Deacclimation Treatment Research Articles

Vessel development in compound buds of interspecific hybrid grape induced by artificial deacclimation treatments.

Grape compound buds adapt to subfreezing temperatures in winter by supercooling, but the supercooling ability is thought to be lost upon formation of xylem connections between canes and buds. It was reported that compound buds of the Vitis vinifera variety 'Chardonnay' lack xylem cells in mid-winter, and that vessels differentiate during deacclimation. However, the pattern of vessel formation in compound buds may differ in cold-hardy Vitis species and interspecific hybrid varieties grown in colder regions. We investigated vessel formation in compound buds of the interspecific hybrid variety 'Yamasachi', which were harvested in mid-winter, during artificial deacclimation treatments. Before these treatments, 'Yamasachi' buds had a high supercooling ability (approx. -30°C) and contained cells with characteristics of vessel elements, that is, secondary wall thickening and lignification, at the basal parts. However, the cells still contained organelles and did not have a hydraulic conductivity function. Xylem continuity between the canes and buds was established from day 7 of deacclimation at 20°C. The different pattern of seasonal vessel formation in compound buds of 'Yamasachi' from that of V. vinifera may reflect the rapid development traits of Vitis species growing in cold regions with short growing seasons.

Deacclimation and reacclimation of apple (Malus × domestica Borkh.), blackcurrant (Ribes nigrum L.) and raspberry (Rubus idaeus L.) shoots and buds under controlled conditions

In the future climate scenario the transient warm spells during winter are predicted to become more frequent and potentially increase the risk of frost damage in perennial horticultural crops. The aim of our study was to examine, whether apple (Malus × domestica Borkh.), blackcurrant (Ribes nigrum L.), and raspberry (Rubus idaeus L.) cultivars differing in winter hardiness have a different susceptibility to deacclimation during a warm spell and the ability to reacclimate in response to a subsequent cold period. Shoot samples were collected from commercial orchards in Finland on Feb. 6, 2019. Samples were subjected to a deacclimation treatment (+5°C, 4 d) followed by a reacclimation treatment (-7°C, 7 d). Controlled freezing tests were conducted immediately after sampling, and at the end of deacclimation and reacclimation treatments to determine frost hardiness (FH). FH was most stable in those cultivars that are known to be hardy in the Finnish climate conditions, i.e. ‘Pirja’ apple, ‘Mikael’ and ‘Öjebyn’ blackcurrants, and ‘Maurin Makea’ raspberry. Buds were consistently less hardy than shoots, the difference being largest in blackcurrant, 25°C. The buds of all cultivars, except ‘Pirja’ apple, deacclimated during four days at +5°C, but only ‘Ben Tron’ blackcurrant buds were able to reacclimate. The depth of dormancy was determined by forcing the shoot samples in a greenhouse to examine the relationship of the FH stability to the dormancy status in the cultivars. Sixty to 95 % of apple, 98 to 100 % of blackcurrant, and 55 to 67 % of raspberry buds broke during five weeks in forcing. Only the apple cultivars exhibited cultivar differences in the dormancy status in the beginning of February. ‘Pirja’ despite having the most stable FH of the apple cultivars, showed the most complete and fastest bud break in forcing. Consequently, the susceptibility to deacclimation during a warm spell and the ability to reacclimate at subsequent low temperatures were not related to the status of dormancy in these cultivars.

Genome-Wide Association Studies and Transcriptome Changes during Acclimation and Deacclimation in Divergent Brassica napus Varieties.

Information concerning genes and signals regulating cold acclimation processes in plants is abundant; however, less is known about genes and signals regulating the deacclimation process. A population of primarily winter B. napus varieties was used to conduct a genome-wide association study and to compare the transcriptomes from two winter B. napus varieties showing time-dependent differences in response to cold acclimation and deacclimation treatments. These studies helped to identify loci, candidate genes, and signaling processes impacting deacclimation in B. napus. GWAS identified polymorphisms at five different loci associated with freezing tolerance following deacclimation. Local linkage decay rates near these polymorphisms identified 38 possible candidate genes. Several of these genes have been reported as differentially regulated by cold stress in arabidopsis (Arabidopsis thaliana), including a calcium-binding EF-hand family protein (encoded by BnaCnng10250D) that was also differentially expressed during deacclimation in this study. Thousands of other genes differentially expressed during the acclimation and deacclimation treatments implicated processes involving oxidative stress, photosynthesis, light-regulated diurnal responses, and growth regulation. Generally, responses observed during acclimation were reversed within one week of deacclimation. The primary differences between the two winter B. napus varieties with differential deacclimation responses involved protection from oxidative stress and the ability to maintain photosynthesis.

Temporal proteomics of Arabidopsis plasma membrane during cold- and de-acclimation

Freezing stress is one of the most important limiting factors of plant survival. Plants have developed a freezing adaptation mechanism upon sensing low temperatures (cold acclimation). Compositional changes in the plasma membrane, one of the initial sites of freezing injury, is prerequisite of achieving cold acclimation and have been investigated in several plant species. Conversely, the cold dehardening process at elevated temperatures (de-acclimation) has not yet been fully characterized and few studies have addressed the importance of the plasma membrane in the de-acclimation process. In the present study, we conducted shotgun proteomics with label-free semiquantification on plasma membrane fractions of Arabidopsis leaves during cold acclimation and de-acclimation. We consequently obtained a list of 873 proteins with significantly changed proteins in response to the two processes. Although the cold-acclimation-responsive proteins were globally returned to non-acclimated levels by de-acclimation, several representative cold-acclimation-responsive proteins tended to remain at higher abundance during de-acclimation process. Taken together, our results suggest plants deharden right after cold acclimation to restart growth and development but some cold-acclimation-induced changes of the plasma membrane may be maintained under de-acclimation to cope with the threat of sudden freezing during de-acclimation process. SignificancePlant freezing tolerance can be enhanced by low temperature treatment (cold acclimation), while elevated temperatures right after cold acclimation can result in the dehardening of freezing tolerance (de-acclimation). However, the de-acclimation process, particularly its relevance to the plasma membrane as the primary site of freezing injury, has not been elucidated. In the present study, a comprehensive proteomic analysis of the plasma membrane during cold acclimation and de-acclimation was carried out as a first step to elucidating how plants respond to rising temperatures. Cold acclimation induced a number of proteomic changes as reported in previous studies, but most proteins, in general, immediately returned to NA levels during de-acclimation treatment for two days. However, the abundances of stress-related proteins (e.g. LTI29, COR78 and TIL) decreased slower than other functional proteins during de-acclimation. Therefore, plants harden during cold acclimation by aborting growth and development and accumulating stress-responsive proteins but seem to deharden quickly under subsequent elevated temperature to resume these processes while guarding against the threat of sudden temperature drops.

Bark cells and xylem cells in Japanese white birch twigs initiate deacclimation at different temperatures

Appropriate timing of cold deacclimation is an important component of winter survival of perennial plants, such as trees, in temperate and boreal zones. Recently, concerns about predicted global climate change disturbing deacclimation timing have been increasing. The relationship between ambient temperatures and the manner by which cells' freezing resistance changes is essential for forecasting the timing of deacclimation. In this study, Japanese white birch twigs that underwent deacclimation treatment at a constant temperature of −2, 0, 4, 10, or 20 °C were separated into bark in which cells adapted to subfreezing temperatures by extracellular freezing and xylem in which cells adapted to subfreezing temperatures by deep supercooling, and the freezing resistance of cells in each tissue type was investigated by measuring percentage electrolyte leakage. Birch cells deacclimated in a different manner according to tissue type. Within 7 days under deacclimation treatment, xylem cells decreased their freezing resistance significantly at a high subfreezing temperature (−2 °C). In contrast, bark cells required a temperature of 10 or 20 °C for a detectable decrease in freezing resistance to occur within the same period. At a temperature lower than 0 °C, bark cells did not decrease their freezing resistance, even after 28 days of treatment. The difference in freezing behavior of cells might involve the difference in how deacclimation occurred in bark and xylem cells.

Metabolic Changes During Cold Acclimation and Deacclimation in Five Bermudagrass Varieties. I. Proline, Total Amino Acid, Protein, and Dehydrin Expression

ABSTRACTBermudagrasses (Cynodon spp.) grown in the U.S. transition zone and other regions with a similar climate undergo cold acclimation in fall and deacclimation in spring. Physiological mechanisms of cold acclimation and deacclimation are not well documented or understood. This study investigated changes in quality, photochemical efficiency, N metabolite (proline, total amino acid [AA], and protein) content, and dehydrin expression during cold acclimation and deacclimation in five bermudagrass entries. One ecotype (GA‐851) and four cultivars (Patriot, Riviera, Tifway, and Princess‐77) were subjected to cold acclimation at 8/4°C (day/night; 10‐h photoperiod) for 28 d and then deacclimation at 10/5, 21/7, 23/8, and 26/14°C sequentially (11‐h photoperiod) for either 3 wk (standard deacclimation) or 1 wk (fast deacclimation treatment) at each temperature. In response to cold acclimation, turfgrass quality and photochemical efficiency declined, while proline, AA, protein, and abundance of 25 kDa dehydrin increased. Patriot and Riviera had higher levels of stolon proline, AA, protein, and abundance of 25 kDa dehydrin relative to Princess‐77 at the end of cold acclimation. Significant deacclimation occurred as temperature changed from 21/7 to 23/8°C. Patriot, GA‐851, and Tifway had greater turfgrass quality ratings and photochemical efficiency and also higher levels of N metabolites relative to Princess‐77 and Riviera during deacclimation. A similar response was observed with fast deacclimation treatment. The results suggest that selection and use of entries with higher levels of N metabolites during cold acclimation and deacclimation could improve bermudagrass persistence and spring green‐up in transition zone climates.

Metabolic Changes During Cold Acclimation and Deacclimation in Five Bermudagrass Varieties: II. Cytokinin and Abscisic Acid Metabolism

ABSTRACTBermudagrasses (Cynodon spp.) grown in the U.S. transition zone and other regions with a similar climate undergo cold acclimation in fall and deacclimation in spring. Physiological mechanisms of cold acclimation and deacclimation associated with freezing tolerance and spring green‐up are not well documented. This study investigated changes in cytokinin (t‐zeatin riboside [t‐ZR]) and abscisic acid (ABA) during cold acclimation and deacclimation in five bermudagrass entries in growth chambers. One ecotype (GA‐851) and four cultivars (Patriot, Riviera, Tifway, and Princess‐77) were subjected to cold acclimation at 8/4°C (day/night) for 28 d and then deacclimation at 10/5, 21/7, 23/8, and 26/14°C for either 3 wk (standard deacclimation) or 1 wk (fast deacclimation treatment). Stolon t‐ZR content declined while ABA content increased during cold acclimation. Patriot and Riviera had higher levels of stolon ABA relative to Princess‐77 at the end of cold acclimation. During deacclimation, t‐ZR increased as the temperature increased to 26/14°C, while ABA declined as the temperature increased from 10/5 to 21/7°C. Patriot, GA‐851, and Tifway had higher levels of t‐ZR relative to Riviera and Princess‐77. Abscisic acid level during cold acclimation may be associated with freezing tolerance, while cytokinin level during deacclimation may be associated with rate of spring green‐up of bermudagrass. The results suggest that selection and use of entries with higher levels of ABA during cold acclimation and cytokinin during deacclimation could improve bermudagrass winter survival and spring green‐up in transition zone climates.

Validation of reference genes for real-time qRT-PCR normalization during cold acclimation in Eucalyptus globulus

During the last few years, many studies have directed their efforts at elucidating the molecular mechanisms that regulate plant response to cold stress using gene expression analysis. Quantitative real-time qRT-PCR has great advantages compared to traditional transcriptional detection methods due to its high sensibility, reproducibility, and specificity for the detection of low quantities of RNA. However, this technique requires the use of one or several housekeeping genes. In this work, the expression stabilities of six housekeeping genes (EF1α, ACT, α-TUB, PDF, SAND, and UBC) during the cold acclimation of E. globulus plants was analyzed. An ELIP gene that responds to photooxidative stress caused by light and cold stress was used as the target gene to identify the most suitable internal control for normalizing real-time qRT-PCR. Two additional genes involved in the ABA biosynthesis pathway (NCED) and sugar metabolism (GS) were analyzed with the most stable internal control genes in order to check the results found with the ELIP gene. The expressions of UBC, α-TUB and EF1α were the most stable across acclimation and de-acclimation treatments. The expressions of the other housekeeping genes tested varied depending upon the conditions. The relative quantification of ELIP changed according to identities and the number of reference genes used, thus demonstrating the importance of selecting an appropriate number of reference genes in order to achieve an accurate and reliable normalization of gene expression during cold acclimation in E. globulus.

Identification of a Gene for Putative myo-Inositol Oxygenase That Is Specifically Induced by Cold Deacclimation Treatment in Arabidopsis thaliana

Identification of a Gene for Putative myo-Inositol Oxygenase That Is Specifically Induced by Cold Deacclimation Treatment in Arabidopsis thaliana

Cold Tolerance in Oilseed Rape over Varying Acclimation Durations

Winter rapeseed (Brassica napus L.) promises to be an important crop in the southern Great Plains. To increase the crop's consistency in the region, cultivars with improved winter hardiness and management recommendations that utilize all of a genotype's winter hardiness need to be developed. Better understanding of the variability in cold tolerance over the winter season need to be determined to help achieve these goals. The objectives of this study were to evaluate variability in cold tolerance over prolonged acclimation durations in oilseed rape by means of laboratory freezing tolerance procedures, and determine changes in freezing tolerance brought about by high temperature treatments. A warming period to simulate possible deacclimation events was included both before and after vernalization saturation had taken place. Maximum cold tolerance was achieved by 3 d of acclimation in the spring cultivar and between 6 and 9 d in the winter cultivars. A 7-d warming period reduced cold tolerance in all lines tested, but it did not reduce cold tolerance to the level of unacclimated plants. All tested lines were able to recover cold tolerance to the same level as before the deacclimation treatment after reexposure to 5°C conditions for 7 d. Cold tolerance did tend to decrease with prolonged acclimation durations. This information can help in the planning of strategies to develop rapeseed lines better adapted to the winter conditions of the southern Great Plains.

Cold Tolerance in Oilseed Rape over Varying Acclimation Durations

Winter rapeseed (Brassica napus L.) promises to be an important crop in the southern Great Plains. To increase the crop's consistency in the region, cultivars with improved winter hardiness and management recommendations that utilize all of a genotype's winter hardiness need to be developed. Better understanding of the variability in cold tolerance over the winter season need to be determined to help achieve these goals. The objectives of this study were to evaluate variability in cold tolerance over prolonged acclimation durations in oilseed rape by means of laboratory freezing tolerance procedures, and determine changes in freezing tolerance brought about by high temperature treatments. A warming period to simulate possible deacclimation events was included both before and after vernalization saturation had taken place. Maximum cold tolerance was achieved by 3 d of acclimation in the spring cultivar and between 6 and 9 d in the winter cultivars. A 7‐d warming period reduced cold tolerance in all lines tested, but it did not reduce cold tolerance to the level of unacclimated plants. All tested lines were able to recover cold tolerance to the same level as before the deacclimation treatment after reexposure to 5°C conditions for 7 d. Cold tolerance did tend to decrease with prolonged acclimation durations. This information can help in the planning of strategies to develop rapeseed lines better adapted to the winter conditions of the southern Great Plains.

数種のカキ属植物とカキ品種における耐凍性とアントシアニン形成との関係

The freezing resistances of three Diospyros species and three cultivars of D. kaki were evalu- ated by survival of twigs and electrolyte leakage from the tissues after freezing treatments. Dormant 1-year-old twigs were cooled from -5° to -5°- 30°C within 5 hr, maintained at each temperature for 5 hr and thawed gradually to 5°C for 5 hr. The twigs soaked in water were held for 20 days under 20°C to determine recovery.The hardiest species during the coldest period of the season was D. lotus followed by D. kaki, and the least hardy was D. taitoensis which is distributed in subtropical Taiwan. The critical low temperatures that did not injure the plants were -10°C for D. taitoensis, -15°C for D. kaki and -20°C for D. lotus; the temperatures at which half of the test twigs was killed (LT50) were - 12°, -20° and -25°C, respectively. Their electrolyte leakage at LT50 ranged from 25 to 28%.Among three cultivars of D. kaki, Eiratanenashi' which is native to the northern region of Japan, was most tolerant to freezing during mid-winter (true freezing resistance), however, it was the most sensitive to freezing before cold acclimation in early autumn and after cold acclimation in spring.Starch hydrolyzed to sugars in twigs of three cultivars of D. kaki under natural conditions during mid-winter. A close relation was found between the freezing resistance, evaluated by electrolyte leakage from twig cells, and anthocyanin in the cortical tissues. Anthocyanin con- tents in cortical tissues reached a maximum in mid-February; the pigment levels tended to increase when plants were exposed to -10°- 30°C which were below the ambient tem- perature. Moreover, anthocyanin contents in the cortex decreased, and the twigs became less hardy by the deacclimation treatment during the coldest part of the season. Conversely, twigs under the chilling treatment before cold acclimation in early autumn became hardy; the change was accompanied by an elevation of anthocyanin content.

Ethephon Prolongs Dormancy and Enhances Supercooling in Peach Flower Buds

The heat requirement for flower bud growth of container-grown peach trees [Prunus persica (L.) Batsch. cvs. Redhaven and Springold] in the greenhouse varied inversely and linearly with the length of the cold-storage period (SC) provided to break bud dormancy. Ethephon reduced the rest-breaking effectiveness of the 5C treatment. Buds from ethephon-treated trees grew more slowly than buds from untreated trees upon exposure to 20 to 25C, resulting in later bloom dates. The effect of ethephon on flower bud hardiness in field-grown trees of `Jerseydawn' and `Jerseyglo' was studied using exotherm analysis after deacclimation treatments. Bud deacclimation varied with reacclimating temperature (7 or 21 C), cultivar, ethephon treatment, and sampling date. All buds were more susceptible to injury in March than in January or February. Buds reacclimated more rapidly at 21C than at 7C. `Jerseyglo' reacclimated more rapidly than `Jerseydawn'. Untreated buds were less hardy and also reacclimated more rapidly than treated buds. Ethephon enhanced flower bud hardiness in three distinct ways: 1) it decreased the mean low-temperature exotherm of pistils, 2) it increased the number of buds that supercooled after exposure to reacclimating temperatures, and 3) it decreased the rate of deacclimation, especially at 21C. Ethephon prolongs flower bud dormancy by increasing the chilling requirement. The rate at which flower buds become increasingly sensitive to moderate temperatures in late winter and spring is thus reduced by ethephon. Thus, ethephon delays deacclimation during winter and delays bloom in the spring. Chemical name used: (2-chloroethyl) phosphoric acid (ethephon).

Induction of Freezing Tolerance in Spinach Is Associated with the Synthesis of Cold Acclimation Induced Proteins

Spinach (Spinacia oleracea L. cv Bloomsdale) seedlings cultured in vitro were used to study changes in protein synthesis during cold acclimation. Seedlings grown for 3 weeks postsowing on an inorganic-nutrient-agar medium were able to increase their freezing tolerance when grown at 5 degrees C. During cold acclimation at 5 degrees C and deacclimation at 25 degrees C, the kinetics of freezing tolerance induction and loss were similar to that of soil-grown plants. Freezing tolerance increased after 1 day of cold acclimation and reached a maximum within 7 days. Upon deacclimation at 25 degrees C, freezing tolerance declined within 1 day and was largely lost by the 7th day. Leaf proteins of intact plants grown at 5 and 25 degrees C were in vivo radiolabeled, without wounding or injury, to high specific activities with [(35)S]methionine. Leaf proteins were radiolabeled at 0, 1, 2, 3, 4, 7, and 14 days of cold acclimation and at 1, 3, and 7 days of deacclimation. Up to 500 labeled proteins were separated by two-dimensional gel electrophoresis and visualized by fluorography. A rapid and stable change in the protein synthesis pattern was observed when seedlings were transferred to the low temperature environment. Cold-acclimated leaves contained 22 polypeptides not found in nonacclimated leaves. Exposure to 5 degrees C induced the synthesis of three high molecular weight cold acclimation proteins (CAPs) (M(r) of about 160,000, 117,000, and 85,000) and greatly increased the synthesis of a fourth high molecular weight protein (M(r) 79,000). These proteins were synthesized during day 1 and throughout the 14 day exposure to 5 degrees C. During deacclimation, the synthesis of CAPs 160, 117, and 85 was greatly reduced by the first day of exposure to 25 degrees C. However, CAP 79 was synthesized throughout the 7 day deacclimation treatment. Thus, the induction at low temperature and termination at warm temperature of the synthesis of CAPs 160, 117, and 85 was highly correlated with the induction and loss of freezing tolerance. Cold acclimation did not result in a general posttranslational modification of leaf proteins. Most of the observed changes in the two-dimensional gel patterns could be attributed to the de novo synthesis of proteins induced by low temperature. In spinach leaf tissue, heat shock altered the pattern of protein synthesis and induced the synthesis of several heat shock proteins (HSPs). One polypeptide synthesized in cold-acclimated leaves had a molecular weight and net charge (M(r) 79,000, pI 4.8) similar to that of a HSP (M(r) 83,000, pI 4.8). However, heat shock did not increase the freezing tolerance, and cold acclimation did not increase heat tolerance over that of nonacclimated plants, but heat-shocked leaf tissue was more tolerant to high temperatures than nonacclimated or cold-acclimated leaf tissue. When protein extracts from heat-shocked and cold-acclimated leaves were mixed and separated in the same two-dimensional gel, the CAP and HSP were shown to be two separate polypeptides with slightly different isoelectric points and molecular weights.