Pre-freeze mortality in three species of aphids from sub-Antarctic Marion Island

Understanding the mechanisms by which aphids survive low temperature is fundamental in forecasting the risk of pest outbreaks. Aphids are chill susceptible and die at a temperature close to that at which a small exothermal event is produced. This event, which can be identified using differential scanning calorimetry (DSC), normally occurs at a higher temperature than the supercooling point (SCP) and has been termed a pre-freeze event (PFE). However, it is not known what causes the PFE or whether it signifies the death of the aphid. These questions are addressed here by using a sensitive DSC to quantify the PFE and SCP and to relate these thermal events to the lower lethal temperature (LT₅₀) of sub-Antarctic aphids acclimated to low temperatures. PFEs were observed in each of the 3 species of aphids examined. They occurred over a narrower temperature range and at a higher temperature range than the SCP (−8.2 to −13.8 and −5.6 to −29.8 °C, respectively). Increased acclimation temperature resulted in increased SCPs in Myzus ascalonicus but not in Rhopalosiphum padi. The LT₅₀ reduced by approximately 1 °C from −9.3 to −10.5 °C with reduced acclimation temperature (10–0 °C). The LT₅₀ was close to the temperature at which the PFE occurred but statistically significantly higher than either the PFE or the SCP. In the majority of cases the PFE exotherm occurred well before the main exotherm produced by the bulk of the insect’s body water freezing (SCP). However, in a few cases it occurred at the same temperature or before the super-cooling point making the term, pre-freeze event (PFE), rather misleading. The possible origins of the PFE are discussed.     

Effect of altitude on thermal responses of Liolaemus pictus argentinus in Argentina

Reptiles that live in cooler environments hibernate longer and, when active, limit daily activity times, allocate more time and energy toward thermoregulation, and consequently experience life-history constraints such as reduced fecundity and supra-annual reproductive cycles. This pattern becomes more extreme with increasing latitude and altitude. We compared the thermal biology of two populations of Liolaemus pictus argentinus living at two altitudes (771 and ∼1700 m asl). Environmental, microenvironmental, and operative temperatures were studied in order to describe the capture sites, sources of heat, and availability of microenvironments appropriate for thermoregulation. The body temperatures of L. p. argentinus at capture (T_b) and the preferred temperatures in the laboratory (T_p) were recorded and integrated with operative temperatures to calculate the effectiveness of thermoregulation. The high-altitude population was found to have a lower mean T_b (29 °C compared to 33 °C), while the T_p values for both populations were similar (36.7 °C). The analysis of operative temperatures and T_b in relation to T_p showed that L. p. argentinus behaves as a moderate thermoregulator at high altitude and as a poor thermoregulator at the low-altitude site probably due in part to the avoidance of predation risk.     

Can Boreal and Temperate Forest Management be Adapted to the Uncertainties of 21st Century Climate Change?

Considerable uncertainties remain about magnitude and character, if not general direction of anthropogenic climate change. Global mean temperature could increase by 1.5–4.5°C or more over historic levels, and extreme weather events—drought, storms, and flooding—are likely to increase greatly in frequency. Although ecologists and foresters agree that the practice of forestry will be transformed under climate change, these uncertainties compound the challenge of achieving sustainable, adaptive forest management. In this aritcle, we (i) present a multidisciplinary synthesis of current knowledge of responses of temperate and boreal tree species and forest communities to climate change, and (ii) outline silvicultural strategies for adapting temperate and boreal forests to confront climate change. Our knowledge synthesis proceeds through critical appraisals of efforts to model future tree distributions and responses to climate change, and reviews physiological, phenological, acclimation, and epigenetic responses to climate. As is the case of climate change itself, there are numerous uncertainties about tree species and provenance responses to climate change. For example, acclimation of respiration and epigenetic conditioning of seed embryos has the potential to buffer species against limited warming. Provenances within species also display idiosyncratic responses to altered climates, implying that soemm varieties will be more resilient or resistant to climate change than others. Genetically determined limits to climatic tolerance, and the limits of tree community resistance and resilience (speed of recovery from disturbance) in the face of climate-related disturbances are largely unknown. These unknowns require managers to adopt a portfolio of silvicultural strategies, which may range from minor modifications of current practices to design of novel multi-species stands that may have no historical analogue. Forest managers must be prepared to respond nimbly as they develop, incorporate new insights about climate change and species responses to warming into their practices. Marshalling all strategies and sources of knowledge should enable forest managers to mount (at least) a partially successful response to the challenges of climate change.     

草菇低温诱导蛋白研究初探

对低温处理的草菇Volvariella volvacea菌丝体的可溶性蛋白进行分析,发现草菇菌丝在低温协迫中有新的可溶性蛋白产生,应用电泳技术分离纯化了草菇菌丝体中的一个低温诱导蛋白,经等电聚焦分析,该蛋白质的等电点6.79,SDS-聚丙烯酰胺凝胶电泳分析该蛋白质是由分子最为70kD和48kD的两条多肽所组成。     

Protein adaptation to low temperatures: a comparative study of α-tubulin sequences in mesophilic and psychrophilic algae

The α-tubulin genes from two psychrophilic algae belonging to the genus Chloromonas (here named ANT1 and ANT3) have been isolated and sequenced. The genes ant1 and ant3 contain 4 and 2 introns, respectively. The coding DNA sequences are 90% identical but the degree of isology is very high at the polypeptide level (more than 97% strict identities). The ANT1 and ANT3 α-tubulin amino acid sequences were compared to the corresponding sequence of the mesophilic alga Chlamydomonas reinhardtii. Of the 15 substitutions detected in ANT1 and/or ANT3, 5 are common to both psychrophilic algae. The recorded substitutions have been analyzed in terms of cold adaptation on the basis of the available three-dimensional structure of the α,β-tubulin heterodimer from pig brain. Most of these are subtle changes, but two substitutions, M268V and A295V occurring in the region of interdimer contacts, could be of great significance for the cold stability of Antarctic algae microtubules due to the fact that the entropic control of microtubule assembly is particularly high in cold adaptes species. Received: December 24, 1998 / Accepted: April 2, 1999     

Determination of the Role of Cold Acclimation-Induced Diverse Changes in Plant Cells from the Viewpoint of Avoidance of Freezing Injury

Received 4 January 1999/ Accepted in revised form 7 April 1999     

Alterations of gene expression in potato (Solanum commersonii) during cold acclimation

Plantlets of Solanum commersonii stem-culture were acclimated at 5°C day/night temperature for 14 days. Cold hardiness increased from – 3.5°C to – 8.6°C. During the course of acclimation, the synthesis of polypeptides was investigated and poly (A⁺) RNA was isolated. Translation products of poly(A⁺) RNA in a rabbit rcticulocyte lysate system were then analyzed. During the 14 days of acclimation, 23 cold-induced polypeptides were identified. Most of them disappeared following 1 day of de-acclimation at a 20/15°C day/night regime. The synthesis of one group of polypeptides is prominent and stable throughout the acclimation period. The other group is transient. The most prominent and stable polypeptides have molecular weights of 21, 22, 31 and 83 kDa.
Acclimation alters translatable mRNA population during the development of cold hardiness. Two mRNAs encoding in vitro translation products at 26 and 27 kDa were identified during the course of acclimation. These proteins may play important roles in the overall programming for the development of cold hardiness in tuber-bearing S. commersonii.