Lijun Wang

Stilbenes are inducible plant specialized metabolites, best exemplified by resveratrol, a phytoalexin that links environmental perception, defense responses, and phenylpropanoid resource allocation. Stilbene accumulation may be controlled at 3 mechanistically distinct levels: signaling cascades that connect environmental and hormonal cues to kinase-dependent activation; combinatorial transcriptional control, which governs the response amplitude and specificity of stilbene synthase (STS) genes; and branch selection together with product disposition, which shapes the final metabolic output. Within this framework, MYB and WRKY proteins serve as major transcriptional nodes as activators or repressors, yet their regulatory effects depend on combinatorial interactions, phosphorylation events, competitive promoter occupancy, and metabolic context. We explicitly distinguish strongly supported mechanisms, defined by genetic perturbation, direct target validation, and metabolite quantification from emerging models built primarily on transient expression assays or co-expression correlations. This distinction avoids equating regulators supported by disparate levels of experimental evidence, identifies the most robust principles governing pathway control, and highlights experiments required to turn descriptive associations into causal mechanistic models. We further highlight conceptual insights extending beyond stilbene metabolism to inducible specialized metabolism in general, and outline research priorities for comparative genetics, cell-resolved analysis, and predictive pathway engineering.

Grapevines (Vitis vinifera) are economically important crops increasingly threatened by climate change–induced heat stress. Wild species such as V. davidii display markedly higher thermotolerance than the widely cultivated V. vinifera. Our previous research indicated that heat shock transcription factor A2 (VdHSFA2) from V. davidii confers higher thermotolerance than VvHSFA2 from V. vinifera, with HSFB2a as a potential downstream target of HSFA2. However, the precise mechanism by which HSFA2 modulates thermotolerance is not fully understood. Here, we demonstrated that HSFA2 directly activates HSFB2a, which in turn represses the transcription factor WRKY10. DAP-seq, yeast one-hybrid, and electrophoretic mobility shift assays confirmed HSFB2a binds to the WRKY10 promoter, and functional assays indicated that WRKY10 diminishes thermotolerance by repressing L-ascorbate peroxidase 3 (APX3) and 18.1 kDa class I heat shock protein (HSP18.1). However, HSFA2 does not bind to the WRKY10 promoter, and HSFA2, HSFB2a, and WRKY10 do not physically interact with one another. Transient expression in grapevine plants and stable transformation of suspension cells demonstrated that HSFB2a enhances, whereas WRKY10 reduces, thermotolerance-associated physiological performance. Notably, the V. davidii HSFB2a promoter is more active than that of V. vinifera HSFB2a, potentially contributing to species-level differences in thermotolerance. Our findings reveal the HSFA2-HSFB2a-WRKY10 transcriptional cascade modulating heat stress responses in grapevine, providing molecular targets for breeding heat-resilient cultivars.

With the increasing challenges posed by global warming and climate change, heat stress has become a significant threat to the sustainable production of grapevines. However, the genetic basis of grapevine thermotolerance remains poorly understood. Here, we combine genome-wide association study with transcriptomic profiling to identify TTC4 (thermotolerance on chromosome 4), a gene encoding a WRKY transcription factor, as a key determinant of thermotolerance in grapevine. TTC4 directly activates two thermotolerance-related genes, HSP18.1 and APX3. We also identify a heat-suppressed repressor SPL13 (SQUAMOSA-promoter binding protein-like 13) that cannot bind to the GTAT element (TTC4^T(7631)) in intron 2 of TTC4, but can bind to the natural variant, GTAC (TTC4^C(7631)). Grapevine accessions with TTC4^C/C(7631) genotype exhibit significantly lower thermotolerance compared to those with the TTC4^T/T(7631) and TTC4^C/T(7631) genotypes. This fine-tuned regulation contributes to thermotolerance divergence among grapevine populations. The TTC4^T(7631) haplotype holds significant potential as a genetic resource for breeding thermotolerant grapevine varieties.

Temperature plays a pivotal role in modulating growth, development, and distribution of plants. Grapevine (Vitis spp.), a perennial plant, must withstand changes in both low and high temperatures due to its sessile nature. However, the extensively cultivated Vitis vinifera L. is sensitive to both cold and heat, and cannot withstand extremely low and high temperatures. In contrast, certain wild germplasms such as Vitis amurensis, Vitis riparia, and Vitis davidii demonstrate excellent tolerance to cold and heat stressors. In recent years, substantial advancements have occurred in the understanding of grapevine resistance, focusing extensively on physiological mechanisms, metabolic pathways, and molecular regulatory processes. However, our understanding of the mechanisms underlying grapevine cold and heat resistance remains insufficient. This review aims to summarize the main progress in research on cold and heat tolerance in grapevines, while also addressing existing gaps and identifying relevant topics for further investigation.

Anthocyanins are essential for the quality of perennial horticultural crops, such as grapes. In grapes, ELONGATED HYPOCOTYL 5 (HY5) and MYBA1 are two critical transcription factors that regulate anthocyanin biosynthesis. Our previous work has shown that Vitis vinifera B-box protein 44 (VvBBX44) inhibits anthocyanin synthesis and represses VvHY5 expression in grape calli. However, the regulatory mechanism underlying this regulation was unclear. In this study, we found that loss of VvBBX44 function resulted in increased anthocyanin accumulation in grapevine callus. VvBBX44 directly represses VvMYBA1, which activates VvBBX44. VvMYBA1, but not VvBBX44, directly modulates the expression of grape UDP flavonoid 3-O-glucosyltransferase (VvUFGT). We demonstrated that VvBBX44 represses the transcriptional activation of VvUFGT and VvBBX44 induced by VvMYBA1. However, VvBBX44 and VvMYBA1 did not physically interact in yeast. The application of exogenous anthocyanin stimulated VvBBX44 expression in grapevine suspension cells and tobacco leaves. These findings suggest that VvBBX44 and VvMYBA1 form a transcriptional feedback loop to prevent overaccumulation of anthocyanin and reduce metabolic costs. Our work sheds light on the complex regulatory network that controls anthocyanin biosynthesis in grapevine.

The quality of planting materials is the foundation for productivity, longevity, and berry quality of perennial grapevines with a long lifespan. Manipulating the nursery light spectrum may speed up the production of healthy and high-quality planting vines but the underlying mechanisms remain elusive. Herein, the effects of different monochromatic lights (green, blue, and red) on grapevine growth, leaf photosynthesis, whole-plant carbon allocation, and transcriptome reprograming were investigated with white light as control. Results showed that blue and red lights were favorable for plantlet growth in comparison with white light. Blue light repressed excessive growth, significantly increased the maximum net photosynthetic rate (Pn) of leaves by 39.58% and leaf specific weight by 38.29%. Red light increased the dry weight of the stem by 53.60%, the starch content of the leaf by 53.63%, and the sucrose content of the stem by 230%. Green light reduced all photosynthetic indexes of the grape plantlet. Photosynthetic photon flux density (PPFD)/Ci–Pn curves indicated that blue light affected photosynthetic rate depending on the light intensity and CO₂ concentration. RNA-seq analysis of different organs (leaf, stem, and root) revealed a systematic transcriptome remodeling and VvCOP1 (CONSTITUTIVELY PHOTOMORPHOGENIC 1), VvHY5 (ELONGATED HYPOCOTYL5), VvHYH (HY5 HOMOLOG), VvELIP (early light-induced protein) and VvPIF3 (PHYTOCHROME INTERACTING FACTOR 3) may play important roles in this shoot-to-root signaling. Furthermore, the correlation network between differential expression genes and physiological traits indicated that VvpsbS (photosystem II subunit S), Vvpsb28 (photosystem II subunit 28), VvHYH, VvSUS4 (sucrose synthase 4), and VvALDA (fructose-bisphosphate aldolase) were pertinent candidate genes in responses to different light qualities. Our results provide a foundation for optimizing the light recipe of grape plantlets and strengthen the understanding of light signaling and carbon metabolism under different monochromatic lights.

Grape is a widely cultivated crop with high economic value. Most cultivars derived from mild or cooler climates may not withstand increasing heat stress. Therefore, dissecting the mechanisms of heat tolerance in grapes is of particular significance. Here, we performed comparative transcriptome analysis of Vitis davidii ‘Tangwei’ (heat tolerant) and Vitis vinifera ‘Jingxiu’ (heat sensitive) grapevines after exposure to 25°C, 40°C, or 45°C for 2 h. More differentially expressed genes (DEGs) were detected in ‘Tangwei’ than in ‘Jingxiu’ in response to heat stress, and the number of DEGs increased with increasing treatment temperatures. We identified a class B Heat Shock Factor, HSFB1, which was significantly upregulated in ‘Tangwei’, but not in ‘Jingxiu’, at high temperature. VdHSFB1 from ‘Tangwei’ and VvHSFB1 from ‘Jingxiu’ differ only one amino acid, and both showed similar transcriptional repression activities. Overexpression and RNA interference of HSFB1 in grape indicated that HSFB1 positively regulates the heat tolerance. Moreover, the heat tolerance of HSFB1-overexpressing plants was positively correlated to HSFB1 expression level. The activity of the VdHSFB1 promoter is higher than that of VvHSFB1 under both normal and high temperatures. Promoter analysis showed that more TATA-box and AT~TATA-box cis-elements are present in the VdHSFB1 promoter than the VvHSFB1 promoter. The promoter sequence variations between VdHSFB1 and VvHSFB1 likely determine the HSFB1 expression levels that influence heat tolerance of the two grape germplasms with contrasting thermotolerance. Collectively, we validated the role of HSFB1 in heat tolerance, and the knowledge gained will advance our ability to breed heat-tolerant grape cultivars.

The tree-fruit industry is extremely vulnerable to climate change. We are already seeing that global warming is increasing the incidence and severity of extreme high temperature weather. This means fruit trees are more often experiencing damage due to high temperatures which upsets their growth and development. Heat stress disturbs not only cellular homeostasis but also a fruit’s normal physiological and metabolic processes. Together these effects are proving to be a major adverse factor that compromise both fruit yield and fruit quality. Hence, a better understanding of the response mechanisms of fruit trees to repeated incidences of high temperature is hugely significant for the sustainability of tree-fruit production, justifying this research as one of the main focuses of fruit biology today. In this review, we summarize the physiological and molecular mechanisms through which high temperatures affect tree-fruit species and discuss possible new directions for future study.