Physiology and proteomics research on the leaves of ancient Platycladus orientalis (L.) during winter

Effects of Different Donor Ages on the Growth of Cutting Seedlings Propagated from Ancient Platycladus orientalis

The effects of tree age on the growth of cutting seedlings propagated from ancient trees have been an important issue in plant breeding and cultivation. In order to understand seedling growth and stress resistance stability, phenotypic measurements, physiological assays, and high-throughput transcriptome sequencing were performed on sown seedlings propagated from 5-year-old donors and cutting seedlings propagated from 5-, 300-, and 700-year-old Platycladus orientalis donors. In this study, the growth of cutting seedlings propagated from ancient trees was significantly slower; the soluble sugar and chlorophyll contents gradually decreased with the increase in the age of donors, and the flavonoid and total phenolic contents of sown seedlings were higher than those of cutting seedlings. Enrichment analysis of differential genes showed that plant hormone signal transduction, the plant-pathogen interaction, and the flavone and flavonol biosynthesis pathways were significantly up-regulated with the increasing age of cutting seedlings propagated from 300- and 700-year-old donors. A total of 104,764 differentially expressed genes were calculated using weighted gene co-expression network analysis, and 8 gene modules were obtained. Further, 10 hub genes in the blue module were identified, which revealed that the expression levels of JAZ, FLS, RPM1/RPS3, CML, and RPS2 increased with the increase in tree age. The results demonstrated that the age of the donors seriously affected the growth of P. orientalis cutting seedlings and that cutting propagation can preserve the resistance of ancient trees. The results of this study provide important insights into the effects of age on asexually propagated seedlings, reveal potential molecular mechanisms, and contribute to an improvement in the level of breeding and conservation of ancient germplasm resources of P. orientalis trees.

Effects of Donor Ages and Propagation Methods on Seedling Growth of Platycladus orientalis (L.) Franco in Winter

To evaluate the effects of donor ages on growth and stress resistance of 6-year-old seedlings propagated from 5-, 2000-, and 3000-year-old Platycladus orientalis donors with grafting, cutting, and seed sowing, growth indicators and physiological and transcriptomic analyses were performed in 6-year-old seedlings in winter. Results showed that basal stem diameters and plant heights of seedlings of the three propagation methods decreased with the age of the donors, and the sown seedlings were the thickest and tallest. The contents of soluble sugar, chlorophyll, and free fatty acid in apical leaves of the three propagation methods were negatively correlated with donor ages in winter, while the opposite was true for flavonoid and total phenolic. The contents of flavonoid, total phenolic, and free fatty acid in cutting seedlings were highest in the seedlings propagated in the three methods in winter. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis of differentially expressed genes showed phenylpropanoid biosynthesis and fatty acid metabolism pathways, and their expression levels were up-regulated in apical leaves from 6-year-old seedlings propagated from 3000-year-old P. orientalis donors. In addition, hub genes analysis presented that C4H, OMT1, CCR2, PAL, PRX52, ACP1, AtPDAT2, and FAD3 were up-regulated in cutting seedlings, and the gene expression levels decreased in seedlings propagated from 2000- and 3000-year-old donors. These findings demonstrate the resistance stability of cuttings of P. orientalis and provide insights into the regulatory mechanisms of seedlings of P. orientalis propagated from donors at different ages in different propagation methods against low-temperature stress.

Chemotaxonomic Variation in Volatile Component Contents in Ancient Platycladus orientalis Leaves with Different Tree Ages in Huangdi Mausoleum

To gain insight into the differences in the composition and volatile components content in ancient Platycladus orientalis leaves with different tree ages in Huangdi Mausoleum, the volatile components were identified by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) method. The volatile components were statistically analyzed by orthogonal partial least squares discriminant analysis and hierarchical cluster analysis, and the characteristic volatile components were screened. The results exhibited that a total of 72 volatile components were isolated and identified in 19 ancient Platycladus orientalis leaves with different tree ages, and 14 common volatile components were screened. Among them, the contents of α-pinene (6.40-16.76%), sabinene (1.11-7.29%), 3-carene (1.14-15.12%), terpinolene (2.17-4.95%), caryophyllene (8.04-13.53%), α-caryophyllene (7.34-14.41%), germacrene D (5.27-12.13%), (+)-Cedrol (2.34-11.30%) and α-terpinyl acetate (1.29-25.68%) were relatively higher (>1%), accounting for 83.40-87.61% of the total volatile components. Nineteen ancient Platycladus orientalis trees were clustered into three groups through the HCA method based on the 14 common volatile components content. Combined with the results of OPLS-DA analysis, (+)-cedrol, germacrene D, α-caryophyllene, α-terpinyl acetate, caryophyllene, β-myrcene, β-elemene and epiglobulol were the differential volatile components to distinguish ancient Platycladus orientalis with different tree ages. The results revealed that the composition of the volatile components in ancient Platycladus orientalis leaves with different tree ages was different, showing different aroma characteristics, which provided a theoretical reference for the differential development and application of volatile components in ancient Platycladus orientalis leaves.

Proteome analysis reveals a systematic response of cold-acclimated seedlings of an exotic mangrove plant Sonneratia apetala to chilling stress

Low temperature in winter was the most crucial abiotic stress that limits the mangrove afforestation northward. Previous study demonstrated that Sonneratia apetala initially transplanted to high latitude area exhibited a stronger plasticity of cold tolerance. To clarify the underlying mechanism, the physiological and proteomic responses to chilling stress were investigated in S. apetala leaves. Our results found that cold-acclimated seedlings had lower relative electrolyte leakage and MDA content than non-acclimated seedlings. On the contrary, higher chlorophyll content and photosynthetic capacity were observed in cold-acclimated seedlings. With proteomic analyses, the differentially accumulated proteins (DAPs) involved in ROS scavenging, photosynthesis and energy metabolism, carbohydrate metabolism, cofactor biosynthesis, and protein folding were suggested to play important roles in enhancing the cold tolerance of S. apetala. However, the down-regulation DAPs were suggested as a tradeoff between plant growth and chilling response. By the protein-protein interaction analyses, translation elongation factor G, chlorophyll A-B binding protein and ascorbate peroxidase 1 were suggested as the important regulators in cold-acclimated S. apetala seedlings under chilling stress. Based on the above results, a schematic diagram describing the mechanism of cold tolerance of exotic mangrove species S. apetala that was achieved by cold acclimation was presented in this study. SIGNIFICANCE: The major environmental factor limits the mangrove afforestation northward is the low temperature in winter. Previous study reported that Sonneratia apetala grew in high latitude exhibited a higher cold tolerance than that in low latitude, which was suggested as a result of cold acclimation. To further understand "how cold acclimation enhance the cold tolerance in S. apetala", the response of S. apetala subjected to chilling stress with or without cold acclimation was investigated in this study at the physiological and proteomic aspects. Our physiological results showed that S. apetala seedlings treated with cold acclimation exhibited a higher tolerance under chilling stress than that without cold acclimation. By using the comparative proteomic approaches and bioinformatic analyses, various biological processes were suggested to play an important role in enhancing the cold tolerance of S. apetala under chilling stress, such as ROS scavenging, photosynthesis and energy metabolism, carbohydrate metabolism, cofactor biosynthesis, and protein folding. Among these differentially accumulated proteins, translation elongation factor G (eEF-G), chlorophyll A-B binding protein (CAB) and ascorbate peroxidase 1 (APX1) were identified as the hub proteins function in coordinated regulating ROS scavenging, photosynthesis and protein biosynthesis in chloroplast and subsequently enhanced the cold tolerance of S. apetala under chilling stress. Our results provided a further understanding of cold acclimation in improving the cold tolerance in exotic mangrove species S. apetala.

iTRAQ-based quantitative proteomic analysis of heat stress-induced mechanisms in pepper seedlings

Background

As one of the most important vegetable crops, pepper has rich nutritional value and high economic value. Increasing heat stress due to the global warming has a negative impact on the growth and yield of pepper.

Methods

To understand the heat stress response mechanism of pepper, an iTRAQ-based quantitative proteomic analysis was employed to identify possible heat-responsive proteins and metabolic pathways in 17CL30 and 05S180 pepper seedlings under heat stress.

Result

In the present study, we investigated the changes of phenotype, physiology, and proteome in heat-tolerant (17CL30) and heat-sensitive (05S180) pepper cultivars in response to heat stress. Phenotypic and physiological changes showed that 17CL30 had a stronger ability to resist heat stress compared with 05S180. In proteomic analysis, a total of 3,874 proteins were identified, and 1,591 proteins were considered to participate in the process of heat stress response. According to bioinformatic analysis of heat-responsive proteins, the heat tolerance of 17CL30 might be related to a higher ROS scavenging, photosynthesis, signal transduction, carbohydrate metabolism, and stress defense, compared with 05S180.

Physiological and TMT-labeled proteomic analyses reveal important roles of sugar and secondary metabolism in Citrus junos under cold stress

Citrus junos is a widely used citrus grafting rootstock in china because of its excellent tolerance to cold stress. However, the physiological and molecular mechanisms underlying this process remain unknown. In this study, physiological and tandem mass tag-based proteomic analyses were performed to elucidate the mechanism of the Citrus junos response to cold stress. Physiological data showed that severe cold stress decreased photosynthetic parameters and caused cell membrane damage and membrane lipid peroxidation in Citrus junos leaves compared to the control. A total of 6, 678 distinct proteins species were identified, and 413 proteins species were significantly differentially accumulated in the leaves of Citrus junos seedling after cold stress. Bioinformatics analysis revealed that the differentially abundance protein species mainly related to the starch and sucrose metabolism, secondary metabolites biosynthesis and phenylpropanoid biosynthesis in the leaves of Citrus junos seedling after cold stress. Further physiological assays showed that the contents of soluble starch, fructose, glucose and phenols were significantly increased in Citrus junos leaves after cold stress. Collectively, our data reveals that sugar and secondary metabolism could play important roles in Citrus junos in response to cold stress.

Nucleic acid damage and DNA repair are affected by freezing stress in annual wheat (Triticum aestivum) and by plant age and freezing in its perennial relative (Thinopyrum intermedium)

PREMISE

Nucleic acid integrity can be compromised under many abiotic stresses. To date, however, few studies have considered whether nucleic acid damage and damage repair play a role in cold-stress adaptation. A further insufficiently explored question concerns how age affects cold stress adaptation among mature perennials. As a plant ages, the optimal trade-off between growth and stress tolerance may shift.

METHODS

Oxidative damage to RNA and expression of genes involved in DNA repair were compared in multiple mature cohorts of Thinopyrum intermedium (an emerging perennial cereal) and in wheat and barley under intermittent freezing stress and under nonfreezing conditions. Activity of glutathione peroxidase (GPX) and four other antioxidative enzymes was also measured under these conditions. DNA repair genes included photolyases involved in repairing ultraviolet-induced damage and two genes involved in repairing oxidatively induced damage (ERCC1, RAD23).

RESULTS

Freezing stress was accompanied by large increases in photolyase expression and ERCC1 expression (in wheat and Thinopyrum) and in GPX and GR activity (particularly in Thinopyrum). This is the first report of DNA photolyases being overexpressed under freezing stress. Older Thinopyrum had lower photolyase expression and less freezing-induced overexpression of ERCC1. Younger Thinopyrum plants sustained more oxidative damage to RNA.

CONCLUSIONS

Overexpression of DNA repair genes is an important aspect of cold acclimation. When comparing adult cohorts, aging was associated with changes in the freezing stress response, but not with overall increases or decreases in stress tolerance.

iTRAQ-based quantitative proteomics analysis of cantaloupe (Cucumis melo var. saccharinus) after cold storage

Background

Cantaloupe is susceptible to cold stress when it is stored at low temperatures, resulting in the loss of edible and commercial quality. To ascertain the molecular mechanisms of low temperatures resistance in cantaloupe, a cold-sensitive cultivar, Golden Empress-308 (GE) and a cold-tolerant cultivar, Jia Shi-310 (JS), were selected in parallel for iTRAQ quantitative proteomic analysis.

Results

The two kinds of commercial cultivars were exposed to a temperature of 0.5 °C for 0, 12 and 24 days. We found that the cold-sensitive cultivar (GE) suffered more severe damage as the length of the cold treatment increased. Proteomic analysis of both cultivars indicated that the number of differentially expressed proteins (DEPs) changed remarkably during the chilly treatment. JS expressed cold-responsive proteins more rapidly and mobilized more groups of proteins than GE. Furthermore, metabolic analysis revealed that more amino acids were up-regulated in JS during the early phases of low temperatures stress. The DEPs we found were mainly related to carbohydrate and energy metabolism, structural proteins, reactive oxygen species scavenging, amino acids metabolism and signal transduction. The consequences of phenotype assays, metabolic analysis and q-PCR validation confirm the findings of the iTRAQ analysis.

Conclusion

We found that the prompt response and mobilization of proteins in JS allowed it to maintain a higher level of cold tolerance than GE, and that the slower cold responses in GE may be a vital reason for the severe chilling injury commonly found in this cultivar. The candidate proteins we identified will form the basis of future studies and may improve our understanding of the mechanisms of cold tolerance in cantaloupe.

Effects of T-2 toxin on the muscle proteins of shrimp (Litopenaeus vannamei) - a proteomics study

BACKGROUND

T-2 toxin (T-2) is a potent mycotoxin and a common contaminant of aquatic animal feed, posing a serious risk to health and aquatic animals. We investigated the effect of T-2 on shrimp muscle proteins using proteomics and conventional biochemical methods. Shrimp were fed a diet containing T-2 at 0-12.2 mg kg^-1 for 20 days, and changes to the muscle protein composition, ATPase activities, and the sulfhydryl (SH) content and hydrophobicity of actomyosin (AM) were determined. A proteomics study of the proteins was conducted with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional (2D) electrophoresis, and matrix-assisted laser desorption/ionization - time of flight mass spectrometry (MALDI-TOF/TOF MS).

RESULTS

Exposure to T-2 markedly affected the muscle protein composition of shrimp in a concentration-responsive manner that displayed a diphasic effect. At a low T-2 concentration (1.2 mg kg^-1 ), the levels of three major muscle proteins (myofibrillar, sarcoplasmic, and stroma) increased but at higher concentrations they declined progressively. T-2 exposure also led to a breakdown of muscle proteins as evidenced by increases in alkali-soluble protein and the surface hydrophobicity (SoANS) of AM. Thirty differentially expressed proteins were detected, 12 of which showed a concentration-response relationship with T-2 exposure. Among them, 11 homologous proteins were identified by mass spectrometry (MS), with several being key enzymes in energy metabolism.

CONCLUSION

This study demonstrated that T-2 exposure at medium to high concentrations could significantly affect the protein composition and quality of shrimp muscle, and potentially some of its key metabolisms. One of the arginine kinases (spot 27) was particularly responsive to T-2 and could potentially be used as a biomarker protein for T-2 intoxication by shrimp. © 2019 Society of Chemical Industry.

Tree age did not affect the leaf anatomical structure or ultrastructure of Platycladus orientalis L. (Cupressaceae)

Tree aging is a new research area and has attracted research interest in recent years. Trees show extraordinary longevity; Platycladus orientalis L. (Cupressaceae) has a lifespan of thousands of years. Ancient trees are precious historical heritage and scientific research materials. However, tree aging and tree senescence have different definitions and are poorly understood. Since leaves are the most sensitive organ of a tree, we studied the structural response of leaves to tree age. Experiments investigating the leaf morphological structure, anatomical structure and ultrastructure were conducted in healthy P. orientalis at three different ages (ancient trees >2,000 years, 200 years < middle-aged trees <500 years, young trees <50 years) at the world’s largest planted pure forest in the Mausoleum of the Yellow Emperor, Shaanxi Province, China. Interestingly, tree age did not significantly impact leaf cellular structure. Ancient P. orientalis trees in forests older than 2,000 years still have very strong vitality, and their leaves still maintained a perfect anatomical structure and ultrastructure. Our observations provide new evidence for the unique pattern of tree aging, especially healthy aging. Understanding the relationships between leaf structure and tree age will enhance the understanding of tree aging.

Leaf anatomy and ultrastructure in senescing ancient tree, Platycladus orientalis L. (Cupressaceae)

Platycladus orientalis L. (Cupressaceae) has a lifespan of thousands of years. Ancient trees have very high scientific, economic and cultural values. The senescence of ancient trees is a new research area but is poorly understood. Leaves are the primary and the most sensitive organ of a tree. To understand leaf structural response to tree senescence in ancient trees, experiments investigating the morphology, anatomy and ultrastructure were conducted with one-year leaves of ancient P. orientalis (ancient tree >2,000 years) at three different tree senescent levels (healthy, sub-healthy and senescent) at the world's largest planted pure forest in the Mausoleum of Yellow Emperor, Shaanxi Province, China. Observations showed that leaf structure significantly changed with the senescence of trees. The chloroplast, mitochondria, vacuole and cell wall of mesophyll cells were the most significant markers of cellular ultrastructure during tree senescence. Leaf ultrastructure clearly reflected the senescence degree of ancient trees, confirming the visual evaluation from above-ground parts of trees. Understanding the relationships between leaf structure and tree senescence can support decision makers in planning the protection of ancient trees more promptly and effectively by adopting the timely rejuvenation techniques before the whole tree irreversibly recesses.

Seasonal variation in non-structural carbohydrates, sucrolytic activity and secondary metabolites in deciduous and perennial Diospyros species sampled in Western Mexico

This study was performed to test the working hypothesis that the primary determinants influencing seasonal driven modifications in carbon mobilization and other key biochemical parameters in leaves of poorly known Diospyros digyna (Ddg; semi-domesticated; perennial) and D. rekoi (Dre; undomesticated; deciduous) trees are determined by environmental growing conditions, agronomic management and physiological plasticity. Thus, biochemical changes in leaves of both trees were recorded seasonally during two successive fruiting years. Trees were randomly sampled in Western Mexico habitats with differing soil quality, climatic conditions, luminosity, and cultivation practices. Leaves of Ddg had consistently higher total chlorophyll contents (CT) that, unexpectedly, peaked in the winter of 2015. In Dre, the highest leaf CT values recorded in the summer of 2015 inversely correlated with low average luminosity and high Chl a/ Chlb ratios. The seasonal CT variations in Dre were congruent with varying luminosity, whereas those in Ddg were probably affected by other factors, such as fluctuating leaf protein contents and the funneling of light energy to foliar non-structural carbohydrates (NSCs) accumulation, which were consistently higher than those detected in Dre leaves. Seasonal foliar NSC fluctuations in both species were in agreement with the carbon (C) demands of flowering, fruiting and/ or leaf regrowth. Seasonal changes in foliar hexose to sucrose (Hex/ Suc) ratios coincided with cell wall invertase activity in both species. In Dre, high Hex/ Suc ratios in spring leaves possibly allowed an accumulation of phenolic acids, not observed in Ddg. The above results supported the hypothesis proposed by showing that leaf responses to changing environmental conditions differ in perennial and deciduous Diospyros trees, including a dynamic adjustment of NSCs to supply the C demands imposed by reproduction, leaf regrowth and, possibly, stress.