Heat shock,with recovery,promotes protection of Nicotiana tabacum during subsequent exposure to Ralstonia solanacearum

Host–pathogen interactions in plants are complex and potentially influenced by heat shock/stress (HS). Host HS proteins (HSPs) induced prior to bacterial exposure may facilitate the folding of newly synthesized defense proteins and promote incompatible host–pathogen interactions. We hypothesized that a non-lethal HS, with recovery, promotes protection of Nicotiana tabacum during subsequent exposure to avirulent soilborne necrotrophic pathogen Ralstonia solanacearum. The objective of this study included investigating the effects of HS with or without recovery on the outcome of bacterial exposure to a virulent and avirulent biovar of R. solanacearum in N. tabacum cell suspensions. This was assessed by quantifying host Hsp70/Hsc70 levels, mitochondrial electron (e⁻) transport activity as a marker of viability, and phosphatidylserine externalization and DNA fragmentation as markers of apoptosis. Our findings support the hypothesis that HS, with recovery, promotes protection of N. tabacum during subsequent exposure to R. solanacearum, suggesting a role for Hsp70/Hsc70 in the observed protection of e⁻ transport, increased apoptosis, and DNA fragmentation.     

miR-184 Regulates Pancreatic β-Cell Function According to Glucose Metabolism

In response to fasting or hyperglycemia, the pancreatic β-cell alters its output of secreted insulin; however, the pathways governing this adaptive response are not entirely established. Although the precise role of microRNAs (miRNAs) is also unclear, a recurring theme emphasizes their function in cellular stress responses. We recently showed that miR-184, an abundant miRNA in the β-cell, regulates compensatory proliferation and secretion during insulin resistance. Consistent with previous studies showing miR-184 suppresses insulin release, expression of this miRNA was increased in islets after fasting, demonstrating an active role in the β-cell as glucose levels lower and the insulin demand ceases. Additionally, miR-184 was negatively regulated upon the administration of a sucrose-rich diet in Drosophila, demonstrating strong conservation of this pathway through evolution. Furthermore, miR-184 and its target Argonaute2 remained inversely correlated as concentrations of extracellular glucose increased, underlining a functional relationship between this miRNA and its targets. Lastly, restoration of Argonaute2 in the presence of miR-184 rescued suppression of miR-375-targeted genes, suggesting these genes act in a coordinated manner during changes in the metabolic context. Together, these results highlight the adaptive role of miR-184 according to glucose metabolism and suggest the regulatory role of this miRNA in energy homeostasis is highly conserved.     

Food-deprivation induces HSP70 and HSP90 protein expression in larval gilthead sea bream and rainbow trout

Heat shock proteins (HSPs) expression is commonly used as indicators of cellular stress in animals. However, very little is known about either the expression patterns of HSPs or their role in the stress-tolerance phenomenon in early life stages of fish. To this end, we examined the impact of food-deprivation (12 h), reduced oxygen levels (3.5 mg/L for 1 h) and heat shock (HS: + 5 °C for 1 h) on HSP70 and HSP90 protein expression in early life stages of the gilthead sea bream (Sparus aurata), a warm-water aquaculture species. Also, we investigated HSP70 and HSP90 response to food-deprivation (7 days) in early life stages of rainbow trout (Oncorhynchus mykiss), a cool-water aquaculture species, and the tolerance of this larvae to heat shock (either + 5 or + 10 °C for 1 h). Our results clearly demonstrate that food-deprivation enhances HSP70 and HSP90 protein expression in larvae of both species. In gilthead sea bream larvae, the stressors-induced HSP70 and HSP90 (only in the reduced oxygen group) protein expression returned to unstressed levels after 24 h recovery. In fed trout larvae, a + 5 °C heat shock did not elevate HSP70 and HSP90 expression, whereas 100% mortality was evident with a + 10 °C HS. However, food-deprived trout larvae, which had higher HSP70 and HSP90 protein content, survived HS and showed HS-dependent increases in HSP70, but not HSP90 expression. Overall, HSP70 and HSP90 protein expression in early life stages of fish have the potential to be used as markers of nutritional stress, while elevation of the tissue HSPs content may be used as a means to increase stress tolerance during larval rearing.     

Characterization of the heat shock response in cultured sugarcane cells : I. Physiology of the heat shock response and heat shock protein synthesis

Effect of heat shock on the growth of cultured sugarcane cells (Saccharum officinarum L.) was measured. Heat shock (HS) treatment at 36 to 38°C (2 hours) induced the development of maximum thermotolerance to otherwise nonpermissive heat stress at 54°C (7 minutes). Optimum thermotolerance was observed 8 hours after heat shock. Development of thermotolerance was initiated by treatments as short as 30 minutes at 36°C. Temperatures below 36°C or above 40°C failed to induce maximum thermotolerance. In vivo labeling revealed that HS at 32 to 34°C induced several high molecular mass heat shock proteins (HSPs). A complex of 18 kilodalton HSPs required at least 36°C treatment for induction. The majority of the HSPs began to accumulate within 10 minutes, whereas the synthesis of low molecular mass peptides in the 18 kilodalton range became evident 30 minutes after initiation of HS. HS above 38°C resulted in progressively decreased HSP synthesis with inhibition first observed for HSPs larger than 50 kilodaltons. Analysis of two-dimensional gels revealed a complex pattern of label incorporation including the synthesis of four major HSPs in the 18 kilodalton range and continued synthesis of constitutive proteins during HS.     

Gambogic acid and gambogenic acid induce a thiol-dependent heat shock response and disrupt the interaction between HSP90 and HSF1 or HSF2

Cancer cells rely on heat shock proteins (HSPs) for growth and survival. Especially HSP90 has multiple client proteins and plays a critical role in malignant transformation, and therefore different types of HSP90 inhibitors are being developed. The bioactive natural compound gambogic acid (GB) is a prenylated xanthone with antitumor activity, and it has been proposed to function as an HSP90 inhibitor. However, there are contradicting reports whether GB induces a heat shock response (HSR), which is cytoprotective for cancer cells and therefore a potentially problematic feature for an anticancer drug. In this study, we show that GB and a structurally related compound, called gambogenic acid (GBA), induce a robust HSR, in a thiol-dependent manner. Using heat shock factor 1 (HSF1) or HSF2 knockout cells, we show that the GB or GBA-induced HSR is HSF1-dependent. Intriguingly, using closed form ATP-bound HSP90 mutants that can be co-precipitated with HSF1, a known facilitator of cancer, we show that also endogenous HSF2 co-precipitates with HSP90. GB and GBA treatment disrupt the interaction between HSP90 and HSF1 and HSP90 and HSF2. Our study implies that these compounds should be used cautiously if developed for cancer therapies, since GB and its derivative GBA are strong inducers of the HSR, in multiple cell types, by involving the dissociation of a HSP90-HSF1/HSF2 complex.     

Expression pattern of bta-mir-2898 miRNA and their correlation with heat shock proteins during summer heat stress among native vs crossbred cattle

Earlier studies identified the role of bta-mir-2898 in bovine. Our earlier study identified that, bta-mir-2898 can be over expressed in crossbred cattle during heat stress. Nevertheless the differential expression of bta-mir-2898 among native vs crossbred cattle during summer stress along with it's correlation with different heat shock proteins (HSPs) is not yet studied. In the present context, we studied the differential expression of bta-mir-2898 among Frieswal (Bos indicus x Bos taurus) and Sahiwal (Bos indicus) breeds of cattle during a range of environmental air temperatures and further investigated the correlation of bta-mir-2898 with different HSPs (HSP70, HSP90, HSP60. HSF, HSPB8 and HSP27). It was observed that, at peak air temperature the relative miRNA expression level (p < 0.05) of bta-mir-2898 was 3.4 ± 0.41 and 0.79 ± 0.22 among Frieswal and Sahiwal, respectively. We also observed significant levels (p < 0.05) of mRNA abundance of HSP70, HSP90, HSPB8 and HSP27 among the breeds. In all the cases Sahiwal found to exhibited higher level of HSPs in comparison to Frieswal. Studies revealed that the expression profile of bta-mir-2898 was negatively correlated with the expression of all the HSPs during thermal stress in post anti-mir2898 treated PBMC invitro cultured model originated from both Frieswal and Sahiwal cattle breeds. However, significantly (p < 0.05) higher negative correlations were observed between bta-mir-2898 and HSP70, HSP60 and HSPB8. Present findings highlighted the preliminary role of overexpressed bta-mir-2898 in cattle during thermal stress and its impact on different heat shock proteins.     

Non-lethal heat shock protects gnotobiotic Artemia franciscana larvae against virulent Vibrios

Brine shrimp Artemia were exposed under gnotobiotic conditions to a non-lethal heat shock (NLHS) from 28 to 32, 37 and 40 degrees C. Different recovery periods (2, 6, 12 and 24h) and different heat-exposure times (15, 30, 45 and 60 min) were tested. After these NLHS, Artemia was subsequently challenged with Vibrio. Challenge tests were performed in stressed and unstressed nauplii at concentrations of 10(7) cells ml(-1) of pathogenic bacteria, Vibrio campbellii and Vibrio proteolyticus. A NLHS with an optimal treatment of 37 degrees C for 30 min and a subsequent 6h recovery period resulted in a cross-protection against pathogenic Vibrio. A 100% increase in the larval survival (P < 0.05) was observed. We have also demonstrated by Western blot that a NLHS increases the expression of HSP-70 in heat-shocked (HS) treated animals. This report is the first to reveal a cross protection of a NLHS against deleterious bacterial challenges in living crustaceans. The putative role of heat shock proteins (HSPs) in this process is discussed.     

Expression of heat shock proteins in adult honey bee (Apis mellifera L.) workers under hot-arid subtropical ecosystems

Heat stress elicits the expression of heat shock proteins (HSPs) in honey bee subspecies. These highly conserved proteins have significant role in protecting cells from thermal-induced stresses. Honey bees in subtropical regions face extremely dry and hot environment. The expression of HSPs in the nurses and foragers of indigenous (Apis mellifera jemenitica) and imported European (Apis mellifera ligustica and Apis mellifera carnica) honey bee subspecies after heat shock treatment were compared using SDS-PAGE. Hsp70 and Hsp82 were equally expressed in the nurses of all tested bee subspecies when exposed to 40 °C and 45 °C for 4 h. The forager bees exhibited differential expression of HSPs after heat stress. No HSPs was expressed in the foragers of A. m. jemenitica, and Hsp70 was expressed only in the foragers of A. m. ligustica and A. m. carnica at 40 °C. A prominent diversity in HSPs expression was also exhibited in the foragers at 45 °C with one HSP (Hsp70) in A. m. jemenitica, two HSPs (Hsp40 and Hsp70) in A. m. carnica, and three HSPs (Hsp40, Hsp60 and Hsp70) in A. m. ligustica. No HSPs was expressed in the control nurse and forager bees at any of the tested temperatures. These findings illustrated the differences in HSP expression among nurse and forager bees. It is obvious that the native foragers are more heat tolerant with least HSPs expression than exotic bee races. Further investigations will help to understand the potential role of HSPs in the adaptability, survival, and performance of bee subspecies in harsh climate of the subtropical regions.     

Ethanol treatment triggers a heat shock-like response but no thermotolerance in soybean (Glycine max cv. Kaohsiung No.8) seedlings

Non‐lethal heat‐shock (HS) treatment has previously been shown to induce thermotolerance in soybean (Glycine max cv. Kaohsiung No.8) seedlings. This acquired thermotolerance correlates with the de novo synthesis of heat‐shock proteins (HSPs). Interestingly, we found that ethanol treatments also elicited HS‐like responses in aetiolated soybean seedlings at their normal growth temperature of 28 °C. Northern blot analyses revealed that the expression of HS genes hsp17.5, hsp70 and hsc 70 was induced by ethanol. Radioactive amino acids were preferentially incorporated into high molecular weight (HMW) HSPs rather than class I low molecular weight (LMW) HSPs during non‐lethal ethanol treatments. Immunoblot analysis confirmed that no accumulation of class I LMW HSPs occurred after non‐lethal ethanol treatment. Pre‐treatment with a non‐lethal dose of ethanol did not provide thermotolerance, as the aetiolated soybean seedlings could not survive a subsequent heat shock of 45 °C for 2 h. In contrast, non‐lethal HS pre‐treatment, 40 °C for 2 h, conferred tolerance on aetiolated soybean seedlings to otherwise lethal treatments of 7·5% ethanol for 8 h or 10% ethanol for 4 h. These results suggest that plant class I LMW HSPs may play important roles in providing both thermotolerance and ethanol tolerance.     

Acquisition of thermotolerance in bay scallops, Argopecten irradians irradians, via differential induction of heat shock proteins

Many cells and organisms are rendered transiently resistant to lethal heat shock by short exposure to sublethal temperatures. This induced thermotolerance is thought to be related to increased amounts of heat shock proteins (HSPs) which, as molecular chaperones, protect cells from stress-induced damage. As part of a study on bivalve stress and thermotolerance, work was undertaken to examine the effects of sublethal heat shock on stress tolerance of juveniles of the northern bay scallop, Argopecten irradians irradians, in association with changes in the levels of cytoplasmic HSP70 and 40. Juvenile bay scallops heat-shocked at a sublethal temperature of 32 °C survived an otherwise lethal heat treatment at 35 °C for at least 7 days. As determined by ELISA, acquisition of induced thermotolerance closely paralleled HSP70 accumulation, whereas HSP40 accrual appeared less closely associated with thermotolerance. Quantification of scallop HSPs following lethal heat treatment, with or without conditioning, suggested a causal role for HSP70 in stress tolerance, with HSP40 contributing to a lesser, but significant extent. Overall, this study demonstrated that sublethal heat shock promotes survival of A. irradians irradians juveniles upon thermal stress and the results support the hypothesis that HSPs have a role in this induced thermotolerance. Exploitation of the induced thermotolerance response shows promise as a means to improve survival of bay scallops in commercial culture.