Adaptations and plastic phenotypic responses of marine animals to the environmental challenges of the high intertidal zone

The high intertidal zone is home to an incredible variety of marine animals, as it offers an escape from low intertidal/subtidal predation and competition, among other advantages. However, this area of the shore also comes with many tide-driven and emersion-associated environmental stressors, such as desiccation, high temperatures and freezing stress, hypoxia, salinity fluctuations, nitrogenous waste accumulation, ultraviolet (UV) radiation, wave and ice disturbance, and hydrogen sulphide (H2S) toxicity. This review explores the diversity of evolutionary adaptations and plastic phenotypic responses that high intertidal animals use to cope with these challenges. Examples are provided of behavioural, morphological, physiological and biochemical adaptations/responses, along with some of the underlying molecular mechanisms that have been elucidated to date. Adaptations of many different worms, anemones, molluscs, crustaceans and fishes are highlighted. Many adaptations and mechanisms of plasticity are universal among animal phyla, and some are multifunctional (serve more than one function) or provide tolerance to multiple stressors (i.e., ‘cross-tolerance’). High intertidal animals have received considerable attention by scientists, given their accessibility and that they can provide valuable insights in the transition from a marine to a terrestrial lifestyle. Nevertheless, further research is needed to understand the adaptations/responses of these animals more thoroughly, and the future holds great promise for accomplishing this with recent advances in epigenetics, transcriptomics, protein biochemistry and other molecular tools.

Assessing Waterlogging Stress Level of Winter Wheat from Hyperspectral Imagery Based on Harmonic Analysis

Frequent waterlogging disasters can have serious effects on regional ecology, food safety, and socioeconomic sustainable development. Early monitoring of waterlogging stress levels is vital for accurate production input management and reduction of crop production-related risks. In this study, a pot experiment on winter wheat was designed using three varieties and seven gradients of waterlogging stress. Hyperspectral imagery of the winter wheat canopy in the jointing stage, heading stage, flowering stage, filling stage, and maturation stage were measured and then classified. Wavebands of imaging data were screened. Waterlogging stress level was assessed by a combined harmonic analysis method, and application of this method at field scale was discussed preliminarily. Results show that compared to the k-nearest neighbor and support vector machine algorithms, the random forest algorithm is the best batch classification method for hyperspectral imagery of potted winter wheat. It can recognize waterlogging stress well in the wavebands of red absorption valley (RW: 640–680 nm), red-edge (RE: 670–737 nm), and near-infrared (NIR: 700–900 nm). In the RW region, amplitudes of the first three harmonic sub-signals (c1, c2, and c3) can be used as indexes to recognize the waterlogging stress level that each winter wheat variety undertakes. The third harmonic sub-signal amplitude c3 of the RE region is also suitable for judging stress levels of JM31 (one of the three varieties which is highly sensitive to water content). This study has important theoretical significance and practical application values related to the accurate control of waterlogging stress, and functions as a new method to monitor other types of environmental stress levels such as drought stress, freezing stress, and high-temperature stress levels.

Salicylic Acid-Mediated Diacylglycerol/Triacylglycerol Conversion Affects the Freezing Tolerance of Arabidopsis

Diacylglycerol (DAG) is likely converted to triacylglycerol (TAG) by the enzyme diacylglycerol acyltransferase (DGAT), and this conversion is important in freezing tolerance of Arabidopsis. The phytohormone salicylic acid (SA) plays important roles in the chilling and freezing tolerance of plants. In our study, we analysed the chilling phenotype, proline and sugar accumulation, phytohormone measurement, and lipid profiling of dgat1 mutants during chilling or freezing stress. We found that dgat1-1 mutants exhibited higher sensitivity to long exposure to cold stress and showed lower proline and sugar accumulation under cold acclimation conditions. The freezing-sensitive phenotype of dgat1 mutants can be ameliorated by mutations of key salicylic acid (SA) signalling components SAG101, EDS1, and PAD4 through phenotyping analysis of double mutants. Dgat1 mutants accumulated more SA, ABA, JA-Ile (jasmonate isoleucine) and OPDA (12- oxyphytodienoic acid) during freezing stress and after recovery. In addition, the DAG/TAG content in the SA-deficient mutant sid2 was lower than that in the wild type, while the SA-excessive accumulated mutant siz1 showed the opposite trend. In summary, SA could mediate the freezing tolerance of Arabidopsis by regulating the ratio of DAG and TAG, which influences the integrity of the membrane.

Cold Acclimation Affects Physiological and Biochemical Characteristics of Betula platyphylla S. under Freezing Stress

Cold and freezing stress is one of the most harmful environmental stresses, especially in temperate and subtropical areas, that adversely affects plant growth, development, and yield production. Betula platyphylla Sukaczev, also known as white birch, is one of the most valuable, important, and widely distributed tree species in East Asia. This study explored the effects of cold acclimation (CA) in reducing the destructive effect of freezing stress in B. platyphylla seedlings. We measured the physiological and biochemical characteristics of B. platyphylla seedlings, such as chlorophyll content, electrolyte leakage (EL), malondialdehyde (MDA), antioxidant enzymes (such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), and proline content before and after freezing stress to observe the contribution of CA in reducing the detrimental effects of freezing stress. The results showed that CA increased physiological and biochemical characteristics of B. platyphylla seedlings before and after freezing stress, except for chlorophyll content. Antioxidant enzymes were significantly positively correlated with proline, MDA, and EL content, and negatively correlated with chlorophyll content. Moreover, histochemical detection (H2O2 and O2−) and cell death were revealed to be induced by cold stress in B. platyphylla seedlings. Furthermore, it was revealed that increased time and decreased temperature of the CA process significantly influenced the physiological and biochemical parameters. Overall, the CA process significantly reduced the detrimental effects of freezing stress compared to the control treatment in B. platyphylla seedlings. Taken together, these findings provide beneficial information toward understanding the mechanism of CA and freezing stress in B. platyphylla. Furthermore, the substantial activity of physiological and biochemical results could be used as selection criteria for screening time and temperature points of cold/freezing stress in further omics analyses. In addition, the combination of current study results, further omics analyses, and genetic engineering techniques directly contribute to sustainable forest management systems, tree plantations, and conservation of tree species, especially non-cold/non-freezing tolerant tree species.

iTRAQ-based quantitative proteome analysis insights into cold stress of Winter Rapeseed (Brassica rapa L.) grown in the field

Winter rapeseed (Brassica rapa L.) is a major oilseed crop in Northern China, where its production was severely affected by chilling and freezing stress. However, not much is known about the role of differentially accumulated proteins (DAPs) during the chilling and freezing stress. In this study, isobaric tag for relative and absolute quantification (iTRAQ) technology was performed to identify DAPs under freezing stress. To explore the molecular mechanisms of cold stress tolerance at the cellular and protein levels, the morphological and physiological differences in the shoot apical meristem (SAM) of two winter rapeseed varieties, Longyou 7 (cold-tolerant) and Lenox (cold-sensitive), were explored in field-grown plants. Compared to Lenox, Longyou 7 had a lower SAM height and higher collar diameter. The level of malondialdehyde (MDA) and indole-3-acetic acid (IAA) content was also decreased. Simultaneously, the soluble sugars (SS) content, superoxide dismutase (SOD) activity, peroxidase (POD) activity, soluble protein (SP) content, and collar diameter were increased in Longyou 7 as compared to Lenox. A total of 6330 proteins were identified. Among this, 98, 107, 183 and 111 DAPs were expressed in L7 CK/Le CK, L7 d/Le d, Le d/Le CK and L7 d/L7 CK, respectively. Quantitative real-time PCR (RT-qPCR) analysis of the coding genes for seventeen randomly selected DAPs was performed for validation. These DAPs were identified based on gene ontology enrichment analysis, which revealed that glutathione transferase activity, carbohydrate-binding, glutathione binding, metabolic process, and IAA response were closely associated with the cold stress response. In addition, some cold-induced proteins, such as glutathione S-transferase phi 2(GSTF2), might play an essential role during cold acclimation in the SAM of Brassica rapa. The present study provides valuable information on the involvement of DAPs during cold stress responses in Brassica rapa L, and hence could be used for breeding experiments.

Static Load Test and Numerical Analysis of Influencing Factors of the Ultimate Bearing Capacity of PHC Pipe Piles in Multilayer Soil

Prestressed high-strength concrete (PHC) pipe piles have been widely used in engineering fields in recent years; however, the influencing factors of their ultimate bearing capacity (UBC) in multilayer soil need to be further studied. In this paper, a static load test (SLT) and numerical analysis are performed to obtain the load transfer and key UBC factors of pipe piles. The results show that the UBC of the test pile is mainly provided by the pile shaft resistance (PSR), but the pile tip resistance (PTR) cannot be ignored. Many factors can change the UBC of pipe piles, but their effects are different. The UBC of the pipe pile is linearly related to the friction coefficient and the outer-to-inner diameter ratio. Changes in the pile length make the UBC increase sharply. Low temperatures can produce freezing stress at the pile–soil interface. The effect of changing the Young modulus of pile tip soil is relatively small.

A method for obtaining field wheat freezing injury phenotype based on RGB camera and software control

Background Low temperature freezing stress has adverse effects on wheat seedling growth and final yield. The traditional method to evaluate the wheat injury caused by the freezing stress is by visual observations, which is time-consuming and laborious. Therefore, a more efficient and accurate method for freezing damage identification is urgently needed. Results A high-throughput phenotyping system was developed in this paper, namely, RGB freezing injury system, to effectively and efficiently quantify the wheat freezing injury in the field environments. The system is able to automatically collect, processing, and analyze the wheat images collected using a mobile phenotype cabin in the field conditions. A data management system was also developed to store and manage the original images and the calculated phenotypic data in the system. In this experiment, a total of 128 wheat varieties were planted, three nitrogen concentrations were applied and two biological and technical replicates were performed. And wheat canopy images were collected at the seedling pulling stage and three image features were extracted for each wheat samples, including ExG, ExR and ExV. We compared different test parameters and found that the coverage had a greater impact on freezing injury. Therefore, we preliminarily divided four grades of freezing injury according to the test results to evaluate the freezing injury of different varieties of wheat at the seedling stage. Conclusions The automatic phenotypic analysis method of freezing injury provides an alternative solution for high-throughput freezing damage analysis of field crops and it can be used to quantify freezing stress and has guiding significance for accelerating the selection of wheat excellent frost resistance genotypes.

Physiological and biochemical responses of strawberry crown and leaf tissues to freezing stress

Background In northern Iran and other cold regions, winter freezing injury and resultant yield instability are major limitations to strawberry production. However, there is scarcity of information on the physiological and biochemical responses of strawberry cultivars to freezing stress. This study aimed to investigate the physiological and biochemical responses of strawberry cultivars (Tennessee Beauty, Blakemore, Kurdistan, Queen Elisa, Chandler, Krasnyy Bereg, and Yalova) to different freezing temperature treatments (− 5, − 10, − 15, − 20, and − 25 °C) under controlled conditions. Results All measured physiological and biochemical features were significantly affected by the interaction effect between low temperatures and cultivars. Tennessee Beauty showed the highest RWC at − 25 °C. The highest Fv/Fm was observed in Queen Elisa. Krasnyy Bereg had the least freezing injury (FI) in crown and leaf, while Yalova and Chandler showed the highest crown and leaf FI, respectively. At − 20 to − 25 °C, the highest carbohydrates contents of crown and leaf were noted in Blakemore and Krasnyy Bereg cultivars, respectively. The Yalova showed the highest protein content in both crown and leaf tissues at − 25 °C. The Tennessee Beauty and Blackmore cultivars showed the highest proline in crowns and leaves at − 15 °C, respectively. The highest ThioBarbituric Acid Reactive Substances (TBARS) contents in the crown and leaf were observed in Kurdistan and Queen Elisa, respectively. Queen Elisa and Krasnyy Bereg cultivars showed SOD and POD peaks in the crown at − 15 °C, respectively. Conclusion Freezing stress was characterized by decreased Fv/Fm and RWC, and increased FI, TBARS, total carbohydrates, total proteins, proline content, and antioxidant enzyme activity. The extent of changes in above mentioned traits was cultivar dependent. FI and TBARS were the best traits among destructive parameters for evaluating freezing tolerance. Moreover, maximum quantum yield of PSII (Fv/Fm index), as non-destructive parameters, showed a significant efficiency in rapid assessment for screening of freezing tolerant strawberry cultivars. The cultivars Krasnyy Bereg, Queen Elisa, and Kurdistan were the most tolerant cultivars to freezing stress. These cultivars can be used as parents in breeding programs to develop new freezing tolerant cultivars.

Saussurea involucrata (Snow Lotus) ICE1 and ICE2 Orthologues Involved in Regulating Cold Stress Tolerance in Transgenic Arabidopsis

As with other environmental stresses, cold stress limits plant growth, geographical distribution, and agricultural productivity. CBF/DREB (CRT-binding factors/DRE-binding proteins) regulate tolerance to cold/freezing stress across plant species. ICE (inducer of CBF expression) is regarded as the upstream inducer of CBF expression and plays a crucial role as a main regulator of cold acclimation. Snow lotus (Saussurea involucrata) is a well-known traditional Chinese herb. This herb is known to have greater tolerance to cold/freezing stress compared to other plants. According to transcriptome datasets, two putative ICE homologous genes, SiICE1 and SiICE2, were identified in snow lotus. The predicted SiICE1 cDNA contains an ORF of 1506 bp, encoding a protein of 501 amino acids, whereas SiICE2 cDNA has an ORF of 1482 bp, coding for a protein of 493 amino acids. Sequence alignment and structure analysis show SiICE1 and SiICE2 possess a S-rich motif at the N-terminal region, while the conserved ZIP-bHLH domain and ACT domain are at the C-terminus. Both SiICE1 and SiICE2 transcripts were cold-inducible. Subcellular localization and yeast one-hybrid assays revealed that SiICE1 and SiICE2 are transcriptional regulators. Overexpression of SiICE1 (35S::SiICE1) and SiICE2 (35S::SiICE2) in transgenic Arabidopsis increased the cold tolerance. In addition, the expression patterns of downstream stress-related genes, CBF1, CBF2, CBF3, COR15A, COR47, and KIN1, were up-regulated when compared to the wild type. These results thus provide evidence that SiICE1 and SiICE2 function in cold acclimation and this cold/freezing tolerance may be regulated through a CBF-controlling pathway.

Transcriptome and Metabolome Analysis Revealed the Freezing Resistance Mechanism in 60-Year-Old Overwintering Camellia sinensis

Freezing stress in winter is the biggest obstacle to the survival of C. sinensis in mid-latitude and high-latitude areas, which has a great impact on the yield, quality, and even life of C. sinensis every year. In this study, transcriptome and metabolome were used to clarify the freezing resistance mechanism of 60-year-old natural overwintering C. sinensis under freezing stress. Next, 3880 DEGs and 353 DAMs were obtained. The enrichment analysis showed that pathways of MAPK and ABA played a key role in the signal transduction of freezing stress, and Pyr/PYL-PP2C-SnRK2 in the ABA pathway promoted stomatal closure. Then, the water holding capacity and the freezing resistance of C. sinensis were improved. The pathway analysis showed that DEGs and DAMs were significantly enriched and up-regulated in the three-related pathways of phenylpropanoid biosynthesis, flavone and flavonol biosynthesis, and flavonoid biosynthesis. In addition, the carbohydrate and fatty acid synthesis pathways also had a significant enrichment, and the synthesis of these substances facilitated the freezing resistance. These results are of great significance to elucidate the freezing resistance mechanism and the freezing resistance breeding of C. sinensis.