Temperature Stress Resistance Research Articles

Transcriptomic and metabolomic investigations of methyl jasmonate-mediated enhancement of low temperature stress resistance in Cassia obtusifolia L.

Low temperature stress negatively impacts plant growth and development, reducing crop yields by disrupting metabolite production and accumulation. Cassia obtusifolia L., a widely cultivated medicinal plant in subtropical regions, is particularly vulnerable to such stress. Methyl jasmonate (MeJA) regulates plant growth, defense mechanisms, and secondary metabolite production. This study investigated how C. obtusifolia responds to low temperature stress under MeJA treatment using transcriptomic and metabolomic approaches. MeJA treatment upregulated several transcription factor families, including APE/ERF-ERF, WRKY, NAC, and MYB-related, which modulated the plant's response to cold stress. These transcription factors influenced the expression of genes involved in glycolysis, sugar metabolism, and amino acid pathways, contributing to the plant's adaptive responses. Differentially expressed genes were associated with key metabolic processes such as flavonoid biosynthesis, ribosome function, glycolysis/gluconeogenesis, and sugar metabolism. Using H-NMR and LC-MS techniques, we observed that MeJA induced the accumulation of sugars and amino acids in the leaves of C. obtusifolia seedlings under cold stress, while levels of three flavonoid compounds Isoliquiritigenin, Kaempferol-7-O-glucoside, and Phloretin significantly decreased. Enrichment analysis indicated that MeJA modulates the biosynthetic pathways of these compounds in a dose-dependent manner. Integrating metabolomic and transcriptomic data further elucidated alterations in the flavonoid biosynthetic network and other metabolic pathways under low temperature stress. These findings offer insights into the molecular mechanisms underlying flavonoid synthesis and other metabolic adjustments in C. obtusifolia under MeJA treatment.

Enhancing temperature resilience in dioecious Salix myrtillacea: The role of acetic acid in eco-physiological and microbial adaptations

The effects of climate change on dioecious plants are of growing concern. Dioecious plants have sex-specific eco-physiological responses. This study investigated the response of Salix myrtillacea, a dioecious wood-producing plant with industrial potential, to high (35°C) and low (15°C) temperature stresses. The efficacy of exogenously applied acetic acid (AA) in enhancing sex-specific temperature stress tolerance was also investigated. The research found that female willows showed greater resilience to both temperature extremes than males. The average stress intensity indices for height and basal diameter growth rate were 19.20 % and 10.87 % higher in males than in females, respectively. This was also evidenced by greater physiological adaptations (antioxidant enzyme activity, hormone accumulation) and nutrient assimilation. Compared with high temperature, willows showed better adaptation to low temperature, resulting in a significant stress reduction. In addition, the application of AA significantly reduced stress in both sexes, while distinct sex-specific differences were observed in the composition of the rhizosphere microbial community. The application of AA particularly influenced certain microbial phyla. For example, it increased the relative abundance of Bacteroidetes by 46.11 % and Chloroflexi by 42.16 %, while decreased Acidobacteria by 29.28 %. This supported carbon uptake and storage to improve stress tolerance in females under high temperature stress. Conversely, males showed a stronger association with fungi to maintain stability. In conclusion, the application of AA significantly improved the temperature stress resistance of dioecious willows. There were pronounced improvements in growth, physiological adaptations, and microbial interactions. These effects were particularly evident in female plants. These findings highlight the potential of AA in tailoring climate resilience strategies for dioecious species.

Study on the protective performance of coating system for thermal spraying zinc on radar

In response to the harsh marine environment protection needs of radar, the protective performance of 9 types of coating systems for thermal spraying zinc was studied through condensation tests, salt spray tests, and temperature tests. The blistering phenomenon of the radar thermal spraying zinc matching protective coating system was analyzed. The research results showed that the blistering of the thermal spraying zinc matching protective coating system may be related to the pores of the sealing coating. Among the 9 coating systems, the comprehensive performance of B and D coating systems in terms of moisture resistance, salt spray resistance, and temperature stress resistance is significantly superior to other coatings. The radar using B and D coating systems has been successfully applied to various types of harsh marine environments, improving the radar’s protective performance.

Effects of enriched Artemia urmiana with polyunsaturated fatty acids and vitamin C on reproductive performance and larval temperature stress resistance of Severum Heros severus

ABSTRACT The influence of enriched adult Artemia urmiana with essential fatty acids (EFA) and vitamin C on aquarium-raised Severum Heros severus reproductive performance, larval resistance to high temperature stress (34°C), and intervals between each spawning were determined. Broodstock were fed with formulated pellet diet (P), P + adult Artemia, Artemia + EFA (30%), Artemia + EFA- +0.5 g vitamin C and Artemia + EFA +1 g vitamin C for 10 weeks. Results indicated that enriched Artemia with EFA + 1 g vitamin C had significantly higher larval resistance to high temperature, and shorter intervals for the eight spawning cycles than the other experimental diets. Artemia + EFA +0.5 g vitamin C resulted in higher fertilization and hatching rates than the other treatments. Our results indicated that feeding live feed reduced the whole time for the eight spawning cycles, increased reproductive performance, decreased the interspawning time, and increased the larvae quality in terms of resistance to stress and higher survival rate.

Comprehensive characterization and expression analysis of enzymatic antioxidant gene families in passion fruit (Passiflora edulis)

Passion fruit, a valuable tropical fruit, faces climate-related growth challenges. Antioxidant enzymes are vital for both stress protection and growth regulation in plants. We first provided systemic analysis of enzymatic antioxidant gene families in passion fruit, identifying 90 members including 11 PeSODs, 45 PeAPXs, 8 PeCATs, 7 PeGPXs, 6 PeMDHARs, 8 PeDHARs, and 5 PeGRs. Gene members in each gene family with same subcellular localization showed closer phylogenetic relationship. Many antioxidant genes exhibited tissue- or developmental stage-specific expression patterns during floral and fruit development, with some widely expressed. Their co-expressed genes were linked to photosynthesis and energy metabolism, suggesting roles in protecting highly proliferating tissues from oxidative damage. Potential genes for enhancing temperature stress resistance were identified. The involvement of diverse regulatory factors including miRNAs, transcription factors, and CREs might contribute to the complex roles of antioxidant genes. This study informs future research on antioxidant genes and passion fruit breeding.

Economical production of Pichia pastoris single cell protein from methanol at industrial pilot scale

BackgroundMethanol, synthesized from CO2, is a potentially sustainable one-carbon (C1) resource for biomanufacturing. The use of methanol as a feedstock to produce single cell protein (SCP) has been investigated for decades as an alternative to alleviate the high global demand for animal-derived proteins. The methylotrophic yeast Pichia pastoris is an ideal host for methanol-based SCP synthesis due to its natural methanol assimilation ability. However, improving methanol utilization, tolerance to higher temperature, and the protein content of P. pastoris are also current challenges, which are of great significance to the economical industrial application using methanol as a feedstock for SCP production.ResultsIn the present work, adaptive laboratory evolution (ALE) has been employed to overcome the low methanol utilization efficiency and intolerance to a higher temperature of 33 °C in P. pastoris, associated with reduced carbon loss due to the lessened detoxification of intracellular formaldehyde through the dissimilation pathway and cell wall rearrangement to temperature stress resistance following long-term evolution as revealed by transcriptomic and phenotypic analysis. By strengthening nitrogen metabolism and impairing cell wall synthesis, metabolic engineering further increased protein content. Finally, the engineered strain via multi-strategy produced high levels of SCP from methanol in a pilot-scale fed-batch culture at 33 °C with a biomass of 63.37 g DCW/L, methanol conversion rate of 0.43 g DCW/g, and protein content of 0.506 g/g DCW. SCP obtained from P. pastoris contains a higher percentage of protein compared to conventional foods like soy, fish, meat, whole milk, and is a source of essential amino acids, including methionine, lysine, and branched-chain amino acids (BCAAs: valine, isoleucine, leucine).ConclusionsThis study clarified the unique mechanism of P. pastoris for efficient methanol utilization, higher temperature resistance, and high protein synthesis, providing a P. pastoris cell factory for SCP production with environmental, economic, and nutritional benefits.

Transcriptome Analysis of the Regulatory Mechanism of Exogenous Spermidine in High Temperature Stress Resistance of Tomato Seedlings

Previous studies have shown that spermidine (Spd) can improve tolerance to high temperature stress in tomato seedlings. To further understand how Spd regulates the molecular components of high temperature stress signaling pathways, we performed a genome-wide transcriptome analysis in tomato seedlings treated with high temperature and/or exogenous Spd. The results demonstrate that, under high temperature conditions, Spd significantly alleviated the inhibition of plant growth, as well as improving the net photosynthetic rate and pigment contents. The transcriptome analysis revealed thousands of differentially expressed genes (DEGs) in response to high temperature with or without Spd treatment. Half of the genes were induced by high temperature, part of the genes were induced by high temperature with exogenous Spd, and some were induced by the coordinated effect of high temperature and Spd. A GO analysis indicated that genes involved in cellular processes, metabolic processes, and nucleotide binding in the sample were subjected to high temperature. Some DEGs were also involved in plant physiological processes. These results suggest potential genes and molecular pathways were involved in the exogenous Spd-mediated tolerance to high temperature stress in tomato plants. A JA signaling test was designed, which indicated that MYC2 and JAS1 in heat-resistant materials were both increased, through quantitative RT-PCR.

Genome-Wide Identification and Expression Analysis of BraGLRs Reveal Their Potential Roles in Abiotic Stress Tolerance and Sexual Reproduction

Glutamate receptors (GLRs) are involved in multiple functions during the plant life cycle through affecting the Ca2+ concentration. However, GLRs in Brassica species have not yet been reported. In this study, 16 glutamate receptor-like channels (GLR) belonged to two groups were identified in the Brassica rapa (B. rapa) genome by bioinformatic analysis. Most members contain domains of ANF_receptor, Peripla_BP_6, Lig_chan, SBP_bac_3, and Lig_chan_Glu_bd that are closely related to glutamate receptor channels. This gene family contains many elements associated with drought stress, low temperature stress, methyl jasmonate (MeJA), salicylic acid (SA), and other stress resistance. Gene expression profiles showed that BraGLR genes were expressed in roots, stems, leaves, flowers, and siliques. BraGLR5 expression was elevated after drought stress in drought-sensitive plants. BraGLR1, BraGLR8, and BraGLR11 expression were significantly upregulated after salt stress. BraGLR3 expression is higher in the female sterile-line mutants than in the wild type. The expression levels of BraGLR6, BraGLR9, BraGLR12, and BraGLR13 were significantly higher in the male sterile-line mutants than in the wild type. The expression of most BraGLRs increased after self-pollination, with BraGLR9 exhibiting the greatest increase. These results suggest that BraGLRs play an important role in abiotic stress tolerance and sexual reproduction.

Interaction effects of desiccation and temperature stress resistance across Spodoptera frugiperda (Lepidoptera, Noctuidae) developmental stages

Insects encounter multiple overlapping physiologically challenging environmental stressors in their habitats. As such, the ability of insects to withstand these stressors singly or interactively is fundamental in population persistence. Following its invasion in Africa, Spodoptera frugiperda (Lepidoptera: Noctuidae) has successfully established and spread in most parts of the continent. However, the mechanisms behind its successful survival across arid and semi-arid African environments are relatively unknown. Here, we investigated the water balance of S. frugiperda across its developmental stages. Given the relationships between desiccation stress, temperature stress and other life history traits in arid ecosystems, we also measured interaction effects across metrics of these traits. Specifically, we measured basal body water content (BWC), water loss rates (WLRs) and the effects of desiccation pre-treatment on critical thermal minimum (CTmin), critical thermal maximum (CTmax) and fecundity. Body water content and WLR increased with age across larval instars. However, the effects of desiccation environments on WLRs were more dramatic for 5th and 6th larval instars. The 5th and 6th instars exhibited highest BWC and magnitude of WLRs plastic responses following desiccation treatment. The effects of desiccation pre-treatment on temperature tolerance were less apparent, only significantly improving CTmin in 2nd and 3rd larval instars and reducing CTmax in 5th instars. In addition, desiccation pre-treatment showed no significant effects on fecundity. These results show that water balance traits differ with developmental stage, while the effects of desiccation pre-treatment were more dramatic and inconclusive. The differential desiccation resistance, high proportional BWC and no desiccation pre-treatment effects on fecundity may help the species survive in arid and semi-arid environments. This information provides insights into understanding S. frugiperda survival under desiccating arid and semi-arid tropical environments and is significant in predicting pest outbreaks.

Comparative transcriptome analysis to reveal the genes and pathways associated with adaptation strategies in two different populations of Manila clam (Ruditapes philippinarum) under acute temperature challenge

Increasing temperature is causing rapid changes in oceanic environments. Understanding the responses of marine animals to such changes remains a major challenge, yet it is key to predicting future biodiversity loss or gain. In this study, we investigated molecular mechanisms of adaptation to acute temperature change in low and high latitude populations of the Manila clam Ruditapes philippinarum. Using transcriptome analysis, we studied temperature-responsive genes and pathways in clams cultured under acute temperature stress (−1°C and 28°C) and identified an extensive set of genes and pathways that respond to acute temperature stress. Physiological changes at the molecular level were compared to explore potential differences in the response of clams and their adaptation to temperature change and to uncover the underlying mechanisms of resilience or sensitivity to stress conditions in the two clam populations. The enrichment of genes involved in protein processing in the endoplasmic reticulum was integral to the adaptation of clams to stressful conditions. Furthermore, phagosome-related genes and pathways were significantly enriched under acute high temperature stress. The upregulation of xenobiotic metabolism by cytochrome P450 showed a population-specific response in the low-latitude clams under both heat and cold stress but not in the high-latitude clams, whereas genes encoding peroxisomes were upregulated in high-latitude clams under heat stress but not in low-latitude clams. This study provides useful information related to the response of R. philippinarum to temperature stress, which could be helpful for improving the temperature stress resistance of these clams in the aquaculture industry. Our results may also help predict future biodiversity trends under temperature change scenarios.

Comparison of growth, survival and fertility of the southern and northern populations of Crassostrea ariakensis and their hybrids in southern China

Crassostrea ariakensis is widely distributed in the estuaries of China and has the advantages of wide salinity adaptation and strong resistance, but the artificial aquaculture of C. ariakensis is mainly concentrated in southern China. Long-term geographical isolation resulted in genetic variation between the northern and southern C. ariakensis populations. In this study, the reproductive isolation between two independent population of C. ariakensis was evaluated by hybridization. Results showed that the fertilization rate, cleavage rate and D Larval rate of interpopulation hybrids (NS- northern ♂ × southern ♀ and SN- southern ♂ × northern ♀) were significantly lower than those of intrapopulation inbreed groups (SS and NN). Moreover, southern maternal larvae (SS and NS) have significant survival advantages. The growth trend between the two sites was very different in early stage (from 90th to 210th day), but it was consistent in late stage (from 210th to 480th day), with a significant decreasing trend of SS > NS > SN > NN. The survival rates of SN and NS was significantly higher than that of NN, indicating that the high temperature tolerance and stress resistance of hybrids were improved. The positive maternal effect advantages (MEAs) at most time points of both sites demonstrated that parental origin, especially the maternal origin, had a significant effect on the survival and growth of progeny. Hybrid advantages (HAs) for growth of both sites were opposite, and positive HAs of survival accounted for most of both sites, indicating that environmental conditions and survival could significantly affect the growth, and interpopulation hybrids did not necessarily always show positive HAs. Moreover, the maternal origin would affect the shell shape and shell hardness, resulted in NS similar to SS and SN similar to NN, respectively. Additionally, all interpopulation hybrids could produce mature gametes. These results confirmed that there was no serious reproductive isolation between the two populations. The southern maternal groups, especially SS, had better growth and survival advantages, could be used as good new strains for large-scale breeding in southern China, and also provided basic data for the commercial promotion of C. ariakensis in southern China.

Heterochromatic foci and transcriptional repression by an unstructured MET-2/SETDB1 co-factor LIN-65.

The segregation of the genome into accessible euchromatin and histone H3K9-methylated heterochromatin helps silence repetitive elements and tissue-specific genes. In Caenorhabditis elegans, MET-2, the homologue of mammalian SETDB1, catalyzes H3K9me1 and me2, yet like SETDB1, its regulation is enigmatic. Contrary to the cytosolic enrichment of overexpressed MET-2, we show that endogenous MET-2 is nuclear throughout development, forming perinuclear foci in a cell cycle-dependent manner. Mass spectrometry identified two cofactors that bind MET-2: LIN-65, a highly unstructured protein, and ARLE-14, a conserved GTPase effector. All three factors colocalize in heterochromatic foci. Ablation of lin-65, but not arle-14, mislocalizes and destabilizes MET-2, resulting in decreased H3K9 dimethylation, dispersion of heterochromatic foci, and derepression of MET-2 targets. Mutation of met-2 or lin-65 also disrupts the perinuclear anchoring of genomic heterochromatin. Loss of LIN-65, like that of MET-2, compromises temperature stress resistance and germline integrity, which are both linked to promiscuous repeat transcription and gene expression.

Effect of Salt and Temperature Stress Resistance on the Tolerance of Candida parapsilosis to Extreme Conditions

Effect of Salt and Temperature Stress Resistance on the Tolerance of Candida parapsilosis to Extreme Conditions

A Study on Adiabatic Temperature Rise Test and Temperature Stress Simulation of Rock-Fill Concrete

In the present study, we investigate the effect of the adiabatic temperature rise property of rock-fill concrete (RFC) on the temperature stress and crack resistance of RFC gravity dams. We conducted tests on the adiabatic temperature rise of RFC with a rock-fill ratio of 42%, 49%, and 55%, respectively. Based on the regression analysis of the test data, a calculation model of the adiabatic temperature rise, considering the rock-fill ratio, is developed, and the finite element analysis software ANSYS is employed to simulate the whole process of the temperature and temperature stress fields of a RFC gravity dam. The main findings of the study are as follows: (1) Both the adiabatic temperature rise rate and the final adiabatic temperature rise of RFC are negatively correlated with the rock-fill ratio. (2) The calculation model of the adiabatic temperature rise of RFC is characterized by its high accuracy, which can help predict the adiabatic temperature rise of RFC with different rock-fill ratios. (3) Without any temperature control measures, the maximum temperature stress of RFC generated by the temperature rise of hydration heat in the RFC gravity dam is 0.93 MPa, which meets the standard of temperature stress control. The results of the present study indicate that dam construction with RFC can simplify the measures of temperature control and crack prevention, improve the construction efficiency, and reduce the cost of dam construction.

Co-overexpression of the Constitutively Active Form of OsbZIP46 and ABA-Activated Protein Kinase SAPK6 Improves Drought and Temperature Stress Resistance in Rice.

Drought is one of the major abiotic stresses threatening rice (Oryza sativa) production worldwide. Drought resistance is controlled by multiple genes, and therefore, a multi-gene genetic engineering strategy is theoretically useful for improving drought resistance. However, the experimental evidence for such a strategy is still lacking. In this study, a few drought-responsive genes from rice were assembled by a multiple-round site-specific assembly system, and the constructs were introduced into the rice cultivar KY131 via Agrobacterium-mediated transformation. The transgenic lines of the multi-gene and corresponding single-gene constructs were pre-evaluated for drought resistance. We found that the co-overexpression of two genes, encoding a constitutively active form of a bZIP transcription factor (OsbZIP46CA1) and a protein kinase (SAPK6) involved in the abscisic acid signaling pathway, showed significantly enhanced drought resistance compared with the single-gene transgenic lines and the negative transgenic plants. Single-copy lines of this bi-gene combination (named XL22) and the corresponding single-gene lines were further evaluated for drought resistance in the field using agronomical traits. The results showed that XL22 exhibited greater yield, biomass, spikelet number, and grain number under moderate drought stress conditions. The seedling survival rate of XL22 and the single-gene overexpressors after drought stress treatment also supported the drought resistance results. Furthermore, expression profiling by RNA-Seq revealed that many genes involved in the stress response were specifically up-regulated in the drought-treated XL22 lines and some of the stress-related genes activated in CA1-OE and SAPK6-OE were distinct, which could partially explain the different performances of these lines with respect to drought resistance. In addition, the XL22 seedlings showed improved tolerance to heat and cold stresses. Our results demonstrate that the multi-gene assembly in an appropriate combination may be a promising approach in the genetic improvement of drought resistance.

Variation in adult stress resistance does not explain vulnerability to climate change in copper butterflies.

Ongoing climate change is a major threat to biodiversity. However, although many species clearly suffer from ongoing climate change, others benefit from it, for example, by showing range expansions. However, which specific features determine a species' vulnerability to climate change? Phenotypic plasticity, which has been described as the first line of defence against environmental change, may be of utmost importance here. Against this background, we here compare plasticity in stress tolerance in 3 copper butterfly species, which differ arguably in their vulnerability to climate change. Specifically, we investigated heat, cold and desiccation resistance after acclimatization to different temperatures in the adult stage. We demonstrate that acclimation at a higher temperature increased heat but decreased cold tolerance and desiccation resistance. Contrary to our predictions, species did not show pronounced variation in stress resistance, though plastic capacities in temperature stress resistance did vary across species. Overall, our results seemed to reflect population-rather than species-specific patterns. We conclude that the geographical origin of the populations used should be considered even in comparative studies. However, our results suggest that, in the 3 species studied here, vulnerability to climate change is not in the first place determined by stress resistance in the adult stage. As entomological studies focus all too often on adults only, we argue that more research effort should be dedicated to other developmental stages when trying to understand insect responses to environmental change.

Independent suppression of ribosomal +1 frameshifts by different tRNA anticodon loop modifications

ABSTRACTRecently, a role for the anticodon wobble uridine modification 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U) has been revealed in the suppression of translational +1 frameshifts in Saccharomyces cerevisiae. Loss of either the mcm5U or s2U parts of the modification elevated +1 frameshift rates and results obtained with reporters involving a tRNALysUUU dependent frameshift site suggested these effects are caused by reduced ribosomal A-site binding of the hypomodified tRNA. Combined loss of mcm5U and s2U leads to increased ribosome pausing at tRNALysUUU dependent codons and synergistic growth defects but effects on +1 frameshift rates remained undefined to this end. We show in here that simultaneous removal of mcm5U and s2U results in synergistically increased +1 frameshift rates that are suppressible by extra copies of tRNALysUUU. Thus, two distinct chemical modifications of the same wobble base independently contribute to reading frame maintenance, loss of which may cause or contribute to observed growth defects. Since the thiolation pathway is sensitive to moderately elevated temperatures in yeast, we observe a heat-induced increase of +1 frameshift rates in wild type cells that depends on the sulfur transfer protein Urm1. Furthermore, we find that temperature-induced frameshifting is kept in check by the dehydration of N6-threonylcarbamoyladenosine (t6A) to its cyclic derivative (ct6A) at the anticodon adjacent position 37. Since loss of ct6A in elp3 or urm1 mutant cells is detrimental for temperature stress resistance we assume that conversion of t6A to ct6A serves to limit deleterious effects on translational fidelity caused by hypomodified states of wobble uridine bases.

Characterization of the Fatty Acid Desaturase Genes in Cucumber: Structure, Phylogeny, and Expression Patterns

Fatty acid desaturases (FADs) introduce double bonds into the hydrocarbon chains of fatty acids to produce unsaturated fatty acids, and therefore play a critical role in plant development and acclimation to environmental stresses. In this study, 23 full-length FAD genes in cucumber (Cucumis sativus L.) were identified through database searches, including three CsFAB2 genes, two CsFAD2 genes, fourteen CsFAD5 genes, and one gene each for CsFAD3, CsFAD4, CsFAD6 and CsFAD7. These cucumber FAD genes were distributed on all seven chromosomes and two additional scaffolds. Based on a phylogenetic analysis, the cucumber FAD proteins were clustered into five subfamilies with their counterparts from other plants. Gene structures and protein sequences were considerably conserved in each subfamily. All three CsFAB2 proteins shared conserved structure with the known plant soluble FAD proteins. The other cucumber FADs belonged to the membrane-bound FADs and contained three highly conserved histidine boxes. Additionally, the putative endoplasmic reticulum retention signal was found at the C-termini of the CsFAD2 and CsFAD3 proteins, while the N-termini of CsFAD4, CsFAD5, CsFAD6, CsFAD7 and three CsFAB2s contained a predicted chloroplast signal peptide, which was consistent with their associated metabolic pathways. Furthermore, a gene expression analysis showed that CsFAD2 and CsFAD3 were universally expressed in all tested tissues, whereas the other cucumber FAD genes were preferentially expressed in the cotyledons or leaves. The tissue-specific expression patterns of cucumber FAD genes were correlated well with the differences in the fatty acid compositions ofroots and leaves. Finally, the cucumber FAD genes showed a cold-induced and heat-repressed expression pattern, although with distinct regulatory time courses among the different CsFAD members, which indicates the potential roles of the FADs in temperature stress resistance in cucumber.

Temperature-stress resistance and tolerance along a latitudinal cline in North American Arabidopsis lyrata.

The study of latitudinal gradients can yield important insights into adaptation to temperature stress. Two strategies are available: resistance by limiting damage, or tolerance by reducing the fitness consequences of damage. Here we studied latitudinal variation in resistance and tolerance to frost and heat and tested the prediction of a trade-off between the two strategies and their costliness. We raised plants of replicate maternal seed families from eight populations of North American Arabidopsis lyrata collected along a latitudinal gradient in climate chambers and exposed them repeatedly to either frost or heat stress, while a set of control plants grew under standard conditions. When control plants reached maximum rosette size, leaf samples were exposed to frost and heat stress, and electrolyte leakage (PEL) was measured and treated as an estimate of resistance. Difference in maximum rosette size between stressed and control plants was used as an estimate of tolerance. Northern populations were more frost resistant, and less heat resistant and less heat tolerant, but—unexpectedly—they were also less frost tolerant. Negative genetic correlations between resistance and tolerance to the same and different thermal stress were generally not significant, indicating only weak trade-offs. However, tolerance to frost was consistently accompanied by small size under control conditions, which may explain the non-adaptive latitudinal pattern for frost tolerance. Our results suggest that adaptation to frost and heat is not constrained by trade-offs between them. But the cost of frost tolerance in terms of plant size reduction may be important for the limits of species distributions and climate niches.

Are Different Allozyme Genotypes of the ButterflyPolyommatus coridonAdapted to Resist Cold and Heat Shocks?

Polymorphisms are widely known in allozymes and are often assumed neutral in the context of phylogenetic and population genetic analyses. However, several studies revealed that, in some loci and species, selection is strongly acting on allozymes and that temperature seems to be an important selective agent. Therefore, we individually determined the recovery time from chill-coma and heat knock-down time of 542 individuals of P. coridon sampled at four sites. Afterwards, we analyzed patterns of allozyme variations in these butterflies by allozyme electrophoresis of eleven loci to test the enzymes' performance under thermal stress conditions and to investigate the possibility of adaptive genotypic variation in relation to temperature stress resistance traits. We obtained significant differences of reactions to cold and heat shocks between the sexes and between reared and wild-captured individuals, but no significant differences among genotypes were found for most of the investigated allozyme loci. However, the Aat1 locus showed significant differences between different genotypes in chill-coma recovery times (p < 0.001), and marginal differences in heat knock-down times (p = 0.073). Thus, Aat1 might be a target for thermal selection. Consequently, our results revealed no clear influence of temperature on most allozyme loci and the otherwise observed differentiation in P. coridon might be explained by stochasticity, and thus geographic structuring should reflect biogeographic processes.