Thermotolerant cyclamen with reduced acrolein and methyl vinyl ketone.
ABSTRACT: Reduced levels of trienoic fatty acids (TAs) in chloroplast membranes induce thermotolerance in several plant species, but the underlying mechanisms remain unclear. TA peroxidation in plant cell membranes generates cytotoxic, TA-derived compounds containing ?,?-unsaturated carbonyl groups. The relationship between low TA levels and the amounts of cytotoxic TA-derived compounds was examined using thermotolerant transgenic cyclamen (Cyclamen persicum Mill.) with low TA contents. Changes in the levels of the cytotoxic TA-derived acrolein (ACR), methyl vinyl ketone (MVK), (E)-2-hexenal, 4-hydroxy-2-nonenal, and malondialdehyde were analysed in the leaf tissues of wild-type (WT) and thermotolerant transgenic cyclamen under heat stress. Levels of ACR and MVK in the WT increased in parallel with the occurrence of heat-induced tissue damage, whereas no such changes were observed in the thermotolerant transgenic lines. Furthermore, exogenous ACR and MVK infiltrated into leaves to concentrations similar to those observed in heat-stressed WT leaves caused similar disease symptoms. These results suggest that thermotolerance in transgenic cyclamen depends on reduced production rates of ACR and MVK under heat stress, due to the low level of TAs in these plants.
Project description:Numerous regulatory genes participate in plant thermotolerance. In Arabidopsis, HEAT-INDUCED TAS1 TARGET2 (HTT2) is an important thermotolerance gene that is silenced by ta-siR255, a trans-acting siRNA. ta-siR255 is absent from heading Chinese cabbage (Brassica rapa ssp. pekinensis). Our previous attempt to overexpress the endogenous BrpHTT2 gene of heading Chinese cabbage (B. rapa ssp. pekinensis) failed because of cosuppression. In theory, heading Chinese cabbage can overexpress Arabidopsis HTT2 to improve thermotolerance in the absence of ta-siR255-mediated gene silencing and the weak potential of coexpression.To test the potential application of HTT2 in improving crop thermotolerance, we transferred p35S::HTT2 to heading Chinese cabbage. We tested the leaf electrical conductivity, hypocotyl elongation, and survival percentage of p35S::HTT2 plants subjected to high-temperature (38 °C) and heat-shock (46 °C) treatment. The leaf electrical conductivity of p35S::HTT2 seedlings under high temperature decreased but did negligibly change under heat shock. The hypocotyl length of p35S::HTT2 seedlings increased under high temperature and heat shock. The survival rate of p35S::HTT2 seedlings increased under heat shock. BrpHsfs, a subset of heat-shock factor genes, were upregulated in p35S::HTT2 plants under high-temperature and heat shock conditions. In the field, transgenic plants with HTT2 appeared greener and formed leafy heads earlier than wild-type plants.Exogenous HTT2 increased the survival rates of heat-shocked heading Chinese cabbage by promoting thermotolerance through decreasing electrical conductivity and extending hypocotyl length. Our work provides a new approach to the genetic manipulation of thermotolerance in crops through the introduction of exogenous thermotolerance genes.
Project description:Most mushrooms are thermo-sensitive to temperatures over 23°C, which greatly restricts their agricultural cultivation. Understanding mushroom's innate heat-tolerance mechanisms may facilitate genetic improvements of their thermotolerance. Agaricus bisporus strain 02 is a relatively thermotolerant mushroom strain, while strain 8213 is quite thermo-sensitive. Here, we compared their responses at proteomic level to heat treatment at 33°C. We identified 73 proteins that are differentially expressed between 02 and 8213 or induced upon heat stress in strain 02 itself, 48 of which with a known identity. Among them, 4 proteins are constitutively more highly expressed in 02 than 8213; and they can be further upregulated in response to heat stress in 02, but not in 8213. One protein is encoded by the para-aminobenzoic acid (PABA) synthase gene Pabs, which has been shown to scavenge the reactive oxygen species in vitro. Pabs mRNA and its chemical product PABA show similar heat stress induction pattern as PABA synthase protein and are more abundant in 02, indicating transcriptional level upregulation of Pabs upon heat stress. A specific inhibitor of PABA synthesis impaired thermotolerance of 02, while exogenous PABA or transgenic overexpression of 02 derived PABA synthase enhanced thermotolerance of 8213. Furthermore, compared to 8213, 02 accumulated less H2O2 but more defense-related proteins (e.g., HSPs and Chitinase) under heat stress. Together, these results demonstrate a role of PABA in enhancing mushroom thermotolerance by removing H2O2 and elevating defense-related proteins.
Project description:Heat shock transcription factor (Hsf) plays an important role in regulating plant thermotolerance. The function and regulatory mechanism of CaHsfA1d in heat stress tolerance of pepper have not been reported yet. In this study, phylogenetic tree and sequence analyses confirmed that CaHsfA1d is a class A Hsf. CaHsfA1d harbored transcriptional function and predicted the aromatic, hydrophobic, and acidic (AHA) motif mediated function of CaHsfA1d as a transcription activator. Subcellular localization assay showed that CaHsfA1d protein is localized in the nucleus. The CaHsfA1d was transcriptionally up-regulated at high temperatures and its expression in the thermotolerant pepper line R9 was more sensitive than that in thermosensitive pepper line B6. The function of CaHsfA1d under heat stress was characterized in CaHsfA1d-silenced pepper plants and CaHsfA1d-overexpression Arabidopsis plants. Silencing of the CaHsfA1d reduced the thermotolerance of the pepper, while CaHsfA1d-overexpression Arabidopsis plants exhibited an increased insensitivity to high temperatures. Moreover, the CaHsfA1d maintained the H2O2 dynamic balance under heat stress and increased the expression of Hsfs, Hsps (heat shock protein), and antioxidant gene AtGSTU5 (glutathione S-transferase class tau 5) in transgenic lines. Our findings clearly indicate that CaHsfA1d improved the plant thermotolerance via regulating the expression of stress- and antioxidant-related genes.
Project description:High temperature at anthesis is one of the most serious stress factors for rice (Oryza sativa L.) production, causing irreversible yield losses and reduces grain quality. Illustration of thermotolerance mechanism is of great importance to accelerate rice breeding aimed at thermotolerance improvement. Here, we identified a new thermotolerant germplasm, SDWG005. Microscopical analysis found that stable anther structure of SDWG005 under stress may contribute to its thermotolerance. Dynamic transcriptomic analysis totally identified 3559 differentially expressed genes (DEGs) in SDWG005 anthers at anthesis under heat treatments, including 477, 869, 2335, and 2210 for 1, 2, 6, and 12 h, respectively; however, only 131 were regulated across all four-time-points. The DEGs were divided into nine clusters according to their expressions in these heat treatments. Further analysis indicated that some main gene categories involved in heat-response of SDWG005 anthers, such as transcription factors, nucleic acid and protein metabolisms related genes, etc. Comparison with previous studies indicates that a core gene-set may exist for thermotolerance mechanism. Expression and polymorphic analysis of agmatine-coumarin-acyltransferase gene OsACT in different accessions suggested that it may involve in SDWG005 thermotolerance. This study improves our understanding of thermotolerance mechanisms in rice anthers during anthesis, and also lays foundation for breeding thermotolerant varieties via molecular breeding.
Project description:Durum wheat is strongly affected by climatic constraints such as high temperatures and drought, which frequently lead to yield reduction. Damages due to high temperatures are related to plant thermotolerance, a trait determined by two components: basal and acquired thermotolerance. In this study, the effect of drought and heat stress imposed singularly or sequentially was investigated in ten durum wheat cultivars (cvs) at the physiological and molecular level. The traits analyzed were cell membrane stability, relative water content, proline content, and expression level of several genes for heat shock proteins (HSPs). Our results indicate that drought priming can induce the acquisition of thermotolerance in most cultivars already classified as able to acquire thermotolerance by heat pre-treatment. Proline accumulation was correlated to cell membrane stability, meaning that the most thermotolerant cvs were able to accumulate higher levels of proline. Acquired thermotolerance is also due to the activation of HSP gene expression; similarly, pre-treatment with water stress was able to activate HSPs expression. The results reported indicate that water stress plays an important role in inducing thermotolerance, comparable to mild heat stress pre-treatment. This is the first report on the effect of drought stress on the acquisition of thermotolerance.
Project description:Understanding how tropical trees will respond to extreme temperatures and drought is essential to predict how future increases in the severity, frequency and duration of extreme climatic events will affect tropical systems. In this study, we investigated leaf thermotolerance by quantifying the temperatures that resulted in a 50 % decrease in photosystem II function (T50) in experimentally grown saplings of 12 tree species from a seasonally dry tropical forest. We examined the relationship of thermotolerance with leaf functional traits and photosynthetic rates. Additionally, we tested how water limitation altered thermotolerance within species, and examined the relationship between thermotolerance and drought tolerance among species. Thermotolerance ranged from 44.5 to 48.1 °C in the least and most thermotolerant species, respectively. The observed variation in thermotolerance indicates that the upper limits of leaf function are critically close to maximum temperatures in this region, and that these species will be vulnerable to, and differentially affected by, future warming. Drought increased temperature tolerance, and species that were more drought tolerant were also more thermotolerant. Importantly, thermotolerance was positively related to the key leaf functional trait-leaf mass per area (LMA), and congruent with this, negatively related to photosynthetic rates. These results indicate that more productive species with lower LMA and higher photosynthetic rates may be more vulnerable to heat and drought stress, and more likely to be negatively affected by future increases in extreme climatic events.
Project description:High temperature is one of the major abiotic stresses that affect cucumber growth and development. Heat stress often leads to metabolic malfunction, dehydration, wilting and death, which has a great impact on the yield and fruit quality. In this study, genetic analysis and quantitative trait loci (QTL) mapping for thermotolerance in cucumber seedlings was investigated using a recombinant inbred line (RILs; HR) population and a doubled haploid (DH; HP) population derived from two parental lines '65G' (heat-sensitive) and '02245' (heat-tolerant). Inheritance analysis suggested that both short-term extreme and long-term mild thermotolerance in cucumber seedlings were determined by multiple genes. Six QTLs for heat tolerance including qHT3.1, qHT3.2, qHT3.3, qHT4.1, qHT4.2, and qHT6.1 were detected. Among them, the major QTL, qHT3.2, was repeatedly detected for three times in HR and HP at different environments, explained 28.3% of the phenotypic variability. The 481.2 kb region harbored 79 genes, nine of which might involve in heat stress response. This study provides a basis for further identifying thermotolerant genes and helps understanding the molecular mechanism underlying thermotolerance in cucumber seedlings.
Project description:Climate change is causing temperature increment in crop production areas worldwide, generating conditions of heat stress that negatively affect crop productivity. Tomato (<i>Solanum lycopersicum</i>), a major vegetable crop, is highly susceptible to conditions of heat stress. When tomato plants are exposed to ambient day/night temperatures that exceed 32 °C/20 °C, respectively, during the reproductive phase, fruit set and fruit weight are reduced, leading to a significant decrease in yield. Processing tomato cultivars are cultivated in open fields, where environmental conditions are not controlled; therefore, plants are exposed to multiple abiotic stresses, including heat stress. Nonetheless, information on stress response in processing tomatoes is very limited. Understanding the physiological response of modern processing tomato cultivars to heat stress may facilitate the development of thermotolerant cultivars. Here, we compared two tomato processing cultivars, H4107 and H9780, that we found to be constantly differing in yield performance. Using field and temperature-controlled greenhouse experiments, we show that the observed difference in yield is attributed to the occurrence of heat stress conditions. In addition, fruit set and seed production were significantly higher in the thermotolerant cultivar H4107, compared with H9780. Despite the general acceptance of pollen viability as a measure of thermotolerance, there was no difference in the percentage of viable pollen between H4107 and H9780 under either of the conditions tested. In addition to observations of similar pollen germination and bud abscission rates, our results suggest that processing tomato cultivars may present a particular case, in which pollen performance is not determining reproductive thermotolerance. Our results also demonstrate the value of combining controlled and uncontrolled experimental settings, in order to validate and identify heat stress-related responses, thus facilitating the development of thermotolerant processing tomato cultivars.
Project description:Thermotolerance development of robust Saccharomyces cerevisiae is necessary to enhance enzyme activity of cellulase, lower cooling costs, and reduce cell harm from the bad-distributed heat transfer in large-scale fermentation. The process-based studies of adaptive evolution have been well documented, but it remains unknown for the underlying molecular mechanism of the improved thermotolerance and the facilitated ethanol fermentability derived from adaptive evolution. Here, a robust thermotolerant S. cerevisiae Z100 was obtained with significantly improved ethanol fermentability under the stress of high temperature (50 oC) after 91 days’ adaptive evolution. RNA sequencing showed that adaptive evolution and its derived thermotolerance contributed to the unique gene transcriptional landscapes of the evolved strain. An interesting phenomenon was that the gene transcriptional signals of carbon metabolism were strengthened not at 50 oC but at 30 oC in S. cerevisiae Z100, and thus suggested that the improved thermotolerance led to the enhanced ethanol fermentability at 30 oC. The deeply repressed gene transcriptional expression indicated ribosome would be another key thermotolerant mechanism for the evolved strain. This study would provide a robust thermotolerant S. cerevisiae for bioethanol production and an important clue for future synthetic biology to thermotolerance engineering of fermentation strains. Overall design: To find out genetic changes in the evolved S. cerevisiae Z100
Project description:The study was conducted in order to find out the differential change in the transcript of tolerant and susceptible wheat cultivar under heat stress and to decipher the mechanism of thermotolerance in wheat by identifying novel genes and transcription factors involved in the pathways. Wheat cultivar HD2985 (thermotolerant) and HD2329 (thermosusceptible) were exposed to heat stress of 42 degree for 4h at pollination stage and samples were collected from both control and heat shock treated plants for further characterization.