Higher Cold Tolerance Research Articles

Comprehensive Evaluation for Cold Tolerance in Wucai (Brassica campestris L.) by the Performance Index on an Absorption Basis (PIabs)

Wucai is a biannual leafy vegetable that is more sensitive to cold than most Brassicaceae vegetables. Here, phenotypic differences in wucai were investigated to identify those genotypes with high cold tolerance at low temperature, which could allow their cultivation in cold climates. In all, on the basis of PIabs, 20 wucai genotypes (10 lower PIabs and 10 higher PIabs) were selected from a collection of 124 genotypes. Both W16-13 and SW-3 (higher PIabs) and the LS-6 and W15-16 (lower PIabs) were screened from the 20 wucai genotypes according to several key plant physiological traits: net photosynthetic rate, electrolyte leakage, chilling injury index, specific leaf area, malondialdehyde contents, and PIabs. To further verify the reliability of PIabs, four genotypes were grown under low temperature gradient conditions and their morphological indexes, chlorophyll content, total antioxidant capacity, fluorescence transients (OJIP transients), leaf cell ultrastructure, and gene expression were measured. These indicators strongly demonstrated that the W16-13 and SW-3, which had higher PIabs, possessed higher resistance to cold stress, while both LS-6 and W15-16 were sensitive to cold. As this study shows, the easily measured performance index, PIabs, could be applied to wucai genotypes to screen for one or more varieties characterized by higher cold tolerance.

Transcriptomic profiling revealed genes involved in response to cold stress in maize

Maize is an important food crop. Chilling stress can decrease maize production by affecting seed germination and seedling growth, especially in early spring. We analysed chlorophyll fluorescence, membrane lipids, secondary metabolites and the transcriptome of two maize inbred lines (chilling-tolerant M54 and chilling-sensitive 753F) after 0, 4 and 24 h cold stress. M54 showed better ability to protect PSII and accumulate secondary metabolites. From RNA sequencing data, we determined that the majority of cold-affected genes were involved in photosynthesis, secondary metabolism, and signal transduction. Genes important for maintaining photosystem structure and for regulating electron transport were less affected by cold stress in M54 than in 753F. Expression of genes related to secondary metabolism and unsaturated fatty acid synthesis were upregulated more strongly in M54 than in 753F and M54 accumulated more unsaturated fatty acids and secondary metabolites. As a result, M54 achieved relatively high cold tolerance by protecting the photosystems and maintaining the stability of cell membranes.

Cold Acclimation Favors Metabolic Stability in Drosophila suzukii.

The invasive fruit fly pest, Drosophila suzukii, is a chill susceptible species, yet it is capable of overwintering in rather cold climates, such as North America and North Europe, probably thanks to a high cold tolerance plasticity. Little is known about the mechanisms underlying cold tolerance acquisition in D. suzukii. In this study, we compared the effect of different forms of cold acclimation (at juvenile or at adult stage) on subsequent cold tolerance. Combining developmental and adult cold acclimation resulted in a particularly high expression of cold tolerance. As found in other species, we expected that cold-acclimated flies would accumulate cryoprotectants and would be able to maintain metabolic homeostasis following cold stress. We used quantitative target GC-MS profiling to explore metabolic changes in four different phenotypes: control, cold acclimated during development or at adult stage or during both phases. We also performed a time-series GC-MS analysis to monitor metabolic homeostasis status during stress and recovery. The different thermal treatments resulted in highly distinct metabolic phenotypes. Flies submitted to both developmental and adult acclimation were characterized by accumulation of cryoprotectants (carbohydrates and amino acids), although concentrations changes remained of low magnitude. After cold shock, non-acclimated chill-susceptible phenotype displayed a symptomatic loss of metabolic homeostasis, correlated with erratic changes in the amino acids pool. On the other hand, the most cold-tolerant phenotype was able to maintain metabolic homeostasis after cold stress. These results indicate that cold tolerance acquisition of D. suzukii depends on physiological strategies similar to other drosophilids: moderate changes in cryoprotective substances and metabolic robustness. In addition, the results add to the body of evidence supporting that mechanisms underlying the different forms of acclimation are distinct.

Response of biomass accumulation in wheat to low-temperature stress at jointing and booting stages

Climate change has resulted in a continuous increase in the frequency, intensity, and duration of extreme low-temperature events and poses a serious threat to wheat production in China. To better understand the effects of low temperature on wheat photosynthetic production and yield formation, two-year temperature controlled experiments in phytotrons were performed with two different cold-sensitive winter wheat cultivars at five daily maximum/minimum temperature levels and three temperature durations—2, 4 and 6 days—at both jointing and booting stages. Except for its effect on mean net assimilation rate (MNAR) at jointing, low temperature level had significant negative effects on mean leaf area index (MLAI), mean net assimilation rate (MNAR), harvest index (HI), biomass per plant (BPPM) and grain yield per plant (GYPP), while photosynthetic duration (D) (except for Yangmai16 at jointing) was significantly positively affected. Moreover, low temperature duration and its interaction with low temperature level had negative effects on MLAI, MNAR, HI, BPPM and GYPP, but only the effects of low temperature duration on HI, BPPM and GYPP and the interaction effect on BPPM and GYPP reached a significant level. In addition, BPPM and GYPP were more sensitive to low temperature at booting than at jointing stage. Furthermore, significant negative linear relationships were observed between the accumulated cold degree days (ACDD) and MLAI, MNAR, HI, BPPM and GYPP, while a significant positive linear relationship was observed between ACDD and D in both cultivars. The contribution of BPPM to the variation of GYPP was greater than that of HI in both cultivars. However, for biomass, from the first day of low-temperature treatment to maturity (BPPT-M), the major variation was caused by MLAI when low temperature occurred at jointing and by MNAR when low temperature occurred at booting. These results could support the improvement of crop model algorithms under cold stress and assist in the wheat breeding with higher cold tolerance.

Registration of ‘HoCP 04‐838’ Sugarcane

‘HoCP 04‐838’ (Reg. No. CV‐181, PI 687221) sugarcane (interspecific hybrids of Saccharum spp.) was selected and evaluated by scientists at the USDA–ARS, working cooperatively with the Louisiana State University Agricultural Center, and the American Sugarcane League, Inc., from a cross between the female parent ‘HoCP 85‐845’ and the male parent ‘LCP 85‐384’. It was released to growers in Louisiana in May 2011. Yields from three crops (plant, first ratoon, and second ratoon) at 12 farm locations compared well with HoCP 96‐540, the most widely grown cultivar in Louisiana during that time. The plant‐cane sucrose yield (Mg ha−1) of HoCP 04‐838 was equivalent to HoCP 96‐540, and cane yield was significantly higher than HoCP 96‐540. HoCP 04‐838 is earlier maturing than HoCP 96‐540 but not as early as ‘HoCP 00‐950’, the high sucrose standard cultivar. Mature stalk cold tolerance was similar to LCP 85‐384, the cold tolerance standard. HoCP 04‐838 is resistant to smut, mosaic caused by Sorghum mosaic virus, brown rust, and ratoon stunt. HoCP 04‐838 is moderately resistant to leaf scald and is susceptible to Sugarcane yellow leaf virus. It is resistant to sugarcane borer. HoCP 04‐838's high yield potential and cold tolerance make it a useful addition to existing commercial sugarcane cultivars in Louisiana.

Signatures of divergent selection for cold tolerance in maize

Divergently selected genotypes can be used for detecting the genomic regions affecting the selected trait (selection signature). Moreover, the genetic distances (GDs) among divergently selected lines can be correlated with the agronomic performances of the crosses among them. Using as source the maize F2 of B73 × IABO78, we previously conducted four cycles of divergent recurrent selection and three cycles of divergent selection in inbreeding for cold tolerance at germination. We finally obtained 10 lines selected for low (L) and 10 lines selected for high (H) cold tolerance, which exhibited a notable divergence for both the selected and associated traits. Herein, we investigated the 20 lines and the 28 single diallel crosses among eight random lines (four L and four H); the main objectives were to identify the putative regions controlling the selected and associated traits and to study the relationships between crosses performances and GDs among their parental lines. Allele frequencies at 932 recombination blocks based on 19,220 polymorphic SNPs were obtained for the two lines’ groups; the F ST calculated across sliding windows indicated 18 regions highly divergent between groups. The increasing alleles for cold tolerance were contributed by both parents, consistently with the transgressive segregations previously found. Several regions associated to DG also affected various agronomic traits. The cross performances showed some relationships with the genetic distances among parental lines for traits affected by dominance, provided that all crosses were considered, while these relationships vanished when only L × H crosses were examined.

Early Cold-Induced Peroxidases and Aquaporins Are Associated With High Cold Tolerance in Dajiao (Musa spp. 'Dajiao').

Banana is an important tropical fruit with high economic value. One of the main cultivars (‘Cavendish’) is susceptible to low temperatures, while another closely related specie (‘Dajiao’) has considerably higher cold tolerance. We previously reported that some membrane proteins appear to be involved in the cold tolerance of Dajiao bananas via an antioxidation mechanism. To investigate the early cold stress response of Dajiao, here we applied comparative membrane proteomics analysis for both cold-sensitive Cavendish and cold-tolerant Dajiao bananas subjected to cold stress at 10°C for 0, 3, and 6 h. A total of 2,333 and 1,834 proteins were identified in Cavendish and Dajiao, respectively. Subsequent bioinformatics analyses showed that 692 Cavendish proteins and 524 Dajiao proteins were predicted to be membrane proteins, of which 82 and 137 differentially abundant membrane proteins (DAMPs) were found in Cavendish and Dajiao, respectively. Interestingly, the number of DAMPs with increased abundance following 3 h of cold treatment in Dajiao (80) was seven times more than that in Cavendish (11). Gene ontology molecular function analysis of DAMPs for Cavendish and Dajiao indicated that they belong to eight categories including hydrolase activity, binding, transporter activity, antioxidant activity, etc., but the number in Dajiao is twice that in Cavendish. Strikingly, we found peroxidases (PODs) and aquaporins among the protein groups whose abundance was significantly increased after 3 h of cold treatment in Dajiao. Some of the PODs and aquaporins were verified by reverse-transcription PCR, multiple reaction monitoring, and green fluorescent protein-based subcellular localization analysis, demonstrating that the global membrane proteomics data are reliable. By combining the physiological and biochemical data, we found that membrane-bound Peroxidase 52 and Peroxidase P7, and aquaporins (MaPIP1;1, MaPIP1;2, MaPIP2;4, MaPIP2;6, MaTIP1;3) are mainly involved in decreased lipid peroxidation and maintaining leaf cell water potential, which appear to be the key cellular adaptations contributing to the cold tolerance of Dajiao. This membrane proteomics study provides new insights into cold stress tolerance mechanisms of banana, toward potential applications for ultimate genetic improvement of cold tolerance in banana.

Thyroid transcriptome analysis reveals different adaptive responses to cold environmental conditions between two chicken breeds.

Selection for cold tolerance in chickens is important for improving production performance and animal welfare. The identification of chicken breeds with higher cold tolerance and production performance will help to target candidates for the selection. The thyroid gland plays important roles in thermal adaptation, and its function is influenced by breed differences and transcriptional plasticity, both of which remain largely unknown in the chicken thyroid transcriptome. In this study, we subjected Bashang Long-tail (BS) and Rhode Island Red (RIR) chickens to either cold or warm environments for 21 weeks and investigated egg production performance, body weight changes, serum thyroid hormone concentrations, and thyroid gland transcriptome profiles. RIR chickens had higher egg production than BS chickens under warm conditions, but BS chickens produced more eggs than RIRs under cold conditions. Furthermore, BS chickens showed stable body weight gain under cold conditions while RIRs did not. These results suggested that BS breed is a preferable candidate for cold-tolerance selection and that the cold adaptability of RIRs should be improved in the future. BS chickens had higher serum thyroid hormone concentrations than RIRs under both environments. RNA-Seq generated 344.3 million paired-end reads from 16 sequencing libraries, and about 90% of the processed reads were concordantly mapped to the chicken reference genome. Differential expression analysis identified 46–1,211 genes in the respective comparisons. With regard to breed differences in the thyroid transcriptome, BS chickens showed higher cell replication and development, and immune response-related activity, while RIR chickens showed higher carbohydrate and protein metabolism activity. The cold environment reduced breed differences in the thyroid transcriptome compared with the warm environment. Transcriptional plasticity analysis revealed different adaptive responses in BS and RIR chickens to cope with the cold, and showed higher responsiveness in BS compared with RIR chickens, suggesting greater adaptability of the thyroid in BS chickens. Moreover, 10,053 differential splicing events were revealed among the groups, with RNA splicing and processing, gene expression, transport, and metabolism being the main affected biological processes, identifying a valuable alternative splicing repertoire for the chicken thyroid. A short isoform of TPO (encoding thyroid peroxidase) containing multiple open reading frames was generated in both breeds by skipping exons 4 and 5 in the cold environment. These findings provide novel clues for future studies of the molecular mechanisms underlying cold adaptation and/or acclimation in chickens.

Registration of Maize Inbred Line Bo23 with High Cold Tolerance and Agronomic Performance for Early Sowing

Bo23 (Reg. No. GP‐599, PI 677346) is a maize (Zea mays L.) inbred line developed at the Department of Agricultural Sciences, University of Bologna (Bologna, Italy), using as source the F2 of the cross B73 × IABO78. B73 is a well‐known inbred from a US Corn Belt germplasm, and IABO78 is an inbred from Italian germplasm not previously used in breeding. Bo23 was released in 2016 due to its high cold tolerance and agronomic performance when sown early. The breeding procedure leading to Bo23 consisted of four cycles of full‐sib recurrent selection and three cycles of selection in inbreeding for germination at low temperature. In the evaluation of selection responses, a line coded as H102 (now Bo23) excelled for cold tolerance in the field and for agronomic traits. Therefore, Bo23 was further evaluated in seven trials conducted in early sowing in the southern Po Valley (Italy). The line again exhibited outstanding performance for cold tolerance and agronomic traits, both per se and as testcross. Bo23 was superior to B73 for most traits, indicating that its performance is also due to alleles of IABO78. This implies that the use of Bo23 in breeding for cold tolerance and agronomic traits can also contribute the beneficial genetic variation from its Italian parent.

English

The aim of this study was to verify differences in the tolerance to suboptimal temperatures of eight rice mutant genotypes in relation to their cultivars of origin in the initial stages of development. During the germination period, the germination percentage and the germination rate index were evaluated at temperatures of 25 and 13°C. For the vegetative stage enzymatic indicators, photosynthetic pigment concentration and electrolyte leakage were verified. The relative decrease in the germination percentage of mutants QUE 47, QUE 30 and QUE 33 was significantly lower (p ≤ 0.01) than that of cv. BRS Querência. The principal component analysis using the values of the relative decreases of the germination percentage and of the germination rate index confirmed this distinction and the mentioned genotypes were classified into the group with a higher cold tolerance than BRS Querência. The BRS Fronteira genotype did not differ from its mutants for the variables analyzed during germination. In the vegetative stage there were no differences (p ≤ 0.05) between the mutant genotypes and BRS Querência for the analyzed variables. The induced mutation increased the tolerance to suboptimal temperature in the germination period in the genotypes QUE 47, QUE 30 and QUE 33, but not for the vegetative stage.   Key words: Oryza sativa, mutation, abiotic stress, low temperature.

Molecular Characterization of Parental Lines of Rice Aiming to Address High Yield and Nutritional Quality Under Drought and Cold Stress Condition

Abiotic stresses limit crop growth at different growth stages resulting low yield of rice. Molecular characterization of parental materials gives precise information on the extent of genetic diversity exists between them. A set of 60 SSRs randomly distributed over 12 chromosomes were used to analyze eight cultivars intend to be used as parent in breeding programs to address cold and drought tolerance, and nutritional quality of rice. A total of 300 alleles were detected across the cultivars for 51 polymophic markers with 5.88 alleles per loci. On average 30.6% of the genotypes shared a common allele at any given locus. UPGMA cluster analysis showed that 67% common alleles were shared by the cultivars. The cultivars were clearly grouped into two distinct clusters at 67.0% genetic similarity. Hbj. BVI showing high tolerance to cold stress at seedling stage differed from cold susceptible BR1, BRRI dhan28 and BRRI dhan29 by 33% alleles while BR18 that showed moderately cold tolerance differed by 29.0 - 29.9% alleles which indicated that only 3-4% alleles difference caused higher cold tolerance in Hbj. BVI. The moderate genetic distance between cold tolerant Hbj. BVI and high yielding BRRI dhan28 and BRRI dhan29 indicated that there is higher possibility of obtaining high yielding cold tolerant segregants from the crosses between them. On the other hand, Kalobokri, which had 31.7 mg zinc a kilogram of polished rice differed by 33.0% alleles from the drought tolerant rainfed low varieties BRRI dhan56 and BRRI dhan57 having moderate level of zinc (~20 mg/kg), which also indicated that crosses between them might produce progenies with higher nutritional quality under drought environment.

Life-history correlations with seasonal cold hardiness in maritime pine.

Plants have developed mechanisms to withstand stressful environmental conditions, but the high energetic cost of these mechanisms may involve exchanges with other key functions. While trade-offs between cold hardiness and growth rates are a general assumption, we lack information regarding genetically based trade-offs between cold hardiness and other life-history traits. Such information has strong implications for tree conservation and breeding, especially in the context of ongoing climate change. We used a common garden progeny test to examine the relationships between seasonal cold hardiness and life-history traits of growth, reproduction, juvenile ontogeny, and phenology in 75 families of six maritime pine (Pinus pinaster Ait.) populations, three of continental and three of coastal origins. We found a clear differentiation among populations with regard to cold hardiness and life-history traits. Two continental Iberian populations showed high cold tolerance and slower growth, but faster ontogenetic development in relation to both vegetative heteroblastic change in juveniles and the onset of female reproduction. The coastal populations displayed the opposite behavior, while the continental Moroccan population presented a unique combination of traits. We confirmed trade-offs between cold-hardiness and growth at the population level, but not within populations. There were no trade-offs with other life-history traits at either level. Relevant local adaptation syndromes were identified in the relationship between cold hardiness and life-history traits. These should be considered in developing tree management guidelines aimed at increasing productivity or adaptability under the expected conditions of climate change.

Effects of the number of pollen grains on cold tolerance at the booting stage in rice lines with QTLs for cold tolerance

This study was conducted to clarify the relationship between the number of pollen grains per anther and spikelet fertility under low temperature conditions in the rice cultivars and lines including lines with quantitative trait loci (QTL) for cold tolerance, adapted to the Tohoku region of northern Japan. Cold-water treatment decreased anther length, the number of pollen grains per anther, and spikelet fertility in all cultivars and lines. The number of pollen grains was proportional to anther length in all cultivars and lines and under all temperatures. Spikelet fertility decreased with decreasing the number of pollen grains in cold-water treatments at 18.5 and 19.3 °C. ‘Ouu 415’, with the qLTB3 QTL for cold tolerance, had 28% more pollen grains and 9% higher spikelet fertility than the recurrent parent, ‘Hitomebore’, in the 18.5 °C cold-water treatment, suggesting that qLTB3 increased both parameters. Lines with the qCTB8 QTL for cold tolerance had significantly more pollen grains in two of the three years and significantly higher spikelet fertility in all three years in the 19.3 °C cold-water treatment, suggesting that qCTB8 reinforced cold tolerance. Ctb1, a proposed cold-tolerance QTL, had no effect on the number of pollen grains or spikelet fertility. In conclusion, the cultivars and lines with more pollen grains had a higher cold tolerance. Some of QTLs were inferred to increase the number of pollen grains and reinforce cold tolerance.

Low-temperature leaf photosynthesis of a Miscanthus germplasm collection correlates positively to shoot growth rate and specific leaf area.

Background and Aims The C4 perennial grass miscanthus has been found to be less sensitive to cold than most other C4 species, but still emerges later in spring than C3 species. Genotypic differences in miscanthus were investigated to identify genotypes with a high cold tolerance at low temperatures and quick recovery upon rising temperatures to enable them to exploit the early growing season in maritime cold climates. Suitable methods for field screening of cold tolerance in miscanthus were also identified.Methods Fourteen genotypes of M. sacchariflorus, M. sinensis, M. tinctorius and M. × giganteus were selected and grown under warm (24 °C) and cold (14 °C) conditions in a controlled environment. Dark-adapted chlorophyll fluorescence, specific leaf area (SLA) and net photosynthetic rate at a photosynthetically active radiation (PAR) of 1000 μmol m–2 s–1 (A1000) were measured. Photosynthetic light and CO2 response curves were obtained from 11 of the genotypes, and shoot growth rate was measured under field conditions.Key Results A positive linear relationship was found between SLA and light-saturated photosynthesis (Asat) across genotypes, and also between shoot growth rate under cool field conditions and A1000 at 14 °C in a climate chamber. When lowering the temperature from 24 to 14 °C, one M. sacchariflorus exhibited significantly higher Asat and maximum photosynthetic rate in the CO2 response curve (Vmax) than other genotypes at 14 °C, except M. × giganteus ‘Hornum’. Several genotypes returned to their pre-chilling A1000 values when the temperature was increased to 24 °C after 24 d growth at 14 °C.Conclusions One M. sacchariflorus genotype had similar or higher photosynthetic capacity than M. × giganteus, and may be used for cultivation together with M. × giganteus or for breeding new interspecies hybrids with improved traits for temperate climates. Two easily measured variables, SLA and shoot growth rate, may be useful for genotype screening of productivity and cold tolerance.

Overwintering biology and limits of cold tolerance in larvae of pistachio twig borer, Kermania pistaciella.

Pistachio twig borer, Kermania pistaciella is an important pest of pistachio trees. It has an univoltine life-cycle and its larvae tunnel and feed inside pistachio twigs for almost 10 months each year. The last larval instars overwinter inside the twigs. Survival/mortality associated with low temperatures during overwintering stage is currently unknown. We found that overwintering larvae of the Rafsanjan (Iran) population of K. pistaciella rely on maintaining a stably high supercooling capacity throughout the cold season. Their supercooling points (SCPs) ranged between -19.4 and -22.7°C from October to February. Larvae were able to survive 24 h exposures to -15°C anytime during the cold season. During December and January, larvae were undergoing quiescence type of dormancy caused probably by low ambient temperatures and/or changes in host tree physiology (tree dormancy). Larvae attain highest cold tolerance (high survival at -20°C) during dormancy, which offers them sufficient protection against geographically and ecologically relevant cold spells. High cold tolerance during dormancy was not associated with accumulation of any low-molecular mass cryoprotective substances. The SCP sets the limit of cold tolerance in pistachio twig borer, meaning that high mortality of overwintering populations can be expected only in the regions or years where or when the temperatures fall below the average larval SCP (i.e., below -20°C). Partial mortality can be expected also when temperatures repeatedly drop close to the SCP on a diurnal basis.

Cold tolerance in field conditions, its inheritance, agronomic performance and genetic structure of maize lines divergently selected for germination at low temperature

Given the importance of early cold tolerance in maize (Zea mays L.), we previously conducted a divergent selection for low (L) and high (H) cold tolerance at germination. The source population was the F2 of B73 × IABO78 single cross. Selection was first conducted as recurrent selection (four cycles) and then in inbreeding (three generations). Ten lines were finally selected for L and ten for H; these lines were then evaluated to investigate: (i) their field cold tolerance in the early autotrophic phase and the relationship with the cold tolerance expressed at emergence and in the heterotrophic phase; (ii) the inheritance of these cold tolerance traits; (iii) their agronomic performance as lines per se and as crosses; (iv) their SNP-based genetic characterization. For all cold tolerance traits, the H group of lines was superior to the L group; selection responses were often symmetric, suggesting the prevalence of additive effects. The relationship among cold tolerance traits was appreciable, suggesting a common genetic basis. Differences among testcrosses were largely due to general combining ability effects and the relationship between line per se and testcross performance was high, confirming the prevalence of additive effects. Correlated responses were also obtained for agronomic traits, the H lines being superior to L lines both per se and as crosses. For SNP-marker loci, the B73 allelic frequency was greater in the H group (61.7 %) than in L group (39.7 %). Across field trials, an H line excelled for all traits, thus proving to deserve further investigations.

Overexpression of Arabidopsis CBF1 Gene in Transgenic Furenzhi banana (Musa spp. AA group) Improves Resistance to Low Temperature

Cold is an environmental factor that limits the growing season of banana and adversely affects fruit quality and productivity. C-repeat/dehydration responsive element binding factor 1 (CBF1) play important roles in the responses of plants to low-temperature and cold. To test the function and potential use of cold-induced factor CBF1 in improving the chill tolerance of banana, AtCBF1 driven by a cauliflower mosaic virus 35S promoter was introduced into banana plants by Agrobacterium -mediated transformation of embryogenic cell suspensions (ECSs) of banana cultivar Furenzhi (AA). The presence of AtCBF1 transgenes in regenerated plants was confirmed by polymerase chain reaction (PCR) and Southern blots. s-glucoronidase (GUS) histochemical assays reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR analysis demonstrated that foreign genes were stably expressed in regenerated plants. Transgenic banana showed growth retardation, thicker leaves and higher chlorophyll content than non-transformed plants. While relative electrolyte leakage (REL) and malondialdehyde (MDA) content were significantly lower in transgenic banana plants than in non-transformed plants under low temperature stress. An obviously higher cold tolerance was observed among the transgenic plants in the cold detection. These results suggest that over-expression of AtCBF 1 in transgenic banana plants plays an important role in improving tolerance to low-temperature.

Enhanced fertility and chill tolerance after cold-induced reproductive arrest in females of temperate species of the Drosophila buzzatii complex.

Long-term exposure to low temperatures during adult maturation might decrease fertility after cold recovery as a consequence of carry-over effects on reproductive tissues. This pattern should be more pronounced in tropical than in temperate species as protective mechanisms against chilling injuries are expected to be more effective in the latter. We initially determined the lower thermal thresholds to induce ovarian maturation in four closely related Drosophila species, two inhabiting temperate regions and the other two tropical areas of South America. As expected, only temperate species regularly experience cold-inducing conditions for reproductive arrest during winter in their natural environment. Subsequently, we exposed reproductively arrested and mature females to cold-inducing conditions for reproductive arrest over a long period. Following cold exposure, tropical species exhibited a dramatic fertility decline, irrespective of reproductive status. In contrast, not only were temperate females fecund and fertile but also fertility was superior in females that underwent cold-induced reproductive arrest, suggesting that it might act as a protecting mechanism ensuring fertility after cold recovery. Based on these findings, we decided to evaluate the extent to which reproductive status affects cold tolerance and energy metabolism at low temperature. We found a lower metabolic rate and a higher cold tolerance in reproductively arrested females, although only temperate species attained high levels of chill tolerance. These findings highlight the role of cold-induced reproductive arrest as part of an integrated mechanism of cold adaptation that could potentially contribute to the spread of temperate species into higher latitudes or altitudes.

Molecular Cloning and Characterization of Spermine Synthesis Gene Associated with Cold Tolerance in Tea Plant (Camellia sinensis).

Spermine synthase (SPMS, EC 2.5.1.22), enzyme of spermine (Spm) biosynthesis, has been shown to be related to stress response. In this study, attempts were made to clone and characterize a gene encoding SPMS from tea plant (Camellia sinensis). The effect of exogenous application of Spm in C. sinensis subjected to low-temperature stress was also investigated. A full-length SPMS complementary DNA (cDNA) (CsSPMS) with an open reading frame of 1113bp was cloned using reverse transcription-PCR and rapid amplification of cDNA ends (RACE) techniques from cultivar "Yingshuang". The CsSPMS gene, which encoded a 371 amino acid polypeptide, in four cultivars is highly homologous. Quantitative real-time PCR indicated that the CsSPMS gene shows tissue-specific expression, mainly in the leaf and root of tea plant. The expression analysis demonstrated that the CsSPMS gene is quickly induced by cold stress and had similar trends in four cultivars. Spm-supplemented "Baicha" cultivar contains higher endogenous polyamines compared to the control, coupling with higher expression levels of ADC and SPMS. In addition, activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), as well as free proline content in the Spm-supplemented samples were higher than the control during the experiment course or at a given time point, indicating that Spm exerted a positive effect on antioxidant systems. Moreover, Agrobacterium-mediated expression of CsSPMS in tobacco leaves showed relatively higher cold tolerance. Taken together, these findings will enhance the understanding of the relationships among CsSPMS gene regulatory, polyamines accumulation, and cold tolerance in tea plant.

Relationships of self-identified cold tolerance and cold-induced vasodilatation in the finger.

This study was conducted to investigate relationships of self-identified cold tolerance and cold-induced vasodilatation (CIVD) in the finger. Nine males and 34 females participated in the following 2 tests: a CIVD test and a self-reported survey. The CIVD test was conducted 30-min cold-water immersion (3.8 ± 0.3 °C) of the middle finger at an air temperature of 27.9 ± 0.1 °C. The self-reported questionnaire consisted of 28 questions about whole and local body cold and heat tolerances. By a cluster analysis on the survey results, the participants were divided into two groups: high self-identified cold tolerance (HSCT, n = 25) and low self-identified cold tolerance (LSCT, n = 18). LSCT had lower self-identified cold tolerance (P < 0.001), preferred hot thermal stimulation (P = 0.006), and wore heavier clothing during daily life (P < 0.001) than HSCT. LSCT had significantly lower maximal finger temperatures (T max) (P = 0.040), smaller amplitude (P = 0.029), and delayed onset time of CIVD (P = 0.080) when compared to HSCT. Some questions examining the self-identified cold or heat tolerance had relationships with cold tolerance index, T max, and amplitude (P < 0.1). These results indicate that self-identified cold tolerance classified through a standardized survey could be a good index to predict physiological cold tolerance.