The mitochondrial small heat-shock protein protects NADH:ubiquinone oxidoreductase of the electron transport chain during heat stress in plants

Subset-specific mitochondrial stress and DNA damage shape T cell responses to fever and inflammation

Heat is a cardinal feature of inflammation, yet its impacts on immune cells remain uncertain. We show that moderate-grade fever temperatures (39°C) increased murine CD4 T cell metabolism, proliferation, and inflammatory effector activity while decreasing regulatory T cell suppressive capacity. However, heat-exposed T helper 1 (TH1) cells selectively developed mitochondrial stress and DNA damage that activated Trp53 and stimulator of interferon genes pathways. Although many TH1 cells subjected to such temperatures died, surviving TH1 cells exhibited increased mitochondrial mass and enhanced activity. Electron transport chain complex 1 (ETC1) was rapidly impaired under fever-range temperatures, a phenomenon that was specifically detrimental to TH1 cells. TH1 cells with elevated DNA damage and ETC1 signatures were also detected in human chronic inflammation. Thus, fever-relevant temperatures disrupt ETC1 to selectively drive apoptosis or adaptation of TH1 cells to maintain genomic integrity and enhance effector functions.

Multi-scale analysis of heat stress acclimation in Arabidopsis seedlings highlights the primordial contribution of energy-transducing organelles

Much progress has been made in understanding the molecular mechanisms of plant adaptation to heat stress. However, the great diversity of models and stress conditions, and the fact that analyses are often limited to a small number of approaches, complicate the picture. We took advantage of a liquid culture system in which Arabidopsis seedlings are arrested in their development, thus avoiding interference with development and drought stress responses, to investigate through an integrative approach seedlings' global response to heat stress and acclimation. Seedlings perfectly tolerate a noxious heat shock (43°C) when subjected to a heat priming treatment at a lower temperature (38°C) the day before, displaying a thermotolerance comparable to that previously observed for Arabidopsis. A major effect of the pre-treatment was to partially protect energy metabolism under heat shock and favor its subsequent rapid recovery, which was correlated with the survival of seedlings. Rapid recovery of actin cytoskeleton and mitochondrial dynamics were another landmark of heat shock tolerance. The omics confirmed the role of the ubiquitous heat shock response actors but also revealed specific or overlapping responses to priming, heat shock, and their combination. Since only a few components or functions of chloroplast and mitochondria were highlighted in these analyses, the preservation and rapid recovery of their bioenergetic roles upon acute heat stress do not require extensive remodeling of the organelles. Protection of these organelles is rather integrated into the overall heat shock response, thus allowing them to provide the energy required to elaborate other cellular responses toward acclimation.

How Does Mitochondrial Protein-Coding Gene Expression in Fejervarya kawamurai (Anura: Dicroglossidae) Respond to Extreme Temperatures?

Unusual climates can lead to extreme temperatures. Fejervarya kawamurai, one of the most prevalent anurans in the paddy fields of tropical and subtropical regions in Asia, is sensitive to climate change. The present study focuses primarily on a single question: how do the 13 mitochondrial protein-coding genes (PCGs) respond to extreme temperature change compared with 25 °C controls? Thirty-eight genes including an extra tRNA-Met gene were identified and sequenced from the mitochondrial genome of F. kawamurai. Evolutionary relationships were assessed within the Dicroglossidae and showed that Dicroglossinae is monophyletic and F. kawamurai is a sister group to the clade of (F. multistriata + F. limnocharis). Transcript levels of mitochondrial genes in liver were also evaluated to assess responses to 24 h exposure to low (2 °C and 4 °C) or high (40 °C) temperatures. Under 2 °C, seven genes showed significant changes in liver transcript levels, among which transcript levels of ATP8, ND1, ND2, ND3, ND4, and Cytb increased, respectively, and ND5 decreased. However, exposure to 4 °C for 24 h was very different in that the expressions of ten mitochondrial protein-coding genes, except ND1, ND3, and Cytb, were significantly downregulated. Among them, the transcript level of ND5 was most significantly downregulated, decreasing by 0.28-fold. Exposure to a hot environment at 40 °C for 24 h resulted in a marked difference in transcript responses with strong upregulation of eight genes, ranging from a 1.52-fold increase in ND4L to a 2.18-fold rise in Cytb transcript levels, although COI and ND5 were reduced to 0.56 and 0.67, respectively, compared with the controls. Overall, these results suggest that at 4 °C, F. kawamurai appears to have entered a hypometabolic state of hibernation, whereas its mitochondrial oxidative phosphorylation was affected at both 2 °C and 40 °C. The majority of mitochondrial PCGs exhibited substantial changes at all three temperatures, indicating that frogs such as F. kawamurai that inhabit tropical or subtropical regions are susceptible to ambient temperature changes and can quickly employ compensating adjustments to proteins involved in the mitochondrial electron transport chain.

Heat stress affects dairy cow health status through blood oxygen availability

BACKGROUND

Rises in global warming and extreme weather occurrence make the risk of heat stress (HS) induced by high ambient temperatures more likely in high-yielding dairy cows, resulting in low milk quality and yield. In animals, oxygen is involved in many physiological and metabolic processes, but the effects of HS on oxygen metabolism remain unclear. Thus, the current study aimed to investigate how oxygen metabolism plays a role in health status of dairy cows by measuring the milk yield, milk composition, and blood biochemical variables of cows under different levels of HS: none (No-HS), mild (Mild-HS), and moderate HS (Mod-HS).

RESULTS

The HS significantly increased rectal temperature (Ptreat < 0.01) and respiration rate (Ptreat < 0.01). Under Mod-HS, greater Na+ (P < 0.05) and lower total CO2, and pH (P < 0.05) were observed relative to those under No-HS and Mild-HS. Oxygen concentrations in both coccygeal artery and mammary vein (Ptreat < 0.01) were lower under Mod-HS than under No-HS. Coccygeal vein concentrations of heat shock protein 90 (HSP90) (P < 0.05) increased during Mod-HS compared with those in cows under No-HS. Malondialdehyde increased during Mod-HS, and glutathione peroxidase (P < 0.01) increased during Mild-HS. Coccygeal vein concentrations of vascular endothelial growth factor (P < 0.01), heme oxygenase-1 (P < 0.01), and hypoxia-inducible factor 1α (P < 0.01) were greater in cows under Mod-HS than those under No-HS. Red blood cell count (P < 0.01) and hemoglobin concentration (P < 0.01) were lower in the coccygeal vein of dairy cows under Mild- and Mod-HS than those of cows under No-HS.

CONCLUSIONS

Exposure to HS negatively impacts the health status and lactation performance of dairy cows by limiting oxygen metabolism and transportation. However, the specific mechanism by which HS affects mammary function in cows remains unclear and requires further exploration.

Novel Insights to Assess Climate Resilience in Goats Using a Holistic Approach of Skin-Based Advanced NGS Technologies

A novel study was conducted to elucidate heat-stress responses on a number of hair- and skin-based traits in two indigenous goat breeds using a holistic approach that considered a number of phenotypic and genomic variables. The two goat breeds, Kanni Aadu and Kodi Aadu, were subjected to a simulated heat-stress study using the climate chambers. Four groups consisting of six goats each (KAC, Kaani Aadu control; KAH, Kanni Aadu heat stress; KOC, Kodi Aadu control; and KOH, Kodi Aadu heat stress) were considered for the study. The impact of heat stress on caprine skin tissue along with a comparative assessment of the thermal resilience of the two goat breeds was assessed. The variables considered were hair characteristics, hair cortisol, hair follicle quantitative PCR (qPCR), sweating (sweating rate and active sweat gland measurement), skin histometry, skin-surface infrared thermography (IRT), skin 16S rRNA V3-V4 metagenomics, skin transcriptomics, and skin bisulfite sequencing. Heat stress significantly influenced the hair fiber characteristics (fiber length) and hair follicle qPCR profile (Heat-shock protein 70 (HSP70), HSP90, and HSP110). Significantly higher sweating rate, activated sweat gland number, skin epithelium, and sweat gland number (histometry) were observed in heat stressed goats. The skin microbiota was also observed to be significantly altered due to heat stress, with a relatively higher alteration being noticed in Kanni Aadu goats than in Kodi Aadi goats. Furthermore, the transcriptomics and epigenetics analysis also pointed towards the significant impact of heat stress at the cellular and molecular levels in caprine skin tissue. The higher proportion of differentially expressed genes (DEGs) along with higher differentially methylated regions (DMRs) in Kanni Aadu goats due to heat stress when compared to Kodi Aadu goats pointed towards the better resilience of the latter breed. A number of established skin, adaptation, and immune-response genes were also observed to be significantly expressed/methylated. Additionally, the influence of heat stress at the genomic level was also predicted to result in significant functional alterations. This novel study thereby highlights the impact of heat stress on the caprine skin tissue and also the difference in thermal resilience exhibited by the two indigenous goat breeds, with Kodi Aadu goats being more resilient.

Proteome Analysis of Nicotiana tabacum Cells following Isonitrosoacetophenone Treatment Reveals Defence-Related Responses Associated with Priming

Proteins play an essential regulatory role in the innate immune response of host plants following elicitation by either biotic or abiotic stresses. Isonitrosoacetophenone (INAP), an unusual oxime-containing stress metabolite, has been investigated as a chemical inducer of plant defence responses. Both transcriptomic and metabolomic studies of various INAP-treated plant systems have provided substantial insight into this compound's defence-inducing and priming capabilities. To complement previous 'omics' work in this regard, a proteomic approach of time-dependent responses to INAP was followed. As such, Nicotiana tabacum (N. tabacum) cell suspensions were induced with INAP and changes monitored over a 24-h period. Protein isolation and proteome analysis at 0, 8, 16 and 24 h post-treatment were performed using two-dimensional electrophoresis followed by the gel-free eight-plex isobaric tags for relative and absolute quantitation (iTRAQ) based on liquid chromatography and mass spectrometry. Of the identified differentially abundant proteins, 125 were determined to be significant and further investigated. INAP treatment elicited changes to the proteome that affected proteins from a wide range of functional categories: defence, biosynthesis, transport, DNA and transcription, metabolism and energy, translation and signalling and response regulation. The possible roles of the differentially synthesised proteins in these functional classes are discussed. Results indicate up-regulated defence-related activity within the investigated time period, further highlighting a role for proteomic changes in priming as induced by INAP treatment.

Fine Tuning of ROS, Redox and Energy Regulatory Systems Associated with the Functions of Chloroplasts and Mitochondria in Plants under Heat Stress

Heat stress severely affects plant growth and crop production. It is therefore urgent to uncover the mechanisms underlying heat stress responses of plants and establish the strategies to enhance heat tolerance of crops. The chloroplasts and mitochondria are known to be highly sensitive to heat stress. Heat stress negatively impacts on the electron transport chains, leading to increased production of reactive oxygen species (ROS) that can cause damages on the chloroplasts and mitochondria. Disruptions of photosynthetic and respiratory metabolisms under heat stress also trigger increase in ROS and alterations in redox status in the chloroplasts and mitochondria. However, ROS and altered redox status in these organelles also activate important mechanisms that maintain functions of these organelles under heat stress, which include HSP-dependent pathways, ROS scavenging systems and retrograde signaling. To discuss heat responses associated with energy regulating organelles, we should not neglect the energy regulatory hub involving TARGET OF RAPAMYCIN (TOR) and SNF-RELATED PROTEIN KINASE 1 (SnRK1). Although roles of TOR and SnRK1 in the regulation of heat responses are still unknown, contributions of these proteins to the regulation of the functions of energy producing organelles implicate the possible involvement of this energy regulatory hub in heat acclimation of plants.

Differential Physiological, Transcriptomic, and Metabolomic Responses of Paspalum wettsteinii Under High-Temperature Stress

Global warming has far-reaching effects on plant growth and development. As a warm-season forage grass, Paspalum wettsteinii is highly adaptable to high temperatures. However, the response mechanism of P. wettsteinii under high-temperature stress is still unclear. Therefore, we investigated the physiological indicators, transcriptome and metabolome of P. wettsteinii under different heat stress treatments. Plant height, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the contents of soluble sugar, proline, chlorophyll a, and chlorophyll b increased and then decreased, while the malondialdehyde (MDA) content decreased and then increased with increasing heat stress. Transcriptomic analysis revealed that genes related to energy and carbohydrate metabolism, heat shock proteins (HSPs), and transcription factors (TFs), secondary metabolite biosynthesis and the antioxidant system significantly changed to varying degrees. Metabolomic analysis showed that only free fatty acids were downregulated, while amino acids and their derivatives, organic acids, flavonoids, and sugars were both up- and downregulated under heat stress. These combined analyses revealed that growth was promoted at 25-40°C, while at 45°C, excess reactive oxygen species (ROS) damage reduced antioxidant and osmoregulatory effects and inactivated genes associated with the light and electron transport chains (ETCs), as well as damaged the PS II system and inhibited photosynthesis. A small number of genes and metabolites were upregulated to maintain the basic growth of P. wettsteinii. The physiological and biochemical changes in response to high-temperature stress were revealed, and the important metabolites and key genes involved in the response to high temperature were identified, providing an important reference for the physiological and molecular regulation of high-temperature stress in plants.

Loss of transcriptional plasticity but sustained adaptive capacity after adaptation to global change conditions in a marine copepod

Adaptive evolution and phenotypic plasticity will fuel resilience in the geologically unprecedented warming and acidification of the earth’s oceans, however, we have much to learn about the interactions and costs of these mechanisms of resilience. Here, using 20 generations of experimental evolution followed by three generations of reciprocal transplants, we investigated the relationship between adaptation and plasticity in the marine copepod, Acartia tonsa, in future global change conditions (high temperature and high CO₂). We found parallel adaptation to global change conditions in genes related to stress response, gene expression regulation, actin regulation, developmental processes, and energy production. However, reciprocal transplantation showed that adaptation resulted in a loss of transcriptional plasticity, reduced fecundity, and reduced population growth when global change-adapted animals were returned to ambient conditions or reared in low food conditions. However, after three successive transplant generations, global change-adapted animals were able to match the ambient-adaptive transcriptional profile. Concurrent changes in allele frequencies and erosion of nucleotide diversity suggest that this recovery occurred via adaptation back to ancestral conditions. These results demonstrate that while plasticity facilitated initial survival in global change conditions, it eroded after 20 generations as populations adapted, limiting resilience to new stressors and previously benign environments.

Rapid adaptation will facilitate species resilience under global climate change, but its effects on plasticity are less commonly investigated. This study shows that 20 generations of experimental adaptation in a marine copepod drives a rapid loss of plasticity that carries costs and might have impacts on future resilience to environmental change.

Mitochondria-Targeted SmsHSP24.1 Overexpression Stimulates Early Seedling Vigor and Stress Tolerance by Multi-Pathway Transcriptome-Reprogramming

Among the diverse array of heat shock proteins across the three domains of life, mitochondria-targeted small heat shock proteins (sHSPs) are evolved in the plant lineage. However, they remained mysterious and understudied. In this study, we reported a systematic study of a novel mitochondria-targeted nuclear sHSP from eggplant (Solanum melongena L.; SmsHSP24.1). Differential expression of SmsHSP24.1 indicated its positive role exerted during stress conditions. Escherichia coli-BL21 cell line overexpressing the SmsHSP24.1 showed excellent thermo-tolerance ability, tolerating up to 52°C. Spectrometry and electron microscopy revealed a multimeric structure of the protein which acted as a molecular chaperone at high temperatures. Overexpression of SmsHSP24.1 significantly enhanced resistance against heat, drought, and salt stresses and showed rapid germination in constitutively overexpressed eggplant lines. RNA-seq analysis reveals an apparent upregulation of a set of reactive oxygen species (ROS) scavenging enzymes of the glutathione (GHS) pathway and mitochondrial electron transport chain (ETC). Significant upregulation was also observed in auxin biosynthesis and cell-wall remodeling transcripts in overexpressed lines. qPCR, biochemical and physiological analysis further aligned with the finding of transcriptome analysis and suggested an essential role of SmsHSP24.1 under various stress responses and positive physiological influence on the growth of eggplants. Therefore, this gene has immense potential in engineering stress-resilient crop plants.

FTSH4 and OMA1 mitochondrial proteases reduce moderate heat stress-induced protein aggregation

The threat of global warming makes uncovering mechanisms of plant tolerance to long-term moderate heat stress particularly important. We previously reported that Arabidopsis (Arabidopsis thaliana) plants lacking mitochondrial proteases FTSH4 or OMA1 suffer phenotypic changes under long-term stress of 30°C, while their growth at 22°C is not affected. Here we found that these morphological and developmental changes are associated with increased accumulation of insoluble mitochondrial protein aggregates that consist mainly of small heat-shock proteins (sHSPs). Greater accumulation of sHSPs in ftsh4 than oma1 corresponds with more severe phenotypic abnormalities. We showed that the proteolytic activity of FTSH4, and to a lesser extent of OMA1, as well as the chaperone function of FTSH4, is crucial for protecting mitochondrial proteins against aggregation. We demonstrated that HSP23.6 and NADH dehydrogenase subunit 9 present in aggregates are proteolytic substrates of FTSH4, and this form of HSP23.6 is also a substrate of OMA1 protease. In addition, we found that the activity of FTSH4 plays an important role during recovery from elevated to optimal temperatures. Isobaric tags for relative and absolute quantification (iTRAQ)-based proteomic analyses, along with identification of aggregation-prone proteins, implicated mitochondrial pathways affected by protein aggregation (e.g. assembly of complex I) and revealed that the mitochondrial proteomes of ftsh4 and oma1 plants are similarly adapted to long-term moderate heat stress. Overall, our data indicate that both FTSH4 and OMA1 increase the tolerance of plants to long-term moderate heat stress by reducing detergent-tolerant mitochondrial protein aggregation.

Responses of leaf respiration to heatwaves

Mitochondrial respiration (R) is central to plant physiology and responds dynamically to daily short-term temperature changes. In the longer-term, changes in energy demand and membrane fluidity can decrease leaf R at a common temperature and increase the temperature at which leaf R peaks (T_max ). However, leaf R functionality is more susceptible to short-term heatwaves. Catalysis increases with rising leaf temperature, driving faster metabolism and leaf R demand, despite declines in photosynthesis restricting assimilate supply and growth. Proteins denature as temperatures increase further, adding to maintenance costs. Excessive heat also inactivates respiratory enzymes, with a concomitant limitation on the capacity of the R system. These competing push-and-pull factors are responsible for the diminishing acceleration in leaf R rate as temperature rises. Under extreme heat, membranes become overly fluid, and enzymes such as the cytochrome c oxidase are impaired. Such changes can lead to over-reduction of the energy system culminating in reactive oxygen species production. This ultimately leads to the total breakdown of leaf R, setting the limit of leaf survival. Understanding the heat stress responses of leaf R is imperative, given the continued rise in frequency and intensity of heatwaves and the importance of R for plant fitness and survival.

Roles of Brassinosteroids in Mitigating Heat Stress Damage in Cereal Crops

Heat stress causes huge losses in the yield of cereal crops. Temperature influences the rate of plant metabolic and developmental processes that ultimately determine the production of grains, with high temperatures causing a reduction in grain yield and quality. To ensure continued food security, the tolerance of high temperature is rapidly becoming necessary. Brassinosteroids (BR) are a class of plant hormones that impact tolerance to various biotic and abiotic stresses and regulate cereal growth and fertility. Fine-tuning the action of BR has the potential to increase cereals' tolerance and acclimation to heat stress and maintain yields. Mechanistically, exogenous applications of BR protect yields through amplifying responses to heat stress and rescuing the expression of growth promoters. Varied BR compounds and differential signaling mechanisms across cereals point to a diversity of mechanisms that can be leveraged to mitigate heat stress. Further, hormone transport and BR interaction with other molecules in plants may be critical to utilizing BR as protective agrochemicals against heat stress. Understanding the interplay between heat stress responses, growth processes and hormone signaling may lead us to a comprehensive dogma of how to tune BR application for optimizing cereal growth under challenging environments in the field.

Impacts of Heat Stress-Induced Oxidative Stress on the Milk Protein Biosynthesis of Dairy Cows

Heat stress (HS) is one of the most important factors posing harm to the economic wellbeing of dairy industries, as it reduces milk yield as well as milk protein content. Recent studies suggest that HS participates in the induction of tissue oxidative stress (OS), as elevated levels of reactive oxygen species (ROS) and mitochondrial dysfunction were observed in dairy cows exposed to hot conditions. The OS induced by HS likely contributes to the reduction in milk protein content, since insulin resistance and apoptosis are promoted by OS and are negatively associated with the synthesis of milk proteins. The apoptosis in the mammary gland directly decreases the amount of mammary epithelial cells, while the insulin resistance affects the regulation of insulin on mTOR pathways. To alleviate OS damages, strategies including antioxidants supplementation have been adopted, but caution needs to be applied as an inappropriate supplement with antioxidants can be harmful. Furthermore, the complete mechanisms by which HS induces OS and OS influences milk protein synthesis are still unclear and further investigation is needed.

Mitochondrial Kinases and the Role of Mitochondrial Protein Phosphorylation in Health and Disease

The major role of mitochondria is to provide cells with energy, but no less important are their roles in responding to various stress factors and the metabolic changes and pathological processes that might occur inside and outside the cells. The post-translational modification of proteins is a fast and efficient way for cells to adapt to ever changing conditions. Phosphorylation is a post-translational modification that signals these changes and propagates these signals throughout the whole cell, but it also changes the structure, function and interaction of individual proteins. In this review, we summarize the influence of kinases, the proteins responsible for phosphorylation, on mitochondrial biogenesis under various cellular conditions. We focus on their role in keeping mitochondria fully functional in healthy cells and also on the changes in mitochondrial structure and function that occur in pathological processes arising from the phosphorylation of mitochondrial proteins.

Mitochondrial Respiratory Chain and Its Regulatory Elements SIRT1 and SIRT3 Play Important Role in the Initial Process of Energy Conversion after Moxibustion at Local Skin

Objectives

To study how thermal energy is converted after moxibustion at local skin from the view of mitochondrial respiratory chain and its key regulatory elements of sirtuins 1 (SIRT1) and sirtuins 3 (SIRT3).

Methods

Two moxibustion temperatures usually used in clinical practice (38°C and 46°C) were applied to Zusanli (ST36) acupoint for 30 minutes in C57BL/6J mice. Local skin samples were harvested at 30 min and 72 h after moxibustion intervention, respectively. The activity of mitochondrial respiratory chain complexes I–V was detected by spectrophotometry. The expression of SIRT1 and SIRT3 protein was detected by immunofluorescence staining or western blot.

Results

Moxibustion at 38°C triggered more significant increase of mitochondrial respiratory chain complexes I–V expression. However, the protein expression of SIRT1 and SIRT3 at 46°C showed more obvious enhancement. In addition, the effect of mitochondrial respiratory chain complexes I–V activity on local skin of ST36 acupoint was more obvious at 30 min after moxibustion, while the expression of SIRT1 and SIRT3 protein was more significant at 72 h after moxibustion.

Conclusion

Mitochondrial respiratory chain and its key regulatory element proteins SIRT1 and SIRT3 play important role in the initial process of thermal energy conversion stimulated by different moxibustion temperatures in local skin.

Heat-response patterns of the heat shock transcription factor family in advanced development stages of wheat (Triticum aestivum L.) and thermotolerance-regulation by TaHsfA2-10

BACKGROUND

Heat shock transcription factors (Hsfs) are present in majority of plants and play central roles in thermotolerance, transgenerational thermomemory, and many other stress responses. Our previous paper identified at least 82 Hsf members in a genome-wide study on wheat (Triticum aestivum L.). In this study, we analyzed the Hsf expression profiles in the advanced development stages of wheat, isolated the markedly heat-responsive gene TaHsfA2-10 (GenBank accession number MK922287), and characterized this gene and its role in thermotolerance regulation in seedlings of Arabidopsis thaliana (L. Heynh.).

RESULTS

In the advanced development stages, wheat Hsf family transcription profiles exhibit different expression patterns and varying heat-responses in leaves and roots, and Hsfs are constitutively expressed to different degrees under the normal growth conditions. Overall, the majority of group A and B Hsfs are expressed in leaves while group C Hsfs are expressed at higher levels in roots. The expression of a few Hsf genes could not be detected. Heat shock (HS) caused upregulation about a quarter of genes in leaves and roots, while a number of genes were downregulated in response to HS. The highly heat-responsive gene TaHsfA2-10 was isolated through homeologous cloning. qRT-PCR revealed that TaHsfA2-10 is expressed in a wide range of tissues and organs of different development stages of wheat under the normal growth conditions. Compared to non-stress treatment, TaHsfA2-10 was highly upregulated in response to HS, H₂O_2, and salicylic acid (SA), and was downregulated by abscisic acid (ABA) treatment in two-leaf-old seedlings. Transient transfection of tobacco epidermal cells revealed subcellular localization of TaHsfA2-10 in the nucleus under the normal growth conditions. Phenotypic observation indicated that TaHsfA2-10 could improve both basal thermotolerance and acquired thermotolerance of transgenic Arabidopsis thaliana seedlings and rescue the thermotolerance defect of the T-DNA insertion mutant athsfa2 during HS. Compared to wild type (WT) seedlings, the TaHsfA2-10-overexpressing lines displayed both higher chlorophyll contents and higher survival rates. Yeast one-hybrid assay results revealed that TaHsfA2-10 had transactivation activity. The expression levels of thermotolerance-related AtHsps in the TaHsfA2-10 transgeinc Arabidopsis thaliana were higher than those in WT after HS.

CONCLUSIONS

Wheat Hsf family members exhibit diversification and specificity of transcription expression patterns in advanced development stages under the normal conditions and after HS. As a markedly responsive transcriptional factor to HS, SA and H₂O₂, TaHsfA2-10 involves in thermotolerance regulation of plants through binding to the HS responsive element in promoter domain of relative Hsps and upregulating the expression of Hsp genes.

Over-Expression of the Heat-Responsive Wheat Gene TaHSP23.9 in Transgenic Arabidopsis Conferred Tolerance to Heat and Salt Stress

The small heat shock proteins (sHSP) are stress-induced proteins with molecular weights ranging from 12 to 42 kDa that act as molecular chaperones to prevent the irreversible aggregation of denaturing proteins. In this study, we cloned the heat responsive gene TaHSP23.9 from wheat (Triticum aestivum) based on TMT-labeled quantitative proteomic analysis in our previous work and examined its function in the response of transgenic Arabidopsis to heat and salt stress. Amino acid alignment and phylogenetic tree analysis showed that TaHSP23.9 contained a typically conserved structure of the alpha-crystallin domain and is closely related to OsHSP23.2 in rice. Transient expression assays demonstrated that TaHSP23.9 is located on the endoplasmic reticulum. Quantitative real-time PCR demonstrated that TaHSP23.9 was expressed much more in filling grains under normal conditions and was significantly upregulated by heat and salt stress. Transgenic Arabidopsis plants that constitutively over-expressed TaHSP23.9 had no visible differences or adverse phenotypes compared with the wild type under normal conditions but exhibited enhanced tolerance to heat and salt stress under stress conditions. In addition, we found that the expression level of TaHSP23.9 was significantly higher in the heat-tolerant wheat varieties than in the heat-sensitive varieties. Our results suggest that TaHSP23.9 may function as a protein chaperone to positively regulate plant responses to heat and salt stress and could be developed as a molecular marker for screening heat-tolerant wheat varieties.

Amyloid-β Causes Mitochondrial Dysfunction via a Ca2+-Driven Upregulation of Oxidative Phosphorylation and Superoxide Production in Cerebrovascular Endothelial Cells

Cerebrovascular pathology is pervasive in Alzheimer's disease (AD), yet it is unknown whether cerebrovascular dysfunction contributes to the progression or etiology of AD. In human subjects and in animal models of AD, cerebral hypoperfusion and hypometabolism are reported to manifest during the early stages of the disease and persist for its duration. Amyloid-β is known to cause cellular injury in both neurons and endothelial cells by inducing the production of reactive oxygen species and disrupting intracellular Ca2+ homeostasis. We present a mechanism for mitochondrial degeneration caused by the production of mitochondrial superoxide, which is driven by increased mitochondrial Ca2+ uptake. We found that persistent superoxide production injures mitochondria and disrupts electron transport in cerebrovascular endothelial cells. These observations provide a mechanism for the mitochondrial deficits that contribute to cerebrovascular dysfunction in patients with AD.

The Mitochondrial Small Heat Shock Protein HSP22 from Pea is a Thermosoluble Chaperone Prone to Co-Precipitate with Unfolding Client Proteins

The small heat shock proteins (sHSPs) are molecular chaperones that share an alpha-crystallin domain but display a high diversity of sequence, expression, and localization. They are especially prominent in plants, populating most cellular compartments. In pea, mitochondrial HSP22 is induced by heat or oxidative stress in leaves but also strongly accumulates during seed development. The molecular function of HSP22 was addressed by studying the effect of temperature on its structural properties and chaperone effects using a recombinant or native protein. Overexpression of HSP22 significantly increased bacterial thermotolerance. The secondary structure of the recombinant protein was not affected by temperature in contrast with its quaternary structure. The purified protein formed large polydisperse oligomers that dissociated upon heating (42 °C) into smaller species (mainly monomers). The recombinant protein appeared thermosoluble but precipitated with thermosensitive proteins upon heat stress in assays either with single protein clients or within complex extracts. As shown by in vitro protection assays, HSP22 at high molar ratio could partly prevent the heat aggregation of rhodanese but not of malate dehydrogenase. HSP22 appears as a holdase that could possibly prevent the aggregation of some proteins while co-precipitating with others to facilitate their subsequent refolding by disaggregases or clearance by proteases.

SWATH-MS-facilitated proteomic profiling of fruit skin between Fuji apple and a red skin bud sport mutant

BACKGROUND

Apple is one of the most popular fruit crops world-wide and its skin color is an important quality consideration essential for commercial value. However, the strategy on genetic breeding for red skin apple and the genetic basis of skin color differentiation is very limited and still largely unknown.

RESULTS

Here, we reported a bud sport mutant of Fuji apple with red skin color and enhanced anthocyanins accumulation. Quantitative SWATH-MS (sequential window acquisition of all theoretical spectra-mass spectrometry) proteomics investigations revealed proteome changes in the apple red skin bud mutation and a total of 451 differentially expressed proteins were identified in apple skin. The mutant showed significantly increased expression levels of photosynthesis-related proteins, stress-related proteins as well as anthocyanins biosynthesis pathway. On the other hand, substantial downregulation of mitogen-activated protein kinase 4 (MAPK4) and mevalonate kinase (MVK) were detected, indicating a promising role for the red skin color development in the mutant. Furthermore, we also hypothesize that a post-transcriptional regulation of the skin color formation occurs in the mutant through the advanced SWATH-MS analysis.

CONCLUSION

Our work provides important information on the application of proteomic methods for analysing proteomes changes in Fuji apple and highlights a clade of regulatory proteins potentially contributing for the molecular breeding of fruit skin color.

The effect of a physiological increase in temperature on mitochondrial fatty acid oxidation in rat myofibers

We investigated the effect of temperature increase on mitochondrial fatty acid (FA) and carbohydrate oxidation in the slow-oxidative skeletal muscles (soleus) of rats. We measured mitochondrial respiration at 35°C and 40°C with the physiological substrates pyruvate + 4 mM malate (Pyr) and palmitoyl-CoA (PCoA) + 0.5 mM malate + 2 mM carnitine in permeabilized myofibers under nonphosphorylating (V˙0) or phosphorylating (V˙max) conditions. Mitochondrial efficiency was calculated by the respiratory control ratio (RCR = V˙max/V˙0). We used guanosine triphosphate (GTP), an inhibitor of uncoupling protein (UCP), to study the mechanisms responsible for alterations of mitochondrial efficiency. We measured hydrogen peroxide (H₂O₂) production under nonphosphorylating and phosphorylating conditions at both temperatures and substrates. We studied citrate synthase (CS) and 3-hydroxyl acyl coenzyme A dehydrogenase (3-HAD) activities at both temperatures. Elevating the temperature from 35°C to 40°C increased PCoA-V˙0 and decreased PCoA-RCR, corresponding to the uncoupling of oxidative phosphorylation (OXPHOS). GTP blocked the heat-induced increase of PCoA-V˙0. Rising temperature moved toward a Pyr-V˙0 increase, without significance. Heat did not alter H₂O₂ production, resulting from either PCoA or Pyr oxidation. Heat induced an increase in 3-HAD but not in CS activities. In conclusion, heat induced OXPHOS uncoupling for PCoA oxidation, which was at least partially mediated by UCP and independent of oxidative stress. The classically described heat-induced glucose shift may actually be mostly due to a less efficient FA oxidation. These findings raise questions concerning the consequences of heat-induced alterations in mitochondrial efficiency of FA metabolism on thermoregulation.NEW & NOTEWORTHY Ex vivo exposure of skeletal myofibers to heat uncouples substrate oxidation from ADP phosphorylation, decreasing the efficiency of mitochondria to produce ATP. This heat effect alters fatty acids (FAs) more than carbohydrate oxidation. Alteration of FA oxidation involves uncoupling proteins without inducing oxidative stress. This alteration in lipid metabolism may underlie the preferential use of carbohydrates in the heat and could decrease aerobic endurance.

Living in Cold Blood: Arcobacter, Campylobacter, and Helicobacter in Reptiles

Species of the Epsilonproteobacteria genera Arcobacter, Campylobacter, and Helicobacter are commonly associated with vertebrate hosts and some are considered significant pathogens. Vertebrate-associated Epsilonproteobacteria are often considered to be largely confined to endothermic mammals and birds. Recent studies have shown that ectothermic reptiles display a distinct and largely unique Epsilonproteobacteria community, including taxa which can cause disease in humans. Several Arcobacter taxa are widespread amongst reptiles and often show a broad host range. Reptiles carry a large diversity of unique and novel Helicobacter taxa, which apparently evolved in an ectothermic host. Some species, such as Campylobacter fetus, display a distinct intraspecies host dichotomy, with genetically divergent lineages occurring either in mammals or reptiles. These taxa can provide valuable insights in host adaptation and co-evolution between symbiont and host. Here, we present an overview of the biodiversity, ecology, epidemiology, and evolution of reptile-associated Epsilonproteobacteria from a broader vertebrate host perspective.

Transcriptomic and Metabolomic Analysis of the Heat-Stress Response of Populus tomentosa Carr

Plants have evolved mechanisms of stress tolerance responses to heat stress. However, little is known about metabolic responses to heat stress in trees. In this study, we exposed Populus tomentosa Carr. to control (25 °C) and heat stress (45 °C) treatments and analyzed the metabolic and transcriptomic effects. Heat stress increased the cellular concentration of H2O2 and the activities of antioxidant enzymes. The levels of proline, raffinose, and melibiose were increased by heat stress, whereas those of pyruvate, fumarate, and myo-inositol were decreased. The expression levels of most genes (PSB27, PSB28, LHCA5, PETB, and PETC) related to the light-harvesting complexes and photosynthetic electron transport system were downregulated by heat stress. Association analysis between key genes and altered metabolites indicated that glycolysis was enhanced, whereas the tricarboxylic acid (TCA) cycle was suppressed. The inositol phosphate; galactose; valine, leucine, and isoleucine; and arginine and proline metabolic pathways were significantly affected by heat stress. In addition, several transcription factors, including HSFA2, HSFA3, HSFA9, HSF4, MYB27, MYB4R1, and bZIP60 were upregulated, whereas WRKY13 and WRKY50 were downregulated by heat stress. Interestingly, under heat stress, the expression of DREB1, DREB2, DREB2E, and DREB5 was dramatically upregulated at 12 h. Our results suggest that proline, raffinose, melibiose, and several genes (e.g., PSB27, LHCA5, and PETB) and transcription factors (e.g., HSFAs and DREBs) are involved in the response to heat stress in P. tomentosa.

Regulation through MicroRNAs in Response to Low-Energy N+ Ion Irradiation in Oryza sativa

MicroRNAs (miRNAs) are a non-coding regulatory RNAs that play significant roles in plant growth and development, especially in the stress response. Low-energy ion radiation, a type of environmental stress, can cause multiple biological effects. To understand the roles of miRNAs in response to low-energy N⁺ ion radiation in Oryza sativa, high-throughput sequencing of small RNAs was carried out to detect the expression of miRNAs in the shoots of the rice after 2 × 10¹⁷ N+/cm² irradiation. The differentially expressed 28 known miRNAs were identified, 17 of these identified miRNAs were validated by real-time quantitative fluorescent PCR (q-PCR), including 9 up-regulated miRNAs (miR1320-3p, miR1320-5p, miR156b-3p, miR156c-5p, miR156c-3p/g-3p, miR1561-5p, miR398b and miR6250) and 8 down-regulated miRNAs (miR156a/e/i, miR156k, miR160f-5p, miR166j-5p, miR1846e and miR399d). In addition, 45 novel radiationresponsive miRNAs were predicted, and 8 of them were verified by q-PCR. The target genes of radiation-responsive miRNAs were predicted and gene function enrichment analysis was performed with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). The expression of 9 targets of 4 known miRNA families (miR156, miR399, miR1320 and miR398) and 2 targets of 2 novel miRNAs were quantified by q-PCR, and a strong negative regulation relation between miRNAs and their targets were observed. Those targets including SQUAMOSA promoterbinding-like protein (SPL) genes, copper/zinc superoxide dismutase (Cu/Zn-SOD), copper chaperone for SOD (CCS1) and electron transporter/ heat-shock protein binding protein (HSP), which are involved in growth and defense against various stresses, especially associated with reactive oxygen species (ROS) scavenging. This work provides important information for understanding the ROS generation and elimination mechanisms closely related to miRNAs in rice seedlings after low-energy N⁺ radiation exposure.

Heat shock factor C2a serves as a proactive mechanism for heat protection in developing grains in wheat via an ABA-mediated regulatory pathway

High temperature at grain filling can severely reduce wheat yield. Heat shock factors (Hsfs) are central regulators in heat acclimation. This study investigated the role of TaHsfC2a, a member of the monocot-specific HsfC2 subclass, in the regulation of heat protection genes in Triticum aestivum. Three TaHsfC2a homoeologous genes were highly expressed in wheat grains during grain filling and showed only transient up-regulation in the leaves by heat stress but were markedly up-regulated by drought and abscisic acid (ABA) treatment. Overexpression of TaHsfC2a-B in transgenic wheat resulted in up-regulation of a suite of heat protection genes (e.g. TaHSP70d and TaGalSyn). Most TaHsfC2a-B target genes were heat, drought and ABA inducible. Transactivation analysis of two representative targets (TaHSP70d and TaGalSyn) showed that TaHsfC2a-B activated expression of reporters driven by these target promoters. Promoter mutagenesis analyses revealed that heat shock element is responsible for transactivation by TaHsfC2a-B and heat/drought induction. TaHsfC2a-B-overexpressing wheat showed improved thermotolerance but not dehydration tolerance. Most TaHsfC2a-B target genes were co-up-regulated in developing grains with TaHsfC2a genes. These data suggest that TaHsfC2a-B is a transcriptional activator of heat protection genes and serves as a proactive mechanism for heat protection in developing wheat grains via the ABA-mediated regulatory pathway.

Heat Stress Reduces Sperm Motility via Activation of Glycogen Synthase Kinase-3α and Inhibition of Mitochondrial Protein Import

The adverse effects of high environmental temperature exposure on animal reproductive functions have been concerned for many decades. However, the molecular basis of heat stress (HS)-induced decrease of sperm motility has not been entirely elucidated. We hypothesized that the deteriorate effects of HS may be mediated by damage of mitochondrial function and ATP synthesis. To test this hypothesis, we use mature boar sperm as model to explore the impacts of HS on mitochondrial function and sperm motility. A 6 h exposure to 42°C (HS) induced significant decrease in sperm progressive motility. Concurrently, HS induced mitochondrial dysfunction that is indicated by decreased of membrane potential, respiratory chain complex I and IV activities and adenosine triphosphate (ATP) contents. Exogenous ATP abolished this effect suggesting that reduced of ATP synthesis is the committed step in HS-induced reduction of sperm motility. At the molecular level, the mitochondrial protein contents were significantly decreased in HS sperm. Notably, the cytochrome c oxidase subunit 4, which was synthesized in cytoplasm and translocated into mitochondria, was significantly lower in mitochondria of HS sperm. Glycogen synthase kinase-3α (GSK3α), a negative regulator of sperm motility that is inactivated by Ser21 phosphorylation, was dephosphorylated after HS. The GSK3α inhibitor CHIR99021 was able to abolish the effects of HS on sperm and their mitochondria. Taken together, our results demonstrate that HS affects sperm motility through downregulation of mitochondrial activity and ATP synthesis yield, which involves dephosphorylation of GSK3α and interference of mitochondrial remodeling.

iTRAQ-Based Quantitative Proteomics Analysis on Rice Anther Responding to High Temperature

As one of the most important crops, rice provides the major food for more than half of the world population. However, its production is limited by many environmental factors, among which high temperature stress (HS) frequently occurs during anthesis and reduces its spikelet fertility. To explore the mechanism of HS tolerance in rice, we conducted a comparative proteomics analysis on the anthers between HS resistant and sensitive cultivars under different levels of high temperature. Under the same HS treatment, the resistant cultivar showed much higher spikelet fertility than the sensitive cultivar. Proteomic data showed that HS lead to the degradation of ribosomal proteins in the sensitive cultivar but not in the resistant one, which might result in the injury of protein biosynthetic machinery. In contrast, HS induced the increase of sHSP, β-expansins and lipid transfer proteins in the resistant cultivar, which might contribute to its ability to tolerate HS. The results provide some new insights into the mechanism of rice HS response.

Thermal limits of leaf metabolism across biomes

High-temperature tolerance in plants is important in a warming world, with extreme heat waves predicted to increase in frequency and duration, potentially leading to lethal heating of leaves. Global patterns of high-temperature tolerance are documented in animals, but generally not in plants, limiting our ability to assess risks associated with climate warming. To assess whether there are global patterns in high-temperature tolerance of leaf metabolism, we quantified T_crit (high temperature where minimal chlorophyll a fluorescence rises rapidly and thus photosystem II is disrupted) and T_max (temperature where leaf respiration in darkness is maximal, beyond which respiratory function rapidly declines) in upper canopy leaves of 218 plant species spanning seven biomes. Mean site-based T_crit values ranged from 41.5 °C in the Alaskan arctic to 50.8 °C in lowland tropical rainforests of Peruvian Amazon. For T_max , the equivalent values were 51.0 and 60.6 °C in the Arctic and Amazon, respectively. T_crit and T_max followed similar biogeographic patterns, increasing linearly (˜8 °C) from polar to equatorial regions. Such increases in high-temperature tolerance are much less than expected based on the 20 °C span in high-temperature extremes across the globe. Moreover, with only modest high-temperature tolerance despite high summer temperature extremes, species in mid-latitude (~20-50°) regions have the narrowest thermal safety margins in upper canopy leaves; these regions are at the greatest risk of damage due to extreme heat-wave events, especially under conditions when leaf temperatures are further elevated by a lack of transpirational cooling. Using predicted heat-wave events for 2050 and accounting for possible thermal acclimation of T_crit and T_max , we also found that these safety margins could shrink in a warmer world, as rising temperatures are likely to exceed thermal tolerance limits. Thus, increasing numbers of species in many biomes may be at risk as heat-wave events become more severe with climate change.

Comparative Genomics of Campylobacter iguaniorum to Unravel Genetic Regions Associated with Reptilian Hosts

Campylobacter iguaniorum is most closely related to the species C. fetus, C. hyointestinalis, and C. lanienae. Reptiles, chelonians and lizards in particular, appear to be a primary reservoir of this Campylobacter species. Here we report the genome comparison of C. iguaniorum strain 1485E, isolated from a bearded dragon (Pogona vitticeps), and strain 2463D, isolated from a green iguana (Iguana iguana), with the genomes of closely related taxa, in particular with reptile-associated C. fetus subsp. testudinum. In contrast to C. fetus, C. iguaniorum is lacking an S-layer encoding region. Furthermore, a defined lipooligosaccharide biosynthesis locus, encoding multiple glycosyltransferases and bounded by waa genes, is absent from C. iguaniorum. Instead, multiple predicted glycosylation regions were identified in C. iguaniorum. One of these regions is > 50 kb with deviant G + C content, suggesting acquisition via lateral transfer. These similar, but non-homologous glycosylation regions were located at the same position on the genome in both strains. Multiple genes encoding respiratory enzymes not identified to date within the C. fetus clade were present. C. iguaniorum shared highest homology with C. hyointestinalis and C. fetus. As in reptile-associated C. fetus subsp. testudinum, a putative tricarballylate catabolism locus was identified. However, despite colonizing a shared host, no recent recombination between both taxa was detected. This genomic study provides a better understanding of host adaptation, virulence, phylogeny, and evolution of C. iguaniorum and related Campylobacter taxa.

A Quantitative Genomic Approach for Analysis of Fitness and Stress Related Traits in a Drosophila melanogaster Model Population

The ability of natural populations to withstand environmental stresses relies partly on their adaptive ability. In this study, we used a subset of the Drosophila Genetic Reference Panel, a population of inbred, genome-sequenced lines derived from a natural population of Drosophila melanogaster, to investigate whether this population harbors genetic variation for a set of stress resistance and life history traits. Using a genomic approach, we found substantial genetic variation for metabolic rate, heat stress resistance, expression of a major heat shock protein, and egg-to-adult viability investigated at a benign and a higher stressful temperature. This suggests that these traits will be able to evolve. In addition, we outline an approach to conduct pathway associations based on genomic linear models, which has potential to identify adaptive genes and pathways, and therefore can be a valuable tool in conservation genomics.

Changes in Drosophila mitochondrial proteins following chaperone-mediated lifespan extension confirm a role of Hsp22 in mitochondrial UPR and reveal a mitochondrial localization for cathepsin D

Hsp22 is a small mitochondrial heat shock protein (sHSP) preferentially up-regulated during aging in Drosophila melanogaster. Its developmental expression is strictly regulated and it is rapidly induced in conditions of stress. Hsp22 is one of the few sHSP to be localized inside mitochondria, and is the first sHSP to be involved in the mitochondrial unfolding protein response (UPR(MT)) together with Hsp60, mitochondrial Hsp70 and TRAP1. The UPR(MT) is a pro-longevity mechanism, and interestingly Hsp22 over-expression by-itself increases lifespan and resistance to stress. To unveil the effect of Hsp22 on the mitochondrial proteome, comparative IEF/SDS polyacrylamide 2D gels were done on mitochondria from Hsp22+ flies and controls. Among the proteins influenced by Hsp22 expression were proteins from the electron transport chain (ETC), the TCA cycle and mitochondrial Hsp70. Hsp22 co-migrates with ETC components and its over-expression is associated with an increase in mitochondrial protease activity. Interestingly, the only protease that showed significant changes upon Hsp22 over-expression in the comparative IEF/SDS-PAGE analysis was cathepsin D, which is localized in mitochondria in addition to lysosome in D. melanogaster as evidenced by cellular fractionation. Together the results are consistent with a role of Hsp22 in the UPR(MT) and in mitochondrial proteostasis.

Conformational perturbation, hydrophobic interactions and oligomeric association are responsible for the enhanced chaperone function of Mycobacterium leprae HSP18 under pre-thermal condition

Chaperone function of HSP18 is enhanced upon pre-heating at 60 °C and above which may be due to structural alterations.

Heat stress effects on livestock: molecular, cellular and metabolic aspects, a review

Elevated ambient temperatures affect animal production and welfare. Animal's reduced production performances during heat stress were traditionally thought to result from the decreased feed intake. However, it has recently been shown that heat stress disturbs the steady state concentrations of free radicals, resulting in both cellular and mitochondrial oxidative damage. Indeed, heat stress reorganizes the use of the body resources including fat, protein and energy. Heat stress reduces the metabolic rates and alters post-absorptive metabolism, regardless of the decreased feed intake. Consequently, growth, production, reproduction and health are not priorities any more in the metabolism of heat-stressed animals. The drastic effects of heat stress depend on its duration and severity. This review clearly describes about biochemical, cellular and metabolic changes that occur during thermal stress in farm animals.

Reactive oxygen species, heat stress and oxidative-induced mitochondrial damage. A review

In recent years there has been enormous interest in researching oxidative stress. Reactive oxygen species (ROS) are derived from the metabolism of oxygen as by-products of cell respiration, and are continuously produced in all aerobic organisms. Oxidative stress occurs as a consequence of an imbalance between ROS production and the available antioxidant defence against them. Nowadays, a variety of diseases and degenerative processes such as cancer, Alzheimer's and autoimmune diseases are mediated by oxidative stress. Heat stress was suggested to be an environmental factor responsible for stimulating ROS production because of similarities in responses observed following heat stress compared with that occurring following exposure to oxidative stress. This manuscript describes the main mitochondrial sources of ROS and the antioxidant defences involved to prevent oxidative damage in all the mitochondrial compartments. It also deals with discussions concerning the cytotoxic effect of heat stress, mitochondrial heat-induced alterations, as well as heat shock protein (HSP) expression as a defence mechanism.

Biogenesis of mitochondria in cauliflower (Brassica oleracea var. botrytis) curds subjected to temperature stress and recovery involves regulation of the complexome, respiratory chain activity, organellar translation and ultrastructure

The biogenesis of the cauliflower curd mitochondrial proteome was investigated under cold, heat and the recovery. For the first time, two dimensional fluorescence difference gel electrophoresis was used to study the plant mitochondrial complexome in heat and heat recovery. Particularly, changes in the complex I and complex III subunits and import proteins, and the partial disintegration of matrix complexes were observed. The presence of unassembled subunits of ATP synthase was accompanied by impairment in mitochondrial translation of its subunit. In cold and heat, the transcription profiles of mitochondrial genes were uncorrelated. The in-gel activities of respiratory complexes were particularly affected after stress recovery. Despite a general stability of respiratory chain complexes in heat, functional studies showed that their activity and the ATP synthesis yield were affected. Contrary to cold stress, heat stress resulted in a reduced efficiency of oxidative phosphorylation likely due to changes in alternative oxidase (AOX) activity. Stress and stress recovery differently modulated the protein level and activity of AOX. Heat stress induced an increase in AOX activity and protein level, and AOX1a and AOX1d transcript level, while heat recovery reversed the AOX protein and activity changes. Conversely, cold stress led to a decrease in AOX activity (and protein level), which was reversed after cold recovery. Thus, cauliflower AOX is only induced by heat stress. In heat, contrary to the AOX activity, the activity of rotenone-insensitive internal NADH dehydrogenase was diminished. The relevance of various steps of plant mitochondrial biogenesis to temperature stress response and recovery is discussed.

Algae sense exact temperatures: small heat shock proteins are expressed at the survival threshold temperature in Cyanidioschyzon merolae and Chlamydomonas reinhardtii

The primitive red alga Cyanidioschyzon merolae inhabits acidic hot springs and shows robust resistance to heat shock treatments up to 63 °C. Microarray analysis was performed to identify the key genes underlying the high temperature tolerance of this organism. Among the upregulated genes that were identified, we focused on two small heat shock proteins (sHSPs) that belong to a unique class of HSP families. These two genes are located side by side in an inverted repeat orientation on the same chromosome and share a promoter. These two genes were simultaneously and rapidly upregulated in response to heat shock treatment (>1,000-fold more than the control). Interestingly, upregulation appeared to be triggered not by a difference in temperatures, but rather by the absolute temperature. Similar sHSP structural genes have been reported in the green alga Chlamydomonas reinhardtii, but the threshold temperature for the expression of these sHSP-encoding genes in Ch. reinhardtii was different from the threshold temperature for the expression of the sHSP genes from Cy. merolae. These results indicate the possible importance of an absolute temperature sensing system in the evolution and tolerance of high-temperature conditions among unicellular microalgae.

Physiological aspects of fruit ripening: the mitochondrial connection

Fruit ripening is a genetically programmed process which leads to an assortment of physiological and metabolic changes that irreversibly alter its characteristics. Depending on the species, fruit maturation can be either climacteric or non-climacteric. In both cases there is a metabolic shift from normal development conditions toward the fully mature state, but climacteric fruit is characterized by a sharp increase in respiration. In non-climacteric fruit, that generally does not display this feature, respiration changes can be affected by processes related to postharvest storage. This review describes some of the many ways in which mitochondrial metabolism is implicated in this crucial reproductive stage, such as the connection between ethylene production and respiration rate, the involvement of alternative oxidase (AOX) and plant uncoupling mitochondrial protein (PUMP) during the ripening and the common alterations of this organelle in fruits affected by different stress conditions.

The heat shock factor family from Triticum aestivum in response to heat and other major abiotic stresses and their role in regulation of heat shock protein genes

Heat shock factors (Hsfs) play a central regulatory role in acquired thermotolerance. To understand the role of the major molecular players in wheat adaptation to heat stress, the Hsf family was investigated in Triticum aestivum. Bioinformatic and phylogenetic analyses identified 56 TaHsf members, which are classified into A, B, and C classes. Many TaHsfs were constitutively expressed. Subclass A6 members were predominantly expressed in the endosperm under non-stress conditions. Upon heat stress, the transcript levels of A2 and A6 members became the dominant Hsfs, suggesting an important regulatory role during heat stress. Many TaHsfA members as well as B1, C1, and C2 members were also up-regulated during drought and salt stresses. The heat-induced expression profiles of many heat shock protein (Hsp) genes were paralleled by those of A2 and A6 members. Transactivation analysis revealed that in addition to TaHsfA members (A2b and A4e), overexpression of TaHsfC2a activated expression of TaHsp promoter-driven reporter genes under non-stress conditions, while TaHsfB1b and TaHsfC1b did not. Functional heat shock elements (HSEs) interacting with TaHsfA2b were identified in four TaHsp promoters. Promoter mutagenesis analysis demonstrated that an atypical HSE (GAACATTTTGGAA) in the TaHsp17 promoter is functional for heat-inducible expression and transactivation by Hsf proteins. The transactivation of Hsp promoter-driven reporter genes by TaHsfC2a also relied on the presence of HSE. An activation motif in the C-terminal domain of TaHsfC2a was identified by amino residue substitution analysis. These data demonstrate the role of HsfA and HsfC2 in regulation of Hsp genes in wheat.

A comparative proteomic analysis of Pinellia ternata leaves exposed to heat stress

Pinellia ternata is an important traditional Chinese medicinal plant. The growth of P. ternata is sensitive to high temperatures. To gain a better understanding of heat stress responses in P. ternata, we performed a comparative proteomic analysis. P. ternata seedlings were subjected to a temperature of 38 °C and samples were collected 24 h after treatment. Increased relative ion leakage and lipid peroxidation suggested that oxidative stress was frequently generated in rice leaves exposed to high temperature. Two-dimensional electrophoresis (2-DE) was used to analyze heat-responsive proteins. More than 600 protein spots were reproducibly detected on each gel; of these spots, 20 were up-regulated, and 7 were down-regulated. A total of 24 proteins and protein species were successfully identified by MALDI-TOF/TOF MS. These proteins and protein species were found to be primarily small heat shock proteins (58%) as well as proteins involved in RNA processing (17%), photosynthesis (13%), chlorophyll biosynthetic processes (4%), protein degradation (4%) and defense (4%). Using 2-DE Western blot analysis, we confirmed the identities of the cytosolic class II small heat shock protein (sHSPs-CII) identified by MS. The expression levels of four different proteins [cytosolic class I small heat shock protein (sHSPs-CI), sHSPs-CII, mitochondrial small heat shock protein (sHSPs-MIT), glycine-rich RNA-binding protein (GRP)] were analyzed at the transcriptional level by quantitative real-time PCR. The mRNA levels of three sHSPs correlated with the corresponding protein levels. However, GRP was down-regulated at the beginning of heat stress but then increased substantially to reach a peak after 24 h of heat stress. Our study provides valuable new insight into the responses of P. ternata to heat stress.

Analysis of gene sequences indicates that quantity not quality of chloroplast small HSPs improves thermotolerance in C4 and CAM plants

Chloroplast-localized small heat-shock proteins (Cp-sHSP) protect Photosystem II and thylakoid membranes during heat and other stresses, and Cp-sHSP production levels are related to plant thermotolerance. However, to date, a paucity of Cp-sHSP sequences from C4 or CAM species, or from other extremely heat-tolerant species, has precluded an examination to determine if Cp-sHSP genes or proteins might differ among plants with photosynthetic pathways or between heat-sensitive and heat-tolerant species. To investigate this, we isolated and characterized novel Cp-sHSP genes in four plant species: two moderately heat-tolerant C4 species, Spartina alterniflora (monocot) and Amaranthus retroflexus (eudicot), and two very heat-tolerant CAM species, Agave americana (monocot) and Ferocactus wislizenii (eudicot) (respective genes: SasHSP27.12, ArsHSP26.43, AasHSP26.85 and FwsHSP27.52) by PCR-based genome walking and cDNA RACE. Analysis of these Cp-sHSPs has confirmed the presence of conserved domains common to previously examined species. As expected, the transit peptide was found to be the most variable part of these proteins. Promoter analysis of these genes revealed differences in CAM versus C3 and C4 species that were independent of a general difference between monocots and eudicots observed for the entire protein. Heat-induced gene and protein expression indicated that Cp-sHSP protein levels were correlated with thermotolerance of photosynthetic electron transport, and that in most cases protein and transcript levels were correlated. Thus, available evidence indicates little variation in the amino acid sequence of Cp-sHSP mature proteins between heat-sensitive and -tolerant species, but that variation in Cp-sHSP protein production is related to heat tolerance or photosynthetic pathway (CAM vs. C3 and C4) and is driven by promoter differences. Key message We isolated and characterized four novel Cp-sHSP genes with promoters from wild plants, analysis has shown qualitative and quantitative interspecific variations in Cp-sHSPs of C3, C4, and CAM plant thermotolerance.

Proteomic analysis of 'Zaosu' pear (Pyrus bretschneideri Rehd.) and its red skin bud mutation

BACKGROUND

Breeding for strong red skin color is an important objective of the pear breeding program. There are few reports of proteome research in green skin pear and its red skin bud mutation. The manuscript at hand is one of the first studies dealing with 2D-PAGE-based analysis of pear fruits and leaves, establishing a suitable sample preparation and testing different 2D-PAGE protocols. Therefore, it may grant a basis for further studies on the pear proteome being the studies main goal. A proteomic analysis was conducted on leaves and fruits of 'Zaosu' pear (Pyrus bretschneideri Rehd.) and its red skin bud mutation in order to reveal their genetic differences in the protein level.

RESULTS

In the present study, the optimized two-dimensional (2-D) gel electrophoresis system of pear leaf and fruit was set up, and applied to analyze the leaves and fruit protein. The interesting peptide fragments were determined using 4800 Plus MALDI TOF/TOFTM Analyzer mass spectrometer, and the sequence obtained was blasted in NCBInr to identify the differentially-expressed protein. In the 1.5-fold differently-expressed proteins between 'Zaosu' pear and its mutant, 10 out of 35 proteins in fruit and 12 out of 24 ones in leaves were identified successfully. Among the 22 identified proteins, 7 protein spots were related to photosynthesis and energy metabolism; 4 were associated with environmental stress; 4 with disease defense; 2 with amino acid metabolism; 2 with cytoskeleton; 1 with antioxidant function; 1 with calcium metabolism; and 1 with unknown function. Moreover, related physiological index, such as chlorophyll content, Rubisco content and polyphone oxidase activity, were different between 'Zaosu' pear and its mutant.

CONCLUSION

A 2-D gel electrophoresis system of pear leaves and fruits was established, which was suitable for the analysis of proteome comparison. To the best of our knowledge, we have performed the first analysis of the proteomic changes in leaves and fruits of 'Zaosu' pear and its red skin bud mutation. Our study provides important information on the use of proteomic methods for studying protein regulation of 'Zaosu' pear and its red skin bud mutation.