Grapevine Responses to Heat Stress and Global Warming

Abstract

The potential effects of the forthcoming climate change include the rising of the average annual temperature and the accumulation of extreme weather events, like frequent and severe heatwaves, a phenomenon known as global warming. Temperature is an important environmental factor affecting almost all aspects of growth and development in plants. The grapevine (Vitis spp.) is quite sensitive to extreme temperatures. Over the current century, temperatures are projected to continue rising with negative impacts on viticulture. These consequences range from short-term effects on wine quality to long-term issues such as the suitability of certain varieties and the sustainability of viticulture in traditional wine regions. Many viticultural zones, particularly in Mediterranean climate regions, may not be suitable for growing winegrapes in the near future unless we develop heat-stress-adapted genotypes or identify and exploit stress-tolerant germplasm. Grapevines, like other plants, have developed strategies to maintain homeostasis and cope with high-temperature stress. These mechanisms include physiological adaptations and activation of signaling pathways and gene regulatory networks governing heat stress response and acquisition of thermotolerance. Here, we review the major impacts of global warming on grape phenology and viticulture and focus on the physiological and molecular responses of the grapevine to heat stress.

Keywords: Vitis; global warming; grapevine; heat stress; molecular responses; phenology; viticulture; wine.

Figure 1

Phenological shifts based on average onset dates for bud break, flowering, veraison and harvest of four grapevine varieties (“Pinot Gris”, “Pinot Noir”, “Riesling” and “Muller Thurgau”) grown in Hainfeld (Southwest Germany) from 1975 to 2015. Based on data from a previously published study [18].

Figure 2

(a) Chloroplast function under optimum temperature; (b) disturbances of major biochemical processes of chloroplasts in grapevine leaves under heat stress. The activity of Rubisco activase is extremely heat-sensitive, and its inhibition blocks the activation of Rubisco and downstream reactions.

Figure 3

Photosystem II (PSII) is considered the most sensitive physiological system of the grapevine to heat stress. Extreme high temperatures cause dissociation to the oxygen-evolving complex (OEC), which results in the inhibition of the electron transportation from the OEC to the acceptor side of PSII. D1 and D2 are susceptible to heat inactivation, and under high-temperature regimes, chlorophyll degradation occurs due to the increased activities of peroxidase and chlorophyllase.

Figure 4

Summary of the effects of high-temperature stress on grape berry metabolism.

Figure 5

A simplified scheme for the heat-stress signal transduction pathway focusing on major regulatory components and stress-responsive genes identified so far in the grapevine. Protein stress sensor molecules perceive heat-stress signals and transmit them through secondary messengers initiating transcription networks to provide stress tolerance. Abbreviations: IP3, inositol 1,4,5-trisphosphate; cGMP, 3′,5′-cyclic guanosine monophosphate; CDPKs, calcium-dependent protein kinases; MAPKs, mitogen-activated protein kinases; HSPs, heat shock proteins; HSFs, heat stress transcription factors; APX, ascorbate peroxidase; DHAR, dehydroascorbate reductase; ROS, reactive oxygen species.