Monitoring expression profiles of Arabidopsis genes during cold acclimation and deacclimation using DNA microarrays

A comparative analysis of gene expression profiles during cold acclimation and deacclimation is necessary to elucidate the molecular mechanisms of cold stress responses in higher plants. We analyzed gene expression profiles in the process of cold acclimation and deacclimation (recovery from cold stress) using two microarray systems, the 7K RAFL cDNA microarray and the Agilent 22K oligonucleotide array. By both microarray analyses, we identified 292 genes up-regulated and 320 genes down-regulated during deacclimation, and 445 cold up-regulated genes and 341 cold down-regulated genes during cold acclimation. Many genes up-regulated during deacclimation were found to be down-regulated during cold acclimation, and vice versa. The genes up-regulated during deacclimation were classified into (1) regulatory proteins involved in further regulation of signal transduction and gene expression and (2) functional proteins involved in the recovery process from cold-stress-induced damages and plant growth. We also applied expression profiling studies to identify the key genes involved in the biosynthesis of carbohydrates and amino acids that are known to play important roles in cold acclimation. We compared genes that are regulated during deacclimation with those regulated during rehydration after dehydration to discuss the similarity and difference of each recovery process.Electronic Supplementary Material Supplementary materials are available for this article at     

ABA and gibberellin-like substances during prehardening,cold acclimation,de- and reacclimation of oilseed rape

Previously published results showed that high relative reduction state of PSII (PSII excitation pressure) during both early seedling growth (prehardening) as well as cold deacclimation caused significant changes in growth pattern. The differences in elongation growth rate were related to the cold acclimation of photosynthetic apparatus and to frost resistance. To study changes in the hormonal balance connected with alterations in elongation growth rate observed during prehardening and deacclimation under different PSII excitation pressure (modulated by day-temperatures), endogenous concentration of ABA, GA₃ and GA-like substances (GAs) were analysed. Analyses were also performed during cold acclimation and reacclimation of plants characterized by different elongation growth rate triggered by prehardening or deacclimation under different day-temperatures. Growth under high PSII excitation pressure (prehardening) resulted in a significant increase in ABA and a considerable decrease in GAs contents. On the other hand, different ABA content played almost no role in controlling growth rate during cold deacclimation and subsequent reacclimation, when the induction of elongation growth was connected with the changes in concentration of GAs including GA₃. The possible role of ABA and GAs in controlling prehardening, cold acclimation and deacclimation is discussed.     

Differences in cold hardiness,carbohydrates, dehydrins and related gene expressions under an experimental deacclimation and reacclimation in Prunus persica

To boost our understanding of a recent outbreak of freezing injury, we sought to confirm distinctive features between the shoot tissues of the peach (Prunus persica) cultivars Daewol and Kiraranokiwami by mimicking unseasonable changes of temperatures that occur in the early spring through repeated deacclimation and reacclimation treatments. Patterns of cold hardiness declined dramatically during the deacclimation and rose during the reacclimation in both cultivars. Our results indicated that ‘Daewol’ possessed higher capacity in response to repeated deacclimation and reacclimation treatments than ‘Kiraranokiwami’. ‘Daewol’ showed more sensitive changes in the carbohydrates in response to warm and low temperatures compared with ‘Kiraranokiwami’. ‘Daewol’ indicated almost similar repeated down‐ and up‐patterns in soluble sugar content in response to repeated deacclimation and reacclimation, whereas it indicated repeated up‐ and down‐patterns in starch content. However, ‘Kiraranokiwami’ showed a progressive increase in the soluble sugar content and a progressive decrease in starch content. Notably, patterns of accumulation of a 60‐kDa dehydrin protein encoded by the PpDhn1 gene were confirmed through western blotting and paralleled fluctuations of cold hardiness in both cultivars. Expression of this dehydrin was weak in both cultivars during deacclimation but its band intensity increased during reacclimation. Changes in related genes (β‐amylase, PpDhn1, PpDhn2 and PpDhn3) were positively correlated with changes in cold hardiness throughout the experiment. Our results indicate that recent repeated warm periods may cause premature deacclimation in the early spring, and that more cold‐tolerant cultivar may be more resilient to freezing injury caused by unstable temperature conditions.     

Cold deacclimation mechanisms and reacclimation potential in flower buds of blackcurrant (Ribes nigrum)

As a consequence of global climate change, cold acclimation and deacclimation cycles are becoming increasingly frequent during winter in temperate regions. However, little is known about plant deacclimation and in particular reacclimation mechanisms, although deacclimation resistance and the ability to reacclimate may have wide‐ranging consequences regarding plant productivity in a changing climate. Here, we report time‐dependent responses of freezing tolerance, respiration rates, metabolite contents (high‐resolution magic angle spinning NMR) and fatty acid levels (gas chromatography) in flower buds of two ecodormant Ribes nigrum cultivars exposed to three different deacclimation temperatures followed by a reacclimation treatment at 4°C. The data reveal that despite differences in the progression of deacclimation, the capacity of blackcurrant flower buds to reharden in late winter is virtually non‐existing, implying that increasingly irregular temperature patterns is critical for blackcurrant fruit yield. The early phase of deacclimation is associated with a transient increase in respiration and decreasing contents of amino acids, tricarboxylic acid (TCA) cycle intermediates and sugars, indicating an increased need for carbon sources and respiratory energy production for the activation of growth. Decreasing sugar levels may additionally cause loss of freezing tolerance. Deacclimation also involves desaturation of membrane lipids, which likely also contributes to decreased freezing tolerance but may also reflect biosynthesis of signaling molecules stimulating growth and floral organ differentiation. These data provide new insights into the under‐researched deacclimation mechanisms and the ability of blackcurrant to reacclimate following different advancements of deacclimation and contribute to our understanding of plant responses to increasingly irregular temperature patterns.     

Thermal acclimation in Arabidopsis lyrata: genotypic costs and transcriptional changes

Frost and heat events can be challenging for sessile organisms that cannot escape thermal extremes. However, adverse effects of thermal stress on fitness may be reduced by pre‐exposure to cold or heat, a process known as acclimation. To understand the ecological and evolutionary implications of acclimation, we investigated (1) the reduction in performance due to stress pre‐exposure, (2) the magnitude of increased leaf resistance to subsequent stress, (3) the costs of acclimation and (4) the genes differing in expression due to stress pre‐exposure. Plants of Arabidopsis lyrata were raised under three treatments of pre‐exposure: bouts of frost, bouts of heat or constant temperature. Resistance of leaves to subsequent frost and heat stress was then measured by electrolyte leakage. RNA‐seq analysis was performed to examine the genes differentially expressed between stress‐pre‐exposed and control plants. Pre‐exposure to stress during growth decreased plant size and increased leaf resistance to subsequent stress independent of whether pre‐exposure was to frost or heat. But the highest increase in leaf resistance to frost was found after pre‐exposure to frost (as a trend) and in leaf resistance to heat after pre‐exposure to heat. No evidence for costs of acclimation was detected. RNA‐sequencing suggested that acclimation by frost and heat pre‐exposure was caused by distinct mechanisms: modification of the chloroplast membrane and modification of the cell wall and membrane, respectively. Our results suggest that thermal resistance is a labile complex of traits, strongly affected by the previously experienced stress environment, with undetermined costs.     

Temporal cell wall changes during cold acclimation and deacclimation and their potential involvement in freezing tolerance and growth

Plants adapt to freezing stress through cold acclimation, which is induced by nonfreezing low temperatures and accompanied by growth arrest. A later increase in temperature after cold acclimation leads to rapid loss of freezing tolerance and growth resumption, a process called deacclimation. Appropriate regulation of the trade-off between freezing tolerance and growth is necessary for efficient plant development in a changing environment. The cell wall, which mainly consists of polysaccharide polymers, is involved in both freezing tolerance and growth. Still, it is unclear how the balance between freezing tolerance and growth is affected during cold acclimation and deacclimation by the changes in cell wall structure and what role is played by its monosaccharide composition. Therefore, to elucidate the regulatory mechanisms controlling freezing tolerance and growth during cold acclimation and deacclimation, we investigated cell wall changes in detail by sequential fractionation and monosaccharide composition analysis in the model plant Arabidopsis thaliana, for which a plethora of information and mutant lines are available. We found that arabinogalactan proteins and pectic galactan changed in close coordination with changes in freezing tolerance and growth during cold acclimation and deacclimation. On the other hand, arabinan and xyloglucan did not return to nonacclimation levels after deacclimation but stabilized at cold acclimation levels. This indicates that deacclimation does not completely restore cell wall composition to the nonacclimated state but rather changes it to a specific novel composition that is probably a consequence of the loss of freezing tolerance and provides conditions for growth resumption.     

植物抗寒及其基因表达研究进展

植物经过逐渐降低的温度从而提高抗寒能力 ,这个过程被人们称为低温驯化。植物低温驯化过程是一个复杂的生理、生化和能量代谢变化过程 ,这些变化主要包括膜系统的稳定性、可溶性蛋白的积累和小分子渗透物质 ,比如脯氨酸、糖等 ,这些变化中的一些是植物抗寒必需的 ,而另外一些变化不是必需的。主要对冷害和低温生理生化变化、低温诱导表达基因的功能和作用、低温驯化的调节机制及其信号转导方面进行了综述。通过差别筛选 c DNA文库的方法已经鉴定了许多低温诱导表达、进而提高植物抗寒能力的基因 ,其中有脱水素、COR基因和 CBF1转录因子等。低温信号的感受、转导和调节表达是低温驯化的关键环节 ,低温信号的转导过程与干旱胁迫之间具有一定的交叉 ,这为利用 ABA等来提高植物抗寒能力成为可能 ,相信不久的将来人们可以通过提高植物抗寒能力从而增加经济产量成为现实。