Prolonged Chilling Research Articles

Deep learning with a small dataset predicts chromatin remodelling contribution to winter dormancy of apple axillary buds.

Epigenetic changes serve as a cellular memory for cumulative cold recognition in both herbaceous and tree species, including bud dormancy. However, most studies have discussed predicted chromatin structure with respect to histone marks. In the present study, we investigated the structural dynamics of bona fide chromatin to determine how plants recognise prolonged chilling during the initial stage of bud dormancy. The vegetative axillary buds of the 'Fuji' apple, which shows typical low temperature-dependent, but not photoperiod, dormancy induction, were used for the chromatin structure and transcriptional change analyses. The results were integrated using a deep-learning model and interpreted using statistical models, including Bayesian estimation. Although our model was constructed using a small dataset of two time points, chromatin remodelling due to random changes was excluded. The involvement of most nucleosome structural changes in transcriptional changes and the pivotal contribution of cold-driven circadian rhythm-dependent pathways regulated by the mobility of cis-regulatory elements were predicted. These findings may help to develop potential genetic targets for breeding species with less bud dormancy to overcome the effects of short winters during global warming. Our artificial intelligence concept can improve epigenetic analysis using a small dataset, especially in non-model plants with immature genome databases.

Calcium signaling facilitates chilling- and GA- induced dormancy release in tree peony.

Calcium plays a crucial role in plant growth and development, yet little is known about its function in endodormancy regulation. Tree peony (Paeonia suffruticosa), characterized by compound buds and large flowers, is well-known for its ornamental and medicinal value. To break bud dormancy release is a prerequisite of flowering and forcing culture, particularly during the Spring Festival. In this study, the Ca2+ chelator EGTA and Ca2+ channel blocker LaCl3 were applied, resulting in a significant delay in budburst during both chilling- and gibberellin (GA)- induced dormancy release in a dosage-dependent manner. As expected, the retardation of bud break was recovered by the supplementation of 30 mM CaCl2, indicating a facilitating role of calcium in dormancy release. Accordingly, several calcium-sensor-encoding genes including Calmodulin (CaM) and Ca2+-dependent protein kinases (CDPKs) were significantly up-regulated by prolonged chilling and exogenous GAs. Ultrastructure observations revealed a decline in starch grains and the reopening of transport corridors following prolonged chilling. Calcium deposits were abundant in the cell walls and intercellular spaces at the early dormant stage but were enriched in the cytosol and nucleus before dormancy release. Additionally, several genes associated with dormancy release, including EBB1, EBB3, SVP, GA20ox, RGL1, BG6, and BG9, were differentially expressed after calcium blocking and recovery treatments, indicating that calcium might partially modulate dormancy release through GA and ABA pathways. Our findings provide novel insights into the mechanism of dormancy release and offer potential benefits for improving and perfecting forcing culture technology in tree peonies.

PsmiR159b-PsMYB65 module functions in the resumption of bud growth after endodormancy by affecting the cell cycle in tree peony.

Bud endodormancy in perennial plants is a sophisticated system that adapts to seasonal climatic changes. Growth-promoting signals such as low temperature and gibberellins (GAs) are crucial for facilitating budbreak following endodormancy release (EDR). However, the regulatory mechanisms underlying GA-mediated budbreak in tree peony (Paeonia suffruticosa) remain unclear. In tree peony, the expression of PsmiR159b among three differentially expressed miR159 members was inhibited with the prolonged chilling, and overexpression of PsMIR159b delayed budbreak, whereas silencing PsmiR159b promoted budbreak after dormancy. PsMYB65, a downstream transcription factor in the GA pathway, was induced by prolonged chilling and exogenous GA3 treatments. PsMYB65 was identified as a target of PsmiR159b, and promoted budbreak in tree peony. RNA-seq of PsMYB65-slienced buds revealed significant enrichment in the GO terms regulation of 'cell cycle' and 'DNA replication' among differentially expressed genes. Yeast one-hybrid and electrophoretic mobility shift assays demonstrated that PsMYB65 directly bound to the promoter of the type-D cyclin gene PsCYCD3;1. Dual-luciferase reporter assay indicated that PsMYB65 positively regulate PsCYCD3;1 expression, suggesting that miR159b-PsMYB65 module contributes to budbreak by influencing the cell cycle. Our findings revealed that the PsmiR159b-PsMYB65 module functioned in budbreak after dormancy by regulating cell proliferation, providing valuable insights into the endodormancy release regulation mechanism.

Abscisic acid-induced transcription factor PsMYB306 negatively regulates tree peony bud dormancy release.

Bud dormancy is a crucial strategy for perennial plants to withstand adverse winter conditions. However, the regulatory mechanism of bud dormancy in tree peony (Paeonia suffruticosa) remains largely unknown. Here, we observed dramatically reduced and increased accumulation of abscisic acid (ABA) and bioactive gibberellins (GAs) GA1 and GA3, respectively, during bud endodormancy release of tree peony under prolonged chilling treatment. An Illumina RNA sequencing study was performed to identify potential genes involved in the bud endodormancy regulation in tree peony. Correlation matrix, principal component, and interaction network analyses identified a downregulated MYB transcription factor gene, PsMYB306, the expression of which positively correlated with 9-CIS-EPOXYCAROTENOID DIOXYGENASE 3 (PsNCED3) expression. Protein modeling analysis revealed 4 residues within the R2R3 domain of PsMYB306 to possess DNA binding capability. Transcription of PsMYB306 was increased by ABA treatment. Overexpression of PsMYB306 in petunia (Petunia hybrida) inhibited seed germination and plant growth, concomitant with elevated ABA and decreased GA contents. Silencing of PsMYB306 accelerated cold-triggered tree peony bud burst and influenced the production of ABA and GAs and the expression of their biosynthetic genes. ABA application reduced bud dormancy release and transcription of ENT-KAURENOIC ACID OXIDASE 1 (PsKAO1), GA20-OXIDASE 1 (PsGA20ox1), and GA3-OXIDASE 1 (PsGA3ox1) associated with GA biosynthesis in PsMYB306-silenced buds. In vivo and in vitro binding assays confirmed that PsMYB306 specifically transactivated the promoter of PsNCED3. Silencing of PsNCED3 also promoted bud break and growth. Altogether, our findings suggest that PsMYB306 negatively modulates cold-induced bud endodormancy release by regulating ABA production.

Shoot buds of subtropical running bamboos demonstrate endodormancy and chilling requirements for their release

Bamboos, widely distributed in tropical and subtropical regions and significant in ecological, economic and cultural values, are similar to trees in the above-ground growth and to geophytes in the below-ground structure. However, contrary to well-studied endodormancy and the related chilling requirement that synchronize the seasonal development of above-ground buds of tree species and the well-studied below-ground buds of geophytes, it is unknown whether bamboos demonstrate the endodormancy and chilling requirements as those of trees and geophytes, which limits our understanding of how bamboos phenology cope with climate change. Our work mainly examined the effect of temperature on the dormancy release of underground shoot buds of two important subtropical running bamboo species, Lei bamboo (Phyllostachys violascens) and Moso bamboo (Phyllostachys edulis). In the experiments, the bamboo seedlings were first subjected to different durations of natural chilling and subsequently to a regrowth test under high-temperature forcing conditions in whole-tree chambers. In the regrowth test the dormancy state of the shoot buds was examined by observing shoot development, i.e., the emergence of the new shoot aboveground, a significant spring phenological event in many bamboo species. The time required for shooting under the forcing conditions decreased with prolonged chilling, indicating that the shoot buds of these two bamboo species demonstrate the phenomena of endodormancy and a chilling requirement for endodormancy release. For Lei bamboo, the chilling requirement was estimated as 45 Chill Portions (CP) and heat requirement was 9978 ± 6713 GDH℃. As for Moso bamboo, the estimated chilling requirement was 35CP and heat requirement was 6713 ± 3087 GDH℃. Meanwhile, the Vegis effect (an interaction of previous chilling accumulation and forcing temperature) was also found in Lei bamboo: there was a large difference in the time required for shoot development between low and high forcing temperatures after short durations of chilling, but the difference decreased with prolonged chilling. It was also shown that bamboo shoot buds almost received the same heat requirements for emergence at different forcing temperatures under the same chilling requirements. Our results will improve the understanding of temperature regulation of spring phenology in subtropical bamboo forests and promote bamboo production and management.

Prolonged low temperature exposure de-sensitises ABA-induced stomatal closure in soybean, involving an ethylene-dependent process.

Chilling can decrease stomatal sensitivity to abscisic acid (ABA) in some legumes, although hormonal mechanisms involved are unclear. After evaluating leaf gas exchange of 16 European soybean genotypes at 14°C, 6 genotypes representing the range of response were selected. Further experiments combined low (L, 14°C) and high (H, 24°C) temperature exposure from sowing until the unifoliate leaf was visible and L or H temperature until full leaf expansion, to impose four temperature treatments: LL, LH, HL, and HH. Prolonged chilling (LL) substantially decreased leaf water content but increased leaf ethylene evolution and foliar concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, indole-3-acetic acid, ABA and jasmonic acid. Across genotypes, photosynthesis linearly increased with stomatal conductance (Gs), with photosynthesis of HH plants threefold higher than LL plants at the same Gs. In all treatments except LL, Gs declined with foliar ABA accumulation. Foliar ABA sprays substantially decreased Gs of HH plants, but did not significantly affect LL plants. Thus low temperature compromised stomatal sensitivity to endogenous and exogenous ABA. Applying the ethylene antagonist 1 methyl-cyclopropene partially reverted excessive stomatal opening of LL plants. Thus, chilling-induced ethylene accumulation may mediate stomatal insensitivity to ABA, offering chemical opportunities for improving seedling survival in cold environments.

PsRGL1 negatively regulates chilling- and gibberellin-induced dormancy release by PsF-box1-mediated targeting for proteolytic degradation in tree peony.

Tree peony bud endodormancy is a common survival strategy similar to many perennial woody plants in winter, and the activation of the GA signaling pathway is the key to breaking endodormancy. GA signal transduction is involved in many physiological processes. Although the GA-GID1-DELLA regulatory module is conserved in many plants, it has a set of specific components that add complexity to the GA response mechanism. DELLA proteins are key switches in GA signaling. Therefore, there is an urgent need to identify the key DELLA proteins involved in tree peony bud dormancy release. In this study, the prolonged chilling increased the content of endogenously active gibberellins. PsRGL1 among three DELLA proteins was significantly downregulated during chilling- and exogenous GA3-induced bud dormancy release by cell-free degradation assay, and a high level of polyubiquitination was detected. Silencing PsRGL1 accelerated bud dormancy release by increasing the expression of the genes associated with dormancy release, including PsCYCD, PsEBB1, PsEBB3, PsBG6, and PsBG9. Three F-box protein family members responded to chilling and GA3 treatments, resulting in PsF-box1 induction. Yeast two-hybrid and BiFC assays indicated that only PsF-box1 could bind to PsRGL1, and the binding site was in the C-terminal domain. PsF-box1 overexpression promoted dormancy release and upregulated the expression of the dormancy-related genes. In addition, yeast two-hybrid and pull-down assays showed that PsF-box1 also interacted with PsSKP1 to form an E3 ubiquitin ligase. These findings enriched the molecular mechanism of the GA signaling pathway during dormancy release, and enhanced the understanding of tree peony bud endodormancy.

Cytokinin localization and dynamics in rye plants under chilling and kernel priming with zeatin

In the early stages of plant development, a sharp chilling can pose a significant threat to cold-resistant crops, such as winter cereals, in particular, rye. Phytohormones from the cytokinin family play a crucial role in regulating plant response to low-temperature stress. Pre-sowing seed priming with cytokinin solutions is a promising approach to improving the stress tolerance of cereals. The aim of this study was to investigate the impact of chilling on the dynamics and localization of cytokinins in plants of rye cv. Boguslavka in the early stages of development, to determine the possibility of mitigating the adverse effects of cold stress through kernel priming with a zeatin solution, and to assess the effect of this substance on the balance of endogenous cytokinins. Kernels were soaked in either water or a zeatin solution (10—6 М), and plants were grown under controlled conditions of the vegetation chamber. Chilling was induced by exposing 7-day-old plants to the refrigerator for 2 h or twice for 6 h over two days. Endogenous cytokinins were analyzed using the HPLC-MS method. We found significant changes in the cytokinin pool in plants exposed to 2 °C for 2 h while no morphological alterations were observed. The content of trans-zeatin and trans-zeatin riboside increased considerable in the shoots of the plants grown from the kernels soaked in water, whereas in the roots, the level of these cytokinins dropped sharply. Prolonged chilling led to retarded shoot growth and elongated roots. Simultaneously, the level of trans-zeatin, isopentenyladenosine and isopentenyladenine in the shoots decreased to minimum values, while the amount of trans-zeatin riboside increased almost twofold. Transformations of the cytokinin pool in the roots followed a similar pattern. Overall, under the cold stress at the alarm stage, cytokinin balance changes were aimed at maintaining growth processes, while during the acclimation stage, they contributed to growth inhibition. Pre-sowing priming of rye kernels with a zeatin solution allowed plants to maintain normal growth and morphology under of prolonged chilling. This treatment significantly affected the homeostasis of endogenous cytokinins, resulting in a more moderate rearrangement of the cytokinin pool in stressed plants than in the control. We assume that changes in the balance of cytokinins due to seed priming allow plants to improve cold tolerance. Seed treatment with cytokinins could be a promising approach to increasing the adaptive properties of plants.

Fitness cost of Rhagoletis cerasi (Diptera: Tephritidae) adults emerged from pupae with different dormancy regimes: the case of prolonged chilling.

The European cherry fruit fly, Rhagoletis cerasi (Diptera: Tephritidae), is a univoltine species that overwinters at pupal stage. Under optimum overwintering conditions pupae will develop into adults the next spring. Shorter or longer than optimum chilling periods induce prolonged pupae dormancy. Pupae that enter prolonged dormancy due to a short chilling period exhibit high emergence rates after a second cycle of cold/warm periods. Adults found to be larger and less fecund compared to their counterparts from pupae with annual diapause. On the other hand, extreme long chilling periods at pupal stage results in high mortality rates. However, for one Greek population, a substantial number of adults emerged following prolonged chilling of pupae (ca. 18 consecutive months). In this study, we used three R. cerasi populations in order to address possible geographical variation in fitness cost of adults from pupae with prolonged dormancy. In addition, the fitness traits of these adults emerging after prolonged pupae chilling were compared with that of their counterparts from pupae with annual diapause or prolonged dormancy. Our results reveal no population-specific variation in fitness cost of adults from pupae with prolonged dormancy. Within a population, lifetime fecundity did not differ between adults emerged from pupae with prolonged dormancy and those emerged after prolonged pupae chilling. Adults emerged from pupae exposed to prolonged chilling suffer an additional reduction in adult longevity compared to adults from pupae with prolonged dormancy. Hence, fitness of R. cerasi adults is regulated by diapause regimes of pupae.

Hyperkalaemia, not apoptosis, accurately predicts insect chilling injury.

There is a growing appreciation that insect distribution and abundance are associated with the limits of thermal tolerance, but the physiology underlying thermal tolerance remains poorly understood. Many insects, like the migratory locust (Locusta migratoria), suffer a loss of ion and water balance leading to hyperkalaemia (high extracellular [K+]) in the cold that indirectly causes cell death. Cells can die in several ways under stress, and how they die is of critical importance to identifying and understanding the nature of thermal adaptation. Whether apoptotic or necrotic cell death pathways are responsible for low-temperature injury is unclear. Here, we use a caspase-3 specific assay to indirectly quantify apoptotic cell death in three locust tissues (muscle, nerves and midgut) following prolonged chilling and recovery from an injury-inducing cold exposure. Furthermore, we obtain matching measurements of injury, extracellular [K+] and muscle caspase-3 activity in individual locusts to gain further insight into the mechanistic nature of chilling injury. We found a significant increase in muscle caspase-3 activity, but no such increase was observed in either nervous or gut tissue from the same animals, suggesting that chill injury primarily relates to muscle cell death. Levels of chilling injury measured at the whole animal level, however, were strongly correlated with the degree of haemolymph hyperkalaemia, and not apoptosis. These results support the notion that cold-induced ion balance disruption triggers cell death but also that apoptosis is not the main form of cell damage driving low-temperature injury.

Metabolomics analysis reveals Embden Meyerhof Parnas pathway activation and flavonoids accumulation during dormancy transition in tree peony

BackgroundBud dormancy is a sophisticated strategy which plants evolve to survive in tough environments. Endodormancy is a key obstacle for anti-season culture of tree peony, and sufficient chilling exposure is an effective method to promote dormancy release in perennial plants including tree peony. However, the mechanism of dormancy release is still poorly understood, and there are few systematic studies on the metabolomics during chilling induced dormancy transition.ResultsThe tree peony buds were treated with artificial chilling, and the metabolmics analysis was employed at five time points after 0–4 °C treatment for 0, 7, 14, 21 and 28 d, respectively. A total of 535 metabolites were obtained and devided into 11 groups including flavonoids, amino acid and its derivatives, lipids, organic acids and its derivates, nucleotide and its derivates, alkaloids, hydroxycinnamoyl derivatives, carbohydrates and alcohols, phytohormones, coumarins and vitamins. Totally, 118 differential metabolites (VIP ≥ 1, P < 0.05) during chilling treatment process were detected, and their KEGG pathways involved in several metabolic pathways related to dormancy. Sucrose was the most abundant carbohydrate in peony bud. Starch was degradation and Embden Meyerhof Parnas (EMP) activity were increased during the dormancy release process, according to the variations of sugar contents, related enzyme activities and key genes expression. Flavonoids synthesis and accumulation were also promoted by prolonged chilling. Moreover, the variations of phytohormones (salicylic acid, jasmonic acid, abscisic acid, and indole-3-acetic acid) indicated they played different roles in dormancy transition.ConclusionOur study suggested that starch degradation, EMP activation, and flavonoids accumulation were crucial and associated with bud dormancy transition in tree peony.

Morphological, anatomical and DNA methylation changes of tree peony buds during chilling induced dormancy release

Bud endodormancy in tree peony is a growth cessation-like state, and sufficient chilling perception is necessary to break it. In this study, 120 plants were subjected to 0–4 °C climate chamber for 0–28 d with a weekly interval, morphology and structure changes of buds were studied with a scanning electron microscope (SEM) and paraffin sections during the dormancy process. Dormancy status was evaluated after being transferred to greenhouse for 30 d. Results showed that the diameter of the buds gradually expanded, along with continuous elongation of sepals, petals, stamens and carpels in the chilling accumulation process. Notably, dormancy release was marked with the establishment of xylem vessels in lateral vein of the petal. Meanwhile, DNA methylation was detected by HPLC and immunochemical technology, aimed to illuminate the role of DNA methylation in the dormancy release, we found that 5 mC level fell from 39.4% to 24.2% after exposed to 28 d chilling. These results were consistent with the immunochemical analysis, and inversely related to the sprouting rate after being moved to greenhouse for 30 d. Exogenous application of 5azaC (5-azacytidine) decreased DNA methylation level, accompanied by an improved bud sprouting capacity, while the effect of SAM (S-adenosylmethionine) was the opposite. In summary, prolonged chilling was accompanied by further differentiation and development of the compound bud, which resulted in DNA hypomethylation and promoted dormancy release in tree peony.

Low-Temperature Adaptation of Winter Wheat Seedlings under Excessive Zinc Content in the Root Medium

Cold adaptation of winter wheat (Triticum aestivum L.) seedlings was investigated under excessive zinc content (1000 μM) in the root medium. The ability to adapt to chilling temperatures (4°C) in seedlings exposed over seven days to excessive Zn concentrations was lower than in seedlings exposed to optimal composition of mineral nutrients. The impaired adaptation capacity was evident from the lowered content of photosynthetic pigments in leaves, the decreased stomatal conductance, and the reduced water content in shoot tissues. The negative influence of low temperature on plant physiological parameters was enhanced with the prolongation of cold exposure under Zn excess in the root medium, unlike the alleviation of cold-induced disorders during prolonged chilling under optimal Zn concentration (2 μM). Based on this study, we propose that inhibition of photosynthesis and the disturbance of plant water balance are the main factors that impair the low-temperature adaptation of seedlings exposed to high zinc concentrations.

Enzymatic activities of curry leaves (Murraya koenigii L.) during storage in chilling temperature

Curry leaves are highly susceptible to chilling injury (CI) under prolonged storage at 4-8°C. CI in plants is a complicated process interconnected through several biochemical reactions especially enzymatic activities. Present study monitored the activities of polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), lipoxygenase (LOX), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in curry leaves stored at 4°C under perforated LDPE packaging (100 g package‑1). Leaves without packaging served as control. Surface colour (L*, a*, and b*), electrolytic leakage, chlorophyll content, total phenolic content (TPC) and total antioxidant activity (TAA) were measured in leaf samples. Samples were analysed every 3 days for 15 days. Prolonged chilling temperature induced CI in curry leaves. Leaf surface colour such as (L* and b*) gradually decreased while leaf redness (a*) gradually increased, reflecting browning enzymatic activities and chlorophyll degradation. Electrolytic leakage was severe in control leaves. TPC influenced the TAA activities in curry leaves, and the values tended to decrease with time (P<0.05). During the initial storage period (0-8 days), enzymatic activities remained constant but increased markedly during 9-15 days at 4°C. LOX increased in control leaves throughout storage, and as a consequence, PPO, POD and PAL activities were also higher in control. Similarly, SOD, CAT, and GPX were also found higher in control, indicating that prolonged chilling increased reactive oxygen species in control samples. The LDPE package that acted as a barrier between the package and samples and slightly reduced the CI in curry leaves.

Effects of a Daily Short-Term Temperature Drop on Chilling-Sensitive and Cold-Resistant Plants

A set of physiological and biochemical parameters (leaf growth rate, plant biomass, chlorophyll content, rates of photosynthesis and transpiration, relative water content, leakage of electrolytes, lipid peroxidation intensity, and leaf cold tolerance) were examined with the example of typical cold-resistant (wheat, Triticum aestivum L.) and chilling-sensitive (cucumber, Cucumis sativus L.) plants subjected daily to a short-term temperature drop (DROP treatments) under controlled environmental conditions. For comparison, the plant responses to prolonged chilling were studied with the same species. To accomplish these aims, the cucumber and wheat plants were subjected to: (a) continuous (round-the-clock) cooling at 4°C (wheat), 9°C (cucumber), and 12°C (wheat and cucumber); (b) short-term (3 h) daily cooling to the same temperatures at the end of night periods over 6 days. Although cold-resistant and chilling-sensitive plants showed quantitatively and qualitatively different responses during and after long-term cooling, the plant responses to DROP treatments were qualitatively similar and differed only in their extent depending on cooling temperature. The DROP treatments retarded linear growth of plant organs in both chilling-sensitive and cold-resistant species. They also induced a range of favorable physiological changes promoting plant capability of adaptation. Specifically, photosynthetic rates in DROP-treated plants at chilling temperatures were higher than in untreated plants. In addition, DROP treatments improved the plant chilling tolerance.

An impressive capacity for cold tolerance plasticity protects against ionoregulatory collapse in the disease vector, Aedes aegypti

The mosquito Aedes aegypti is largely confined to tropical and subtropical regions, but its range has recently been spreading to colder climates. As insect biogeography is tied to environmental temperature, understanding the limits of A. aegypti thermal tolerance and their capacity for phenotypic plasticity is important in predicting the spread of this species. In this study, we report on the chill coma onset (CCO) and recovery time (CCRT), as well as low-temperature survival phenotypes of larvae and adults of A. aegypti that developed or were acclimated to 15°C (cold) or 25°C (warm). Cold acclimation did not affect CCO temperatures of larvae but substantially reduced CCO in adults. Temperature and the duration of exposure both affected CCRT, and cold acclimation strongly mitigated these effects and increased rates of survival following prolonged chilling. Female adults were far less likely to take a blood meal when cold acclimated, and exposing females to blood (without feeding) attenuated some of the beneficial effects of cold acclimation on CCRT. Lastly, larvae suffered from haemolymph hyperkalaemia when chilled, but cold acclimation attenuated the imbalance. Our results demonstrate that A. aegypti larvae and adults have the capacity to acclimate to low temperatures, and do so at least in part by better maintaining ion balance in the cold. This ability for cold acclimation may facilitate the spread of this species to higher latitudes, particularly in an era of climate change.

A Prunus persica genome-wide RNA-seq approach uncovers major differences in the transcriptome among chilling injury sensitive and non-sensitive varieties.

Chilling injury represents a major constrain for crops productivity. Prunus persica, one of the most relevant rosacea crops, have early season varieties that are resistant to chilling injury, in contrast to late season varieties, which display chilling symptoms such as mealiness (dry, sandy fruit mesocarp) after prolonged storage at chilling temperatures. To uncover the molecular processes related to the ability of early varieties to withstand mealiness, postharvest and genome-wide RNA-seq assessments were performed in two early and two late varieties. Differences in juice content and ethylene biosynthesis were detected among early and late season fruits that became mealy after exposed to prolonged chilling. Principal component and data distribution analysis revealed that cold-stored late variety fruit displayed an exacerbated and unique transcriptome profile when compared to any other postharvest condition. A differential expression analysis performed using an empirical Bayes mixture modeling approach followed by co-expression and functional enrichment analysis uncover processes related to ethylene, lipids, cell wall, carotenoids and DNA metabolism, light response, and plastid homeostasis associated to the susceptibility or resistance of P. persica varieties to chilling stress. Several of the genes related to these processes are in quantitative trait loci (QTL) associated to mealiness in P. persica. Together, these analyses exemplify how P. persica can be used as a model for studying chilling stress in plants.

Changes in plant hormone contents in Japanese apricot flower buds during prolonged chilling exposure

Changes in plant hormone contents in Japanese apricot flower buds during prolonged chilling exposure

Parasitic Nematode Abundance Aggregation as a Mechanism of the Adaptive Response of the Host Plant to Temperature Variations

The mathematical model of host–parasite relations suggested previously by the authors was applied to analyze the formation of the aggregated distribution of parasites in the case of the host plant–parasitic nematode system. For nearly the same conditions and empirical infection levels, nematode abundances in the host population followed the gamma distribution. Exposure to temperature stresses modifies the resistance of the plant population to infection. Experiments with prolonged chilling of potato plants prior to nematode infestation revealed no statistically reliable increase in the share of resistant plants compared to the control, although the mean and the range of variation of the infection rate, as well as the aggregation of the parasite distribution, decreased. Short-term chilling of the plants prior to infestation led to a reliable decrease in the mean abundance of parasites and to the lowest aggregation of the parasitic nematode in the host plant population. The results of this study showed that this temperature stress caused potatoes to develop a reliably high and uniform resistance to the nematode.

Control of Nematodirus spp. infection by sheep flock owners in Northern Ireland

BackgroundTo address a lack of information on the control of ovine helminth parasites in Northern Ireland (NI), a number of research projects have been undertaken, dealing with gastrointestinal nematodes, tapeworms and liver fluke. This investigation concerns Nematodirus and concentrates on three aspects of disease: farm management strategies for its control, derived from the results of a Questionnaire; the efficacy of treatment used by farmers, as determined by a coprological survey; and the hatching requirements of Nematodirus eggs, that is, whether prolonged chilling is a pre-requisite for hatching.ResultsA Questionnaire was sent to 252 sheep farmers in NI in March 2012 (covering the years 2009–2012) and replies were received from 228 farmers. Under-dosing, inaccurate calibration of equipment and inappropriate product choice were poor practices identified. Following this survey, the efficacy of treatment of Nematodirus spp. in sheep flocks was evaluated in April and May 2012. Sampling kits were sent to 51 flock owners, all of whom returned pre- and post-anthelmintic dosing faecal samples to the laboratory for analysis. At the time of treatment, 41 flocks were positive for Nematodirus (as diagnosed by the presence of eggs). Reduced benzimidazole efficacy was detected in 35.7% of flocks tested (n = 28). Although only involving a small number of flocks, reduced efficacy of levamisole treatment was detected in 50%, of avermectins in 33% and of moxidectin in 75% of flocks tested (n = 2, 6 and 4, respectively). In the egg hatch experiment, carried out under “chilled” and “non-chilled” conditions, 43% of the eggs in the “non-chilled” group were able to hatch, compared to 100% in the “chilled” group.ConclusionsThe identification of inefficient control strategies argues for continued education of stockholders, in order to improve their management programmes. This is particularly important where the practices might impact on the development of anthelmintic resistance, which has been shown to exist on NI farms. The appropriate choice of anthelmintic is a vital part of this plan. The ability of eggs to hatch under non-chilled conditions demonstrates a flexibility in hatching behaviour. This may represent an adaptation to climate change and account for the recent emergence of a second, autumnal peak of infection.