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SSR (simple sequence repeat) DNA markers are widely used for genotype DNA identification, QTL mapping, and analyzing genetic biodiversity. However, SSRs in grapes are still in their early stages, with a few primer pairs accessible. With the whole-genome sequencing (WGS) of several grape varieties, characterization of grape SSR changed to be necessary not only to genomics but to also help SSR development and utility. Based on this, we identified the whole-genome SSR of nine grape cultivars (‘PN40024’, ‘Cabernet Sauvignon’, ‘Carménère’, ‘Chardonnay’, ‘Merlot’, ‘Riesling’, ‘Zinfandel’, ‘Shine Muscat’, and ‘Muscat Hamburg’) with whole-genome sequences released publicly and found that there are great differences in the distribution of SSR loci in different varieties. According to the difference in genome size, the number of SSRs ranged from 267,385 (Cabernet Sauvignon) to 627,429 (Carménère), the density of the SSR locus in the genome of nine cultivars was generally 1 per Kb. SSR motif distribution characteristic analysis of these grape cultivars showed that the distribution patterns among grape cultivars were conservative, mainly enriched in A/T. However, there are some differences in motif types (especially tetranucleotides, pentanucleotides, and hexanucleotides), quantity, total length, and average length in different varieties, which might be related to the size of the assembled genome or the specificity of variety domestication. The distribution characteristics of SSRs were revealed by whole-genome analysis of simple repeats of grape varieties. In this study, 32 pairs of primers with lower polymorphism have been screened, which provided an important research foundation for the development of molecular markers of grape variety identification and the construction of linkage maps of important agronomic traits for crop improvement.

Grapes are widely cultivated around the world and their quality has distinct regional characteristics. In this study, the qualitative characteristics of the ‘Cabernet Sauvignon’ grape variety in seven regions, from half-véraison to maturity, were analyzed comprehensively at physiological and transcriptional levels. The results indicated that the quality traits of ‘Cabernet Sauvignon’ grapes in different regions were significantly different with obvious regionality. Total phenols, anthocyanins, and titratable acids were the main factors of the regionality of berry quality, which were very sensitive to changes in the environment. It should be noted that the changes in titrating acids and total anthocyanin of berries vary greatly from half-véraison to maturity between regions. Moreover, the transcriptional analysis showed that the co-expressed genes between regions characterized the core transcriptome of berry development, while the unique genes of each region reflected the regionality of berries. The differentially expressed genes (DEGs) between half-véraison and maturity can be used to demonstrate that the environment of the regions could promote or inhibit gene expression. The functional enrichment suggested that these DEGs help to understand the interpretation of the plasticity of the quality composition of grapes according to the environment. Taken together, the information generated by this study could contribute to the development of viticultural practices aimed at making better use of native varieties for the development of wines with regional characteristics.

Abstract MicroRNA156 (miR156) is an important conserved miRNA family in plants. Recently, we revealed VvmiR156a could involve in the modulation of gibberellin (GA)‐mediated flower and berry development process of grapevine (Vitis vinifera L.). However, how to manipulate this process is unclear. For this, we used the GA‐induced grapevine parthenocarpy system to investigate the regulatory roles of VvmiR156a during this process. Here, we cloned the mature and precursor sequences of VvmiR156a in Wink grape and identified its potential target gene VvAGL80, which belongs to the MADS‐box gene family. Moreover, using RNA ligase‐mediated 5′ rapid amplification of cDNA ends (RLM‐RACE) and poly(A)polymerase‐mediated 3′ rapid amplification of cDNA (PPM‐RACE) technologies, it confirmed that VvAGL80 was the true target gene of VvmiR159a. Analysis of promoter cis‐elements and β‐glucuronidase (GUS) staining showed that both VvmiR156a and VvAGL80 contained GA‐responsive elements and could respond to GA treatments. Quantitative real‐time–polymerase chain reaction (qRT‐PCR) analysis exhibited the VvmiR156a and VvAGL80 showed opposite expression trends during grapevine flower and berry development, indicating that VvmiR156a negatively regulated the expression of VvAGL80 during this process. After GA treatment, the expression of miR156 in flowers was downregulated significantly, while that of VvAGL80 was upregulated, thereby accelerating grapevine flowering. Furthermore, GA treatment enhanced the negative regulation of VvmiR156a on VvAGL80 in seed, especially at the seed‐coat hardening stage, which was the key period of seed growth and development. Our findings enriched the knowledge of the regulatory mechanism of the miRNA‐mediated grapevine parthenocarpy process.

Different light qualities have various impacts on the formation of fruit quality. The present study explored the influence of different visible light spectra (red, green, blue, and white) on the formation of quality traits and their metabolic pathways in grape berries. We found that blue light and red light had different effects on the berries. Compared with white light, blue light significantly increased the anthocyanins (malvidin-3-O-glucoside and peonidin-3-O-glucoside), volatile substances (alcohols and phenols), and soluble sugars (glucose and fructose), reduced the organic acids (citric acid and malic acid), whereas red light achieved the opposite effect. Transcriptomics and metabolomics analyses revealed that 2707, 2547, 2145, and 2583 differentially expressed genes (DEGs) and (221, 19), (254, 22), (189, 17), and (234, 80) significantly changed metabolites (SCMs) were filtered in the dark vs. blue light, green light, red light, and white light, respectively. According to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, most of the DEGs identified were involved in photosynthesis and biosynthesis of flavonoids and flavonols. Using weighted gene co-expression network analysis (WGCNA) of 23410 highly expressed genes, two modules significantly related to anthocyanins and soluble sugars were screened out. The anthocyanins accumulation is significantly associated with increased expression of transcription factors (VvHY5, VvMYB90, VvMYB86) and anthocyanin structural genes (VvC4H, Vv4CL, VvCHS3, VvCHI1, VvCHI2, VvDFR), while significantly negatively correlated with VvPIF4. VvISA1, VvISA2, VvAMY1, VvCWINV, VvβGLU12, and VvFK12 were all related to starch and sucrose metabolism. These findings help elucidate the characteristics of different light qualities on the formation of plant traits and can inform the use of supplemental light in the field and after harvest to improve the overall quality of fruit.

Cuticular wax covering the surface of fleshy fruit is closely related to fruit glossiness, development, and post-harvest storage quality. However, the information about formation characteristics and molecular mechanisms of cuticular wax in grape berry is limited. In this study, crystal morphology, chemical composition, and gene expression of cuticular wax in grape berry were comprehensively investigated. Morphological analysis revealed high density of irregular lamellar crystal structures, which were correlated with the glaucous appearances of grape berry. Compositional analysis showed that the dominant wax compounds were triterpenoids, while the most diverse were alkanes. The amounts of triterpenoids declined sharply after véraison, while those of other compounds maintained nearly constant throughout the berry development. The amounts of each wax compounds varied among different cultivars and showed no correlation with berry skin colors. Moreover, the expression profiles of related genes were in accordance with the accumulation of wax compounds. Further investigation revealed the contribution of cuticular wax to the water preservation capacity during storage. These findings not only facilitate a better understanding of the characteristics of cuticular wax, but also shed light on the molecular basis of wax biosynthesis in grape.

Exogenous gibberellin (GA) was widely used to improve berry quality through inducing parthenocarpic seedless berries in grapes. We revealed that auxin response factors (ARFs), the key transcription factors in response to auxin, might respond to GA involving modulation of grape parthenocarpy. However, the underlying molecular mechanism in this process remains yet unclear. Here, a total of 19 VvARF members were identified in the ovaries during GA-induced grapes’ parthenocarpy. Interestingly, almost all members were GA-responsive factors, of which 9 could be classified in plant hormone signal transduction (KO04075) and involved in the tryptophan metabolic pathway (K14486). Moreover, VvARFs were predicted to have 310 interacted proteins involved in 19 KEGG pathways. Of them, 32 interacted proteins participated in the KO04075 pathway, including auxin (IAA), salicylic acid (SA), abscisic acid (ABA), cytokinin (CTK), and ethylene signaling pathways by responding to GA-mediated multi-hormone crosstalk. Further analysis demonstrated that VvARF4-2 might be the major factor in the modulation of GA-induced parthenocarpy via the crosstalk of IAA, CTK, SA, and ethylene signaling, followed by VvARF6-1 and VvARF9 involved in SA and ABA signaling pathways, respectively. Finally, we developed a VvARFs-mediated regulatory network by responding to GA-mediated multi-hormone crosstalk during grape parthenocarpy. Collectively, our findings provided novel insights into the regulatory network of VvARFs in GA-guided multi-hormone signaling to modulate grape parthenocarpy, which has great implications for the molecular breeding of high quality seedless grape berries.

Grape (Vitis vinifera L.) is one of the most widely cultivated fruit crops globally. Fruit cracking during fruit growth and development severely affects yield and quality, resulting in significant economic losses. Currently, calcium fertilizer application is used to prevent berry cracking. However, the mechanisms by which calcium fertilizer treatment reduces berry cracking are poorly understood. To explore this, transcriptomics and metabolomics were used to identify the differentially expressed genes (DEGs) and differentially abundant metabolites in V. vinifera ‘90-1’. We found that secondary metabolic pathways were enriched during the veraison and maturity stages, including the flavonoid biosynthesis pathway. Enrichment analysis indicated that most of the DEGs were enriched in the functional category of flavonoid biosynthesis. As secondary metabolites are largely antioxidants, the spraying of calcium fertilizers may improve the antioxidant capacity of the berries by regulating genes related to the flavonoid metabolism pathway, thus reducing the occurrence of berry cracking.