexpression of the single gene SlMYB75 (SlMYB75-OE) is effective at improving multiple fruit quality traits. In these engineered fruits, the anthocyanin content reached 1.86 mg g−1 fresh weight at the red-ripe stage, and these SlMYB75-OE tomatoes displayed a series of physiological changes, including delayed ripening and increased ethylene production. In addition to anthocyanin, the total contents of phenolics, flavonoids and soluble solids in SlMYB75-OE fruits were enhanced by 2.6, 4, and 1.2 times, respectively, compared to those of wild-type (WT) fruits. Interestingly, a number of aroma volatiles, such as aldehyde, phenylpropanoid-derived and terpene volatiles, were significantly increased in SlMYB75-OE fruits, with some terpene volatiles showing more than 10 times higher levels than those in WT fruits. Consistent with the metabolic assessment, transcriptomic profiling indicated that the genes involved in the ethylene signaling, phenylpropanoid and isoprenoid pathways were greatly upregulated in SlMYB75-OE fruits. Yeast one-hybrid and transactivation assays revealed that SlMYB75 is able to directly bind to the MYBPLANT and MYBPZM cis-regulatory elements and to activate the promoters of the LOXC, AADC2 and TPS genes. The identification of SlMYB75 as a key regulator of fruit quality attributes through the transcriptional regulation of downstream genes involved in several metabolic pathways opens new avenues towards engineering fruits with a higher sensory and nutritional quality. A single gene has been identified in tomatoes that regulates multiple aspects of fruit quality, including levels of health-promoting anthocyanins, opening the door to engineering more nutritious and better-tasting tomatoes. Fruit breeders have long-manipulated genes to enhance traits like yield or disease resistance, but it is rare to find a single gene that can improve multiple aspects of fruit quality. In this study, Zhengguo Li at Chongquing University in China and colleagues show that over-expressing a transcription factor called SIMYB75 results in striking deep purple tomatoes enriched in anthrocyanins–antioxidants thought to be protective against various diseases - which tomatoes are usually devoid of. They also had higher levels of other health-promoting phytochemicals and enhanced production of aroma volatiles, which can influence the taste and flavor of fruit.

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SlMYB75, an MYB-type transcription factor, promotes anthocyanin accumulation and enhances volatile aroma production in tomato fruits.

The pivotal role of phytohormones during fruit development and ripening is considered established knowledge in plant biology. Perhaps less well-known is the growing body of evidence suggesting that organic acids play a key function in plant development and, in particular, in fruit development, maturation and ripening. Here, we critically review the connection between organic acids and the development of both climacteric and non-climacteric fruits. By analyzing the metabolic content of different fruits during their ontogenetic trajectory, we noticed that the content of organic acids in the early stages of fruit development is directly related to the supply of substrates for respiratory processes. Although different organic acid species can be found during fruit development in general, it appears that citrate and malate play major roles in this process, as they accumulate on a broad range of climacteric and non-climacteric fruits. We further highlight the functional significance of changes in organic acid profile in fruits due to either the manipulation of fruit-specific genes or the use of fruit-specific promoters. Despite the complexity behind the fluctuation in organic acid content during fruit development and ripening, we extend our understanding on the importance of organic acids on fruit metabolism and the need to further boost future research. We suggest that engineering organic acid metabolism could improve both qualitative and quantitative traits of crop fruits.

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Modifications in Organic Acid Profiles During Fruit Development and Ripening: Correlation or Causation?

Advances and Strategies for Controlling the Quality and Safety of Postharvest Fruit

Pepper (Capsicum annuum L.) fruit development is a complex and genetically programmed process. In this study, we conducted integrative analysis of transcriptome and proteome profiles during pepper ...

Integrative Transcriptome and Proteome Analysis Identifies Major Metabolic Pathways Involved in Pepper Fruit Development.

Transcriptome and proteome analyses on fruit pulp from the blood orange ‘Zaohong’ and the navel orange ‘twenty-first century’ were performed to study Citrus sinensis quality-related molecular changes during consecutive developmental periods, including young fruit, fruit-coloring onset and fruit delayed-harvest for two months, during which fruit remained on the trees. The time-course analysis for the fruit developmental periods indicated a complex, dynamic gene expression pattern, with the numbers of differentially expressed genes (DEGs) between the two cultivars being 119, 426 and 904 at the three continuous stages tested during fruit development and ripening. The continuous increase in total soluble solids over the course of fruit development was correlated with up-regulated sucrose phosphate synthase (SPS) transcription levels in both cultivars. Eleven differentially expressed genes between the two cultivars involved in the flavonoid pathway were significantly enriched at the onset of the fruit-coloring stage when anthocyanins were detected in blood orange alone. Among 5185 proteins, 65 up-regulated and 29 down-regulated proteins were co-expressed with their cognate mRNAs with significant transcription and protein expression levels when the fruits from the two cultivars were compared at the fruit delayed-harvest stage. Additionally, important genes participating in the γ-aminobutyric acid (GABA) shunt were activated in blood orange at two significant expression levels in the fruit delayed-harvest stage. Thus, organic acids in fruit continuously decreased during this stage. This research was the first to provide a more comprehensive understanding of the differentially expressed genes involved in anthocyanin, sucrose and citrate metabolism at the transcriptome and proteome levels in C. sinensis, especially during the fruit delayed-harvest stage.

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Comparative transcriptome and proteome profiling of two Citrus sinensis cultivars during fruit development and ripening

Reliable identification of individual chromosomes in eukaryotic species is the foundation for comparative chromosome synteny and evolutionary studies Unfortunately, chromosome identification has been a major challenge for plants with small chromosomes, such as the Citrus species We developed oligonucleotide-based chromosome painting probes for all nine chromosomes in Citrus maxima (Pummelo) We were able to identify all C maxima chromosomes in the same metaphase cells using multiple rounds of sequential fluorescence in situ hybridization with the painting probes We conducted comparative chromosome painting analysis in six different Citrus and related species We found that each painting probe hybridized to only a single chromosome in all other five species, suggesting that the six species have maintained a complete chromosomal synteny after more than 9 million years of divergence No interchromosomal rearrangement was identified in any species These results support the hypothesis that karyotypes of woody species are more stable than herbaceous plants because woody plants need a longer period to fix chromosome structural variants in natural populations

https://onlinelibrary.wiley.com/doi/epdf/10.1111/tpj.14894

Extraordinarily conserved chromosomal synteny of Citrus species revealed by chromosome-specific painting.

Grapevine virus A (GVA) has a quasispecies nature and is closely associated with the rugose-wood disease complex of Vitis vinifera L. In the different growing regions of table grape in Sichuan, southwest China, the incidence of GVA infection was found to be 16.9% by ELISA detection among 178 grape plants (Vitis vinifera L. × Vitis labrusca L.). The results of restriction fragment length polymorphism (RFLP) studies on the polymerase chain reaction (PCR) products of a total of 139 plasmids, cloned from 15 GVA isolates, suggested that the GVA isolates contained highly divergent variants. The plasmids from each GVA isolate that yielded different PCR-RFLP profiles were preferentially chosen for sequencing and were designated as variants. Furthermore, a phylogenetic study based on the analysis of the GVA coat protein genes and RNA silencing suppressor genes showed that the 40 variants obtained from the 15 GVA isolates represented 4 clades, designated as molecular groups I, II, III, and IV, respectively. The variant-specific PCR detection results indicated that the parts of the tested grape plants were specifically infected by mild variants.

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Genetic variability in Grapevine virus A from Vitis vinifera L. × Vitis labrusca L. in Sichuan, China

The differential expression profiling of the fruit-specific genes between a blood orange (Citrus sinensis cv. Tarocco) and a blonde orange (Citrus sinensis cv. twenty-first century navel orange) was investigated by fruit transcriptome sequencing. The relative expression folds for Cs6g17570 and Cs5g31400 were significantly greater in the “Tarocco” fruits, but Cs9g04810 transcripts had no significant differences between two accessions by digital gene expression profiling. In particular, R2R3-MYB, bHLH-type, and WD40-repeat proteins (encoded by Cs6g17570, Cs5g31400, and Cs9g04810) were transcription factors with each conserved domain and interacted in vitro and in vivo. Moreover, the dihydroflavonol 4-reductase (DFR), a key enzyme involved into anthocyanin biosynthesis pathway, had greater transcription levels in Tarocco fruit and also in the transgenic Arabidopsis thaliana by Cs6g17570 ectopic expression. Furthermore, Cs6g17570 and Cs5g31400 in Tarroco were upregulated by cold induction and then had similar expression profiling during cold storage. In conclusion, Cs6g17570, Cs5g31400, and Cs9g04810 encoding proteins might be involved into anthocyanin regulation in Tarocco by MYB-bHLH-WD40 complex as well as in other fruit trees. Studies on the anthocyanin regulatory mechanism will aid in development of new biotechnological tools for Citrus breeding.

Anthocyanin Biosynthesis Regulation in the Fruit of Citrus sinensis cv. Tarocco

The invention belongs to the field of strawberry seedling propagation, and particularly relates to a method for cultivating strawberry seedlings by a secondary detoxification method. The method is characterized by comprising the following steps: selecting meristem of shoot tips of creeping stems of strawberries, detoxifying for the first time, detoxifying the induced meristem of stems and tips of test-tube plantlets for the second time and the like. The method is used for detoxifying twice by utilizing meristem of shoot tips of creeping stems of strawberries and the induced meristem of stems and tips of test-tube plantlets, and a core stock plant is cultivated. The cultivated detoxified strawberry seedlings are strong in growth vigor, are improved in fruit set percentage, and are high in yield, excellent in quality and economic benefit.

Chen Keling

Papers

Comparative transcriptome and proteome profiling of two Citrus sinensis cultivars during fruit development and ripening

Extraordinarily conserved chromosomal synteny of Citrus species revealed by chromosome-specific painting.

Genetic variability in Grapevine virus A from Vitis vinifera L. × Vitis labrusca L. in Sichuan, China

Anthocyanin Biosynthesis Regulation in the Fruit of Citrus sinensis cv. Tarocco

Method for cultivating strawberry seedlings by secondary detoxification method