The effect of cold acclimation, deacclimation and reacclimation on metabolite profiles and freezing tolerance in winter wheat

Abstract

Global climate change will cause longer and warmer autumns, thus negatively affecting the quality of cold acclimation (CA) and reducing the freezing tolerance (FT) of winter wheat. Insufficient FT and fluctuating temperatures during winter can accelerate the deacclimation (DEA) process, whereas reacclimation (REA) is possible only while the vernalization requirement is unfulfilled. Six winter wheat genotypes with different winter hardiness profiles were used to evaluate the impact of constant low-temperature (2°C) and prolonged higher low-temperature (28 days at 10°C followed by 2°C until day 49) on shoot biomass and metabolite accumulation patterns in leaf and crown tissues throughout 49 days of CA, 7 days of DEA, and 14 days of REA. The FT of winter wheat was determined as LT30 values by conducting freezing tests after CA, DEA, and REA. Shoot biomass accumulation, projected as the green leaf area (GLA), was investigated by non-destructive RGB imaging-based phenotyping. Dynamics of carbohydrates, hexose phosphates, organic acids, proteins, and amino acids were assessed in leaf and crown tissues. Results revealed that exposure to higher low-temperature induced higher accumulation of shoot biomass and had a negative impact on FT of winter wheat. Prolonged higher low-temperature negatively affected the accumulation of soluble carbohydrates, protein content and amino acids, and had a positive effect on starch accumulation in leaf and crown tissues after CA, in comparison with the constant low-temperature treatment. DEA resulted in significantly reduced FT. Lower concentrations of glucose-6-phosphate, sucrose and proline, as well as higher concentrations of starch in leaves and crowns were found after DEA. The majority of the genotypes regained FT after REA; higher concentrations of glucose and malate in leaves, and sucrose in crown tissue were observed, whereas starch accumulation was decreased in both tissues. Negative correlations were determined between FT and starch concentration in leaves and crowns, while proline and proteins, accumulated in crowns, showed positive correlations with FT. This study broadens the knowledge regarding the effect of different low-temperature regimes on the dynamics of metabolite accumulation in winter wheat throughout CA, DEA, and REA, and its relationship to biomass accumulation and FT.

Comparative Analysis of Antioxidant Accumulation under Cold Acclimation, Deacclimation and Reacclimation in Winter Wheat

“…LT 30 (temperature, at which 30% of plants die) of six winter wheat genotypes, determined in our previous study [ 28 ], was used as an indicator of FT in winter wheat ( Figure S2 ). The significance of relationships between antioxidants, measured in leaf and crown tissue under two separate treatments, and FT throughout CA, DEA, and REA was determined ( Table 1 ).…”

“…If the above-ground section of a winter type crop suffers freezing damage, the survival of actively dividing meristematic cells within the crown region ensures the eventual regrowth of the plant [ 42 ]. Our earlier study showed higher levels of amino acids, soluble carbohydrates, hexose phosphates, citrate, and malate in the crowns, compared to the leaves [ 28 ]. Therefore, the concurrently elevated concentration of NAD + further substantiates the increased metabolic activity within the crowns during CA, DEA, and REA, with the ultimate purpose of protecting the meristematic cells from freezing damage.…”

“…Several recent studies have explored the negative effect of prolonged warmer CA temperature on photosynthetic activity and FT in forage grasses [ 24 , 25 ]. Moreover, our recently published research showed that prolonged higher low-temperature during CA results in significant metabolite profile changes, increased shoot biomass accumulation, and lower FT in winter wheat [ 28 ]. Decreased concentrations of antioxidant molecules after CA, DEA, and REA under the PHLT treatment in comparison to the CLT treatment were determined in this study.…”

“…The significantly increased ascorbate and glutathione levels under CLT, in comparison with the PHLT treatment, point to a strong response of redox homeostasis maintenance mechanisms. Moreover, the CLT treatment resulted in a higher FT of winter wheat after 49 days of CA [ 28 ]. Low temperature during CA promotes the activity of enzymes, related to the ascorbate-glutathione cycle, thus, improving ROS scavenging capacity and efficacy of photosynthesis in winter type crops [ 21 , 22 ].…”

“…Nevertheless, the processes of DEA and REA are not yet fully understood and require further investigation [ 16 , 27 ]. Our recent study showed that prolonged higher low temperature during CA significantly affects metabolite accumulation in winter wheat throughout CA, DEA, and REA [ 28 ]. However, there are insufficient studies on the dynamics of specific antioxidants in winter wheat throughout these stages of acclimation.…”