Endogenous serotonin induced by cold acclimation increases cold tolerance by reshaping the MEL/ROS/RNS redox network in Kandelia obovata

Cold stress severely limits the distribution of mangrove species worldwide and it remains unclear how mangroves respond and adapt to cold temperatures.In this study,we investigated the effects of cold acclimation and/or inhibition of serotonin levels on reactive oxygen species(ROS),reactive nitrogen species(RNS),melatonin(MEL)and serotonin(SER)accumulation during cold stress in Kandelia obovata.Morphologic observation and param-eter analysis revealed that cold acclimation mitigated the photoinhibition of photosystem I(PSI)and photosystem II(PSII),maintained optimal ROS and RNS redox homeosta-sis,and increased the contents of SER and MEL in leaves.This suggests that cold acclimation reshapes the MEL/ROS/RNS redox network.In particular,the tryptophan/tryptamine/Ser/N-acetylserotonin/MER pathway was identi-fied as a branch of the MEL synthesis pathway.Inhibition of endogenous SER exacerbated damage caused by cold stress,indicating the crosstalk of SER synthesis and cold acclima-tion.In this study,we report a coordinated regulation of cold stress by a complex defense network in K.obovata.

A Bibliometric Analysis Unveils Valuable Insights into the Past,Present,and Future Dynamics of Plant Acclimation to Temperature

Plant temperature acclimation is closely related to maintaining a positive carbon gain under future climate change.However,no systematic summary of the field has been conducted.Based on this,we analyzed data on plant temperature acclimation from the Web of Science Core Collection database using bibliometric software R,RStudio and VOSviewer.Our study demonstrated that a stabilized upward trajectory was noted in publications(298 papers)from 1986 to 2011,followed by a swift growth(373 papers)from 2012 to 2022.The most impactful journals were Plant Cell and Environment,boasting the greatest count of worldwide citations and articles,the highest H-index and G-index,followed by Global Change Biology and New Phytologist,and Frontiers in Plant Science which had the highest M-index.The USA and China were identified as the most influential countries,while Atkin was the most influential author,and the Chinese Academy of Sciences was the most influential research institution.The most cited articles were published in the Annual Review of Plant Biology in 1999.“Cold acclimation”was the most prominent keyword.Future plant temperature acclimation research is expected to focus on thermal acclimation and photosynthesis,which have important significance for future agricultural production,forestry carbon sequestration,and global food security.In general,this study provides a systematic insight of the advancement,trend,and future of plant temperature acclimation research,enhancing the comprehension of how plants will deal with forthcoming climate change.

Role of CaCl_(2) in Cold Acclimation-Induced Freezing Resistance of Populus tomentosa Cuttings

Populus tomentosa cuttings were treated with 1mmol·L -1 , 5mmol·L -1 , 10mmol·L -1 or 15mmol·L -1 of CaCl 2 for 1\|7 d, respectively, for studying the effects of different concentrations of CaCl 2 on freezing resistance. Results indicated that 10?mmol·L -1 of CaCl 2 has greater effect than other concentrations on the enhancement of freezing resistance, and the optimum time of pretreatment was 5?d. In addition, cuttings used for cold acclimation at -3℃ were pretreated with or without 10?mmol·L -1 of CaCl 2, 3?mmol·L -1 of Ca 2+ chelator EGTA, 0 05?mmol·L -1 of CaM antagonist CPZ or 0 1?mmol·L -1 of Ca 2+ channel inhibitor LaCl 3 The changes in CaM and freezing resistance of all cuttings were investigated. The results showed that cold acclimation at -3℃ increased CaM content and decreased the minimum temperature for 100% survival. The CaCl 2 pretreatment enhanced the effect of cold acclimation and obviously increased CaM content and decreased the minimum temperature for 100% survival, but this effect was strongly inhibited by the EGTA, CPZ or LaCl 3 It is concluded that the effect of CaCl 2 on freezing resistance is associated with its concentration and time of pretreatment, Ca 2+ CaM may be involved in the induction of freezing resistance of the cuttings.

Effects of Cold Acclimation and CaCl_2 on Total Soluble Protein, CaM and Freezing Resistance of Populus tomentosa Seedlings

Populus tomentosa seedlings used for cold acclimation at -3℃ were pretreated with or without 10?mmol·L -1 CaCl 2, 3?mmol·L -1 of Ca 2+ chelator EGTA, 0 1?mmol·L -1 of Ca 2+ channel inhibitor LaCl 3,and 0 05?mmol·L -1 of CaM antagonist CPZ. The changes in the contents of total soluble protein and CaM, and freezing resistance in all pretreated seedlings in various periods ( viz: following cold acclimation, chilling stress and recovery) were investigated. Results showed that cold acclimation increased the contents of total soluble protein and CaM, and freezing resistance of seedlings, which could be strongly reduced by the pretreatments of EGTA CPZ and LaCl 3 Cold acclimation combined with CaCl 2 pretreatment enhanced the effect of cold acclimation on freezing resistance, and obviously increased the contents of total soluble protein and CaM, reduced the declining degree of the contents of total soluble protein and CaM caused by chilling stress as compared with cold acclimation, augmented the increase in the level of total soluble protein and CaM during the recovery periods. Further analysis found that an increase in total soluble protein content during cold acclimation with or without CaCl 2 pretreatment mainly resulted from the increase in content of heat stable protein in total soluble protein. It is suggested that Ca 2+ calmodulin may be involved in the synthesis of total soluble protein, and the induction of freezing resistance of seedlings.

Cold Acclimation-Induced Changes in Total Soluble Protein, RNA, DNA, RNase and Freezing Resistance in Populus tomentosa Cuttings

The changes in the contents of total soluble protein and RNA, the activity of RNase in leaves and branches of Populus tomentosa cuttings at various periods (viz: cold acclimation, deacclimation, chilling stress and the recovery after chilling stress), and the survival rate and the freezing resistance of cuttings during cold acclimation at -3℃ were investigated. Results showed that cold acclimation not only increased the contents of total soluble protein and RNA, the survival rates and the freezing resistance of cuttings, decreased the activity of RNase, but also reduced the declining degree of total soluble protein and RNA contents, and the increasing level of RNase caused by chilling stress as compared with the controls. In addition, cold acclimation augmented the increase in the level of total soluble protein and RNA, and facilitated the decrease of RNase during the recovery periods. Further analysis found that the DNA content of all treatments kept relative stability at various periods. The changes in total soluble protein, RNA and RNase were closely related to the freezing resistance of cuttings. It appears that the increase of RNA content caused by cold acclimation induced decrease of RNase activity may be involved in the accumulation of total soluble protein and the induction of freezing resistance of cuttings.

Dynamics of Essential Metal Elements Contents in Winter Oilseed Rape during Cold Acclimation

[Objective]The paper was to investigate the dynamics of essential metal elements（Ca,Mg,Fe,Mn,Zn and Cu）contents in winter oilseed rape（Brassica napus L.）during cold acclimation,and to reveal the effects and mechanisms of essential elements in cold resistance of oilseed rape.[Method]Three varieties with different cold resistance including Zhongshuang No.11（ZS,freezing sensitive variety）,Ganyouza No.1（GY）and Jinyuyou No.1（JYY,freezing tolerant varieties）were used in the study,and the changes of necessary metal elements in these oilseed rapes during cold acclimation were studied.[Result]The concentration of metal elements in oilseed rape had significant changes during cold acclimation,and the difference between varieties was significant.In plant roots,the concentrations of Ca,Mg,Fe,Mn,Zn and Cu were significantly increased,this might because that low temperature made the transpiration decreased,thus blocking the upward transport of elements.In plant shoots,the concentrations of Ca,Mg and Zn were significantly decreased,while the concentrations of Fe and Mn were significantly increased;the change extent of various elements in ZS variety was the largest.[Conclusion]Maintaining the stability of Ca,Mg and Zn concentrations and increasing Fe,Mn and Cu concentrations in plant shoots might be benefit for increasing the cold tolerance of winter oilseed rape.

Effect of Sugar on the Process of Cold-Acclimation-Induced Freezing Tolerance of Populus tomentosa

Populus tomentosa seedlings for cold-acclimating were pretreated wit h or without 20% saccharose. Changes in the concentrations of total soluble sugar , the survival rates, and freezing tolerance of seedlings during cold acclimatio n were investigated. The results showed that cold acclimation increased the conc entrations of total soluble sugar, the survival rates and freezing tolerance. Co ld acclimation, combined with the saccharose-pretreatment, enhanced the above- ment ioned effect of cold acclimation, and obviously increased the concentrations of total soluble sugar, the survival rates and freezing tolerance of seedlings. Fur ther analysis found that the concentrations of total soluble sugar in branches i ncreased greater than that in leaves during both cold acclimation with or withou t the pretreatment of saccharose. Moreover, an increase of the concentrations of total soluble sugar in branches and leaves was closely related to the freezing tolerance of seedlings. The results indicate the accumulation of soluble sugar i n seedlings induced by cold acclimation may be involved in the induction of free zing tolerance .

Seawater Acclimation of Spirulina

[Objective] This study aimed to seek the cultivation method for Spirulina with seawater. [Method] Spirulina was habituated culture progressively with prepared seawater acclimation solution. The morphological changes of Spirulina were observed and its biochemical indicators were measured. [Result] A new algae species was obtained, which had better stability and greater average length than Spirulina in fresh water. Compared with the Spirulina in fresh water, the new algae species showed no significant change in chlorophyll content, but a 62.8% increase in the concentration of phycocyanin. [Conclusion] The method could save resources and cost, which lays the foundation for large scale production and processing of Spirulina.

Cold acclimation improves photosynthesis by regulating the ascorbate–glutathione cycle in chloroplasts of Kandelia obovata

As the most northerly mangrove species in China, Kandelia obovata may undergo extreme cold event stress. Enhancing the cold tolerance of this species is crucial to its successful afforestation. This study aimed to determine the resistance of K. obovata seedlings to low temperature stress by cold acclimation and to explain the mechanisms for alleviating cold injury. To understand these mechanisms, seedlings that were acclimatized and not acclimatized were exposed to 5℃/- 2℃(day/night)for 48 h.Results showed that low temperature stress reduced leaf photosynthesis of non-acclimatized seedlings by inducing oxidative stress and structural damage to chloroplasts. These phenomena were shown by increasing levels of malondialdehyde (MDA), O2-and H2O2, as well as decreasing enzyme activities in the ascorbate–glutathione (AsA-GSH) cycle. However, cold-acclimatized seedlings had improved photosynthetic rates and efficiency of photosystem II (PSII) under low temperature stress. Compared with non-acclimatized seedlings, leaves of coldacclimatized seedlings under low temperature stress for 48 h exhibited higher anti-oxidative enzyme activities, lower levels of O2^- and H2O2, less damage to chloroplast structure, and removed 33.7% of MDA at low temperature stress for 48 h. The data indicate that cold acclimation enhances photosynthetic capacity by effectively regulating activation in the PSII electron transport and the AsA–GSH cycle to scavenge excess ROS in chloroplasts, while the latter is more important.

Photosynthetic acclimation to long-term high temperature and soil drought stress in two spruce species (Picea crassifolia and P. wilsonii) used for afforestation

Picea crassifolia and P.wilsonii,commonly used for afforestation in northern China,are increasingly likely to be subjected to high temperatures and soil drought stress as a result of global warming.However,little is known about the effects of these stresses on foliar photosynthesis in the two species.To investigate how photosynthetic characteristics and sensitivity respond to prolonged high temperatures and soil drought,foliar gas exchange and other closely related parameters were recorded from four-year-old seedlings of both species.Seedlings were grown under two temperature treatments(25/15 and 35/25 °C) and four soil water regimes [80,60,40 and 20% of maximum field capacity(FC)] for 4 months.Although all treatments significantly reduced photosynthetic rates(Pn) of both species,P.crassifolia exhibited greater photosynthetic acclimation than P.wilsonii.Differences in photosynthetic acclimation were mainly related to variations in stomatal conductance(Cond) and the maximum quantum yield of PSII(Fv/Fm) between treatments.Indeed,higher Cond and Fv/Fmin all treatments were shown for P.crassifolia than for P.wilsonii.Moreover,photosynthesis in P.crassifolia exhibited inherently lower temperature sensitivities(broader span for the temperature response curves; lower b) and higher thermostability(invariable b between treatments).Further,severe drought stress(20% FC) limited the survival of P.wilsonii.Our results indicate that P.wilsonii is more susceptible to high temperatures and soil drought stress.Planting P.crassifolia would be more expected to survive these conditions and hence be of greater benefit to forest stability if predicted increases in drought and temperature in northern China occur.

Photosynthesis, chilling acclimation and the response of antioxidant enzymes to chilling stress in mulberry seedlings

This study investigates the effects of cold-acclimation in conferring chilling tolerance in seedlings of the mulberry(Morus alba) variety ‘Qiuyu’. Changes in photosynthesis and antioxidant enzymes in chilling acclimatized(CA), and non-acclimatized(NA) seedlings were recorded during chilling stress(3 °C) and a recovery period(25 °C) each for 3 days. The results showed that CA plants had higher net photosynthetic rates(P_n), stomatal conductance(G_s), and maximum photochemical efficiency of photosystem Ⅱ(F_v/F_m) in response to chilling stress compared to NA. The seedlings maintained the same trends during the recovery stage. The responses of Q_A reduction degree (1-q_P) and prime electronic transfer rates(F_o) were lower in acclimatized than in non-acclimatized seedlings. Low-temperature acclimation and chilling stress also caused an increase in leaf proline and soluble sugar contents. Leaf malondialdehyde levels were significantly lower while ascorbate peroxidase(APX) activity was significantly higher in acclimatized seedlings, suggesting that elevated osmolytes and APX confer resistance to chilling temperatures. In this study on the response of mulberry seedlings to chilling stress, we also looked at the recovery process. The response to chilling determines whether mulberry leaves can survive under cold temperatures, while the recovery process determines whether photosynthesis can recover as soon as possible to avoid any secondary damage.

Suboptimal Temperature Acclimation Enhances Chilling Tolerance by Improving Photosynthetic Adaptability and Osmoregulation Ability in Watermelon

The temperature drop of plants from the optimal requirements can increase tolerance to severe chilling stress. Photosynthesis and osmoregulators were analyzed during chilling stress to explore the adaptation mechanisms that underlie the induction of chilling tolerance in response to suboptimal temperature. The relationships of these processes to suboptimal temperature acclimation in watermelon were then determined.Suboptimal temperature-acclimated watermelon plants demonstrated tolerance during chilling stress, as indicated by the decreased electrolyte leakage and malondialdehyde accumulation compared with those non-acclimated watermelon plants. Chilling-induced photoinhibition and reduction in CO2 assimilation rate were alleviated after suboptimal temperature acclimation. The xanthophyll cycle level was enhanced by improving thermal dissipation ability and avoiding light damage. Consequently, the chilling tolerance of suboptimal temperature-acclimated watermelon plants was enhanced. The osmoregulation ability induced by suboptimal temperature acclimation protected watermelon plants against chilling injury because of the accumulation of small molecular substances, such as soluble sugar and proline. The protein levels of Rubisco activase(ClRCA) and the gene expression of the Benson–Calvin cycle simultaneously increased in suboptimal temperature-acclimated watermelon plants during chilling stress. Chilling tolerance in watermelon plants induced by suboptimal temperature acclimation is associated with enhanced photosynthetic adaptability and osmoregulation ability.

Recent Advances in the Acclimation Mechanisms and Genetic Improvement of Peanut for Drought Tolerance

Peanut (Arachis hypogaea L.) is one of the most important oilseed crops that are cultivated worldwide. Peanut production is now greatly limited by drought stress, which is a major environmental challenge. The urgent task for current peanut research is thus to study the underlying mechanisms of peanut drought tolerance, to identify genes that are closely associated with drought tolerance, and to create new germplasms/varieties with high drought tolerance. In this review, we summarize recent advances in the acclimation mechanisms to water deficiency and the genetic improvement of peanut for drought tolerance, and propose the perspectives for the future peanut research.

Effects of Cold Acclimation on Several Enzyme Activities in Euonymus radicans ‘Emorald & Gold’and Its Relation to Semi-lethal Temperature

The changes in activities of superoxide dismutase (SOD), peroxidase (POD) and ATPase in the leaves of Euonymus radicans were studied when seedlings were cold-acclimated (at 4 ℃) for 1 week, 2 weeks, 3 weeks and then treated for 1 d under low temperature stress (at 5 ℃). The semi-lethal temperatures of acclimated and unacclimated seedlings were also investigated. The results indicated that the activities of the three enzymes in the leaves of the seedlings treated at 4 ℃ for 1, 2 and 3 weeks were all higher than those of unacclimated seedings (treated at 22 ℃ as controls). The activities of SOD and POD increased continuously with the prolongation of the time of cold acclimation, but stepped up to summits then down to the levels of the controls. The activities of SOD culminated at the first week, and the activities of POD at the second week. When acclimated and unacclimated seedlings were both treated at 5 ℃ for 1 d, the activities of the three enzymes in the leaves of acclimated seedlings were a little lower than those before stress, but higher than those of the controls. Moreover, the decrease rate of enzyme activities was greatly lower than that of the controls. The results showed that cold acclimation could enhance the stability of the three enzymes in the leaves of seedlings under low temperature stress; the semi-lethal temperature was 19.1 ℃ when the seedlings were treated at 4 ℃ for 3 weeks, but it was 5.4 ℃ when the seedlings were treated at 22 ℃. The decline of the semi-lethal temperature caused by the adaptive changes of enzyme activities was one of the foundations of enhancing the cold tolerance.

Differential Regulatory Mechanisms of CBF Regulon Between Nipponbare (Japonica) and 93-11 (Indica) During Cold Acclimation

Nine CBF/DREB1 homologous genes in rice were obtained by BLAST search in the NCBI database, which share conserved amino acid sequences with DREB1 protein in Arabidopsis. Three CBF genes organized in tandem, named OsCBF1, OsCBF2 and OsCBF3, showed a transient induction in the process of cold acclimation, much stronger in indica rice 93-11 compared with japonica rice Nipponbare. The candidate downstream genes OsLIP5 and OsLIP9 were induced in 93-11 but not in Nipponbare. The differential expression of CBF regulon might be caused by polymorphisms within promoter sequences between these two rice varieties. These results could be useful for utilization of CBF/DREB1 genes and illustration of differences in chilling tolerance between indica and japonica rice varieties.

Temperature acclimation affects thermal preference and tolerance in three Eremias lizards(Lacertidae)

We acclimated adult males of three Eremias lizards from different latitudes to 28℃,33℃ or 38℃ to examine whether temperature acclimation affects their thermal preference and tolerance and whether thermal preference and tolerance of these lizards correspond with their latitudinal distributions.Overall,selected body temperature(Tsel)and viable temperature range(VTR)were both highest in E.brenchleyi and lowest in E.multiocellata,with E.argus in between;critical thermal minimum(CTMin)was highest in E.multiocellata and lowest in E.brenchleyi,with E.argus in between;critical thermal maximum(CTMax)was lower in E.multiocellata than in other two species.Lizards acclimated to 28℃ and 38℃ overall selected lower body temperatures than those acclimated to 33℃;lizards acclimated to high temperatures were less tolerant of low temperatures,and vice versa;lizards acclimated to 28℃ were less tolerant of high temperatures but had a wider VTR range than those acclimated to 33℃ and 38℃.Lizards of three species acclimated to the three temperatures always differed from each other in CTMin,but not in Tsel,CTMax and VTR.Our results show that:temperature acclimation plays an important role in influencing thermal preference and tolerance in the three Eremias lizards,although the degrees to which acclimation temperature affects thermal preference and tolerance differ among species;thermal preference rather than tolerance of the three Eremias lizards corresponds with their latitudinal distributions.

Effects of temperature acclimation on body mass and energy budget in the Chinese bulbul Pycnonotus sinensis

Chinese bulbuls （Pycnonotus sinensis） are small passerine birds that inhabit areas of central, southern and eastern China. Previous observations suggest that flee-living individuals of this species may change their food intake in response to seasonal changes in ambient temperature. In the present study, we randomly assigned Chinese bulbuls to either a 30 ~C or 10 ~C group, and measured their body mass （BM）, body temperature, gross energy intake （GEl）, digestible energy intake （DEI）, and the length and mass of their digestive tracts over 28 days of acclimation at these temperatures. As predicted, birds in the 30 ℃ group had lower body mass, GEI and DEI relative to those in the 10 ℃ group. The length and mass of the digestive tract was also lower in the 30 ℃ group and trends in these parameters were positively correlated with BM, GEl and DEI. These results suggest that Chinese bulbuls reduced their absolute energy demands at relatively high temperatures by decreasing their body mass, GEI and DEI, and digestive tract size.

Ultrastructural and Extracellular Protein Changes in Cell Suspension Cultures of Populus euphratica Associated with Low Temperature-induced Cold Acclimation

Populus euphratica Olive is the only tree species that can grow in the saline land and also survive cold winters in northwest China, and it plays a very important role in stabilizing the vulnerable ecosystem there. A cell suspension culture was initiated from callus derived from plantlets of Populus euphratica. Cold acclimation was induced (LT50 of 17.5 ℃) in cell suspension at 45 ℃ in the dark for 30 days and the freezing tolerance increased from LT50 of 12.5 ℃ in nonacclimated cells to LT50 of 17.5 ℃ in cold-acclimated cells. Microvacuolation, cytoplasmic augmentation and accumulation of starch granules were observed in cells that were cold-acclimated by exposure to low temperatures. Several qualitative and quantitative changes in proteins were noted during cold acclimation. Antibodies to carrot extracellular (apoplastic) 36 kD antifreeze protein did not cross react on immunoelectroblots with extracellular proteins in cell suspension culture medium of Populus euphratica, indicating no common epitopes in the carrot 36 kD antifreeze protein and P. euphratica extracellular proteins. The relationship of these changes to cold acclimation in Populus euphratica cell cultures was discussed.