Polyols in grape berry: transport and metabolic adjustments as a physiological strategy for water-deficit stress tolerance in grapevine

Abstract

Polyols are important metabolites that often function as carbon and energy sources and/or osmoprotective solutes in some plants. In grapevine, and in the grape berry in particular, the molecular aspects of polyol transport and metabolism and their physiological relevance are virtually unknown to date. Here, the biochemical function of a grapevine fruit mesocarp polyol transporter (VvPLT1) was characterized after its heterologous expression in yeast. This H(+)-dependent plasma membrane carrier transports mannitol (K m=5.4mM) and sorbitol (K m=9.5mM) over a broad range of polyols and monosaccharides. Water-deficit stress triggered an increase in the expression of VvPLT1 at the fully mature stage, allowing increased polyol uptake into pulp cells. Plant polyol dehydrogenases are oxireductases that reversibly oxidize polyols into monosaccharides. Mannitol catabolism in grape cells (K m=30.1mM mannitol) and mature berry mesocarps (K m=79mM) was, like sorbitol dehydrogenase activity, strongly inhibited (50-75%) by water-deficit stress. Simultaneously, fructose reduction into polyols via mannitol and sorbitol dehydrogenases was stimulated, contributing to their higher intracellular concentrations in water-deficit stress. Accordingly, the concentrations of mannitol, sorbitol, galactinol, myo-inositol, and dulcitol were significantly higher in berry mesocarps from water-deficit-stressed Tempranillo grapevines. Metabolomic profiling of the berry pulp by GC-TOF-MS also revealed many other changes in its composition induced by water deficit. The impact of polyols on grape berry composition and plant response to water deficit stress, via modifications in polyol transport and metabolism, was analysed by integrating metabolomics with transcriptional analysis and biochemical approaches.

Grape berry position affects the diurnal dynamics of its metabolic profile

“…An important group of primary metabolites showing strong positive correlation included the amino acids beta‐alanine, glycine, leucine, proline, serine, threonine and valine, and the polyamine putrescine; the sugar alcohols erythritol, galactitol, and threitol; and the sugars galactinol, galactose, melibiose, turanose, and trehalose. This group consists, to a considerable extent, of metabolites associated with plant response to solar irradiance, heat, and other abiotic stresses (Alcazar et al, ; Conde et al, ; Garg et al, ; Obata & Fernie, ; Pillet et al, ; Reshef et al, ). Another group showing strong positive correlations included ribulose, glycolate, glycerate, and pyruvate, associated with photorespiration; iso‐ascorbate and its metabolite threonate; and indole‐3‐acetate and its precursor tryptophan.…”

Comparison of Salt Tolerance in Soja Based on Metabolomics of Seedling Roots

“…Gallic acid is a polyphenol with strong antioxidant and anti-free radical effects (Zhang et al, 2011). A large amount of hydroxylamine and putrescine were accumulated in wild soybean under neutral salt stress, which can reduce the damage caused by salt stress by eliminating excess ROS (Conde et al, 2015). Additionally, hydroxylamine is an intermediate product of plants using nitrate ions, and its accumulation indicates that wild soybean was able to use more ${\text{NO}}_3^{-}$, which indicates that the nitrogen metabolism of wild soybean increased.…”

Modern viticulture in southern Europe: Vulnerabilities and strategies for adaptation to water scarcity

“…Both sorbitol and mannitol limited size reduction of berry cells under drought (Conde et al, 2015). The authors suggested that grapevine cultivars which accumulate polyols as a tolerance mechanism to drought stress might have adaptive advantages under unfavourable growing conditions as they would require less water along the season to sustain yield and berry quality (Conde et al, 2015). It was also suggested that synthesis, transport and accumulation of sugar alcohols may work as bioindicators of plant health and acclimation and can be used as potential biomarkers in crop breeding (Merchant and Richter, 2011;Conde et al, 2015).…”

“…polyols) in the adaptation to drought in grapevine. The impact of polyols on grape berry composition and plant response to water deficit was described for the variety Tempranillo grown in greenhouse and field conditions (Conde et al, 2015). Both sorbitol and mannitol limited size reduction of berry cells under drought (Conde et al, 2015).…”

“…The impact of polyols on grape berry composition and plant response to water deficit was described for the variety Tempranillo grown in greenhouse and field conditions (Conde et al, 2015). Both sorbitol and mannitol limited size reduction of berry cells under drought (Conde et al, 2015). The authors suggested that grapevine cultivars which accumulate polyols as a tolerance mechanism to drought stress might have adaptive advantages under unfavourable growing conditions as they would require less water along the season to sustain yield and berry quality (Conde et al, 2015).…”