The rapid growth of the global population has resulted in a considerable increase in the demand for food crops. However, traditional crop breeding methods will not be able to satisfy the worldwide demand for food in the future. New gene-editing technologies, the most widely used of which is CRISPR/Cas9, may enable the rapid improvement of crop traits. Specifically, CRISPR/Cas9 genome-editing technology involves the use of a guide RNA and a Cas9 protein that can cleave the genome at specific loci. Due to its simplicity and efficiency, the CRISPR/Cas9 system has rapidly become the most widely used tool for editing animal and plant genomes. It is ideal for modifying the traits of many plants, including food crops, and for creating new germplasm materials. In this review, the development of the CRISPR/Cas9 system, the underlying mechanism, and examples of its use for editing genes in important crops are discussed. Furthermore, certain limitations of the CRISPR/Cas9 system and potential solutions are described. This article will provide researchers with important information regarding the use of CRISPR/Cas9 gene-editing technology for crop improvement, plant breeding, and gene functional analyses.

This research investigated the evolution of both monoterpenoids and expression profiles of related biosynthesis genes in the MEP pathway in seven different table grape varieties from veraison to maturity stage in two seasons, and the correlation was further evaluated between monoterpenoid accumulation and expression of these genes studied in these varieties. Results showed that linalool, trans-furan linalool oxide, geraniol, and cis-furan linalool oxide were the main compounds in the five Muscat varieties two seasons. ‘Zaomeiguixiang’ had the highest contents of geraniol and β-Citronellol. ‘Xiangfei’ had the most abundant of linalool and cis-furan linalool oxide, whereas the neutral varieties of ‘Moldova’ and ‘Christmas Rose’ had the least amount. Monoterpenoid volatiles have been grouped in three evolutionary patterns in the berry development of these varieties. ‘Zaomeiguixiang’ and ‘Xiangfei’ had distinct different pattern of terpenoids evolution profiles. Pearson’s correlation analysis showed that in the MEP pathway, the first biosynthesis gene VvDXS3 was significantly correlated to the accumulation of monoterpenoids, and appeared to be an important candidate gene for synthesis of the monoterpenoids.

Basic/helix-loop-helix (bHLH) transcription factors play critical roles in the regulation of plant secondary metabolism, but the molecular mechanisms involved in monoterpene synthesis by the grape bHLH family have not been systematically resolved. In this research, 12 VvbHLHs were detected in the grape genome, encoding 468–696 amino acids with molecular masses ranging from 52.5 to 77.5 kDa. Phylogenetic analyses showed that grapevine bHLH family members are closely related to dicotyledonous plants such as Pyrus bretschneideri and Malus domestica. These VvbHLHs were mainly localized in the nucleus, and their promoter regions were enriched for cis-acting elements linked to developmental stages and stress resistance. Spatio-temporal expression profiling indicated that VvbHLHs were significantly upregulated during fruit ripening, with the expression of VvbHLH9 (VvbHLH041) significantly and positively correlated with monoterpene accumulation. Subcellular localization analysis showed that VvbHLH9 was localized in the nucleus; and transient overexpression assays revealed that VvbHLH9 significantly activated monoterpene skeleton genes (VvDXS1 and VvDXS4) and synthase genes (VvTPS31, VvTPS32, and VvTPS35) to promote the accumulation of monoterpene metabolites, such as terpinolene, allo-ocimene, nerol, geraniol, cis-furan linalool oxide and linalool. Notably, VvbHLH9 lacked the typical bHLH-MYC_N structural domain, suggesting that it may affect the monoterpene metabolic network through a non-classical regulatory mechanism. The present study uncovers the modulatory function of grapevine bHLHs on the synthesis of monoterpene metabolites, providing new targets for grapevine fruit quality improvement and molecular breeding.

The selection of appropriate grapevine trellis systems is of great importance for regulating vine vigor, forming grape yield, improving fruit quality, and labor-saving field management in the North China Plain. The effects of two trellis systems on the viticultural characteristics and fruit quality of three table grape cultivars: RuiduHongyu (RDHY), RuiduXiangyu (RDXY), and Red Globe (RG) were investigated. The two trellis systems were: (i) T trellis, with shoots positioned horizontally and downwards; and (ii) V trellis, with shoots positioned upright with an inclined angle. Headspace-solid-phase micro-extraction combined with gas chromatography mass spectrometry (HS-SPME-GC-MS) was used to determine the compositions and contents of the monoterpenes in the fruit. The results showed that for RDHY and RG, the T trellis showed better shoot growth consistency. The sugar–acid ratios of RDHY in 2019 and RDXY in 2021 under the T trellis were significantly higher than those under the V trellis. In 2020 and 2021, RDHY showed significantly higher total anthocyanin, flavonoid, and proanthocyanidin concentrations under the T trellis. The total monoterpene content in RDHY berries was significantly higher under the T trellis. The aromatic profiles of RDHY and RDXY grapes were similar and were mainly composed of citrus, other floral, other fruit, and rose aromatic characteristics. Among them, the main aromatic characteristics varied greatly among the different treatments. In conclusion, the Eurasian table grape cultivars with muscat flavor showed a more moderate and controllable vine vigor, consistent shoot growth, better fruit quality and taste, and greater accumulation of polyphenolic compounds and monoterpenes under the T trellis system.