Non-linear loss of suitable wine regions over Europe in response to increasing global warming.

Evaluating the potential climatic suitability for premium wine production is crucial for adaptation planning in Europe. While new wine regions may emerge out of the traditional boundaries, most of the present-day renowned winemaking regions may be threatened by climate change. Here, we analyse the future evolution of the geography of wine production over Europe, through the definition of a novel climatic suitability indicator, which is calculated over the projected grapevine phenological phases to account for their possible contractions under global warming. Our approach consists in coupling six different de-biased downscaled climate projections under two different scenarios of global warming with four phenological models for different grapevine varieties. The resulting suitability indicator is based on fuzzy logic and is calculated over three main components measuring (i) the timing of the fruit physiological maturity, (ii) the risk of water stress and (iii) the risk of pests and diseases. The results demonstrate that the level of global warming largely determines the distribution of future wine regions. For a global temperature increase limited to 2°C above the pre-industrial level, the suitable areas over the traditional regions are reduced by about 4%/°C rise, while for higher levels of global warming, the rate of this loss increases up to 17%/°C. This is compensated by a gradual emergence of new wine regions out of the traditional boundaries. Moreover, we show that reallocating better-suited grapevine varieties to warmer conditions may be a viable adaptation measure to cope with the projected suitability loss over the traditional regions. However, the effectiveness of this strategy appears to decrease as the level of global warming increases. Overall, these findings suggest the existence of a safe limit below 2°C of global warming for the European winemaking sector, while adaptation might become far more challenging beyond this threshold.

Evidence for Hydraulic Vulnerability Segmentation and Lack of Xylem Refilling under Tension.

The vascular system of grapevine (Vitis spp.) has been reported as being highly vulnerable, even though grapevine regularly experiences seasonal drought. Consequently, stomata would remain open below water potentials that would generate a high loss of stem hydraulic conductivity via xylem embolism. This situation would necessitate daily cycles of embolism repair to restore hydraulic function. However, a more parsimonious explanation is that some hydraulic techniques are prone to artifacts in species with long vessels, leading to the overestimation of vulnerability. The aim of this study was to provide an unbiased assessment of (1) the vulnerability to drought-induced embolism in perennial and annual organs and (2) the ability to refill embolized vessels in two Vitis species X-ray micro-computed tomography observations of intact plants indicated that both Vitis vinifera and Vitis riparia were relatively vulnerable, with the pressure inducing 50% loss of stem hydraulic conductivity = -1.7 and -1.3 MPa, respectively. In V. vinifera, both the stem and petiole had similar sigmoidal vulnerability curves but differed in pressure inducing 50% loss of hydraulic conductivity (-1.7 and -1 MPa for stem and petiole, respectively). Refilling was not observed as long as bulk xylem pressure remained negative (e.g. at the apical part of the plants; -0.11 ± 0.02 MPa) and change in percentage loss of conductivity was 0.02% ± 0.01%. However, positive xylem pressure was observed at the basal part of the plant (0.04 ± 0.01 MPa), leading to a recovery of conductance (change in percentage loss of conductivity = -0.24% ± 0.12%). Our findings provide evidence that grapevine is unable to repair embolized xylem vessels under negative pressure, but its hydraulic vulnerability segmentation provides significant protection of the perennial stem.

Ethylene receptors and related proteins in climacteric and non-climacteric fruits.

Fruits have been traditionally classified into two categories based on their capacity to produce and respond to ethylene during ripening. Fruits whose ripening is associated to a peak of ethylene production and a respiration burst are referred to as climacteric, while those that are not are referred to as non-climacteric. However, an increasing body of literature supports an important role for ethylene in the ripening of both climacteric and non-climacteric fruits. Genome and transcriptomic data have become available across a variety of fruits and we leverage these data to compare the structure and transcriptional regulation of the ethylene receptors and related proteins. Through the analysis of four economically important fruits, two climacteric (tomato and apple), and two non-climacteric (grape and citrus), this review compares the structure and transcriptional regulation of the ethylene receptors and related proteins in both types of fruit, establishing a basis for the annotation of ethylene-related genes. This analysis reveals two interesting differences between climacteric and non-climacteric fruit: i) a higher number of ETR genes are found in climacteric fruits, and ii) non-climacteric fruits are characterized by an earlier ETR expression peak relative to sugar accumulation.

Genome-wide analysis of cis-regulatory element structure and discovery of motif-driven gene co-expression networks in grapevine.

Coordinated transcriptional and metabolic reprogramming ensures a plant's continued growth and survival under adverse environmental conditions. Transcription factors (TFs) act to modulate gene expression through complex cis-regulatory element (CRE) interactions. Genome-wide analysis of known plant CREs was performed for all currently predicted protein-coding gene promoters in grapevine (Vitis vinifera L.). Many CREs such as abscisic acid (ABA)-responsive, drought-responsive, auxin-responsive, and evening elements, exhibit bona fide CRE properties such as strong position bias towards the transcription start site (TSS) and over-representation when compared with random promoters. Genes containing these CREs are enriched in a large repertoire of plant biological pathways. Large-scale transcriptome analyses also show that these CREs are highly implicated in grapevine development and stress response. Numerous CRE-driven modules in condition-specific gene co-expression networks (GCNs) were identified and many of these modules were highly enriched for plant biological functions. Several modules corroborate known roles of CREs in drought response, pathogen defense, cell wall metabolism, and fruit ripening, whereas others reveal novel functions in plants. Comparisons with Arabidopsis suggest a general conservation in promoter architecture, gene expression dynamics, and GCN structure across species. Systems analyses of CREs provide insights into the grapevine cis-regulatory code and establish a foundation for future genomic studies in grapevine.