Developmental, molecular and genetic studies on grapevine response to temperature open breeding strategies for adaptation to warming

摘要

Aim: In the long term, genetic improvement is one of the major strategies to support sustainable wine production in a changing climate. Over the past 5 years, we have developed an interdisciplinary research program that aimed to: i) characterize the impact of temperature increase sensed by the entire plant or individual bunches on the development and functioning of the plant, ii) identify the physiological and molecular mechanisms regulating the response of vegetative and reproductive development to heat stress and iii) develop tools to map quantitative trait loci (QTLs) of plant and berry development in duly controlled, stable, and contrasting environmental conditions.Methods and results: Performing high-throughput genomic analyses combined with the use of innovative experimental designs (fruiting cuttings, microvines, single berry sampling) was critical to decipher the ecophysiological and molecular mechanisms involved in the vine response to high temperature.Conclusion: Warming promotes vegetative growth and hampers plant carbon balance, disturbing flower set and young berry development. High temperatures modify primary and secondary fruit metabolisms, desynchronizing sugar and organic acid metabolisms and delaying sugar and polyphenol accumulation during ripening. The study of day and night transcriptomic and proteomic signatures associated with heat highlighted key players of the response to temperature in the fruit.?Significance and impact of the study: Capitalizing on this knowledge, a new program is being proposed for the selection of cultivars limiting the accumulation of sugars in the berry while maintaining other qualitative compounds. Introduction Grapevine performance, including productivity and wine quality, is highly dependent on climate. High temperatures (T°) hamper carbon assimilation beyond a 30°C threshold (Greer and Weedon, 2012) and limit the yield by reducing the number of berries per vine (Rogiers et al., 2011). The composition of the wines also depends on thermal conditions (Spayd et al., 2002; Carbonneau et al., 2015) because T° increases sugar concentration in the berry at the expense of malic acid and secondary metabolites, leading to unbalanced wines.In Europe, wine production relies on close interactions between the variety, the environment and the viticultural practices. Climate change disrupts this balance; hence varietal adaptation is required to maintain traditional and qualitative viticulture in these regions (Torregrosa et al., 2011; Ollat et al., 2014 and 2015). In the long term, genetic improvement is one of the best strategies to support sustainable wine production systems under global warming. Various data confirm that genetic diversity within Vitis may be exploited for photosynthesis adaptation to temperature. For example, photosynthesis was not reduced at T°V. amurensis (Luo et al., 2011), and most wild species and hybrids between V. labrusca and V. vinifera also displayed a better heat tolerance than V. vinifera (Xu et al., 2014). Recently, Hochberg et al. (2015) observed metabolic adaptations resulting in greater growth inhibition of leaves at 35°C for cv. Syrah compared to Cabernet Sauvignon. Unfortunately, the lack of physiological and genetic knowledge on the mechanisms of adaptation of grapevine to T° limits the development of non-empirical breeding programs (Torregrosa et al., 2011), insofar as fruit quality, rather than carbon fixation, is considered as the principal selection target. In the last years, much effort has been carried out under vineyard conditions to identify regulatory mechanisms of primary and secondary metabolisms in berries (Deluc et al., 2008; Boss and Davies, 2009; Hichri et al., 2011; Lecourieux et al., 2014) and to identify transcriptomic changes induced by thermal stress applied to the berry (Pillet et al., 2012) or to the whole plant (Carbonell-Bejerano et al., 2013; Rienth et al., 2014b; Rienth et al., 2016).Despite these recent successes, we are far from a comprehensive picture of the regulatory mechanisms involved in the adaptation of the grape to heat stress. To date, there is no genetic tool or resource suitable to support breeding programs dealing with T° resilience. Over the last 5 years, we have developed a research program aiming to: i) characterize the effects of T° increase, applied at the whole plant or fruit level, on the development and functioning of the plant (organogenesis, biomass partitioning, metabolism of the berry), ii) identify the specific roles of carbon balance and molecular (transcription) mechanisms in regulating yield and quality development under high T° and iii) develop resources to study the genetic structure and stability of developmental and qualitative berry characters against thermal fluctuations.As with other perennial plants, the biological properties of grapevine cause methodological and experimental difficulties for studying the response to environmental changes and genetic diversity. Indeed, i