Chilling Sensitivity Research Articles

Physiological, transcriptomic, and metabolomic analyses of the chilling stress response in two melon (Cucumis melo L.) genotypes.

Chilling stress is a key abiotic stress that severely restricts the growth and quality of melon (Cucumis melo L.). Few studies have investigated the mechanism of response to chilling stress in melon. We characterized the physiological, transcriptomic, and metabolomic response of melon to chilling stress using two genotypes with different chilling sensitivity ("162" and "13-5A"). "162" showed higher osmotic regulation ability and antioxidant capacity to withstand chilling stress. Transcriptome analysis identified 4395 and 4957 differentially expressed genes (DEGs) in "162" and "13-5A" under chilling stress, respectively. Metabolome analysis identified 615 and 489 differential enriched metabolites (DEMs) were identified in "162" and "13-5A" under chilling stress condition, respectively. Integrated transcriptomic and metabolomic analysis showed enrichment of glutathione metabolism, and arginine (Arg)and proline (Pro)metabolism, with differential expression patterns in the two genotypes. Under chilling stress, glutathione metabolism-related DEGs,6-phosphogluconate dehydrogenase(G6PDH), glutathione peroxidase (GPX), and glutathione s-transferase(GST) were upregulated in "162," and GSH conjugates (L-gamma-glutamyl-L-amino acid and L-glutamate) were accumulated. Additionally, "162" showed upregulation of DEGs encoding ornithine decarboxylase, Pro dehydrogenase, aspartate aminotransferase, pyrroline-5-carboxylate reductase, and spermidine synthase and increased Arg, ornithine, and Pro. Furthermore, the transcription factors (TFs),MYB, ERF, MADS-box, and bZIP were significantly upregulated, suggesting their crucial role in chilling tolerance of melon. These findings elucidate the molecular response mechanism to chilling stress in melon and provide insights for breeding chilling-tolerant melon.

Dormancy characteristics of lammas-growth seedlings of subtropical trees and their phenological responses to experimental warming.

Lammas growth of trees means the additional growth of the shoot after the growth cessation and bud set in late summer. In temperate tree species, lammas growth occurs irregularly and is often regarded as abnormal, disturbed growth. In subtropical tree species, however, lammas growth is a prevalent phenomenon, possibly due to the prolonged occurrence of high temperatures in the autumn. The occurrence of lammas growth extends the growing season of trees, but its influence on subsequent dormancy phenomena and bud burst phenology remains largely unexplored. By comparing seedlings showing lammas growth with others not showing it, we carried out an experimental study of how lammas growth affects the bud burst phenology and the underlying dormancy phenomena under both ambient and controlled chilling, forcing, and warming conditions in four subtropical tree species: Carya illinoinensis, Cinnamomum japonicum, Phoebe chekiangensis, and Torreya grandis. With the exception of C. illinoinensis, lammas growth delayed bud burst in all the species under ambient conditions. In a chilling experiment, the delay appeared to be due to higher minimum forcing requirement, higher dormancy depth, and in T. grandis, also to lower chilling sensitivity in the lammas-growth seedlings than in the non-lammas-growth ones. However, a spring warming experiment showed that the sensitivity of bud burst to spring temperatures was higher in the lammas-growth seedlings than in the non-lammas-growth ones. Because of this, the difference between the two phenotypes in the timing of bud burst vanished with increasing warming. Our findings elucidate the significant impact of lammas growth on the dormancy dynamics of subtropical tree species, highlighting the necessity to better understand how the physiological phenomena causing lammas growth change the trees' subsequent environmental responses under changing climatic conditions.

Genetic linkage mapping and quantitative trait locus (QTL) analysis of sweet basil (Ocimum basilicum L.) to identify genomic regions associated with cold tolerance and major volatiles.

Chilling sensitivity is one of the greatest challenges affecting the marketability and profitability of sweet basil (Ocimum basilicum L.) in the US and worldwide. Currently, there are no sweet basils commercially available with significant chilling tolerance and traditional aroma profiles. This study was conducted to identify quantitative trait loci (QTLs) responsible for chilling tolerance and aroma compounds in a biparental mapping population, including the Rutgers advanced breeding line that served as a chilling tolerant parent, 'CB15', the chilling sensitive parent, 'Rutgers Obsession DMR' and 200 F2 individuals. Chilling tolerance was assessed by percent necrosis using machine learning and aroma profiling was evaluated using gas chromatography (GC) mass spectrometry (MS). Single nucleotide polymorphism (SNP) markers were generated from genomic sequences derived from double digestion restriction-site associated DNA sequencing (ddRADseq) and converted to genotype data using a reference genome alignment. A genetic linkage map was constructed and five statistically significant QTLs were identified in response to chilling temperatures with possible interactions between QTLs. The QTL on LG24 (qCH24) demonstrated the largest effect for chilling response and was significant in all three replicates. No QTLs were identified for linalool, as the population did not segregate sufficiently to detect this trait. Two significant QTLs were identified for estragole (also known as methyl chavicol) with only qEST1 on LG1 being significant in the multiple-QTL model (MQM). QEUC26 was identified as a significant QTL for eucalyptol (also known as 1,8-cineole) on LG26. These QTLs may represent key mechanisms for chilling tolerance and aroma in basil, providing critical knowledge for future investigation of these phenotypic traits and molecular breeding.

Preliminary Analysis, Combined with Omics of Chilling Injury Mechanism of Peach Fruits with Different Cold Sensitivities during Postharvest Cold Storage

The storage of peach fruits at 4–5 °C can easily lead to chilling injury and greatly reduce the quality and commercial value of peach fruits. In this study, two kinds of peach fruits (CX and CM) were selected to analyze the mechanisms of chilling injury in fruits with different chilling sensitivity by means of their lipidomic, transcriptome, and dynamic changes in plant hormones. We found that the ethylene, abscisic acid (ABA), and lipid contents changed differently between CX and CM. The ABA and dilactosyl diacylglycerol (DGDG) contents significantly increased after refrigeration in CM fruit, leading to strong cold resistance. However, low temperatures induced a greater accumulation of ethylene, phospholipids, and ABA-GE in CX fruit than in CM fruit, eventually leading to more severe CI symptoms in CX fruit. Additionally, a transcriptional regulatory network for CM and CX fruits during cold storage was constructed, providing a new theoretical reference for the cultivation of cold-resistant peach cultivars and the development of postharvest preservation technology.

Review of recent advances in post-harvest techniques for tropical cut flowers and future prospects: Heliconia as a case-study.

Aesthetic attributes and easy-to-grow nature of tropical cut flowers (TCFs) have contributedto their potential for increased production. The dearth of information regarding agronomic practices and lack of planting materials are the key hindrances against their fast expansion. Unconventional high-temperature storage requirements and the anatomy of the peduncle contribute topoor vase life performance, while troublesome packaging and transport due to unusual size and structureprimarily cause post-harvest quality deterioration. Nonetheless, the exotic floral structuresconsequently increase market demand, particularly in temperate countries. This boosts studies aimed at overcoming post-harvest hindrances. While a few TCFs (Anthurium, Strelitzia, Alpinia, and a few orchids) are under the spotlight, many others remain behind the veil. Heliconia, an emerging specialty TCF (False Bird-of-Paradise, family Heliconiaceae), is one of them. The structural uniquenessand dazzling hues of Heliconia genotypes facilitate shifting its position from the back to the forefrontof the world floriculture trade. The unsatisfactory state-of-the-art of Heliconia research and the absence of any review exclusively on it are the key impetus for structuring this review. In addition to the aforementioned setbacks, impaired water uptake capacity after harvest, high chilling sensitivity, and the proneness of xylem ducts to microbial occlusion may be counted as a few additional factors that hinder its commercialization. This review demonstrates the state-of-the-art of post-harvest research while also conceptualizing the implementation of advanced biotechnological aid to alleviate the challenges, primarily focusing on Heliconia (the model crop here) along with some relevant literature on its other allied members. Standard harvesting indices, grading, and packaging are also part of the entire post-harvest operational chain, but since these phases are barely considered in Heliconia and the majority of tropical ornamentals except a few, a comprehensive account of these aspects has also been given. The hypothesized cues to nip chilling injury, resorting to different bio-chemical treatments, nano-based technology, and advanced packaging techniques, may help overcome preservation difficulties and propel its transition from niche to the commercial flower market. In a nutshell, readers will gain a comprehensive overview of how optimum post-harvest handling practices can rewardingly characterize this unique group of TCFs as the most remunerative component.

Chilling temperatures and controlled atmospheres alter key volatile compounds implicated in basil aroma and flavor.

Use of basil in its fresh form is increasingly popular due to its unique aromatic and sensory properties. However, fresh basil has a short shelf life and high chilling sensitivity resulting in leaf browning and loss of characteristic aroma. Moderate CO2 atmospheres have shown potential in alleviating symptoms of chilling injury in basil during short-term storage but its effect on the flavor volatiles is unclear. Moreover, studies on basil volatile profile as impacted by chilling temperatures are limited. We investigated the response of two basil genotypes to low temperatures and atmosphere modification, with emphasis on the volatile organic compounds responsible for basil aroma and flavor. Leaves were stored for 6 days at 5, 10, or 15°C combined with three different CO2 atmospheres (0.04%, 5% or 10%). Basil volatile profile was assessed using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Leaves suffered severe chilling injury and greater loss of aroma volatiles at 5°C compared to 10°C and 15°C. More than 70 volatiles were identified for each genotype, while supervised multivariate analysis revealed 26 and 10 differentially-accumulated volatiles for 'Genovese' and 'Lemon' basil, respectively, stored at different temperatures. Storage in 5% CO2 ameliorated the symptoms of chilling injury for up to 3 days in 'Genovese', but not in 'Lemon' basil. Both chilling temperatures and controlled atmospheres altered key volatile compounds implicated in basil aroma and flavor, but temperature had a bigger influence on the observed changes in volatile profile.

Desiccation and chilling sensitivity of the recalcitrant seeds of Trichilia dregeana harvested from two provenances

Desiccation and chilling sensitivity of the recalcitrant seeds of Trichilia dregeana harvested from two provenances

A Review of Storage Temperature Recommendations for Apples and Pears.

An exploration of the range of expert opinions on the optimum storage temperature for apples and pears in RA (refrigerated air), CA (controlled atmosphere), and DCA (dynamic controlled atmosphere) is provided, based on the accumulated postharvest data from the last 20 years. Apple cultivars have been divided into two storage temperature groups (0 to 1 °C and >1 °C), based on chilling sensitivity. Increasingly, gradual cooling, rather than rapid cooling, is recommended for apple cultivars, especially for chilling-sensitive cultivars. European pear cultivars are held at storage temperatures close to or just below 0 °C since they are not chilling-sensitive, and most cultivars require a cold temperature to induce ethylene production and ripening, especially if picked early for long-term storage. Asian pears apparently have higher temperature requirements in CA, compared with European pears. The temperature recommendations for RA and CA storage differ in some apple and European pear cultivars. In such cases, the CA recommendation is, on average, approximately 0.9 °C higher for apple cultivars and approximately 0.5 °C higher for pear cultivars, compared with RA. Research evidence suggests that some apple and pear cultivars can be stored at higher temperatures in DCA than in CA, and if the ethylene inhibitor, 1-methylcyclopropene (1-MCP), is applied in CA and/or DCA, leading to possible energy savings and quality benefits. A cool growing season may increase postharvest disorders, depending on cultivar and region. The store or packinghouse manager may choose to mitigate potential postharvest problems by maintaining the storage temperature at or above the temperature listed here and/or using stepwise (gradual) cooling. The storage temperature can affect the humidity and vapour pressure deficit (driving force) in the storage room. Altering the vapour pressure deficit controls the water loss in stored fruit, which can affect various quality parameters and the occurrence of several storage disorders.

Chilling-induced H2O2 signaling activates the antioxidant enzymes in alleviating the photooxidative damage caused by loss of function of 2-Cys peroxiredoxin in watermelon

Cold stress signal transduction refers to a process that involves various physiological and molecular changes. Hydrogen peroxide (H2O2) signaling is stimulated by plants in adapting to various environmental stresses. Here, nine respiratory burst oxidase homolog (ClRboh) genes were identified from the watermelon genome. Chilling stress induced increased gene expression of ClRbohD and H2O2 accumulation in watermelon plants. By using virus-induced gene silencing (VIGS), we found that H2O2-induced chilling tolerance is dependent on ClRbohD by increased electrolyte leakage, membrane lipid peroxidation, and reduced photosystem II activity in ClRbohD-silenced plants compared with control. In addition, silencing of 2-Cys peroxiredoxin (Cl2-CP) increased the chilling sensitivity, while exogenous H2O2 treatment compromised the silencing of Cl2-CP-induced photooxidative damage in watermelon plants. The gene expression and enzyme activities of Cu/Zn-SOD and GR were significantly increased in Cl2-CP-silenced plants rather than pV190 control plants upon H2O2 treatment under chilling stress, suggesting that the activation of antioxidant enzymes by H2O2 serves as an alternative pathway to compensate for the deficiency of Cl2-CP during chilling stress response in watermelon.

Modulation of plant development and chilling stress responses by alternative splicing events under control of the spliceosome protein SmEb in Arabidopsis.

Cold stress resulting from chilling and freezing temperatures substantially inhibits plant growth and reduces crop production worldwide. Tremendous research efforts have been focused on elucidating the molecular mechanisms of freezing tolerance in plants. However, little is known about the molecular nature of chilling stress responses in plants. Here we found that two allelic mutants in a spliceosome component gene SmEb (smeb-1 and smeb-2) are defective in development and responses to chilling stress. RNA-seq analysis revealed that SmEb controls the splicing of many pre-messenger RNAs (mRNAs) under chilling stress. Our results suggest that SmEb is important to maintain proper ratio of the two COP1 splicing variants (COP1a/COP1b) to fine tune the level of HY5. In addition, the transcription factor BES1 shows a dramatic defect in pre-mRNA splicing in the smeb mutants. Ectopic expression of the two BES1 splicing variants enhances the chilling sensitivity of the smeb-1 mutant. Furthermore, biochemical and genetic analysis showed that CBFs act as negative upstream regulators of SmEb by directly suppressing its transcription. Together, our results demonstrate that proper alternative splicing of pre-mRNAs controlled by the spliceosome component SmEb is critical for plant development and chilling stress responses.

Conventional and Biotechnological Approaches for Enhancing Shelf-life of Horticultural Crops

Background: Due to its highly perishable nature and less shelf life, postharvest losses of fruits result in a high gap between production and availability. Various plant traits which need to be genetically modified for higher shelf life include lowered respiration and ethylene production, less sensitivity to ethylene, lowering ripening rates, reduced browning, decreased chilling sensitivity and increased postharvest disease resistance. Methods: The importance of understanding the biochemical process of softening and the use of such information for retarding the ripening process has been demonstrated in this paper. Result: After reviewing the development made in extending the shelf life of fruits, it becomes evident that although success in this field has been inadequate, there are possibilities that fruit breeders will succeed in the near future in evolving superior cultivars with longer shelf life by adopting conventional and biotechnological approaches.

Stronger Spring Phenological Advance in Future Warming Scenarios for Temperate Species With a Lower Chilling Sensitivity.

Spring warming could induce earlier leaf-out or flowering of temperate plant species, and decreased chilling in winter has a delaying effect on spring phenology. However, the relative contribution of the decreased chilling and increased forcing on spring phenological change is unclear. Here, we analyzed the experimental data for 14 temperate woody species in Beijing, China and quantified the forcing requirements (FR) of spring phenology and chilling sensitivity (the ratio of the FR at the low chilling condition to the FR at the high chilling condition) for each species. Furthermore, using species-specific functions between the amount of chilling and FR, we established a phenological model to simulate the annual onset dates of spring events during the past 69 years (1952–2020) and in the future (2021–2099) under RCP 4.5 and RCP 8.5 climate scenarios. We also developed a novel method to quantitatively split the predicted phenological change into the effects caused by changes in forcing and those caused by changes in chilling. The results show that the FR of spring events decreased with the increase in the amount of chilling, and this relationship could be described as an exponential decay function. The basic FR (the FR at the high chilling condition) and chilling sensitivity varied greatly among species. In the 1952–2020 period, the advancing effect of increased forcing was stronger than the effect of chilling, leading to earlier spring events with a mean trend of −1.96 days/decade. In future climate scenarios, the spring phenology of temperate species would continue to advance but will be limited by the decreased chilling. The species with lower chilling sensitivities showed stronger trends than those with high chilling sensitivities. Our results suggested that the delaying effect of declining chilling could only slow down the spring phenological advance to a certain extent in the future.

Low temperature conditioning improves American eggplant (Solanum melongena L.) storage compatibility

ABSTRACT Low-temperature conditioning (LTC) has been reported to effectively control post-harvest chilling injury (CI). Conspicuously, it has not been widely adopted by the industry. This is in part related to an incomplete understanding of the factors governing the treatment's efficacy and consistency along genotypes and maturities. Herein, we evaluated the effect of fruit type (striped and purple) and harvest maturity (baby and large) on the effectiveness of LTC (10°C for 2 days) to control eggplant CI. Purple eggplants showed a strong increase in chilling susceptibility between the baby and large maturity stages. In contrast, striped fruit evidenced no major changes in chilling susceptibility along maturation. Susceptible purple large eggplants benefited far more from LTC than baby fruit. Prestorage LTC not only controlled surface scaled development but also decreased pulp softening and browning. In addition, it substantially improved phenolic antioxidants, anthocyanin, and chlorogenic acid retention during storage at 4°C. Overall, results show, for the first time, that the efficacy of LTC in eggplant is deeply affected by the fruit's genotype and maturity. Low-temperature conditioning may be a valuable tool to improve the storage compatibility of commercial eggplant batches having different chilling injury sensitivity.

Jasmonate resistant 1 and ethylene responsive factor 11 are involved in chilling sensitivity in pepper fruit (Capsicum annuum L.)

Pepper fruit (Capsicum annuum L.) is sensitive to chilling stress with chilling injuries occurring below 7 °C; however, chilling injuries occur at different temperatures depending on the genotype. The present study aimed to identify the factors that affect chilling sensitivity in pepper fruits. A total of 112 F2 pepper fruits crossed between chilling-insensitive 'UZB-GJG-1999–51' and chilling-sensitive 'C00562' pepper were grouped according to the seed browning rate, which is a typical chilling symptom of pepper fruit under chilling conditions. Physiological traits, amino acids, fatty acids, as well as ethylene responsive factor (ERF) and jasmonate resistant 1 (JAR1) expression levels were analyzed, and their correlations with the seed browning rate were confirmed. The expression level of JAR1 showed a strong negative correlation with the seed browning rate (r = − 0.7996). The expression level of ERF11 and content of hydrogen peroxide showed strong positive correlation with the seed browning rate (r = 0.7622 and 0.6607, respectively). From these results, we inferred that JAR1 and ERF11 are important factors influencing the chilling sensitivity of pepper fruit.

Degreening, Softening and Chilling Sensitivity of Early Harvested ‘Zesy002’ Kiwifruit under Elevated Temperature Conditioning in a Controlled Atmosphere

Commercially produced volumes of Actinidia chinensis var. chinensis ‘Zesy002’ (Zespri® SunGold Kiwifruit, Tauranga, New Zealand) are increasing rapidly. One approach to managing the harvest logistics is to start the harvest season earlier by harvesting fruit before they have fully degreened on the vine. However, there are risks: the fruit are chilling-sensitive and they may soften excessively while degreening at elevated temperatures off the vine. Degreening and softening were investigated for ‘Zesy002’ kiwifruit harvested before fully degreened, and then allowed to degreen for 2 or 4 weeks at 10 °C in air or in a controlled atmosphere (CA; 2% oxygen/2% carbon dioxide). Fruit were then stored in air or CA at 1 °C up to 16 weeks from harvest, after which they were assessed for chilling injury. The main findings were that holding fruit in CA rather than air at 10 °C caused slower degreening, delayed the change to rapid softening, and also delayed the loss of chilling sensitivity. It is concluded that if ‘Zesy002’ fruit are to be degreened in CA, then either a longer conditioning period in CA, or more advanced fruit, should be used.

Conventional and Biotechnological Approaches for Enhancing the Shelf-life of Fruits and Vegetables: A Review

Due to highly perishable nature and less shelf-life, post-harvest losses of fruit and vegetables results in high gap between production and availability. Various plants traits which need to be genetically modified for higher shelf-life includes lowered rate of respiration and ethylene production, less sensitivity to ethylene, lowering ripening rate, reduced browning, decreased chilling sensitivity and increased postharvest disease resistance. The importance of understanding the biochemical process of softening and the use of such information for retarding the ripening process has been demonstrated in this paper. After reviewing the development made in extending the shelf-life of fruits, it becomes evident that although success in this field has been inadequate, there are possibilities that fruit breeders will succeed in near future in evolving superior cultivars with longer shelf-life.

Influence of the Position of Mango Fruit on the Tree (Mangifera indica L. CV. ‘Zibda’) on Chilling Sensitivity and Antioxidant Enzyme Activity

Mango fruits sourced from tropical yields have had a high commercial comeback from being viewed as susceptible to chilling injury under long storage durations. When the fruits are exposed to cold storage, this results in physiological changes due to the side effects of the storage on the fruits, expanding the rates of loss during the period between harvest and marketing. It is difficult to harvest mangoes as the fruits show varying maturities and are located in different positions on the trees. The purpose of this study was to test the idea that fruits’ location on the tree influences how the fruit behaves during cold storage. During two seasons (2019–2020), the impact of on-tree fruit location, i.e., sunny side (SUN; fruit exposed to the sun for most of the day), shade (SHA; fruit grown on the shady side of trees), and inside the canopy (INS; fruit grown inside the tree canopy), on the chilling sensitivity and the activities of antioxidant enzymes of ‘Zibda’ mangos stored at a low temperature (4 ± 1 °C) for 35 days was determined. In contrast to SHA and SUN mangos, INS fruits were shown to be progressively tolerant to low storage temperatures. These fruits also showed the highest activities of ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD). In addition, the contents of O2− and H2O2 decreased in INS fruit during storage. Consequently, the cell membrane compartments were maintained, showing low accumulation of both malondialdehyde (MDA) and the protein carbonyl group (PCG) during storage. These results indicate that the fruit positions can also be considered at the time of harvesting for the classification of fruits before cold storage. This classification can also be added to the mango trading protocol to minimize the loss of economic returns by chilling injury.

The truncated TNL receptor TN2-mediated immune responses require ADR1 function.

The loss of function of exocyst subunit EXO70B1 leads to autoimmunity, which is dependent on TIR-NBS2 (TN2), a truncated intracellular nucleotide-binding and leucine-rich repeat receptor (NLR). However, how TN2 triggers plant immunity and whether typical NLRs are required in TN2-activated resistance remain unclear. Through the CRISPR/Cas9 gene editing system and knockout analysis, we found that the spontaneous cell death and enhanced resistance in exo70B1-3 were independent of the full-length NLR SOC3 and its closest homolog SOC3-LIKE 1 (SOC3-L1). Additionally, knocking out SOC3-L1 or TN2 did not suppress the chilling sensitivity conferred by chilling sensitive 1-2 (chs1-2). The ACTIVATED DISEASE RESISTANCE 1 (ADR1) family and the N REQUIREMENT GENE 1 (NRG1) family have evolved as helper NLRs for many typical NLRs. Through CRISPR/Cas9 gene editing methods, we discovered that the autoimmunity of exo70B1-3 fully relied on ADR1s, but not NRG1s, and ADR1s contributed to the upregulation of TN2 transcript levels in exo70B1-3. Furthermore, overexpression of TN2 also led to ADR1-dependent autoimmune responses. Taken together, our genetic analysis highlights that the truncated TNL protein TN2-triggered immune responses require ADR1s as helper NLRs to activate downstream signaling, revealing the importance and complexity of ADR1s in plant immunity regulation.

Modelling the advancement of chilling tolerance breeding in Northeast China

AbstractDespite global warming, chilling injury during the reproductive stage is still a severe climate stress in temperate rice production systems. Much work has been done on stress avoidance by altering sowing dates and cultivar maturation, but stress tolerance has received less attention. The lack of data to inform existing genetic differences in chilling tolerance impedes model‐based investigations exploring this adaptation. Here, from multiple data sources, we composited control experiments of 25 major rice cultivars in Northeast China, which allows determining the genetic differences in chilling tolerance. The results suggest that newer released rice cultivars tend to resist stronger chilling than older cultivars, and there is a coexistence between high‐yielding and more chilling tolerance. By projecting the above statistical relationship to regional yield, our analysis indicates that the lower chilling sensitivity due to such breeding progress may reduce yield fluctuation by approximately 74% in the lousy harvest year since 1960. Our results also indicate that chilling exposure at booting and flowering not only results in sterility but also may impact grain filling. Our study highlights the quantified cultivar difference in chilling tolerance based on the existing rice genotypes that can support further simulation‐driven studies on the genetic adaptation of chilling stress and improve the quantitative evaluation of cultivar chilling tolerance in crop improvement.

Lipid profiling in chilled coral larvae

Coral reefs are disappearing worldwide as a result of several harmful human activities. The establishment of cryobanks can secure a future for these ecosystems. To design effective cryopreservation protocols, basic proprieties such as chilling tolerance and lipid content must be assessed. In the present study, we investigated chilling sensitivity and the effect of chilling exposure on the lipid content and composition of larvae belonging to 2 common Indo-Pacific corals: Seriatopora caliendrum and Pocillopora verrucosa. The viability of coral larvae incubated with 0.5, 1, and 2 M ethylene glycol (EG), propylene glycol (PG), dimethyl sulfoxide (Me2SO), methanol, or glycerol and kept at 5 °C for different time periods was documented. In addition, we investigated the content of cholesterol, triacylglycerol (TAG), wax ester (WE), sterol ester (SE), lysophosphatidylcholine, phosphatidylcholine, phosphatidylethanolamine, and several fatty acid (FA) classes in coral propagules incubated with 1 M PG or EG and kept at 5 °C for 6 h. Moreover, we examined seasonal changes in the aforementioned lipid classes in coral larvae. S. caliendrum incubated with 0.5 M PG or Me2SO and chilled for 2 h exhibited a viability rate of 11 ± 11%, whereas P. verrucosa exhibited a viability rate of 22 ± 14% after being chilled for 4 h. Furthermore, the results indicated that chilling exposure did not affect the content of any investigated lipid class in either species. The higher concentration of SE in P. verrucosa compared to S. caliendrum larvae may have contributed to the different cryotolerance displayed by the 2 larval species. A year-round lipid analysis of both coral larvae species revealed trends of homeoviscous adaptation and seasonal enhancement of lipid fluxes from symbionts to the host. During winter, the cholesterol/phospholipid ratio significantly increased, and P. verrucosa larvae exhibited an averagely decrease in FA chain lengths. During spring and summer, intracellular lipid content in the form of TAGs and WEs significantly increased in both species, and the average content of Symbiodiniaceae-derived FAs increased in P. verrucosa larvae. We concluded that the low cryotolerance displayed by S. caliendrum and P. verrucosa larvae is attributable to their chilling-sensitive membrane lipid profile and the high intracellular lipid content provided by their endosymbionts.