Xiaojun Xi

Resistance (R) genes were used to recognize pathogen effectors directly or indirectly in plants and activate defense signal pathways. Most of these R proteins consist of a nucleotide-binding adaptor (NB-ARC) domain, a leucine-rich repeat (LRR) domain and some also have a coiled-coil (CC) structure. In this study, we cloned a gene which encodes the CC-NB-ARC-LRR R protein (VqCNL) from Chinese wild grapevine Vitis. quinquangularis accession ‘Dan-2’. The transcript of VqCNL was obviously induced by inoculation with Plasmopara viticola and the salicylic acid (SA) treatment. The results of sequence analysis showed that the VqCNL gene contained a CC domain at the N-terminus, along with an NB-ARC and an LRR domain at the C-terminus. We transferred this gene into wildtype Arabidopsis and treated transgenic lines with Hyaloperonospora arabidopsidis (Hpa) and Pseudomonas syringae pv. tomato DC3000 (Pst DC3000); the results demonstrated that VqCNL promotes broad spectrum resistance to pathogens. Furthermore, qPCR analysis displayed that VqCNL may display a significant function in disease resistance via activating SA signaling pathways. In general, these conclusions primarily demonstrated that VqCNL enhances the disease resistance level in plants and contributes to future research of the R gene identification for grape breeding biotechnology.

Seedlessness is one of the highest valued agronomic traits in grapes. Embryo rescue in combination with marker-assisted selection have been widely applied in seedless grape breeding due to the advantages of increasing the ratio of seedless progenies and shortening the breeding cycle. However, the large number of deformed seedlings produced during embryo rescue and the lack of fast, efficient, and low-cost markers severely inhibit the process of seedless grape breeding. In this study, a total of eighty-three grape cultivars (51 seedless and 32 seeded) with diverse genetic backgrounds and two populations derived from embryo rescue, including 113 F1 hybrid individuals (60 seedless and 53 seeded), were utilized. We screened suitable media for converting malformed seedlings into normal seedlings, analyzed the association between the SNP in VviAGL11 and seeded/seedless phenotype, and developed a KASP marker related to stenospermocarpic seedlessness. Our results indicated that the transformation rate of 37.8% was obtained with MS medium supplemented with 2.0 mg·L⁻¹ of 6-BA and 0.5 mg·L⁻¹ of IBA. The presence of an A nucleotide allele at position chr18:26889437 was further confirmed to be fully associated with the stenospermocarpic seedlessness phenotype. The developed KASP marker, based on the verified SNP locus in VviAGL11, successfully distinguished the seedless and seeded genotypes with high precision and throughput. The results will contribute to enhancing the efficiency of embryo rescue and facilitate parent selection and early selection of seedless offspring with molecular markers, thereby accelerating the breeding process in seedless table grapes.

The adverse effects of high temperatures on fruit quality and yield have been reported in many studies of grapevines. MiRNAs play crucial roles in plant growth and development and also fulfill functions in regulating the high-temperature response. In this research, miRNA-based SSR (simple sequence repeat) polymorphisms were analyzed according to the grape genome sequence and then combined with polymerase chain reaction (PCR) amplification and Sanger sequencing methods to analyze the miRNA-SSR diversity of different heat-resistant grape varieties. A statistical analysis of SSR sequences showed that 391 and 12 SSRs were specific to pri-miRNA and pre-miRNA, respectively. In pri-miRNA containing SSR, hexa-nucleotide repeats were the most abundant (52.69%), followed by tetra-nucleotide (13.04%) and minimum penta-nucleotide (4.09%), which were also observed in pre-miRNA sequences. On the other hand, differences in heat resistance among grape varieties were observed. Based on the results of leaf Fv/Fm images, values and phenotypic changes under high-temperature stress, 20 heat-resistant (e.g., Niagara Rosada and Grand Noir) and 20 heat-sensitive (e.g., Shine Muscat and Jumeigui) grape varieties were identified. Further, PCR-Sanger sequencing was used to screen SSR differences in four thermos-tolerant and four thermos-sensitive grape varieties, and finally, eight SSR differential primers were found to be able to distinguish these varieties. Of these, four pairs of primers were selected for validation in 40 grape germplasm resources (20 thermo-tolerance and 20 thermo-sensitivity). The VMIRSSR167c3 highlights that the ratio of SSR (CT) repeat values greater than 17 in heat-resistant varieties was 90%. In conclusion, the VMIRSSR167c3 marker can accurately distinguish between heat-resistant and heat-sensitive grape varieties. The results provide a novel molecular marker for the genetic improvement of grape germplasm resources and will be beneficial to the breeding of heat-resistant varieties in the future.

Extreme temperatures limit grape production and sustainability. Dehydration-responsive element-binding (DREB) transcription factors affect plant responses to temperature related stresses. Therefore, we investigated the role of VvDREB2c, a DREB-coding gene, found in grapes (Vitis vinifera L.). Protein characterization revealed that VvDREB2c is localized to the nucleus and that its AP2/ERF domain contains three β-sheets and one α-helix sheet. Analysis of the VvDREB2c promoter region revealed the presence of light-, hormone-, and stress-related cis-acting elements. Furthermore, we observed that the heterologous expression of VvDREB2c in Arabidopsis improved growth, drought tolerance, and heat tolerance. Furthermore, it improved the leaf quantum yield of regulated energy dissipation [Y(NPQ)], elevated the activities of RuBisCO, and phosphoenolpyruvate carboxylase and reduced the quantum yield of non-regulated energy dissipation [Y(NO)] in plants exposed to high temperatures. VvDREB2c-overexpressing lines also specifically upregulated several photosynthesis-related genes (CSD2, HSP21, and MYB102). In addition, VvDREB2c-overexpressing lines reduced light damage and enhanced photoprotective ability by dissipating excess light energy and converting it into heat, which eventually improves tolerance to high temperature. The contents of abscisic acid, jasmonic acid, and salicylic acid and differentially expressed genes (DEGs) in the mitogen-activated protein kinase (MAPK) signaling pathway were affected by heat stress in VvDREB2c-overexpressing lines, which indicated that VvDREB2c positively regulates heat tolerance via a hormonal pathway in Arabidopsis. VvDREB2c promotes heat tolerance in Arabidopsis by exerting effects on photosynthesis, hormones, and growth conditions. This study may provide useful insights into the enrichment of the heat-tolerance pathways in plants.