Pre-cold acclimation promotes cryoprotectant accumulation and enhances freezing tolerance of Meloidogyne incognita

Strong evidence suggests that cryoprotectant accumulation during pre-cold acclimation protects cells against freezing injuries caused by cellular dehydration. In this study, the concentrations of trehalose and glycerol were measured in Meloidogyne incognita and it was found that both cryoprotectants were significantly accumulated in second-stage juveniles (J2) of M. incognita after acclimation at 4°C. However, compared with non-acclimated samples, only a higher level of trehalose was induced in the egg masses of M. incognita in response to cold treatment. Further characterizations indicated that pre-cold acclimation efficiently accelerated the speed of larvae hatching from egg masses that were subjected to freezing at −1°C. In addition, the survival rate and pathogenicity of M. incognita J2 that had been acclimated prior to freezing were significantly enhanced when compared with non-acclimated J2 individuals. As far as we know, this is the first time that this phenomenon has been reported in M. incognita.     

Effects of fluctuating thermal regimes on cold survival and life history traits of the spotted wing Drosophila(Drosophila suzukii)

Drosophila suzukii is an invasive pest causing severe damages to a large panel of cultivated crops.To facili tate its biocontrol with stratcgies such as sterile or incompatible insect techniques,D.suzukid must be mass-produced and then stored and transported under low temperature.Prolonged cold exposure induces chill injuries that can be mitigated if the cold period is interrupted with short warming intervals,referred to as fluctuating thermal regimes(FTR).In this study,we tested how to optimally use FTR to extend the shelf life of D.suzukii under cold storage.Several FTR parameters were asessed:temperature(15,20,25℃),duration(0.5,1,2,3 h),and frequency(every 12,24,36,48 h)of warming intervals,in two wild-type lines and in two developmental stages(pupac and adults).Generally,FTR improved cold storage tolerance with respect to constant low temperatures(CLT).Cold mortality was lower when recovery temperature was 20℃ or higher,when duration was 2 h per day or longer,and when warming interruptions occurred frequently(every 12 or 24 h).Applying an optimized FTR protocol to adults greatly reduced cold mortality over long-term storage(up to 130 d).Consequences of FTR on fitness-related traits were also investigated.For adults,poststorage survival was unaffected by FTR,as was the case for female fecundity and male mating capacity.On the other hand,when cold storage occurred at pupal stage,postorage survival and male mating capacity were altered under CLT,but not under FTR.After storage of pupae,female fecundity was lower under FTR compared to CLT,suggesting an energy trade-off between repair of chill damages and C22 production.This study provides detailed information on the application and optimization of an FTR-based protocol for cold storage of D.suzuki that could be useful for the biocontrol of this pest.     

Nicotiana tabacum callus studies. X. ABA increases resistance to cold damage

The effects of cis. trans abscisic acid on response to chilling was investigated in callused Nicotiana tabacum L. pith explants. Explants pretreated with 10^-4M ABA underwent approximately 50% less cellular leakage when chilled at 2°C under short-day conditions for 10 d than the comparable non-treated tissue. Growth in terms of fresh and dry weights, although poor in comparison to non-chilled (20°C, long days) treatments, was more than twice that of the non-ABA-treated material. On an absolute dry weight basis proline content increased on chilling from 0.7 to 3.4 mg g^-1 in non-ABA-treated explants, but rose to nearly 17 mg g^-1 in the tissue treated with ABA. Only in the case of cold-hardened. ABA-treated tissue could some cells survive subzero temperatures and regenerate callus again. It is suggested that at least part of the ameliorating effects of ABA result from an increase in the level of proline.     

Latitudinal variation in blue tit and great tit nest characteristics indicates environmental adjustment

Aim The laying of eggs and the building of a nest structure to accommodate them are two of the defining characteristics of members of the class Aves. Nest structures vary considerably across avian taxa and for many species the structure of the completed nest can have important consequences both for parents and their offspring. While nest characteristics are expected to vary adaptively in response to environmental conditions, large‐scale spatial variation in nest characteristics has been largely overlooked. Here, we examine the effects of latitudinal variation in spring temperatures on nest characteristics, including insulatory properties, and reproductive success of blue tits, Cyanistes caeruleus, and great tits, Parus major. Location Great Britain. Methods Nests and reproductive data were collected from seven study sites, spread over 5° of latitude. The nest insulatory properties were then determined before the nests were separated into nest base material and cup lining material. Results As spring temperatures increased with decreasing latitude, the mass of the nest base material did not vary in either species, while the mass of the cup lining material and nest insulatory properties decreased in both species. This suggests that in response to increasing temperatures the breeding female reduces the mass of the cup lining material, thereby maintaining an appropriate microclimate for incubating and brooding. The mean first egg date of both species advanced with decreasing latitude and increasing spring temperatures, although clutch size and brood size at hatching and fledging did not vary. Main conclusions This is the first study to demonstrate that the nest‐construction behaviour of birds varies in response to large‐scale spatial variation in ambient temperatures. Therefore, nest composition reliably indicates environmental conditions and we suggest that studies of nest structure may be sentinels for the early signs of rapid climate change.     

The persistence of short‐term cold acclimation in Drosophila melanogaster (Diptera: Drosophilidae)

Daily and seasonal fluctuations in temperature present significant challenges for the survival of many ectothermic species that can be tempered via thermal acclimation. In the present study, we use multiple naturally derived genotypes of Drosophila melanogaster to determine the persistence of beneficial short‐term thermal acclimation on subsequent survival after cold shock. We found that the benefit of short‐term acclimation persisted for 2 h in most genotypes after a rapid cold hardening treatment. Genotype did not directly influence the persistence of short‐term acclimation benefits, indicating that environmental variation may be more important for the persistence of acclimation benefits rather than genetic capacity for acclimation. The present study extends the current understanding of the limits and importance of short‐term acclimation events, providing greater detail on the timing of the loss of short‐term acclimation benefits in a genetically variable natural population.     

Times for recovery from cold-torpor in the Queensland fruit fly Dacus tryoni: the relation to temperature during and after chilling

Recovery time after experience of a given minimum temperature below torpor threshold is related to the value of that minimum, the length of time spent at that minimum, and the temperature prevailing during the recovery period above torpor threshold. A model can predict recovery time for flies experiencing a given temperature fluctuation if the length of time spent at the minimum is expressed as a proportion of LE₅₀ at that minimum.The model has applications in defining the optimal protocol for chilling insects for use in the Sterile Insect Release Method. The model was confirmed by experiments showing that it is likely that flies will recover from non-lethal frosts before ant predators become active.

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Résumé Le temps de récupération après avoir subi une température minimal située au-dessous du seuil d'engourdissement dépend de la valeur de ce minimum, du temps passé à ce minimum, et de la température au-dessus du seuil d'engourdissement pendant la période de récupération. Un modèle mathématique permet d'estimer le temps de récupération après avoir subi une chute de température déterminée, en fonction du temps passé au minimum thermique exprimé comme une fraction du LE₅₀ (temps nécessaire pour tuer 50% des mouches) à ce minimum.Ce modèle s'est trouvé étayé par des observations montrant qu'il est probable que les mouches se remettent des gelées sublétales avant la reprise d'activité des fourmis prédatrices. Ce modèle peut être utilisé pour définir les conditions optimales de refroidissement des insectes utilisés lors de la libération d'individus stériles.

     

NOVEL ICE‐BINDING PROTEINS FROM A PSYCHROPHILIC ANTARCTIC ALGA (CHLAMYDOMONADACEAE,CHLOROPHYCEAE)1

Many cold‐adapted unicellular plants express ice‐active proteins, but at present, only one type of such proteins has been described, and it shows no resemblance to higher plant antifreezes. Here, we describe four isoforms of a second and very active type of extracellular ice‐binding protein (IBP) from a unicellular chlamydomonad alga collected from an Antarctic intertidal location. The alga is a euryhaline psychrophile that, based on sequences of the alpha tubulin gene and an IBP gene, appears to be the same as a snow alga collected on Petrel Island, Antarctica. The IBPs, which do not resemble any known antifreezes, have strong recrystallization inhibition activity and have an ability to slow the drainage of brine from sea ice. These properties, by maintaining liquid environments, may increase survival of the cells in freezing environments. The IBPs have a repeating TXT motif, which has previously been implicated in ice binding in insect antifreezes and a ryegrass antifreeze.     

Respiratory changes due to extreme cold in the Arctic environment

Effects of acute exposure and acclimatisation to cold stress on respiratory functions were investigated in healthy tropical Indian men (n=10). Initial baseline recordings were carried out at Delhi and thereafter serially thrice at the arctic region and once on return to Delhi. For comparison the respiratory functions were also evaluated on Russian migrants (RM;n=7) and Russian natives (RN;n=6). The respiratory functions were evaluated using standard methodology on a Vitalograph: In Indians, there was an initial decrease in lung vital capacity (VC), forced vital capacity (FVC), forced expiratory volume 1st s (FEV1), peak expiratory flow rate (PEFR) and maximum voluntary ventilation (MVV) on acute exposure to cold stress, followed by gradual recovery during acclimatisation for 4 weeks and a further significant improvement after 9 weeks of stay at the arctic region. On return to India all the parameters reached near baseline values except for MVV which remained slightly elevated. RM and RN showed similar respiratory functions at the beginning of acute cold exposure at the arctic zone. RN showed an improvement after 10 weeks of stay whereas RM did not show much change. The respiratory responses during acute cold exposure are similar to those of initial altitude responses.     

Lipid Peroxidation in the Cortex and Medulla of Rabbit Kidneys Subjected to Cold Ischaemia and the Value of Protective Agents

The storage of rabbit kidneys for 24hr at 0 C in isotonic saline resulted in significantly increased rates of lipid peroxidation, as measured by the formation of thiobarbituric acid-reactive material and Schiff bases during in vitro incubation of homogenates prepared from the cortex and medulla. In addition, the content of thiobarbituric acid-reactive material in the medulla was also significantly elevated as a result of cold storage for 24 hr.

The effects of antioxidants (vitamin E), iron-chelation (desferoxamine) and inhibitors of arachidonic acid oxidation (indomethacin and dazmegrell on the rate of lipid peroxidation in homogenates prepared from ischaemic kidneys were studied. This demonstrated that lipid peroxidation in the cortex was predominantly non-specific and iron-catalysed whereas in the medulla approximately 50% of the TBA-reactive material was formed enzymically from arachidonic acid by cyclooxygenase.