In heating experiments with leaves, the temperature at which dark-level F0 chlorophyll a fluorescence begins to rise, Tcrit, is widely used as an indicator of photosystem II thermotolerance. However, little is known about how Tcrit correlates with irreversible leaf tissue damage. Young and mature leaves of the tropical tree species Calophyllum inophyllum were heated stepwise from 30 to 55°C, at 1°C min-1. Tcrit was 47°C in young leaves and 49°C in mature leaves. Contrary to the higher Tcrit in mature leaves, heating to 55°C elicited greater tissue damage in mature than in young leaves. Young and mature leaves heated to their respective Tcrit or Tcrit + 2°C exhibited no or little tissue necrosis after 14 d of post-culture. It is concluded that measurements of the temperature-dependent F0 fluorescence rise underestimate the thermal thresholds above which significant irreversible leaf damage occurs.

• Klíčová slova
• chlorophyll a fluorescence, global warming, heat tolerance, necrosis, tropical trees,
• MeSH
• Calophyllum * fyziologie   metabolismus   MeSH
• chlorofyl a MeSH
• chlorofyl metabolismus   MeSH
• fluorescence MeSH
• listy rostlin * fyziologie   metabolismus   MeSH
• nekróza MeSH
• stromy fyziologie   MeSH
• termotolerance * fyziologie   MeSH
• tropické klima MeSH
• vysoká teplota * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl a MeSH
• chlorofyl MeSH

Phosphatidylglycerol (1,2-diacyl-sn-glycero-3-phospho-glycerol) (PG) is one of the most abundant lipids in biological membranes. However, the chirality of the carbon atom in glycerol phosphate differs among the three kingdoms: bacteria, archaea, and eukaryotes. It is commonly assumed that archaea, as well as bacteria and eukaryotes, produce only one isomer of PG. Archaeal membranes consist of phospholipids with glycerol-1-phosphate in the S configuration, while the phospholipids of the other two kingdoms contain glycerol-3-phosphate with (R) stereochemistry. Another chiral atom is found in glycerol with non-esterified hydroxy groups. Considering the high temperatures that accompanied the origin of life on Earth, it becomes obvious that it is necessary to clarify the importance of membrane lipids in early evolutionary times. To reconstruct the effect of high temperatures on membrane lipids, it is ideal to use microorganisms originating from a thermophilic environment analogous to the early Earth, such as the thermal groundwater of the famous spa town of Karlovy Vary. Here, we prepared all four isomers of PG, i.e., (R,S, R,R, S,R), and (S,S), by organic synthesis and analyzed the representation of individual molecular species in seven bacteria isolated from the Karlovy Vary thermal springs using chiral chromatography - mass spectrometry. Our results provide evidence that five of these strains produce all four isomers of PG and that this production is highly dependent on the cultivation temperature. Subsequent analysis by chiral chromatography revealed that the ratio of isomers, enantiomers, and diastereoisomers depends on the cultivation temperature of individual strains.

• Klíčová slova
• Chiral chromatography, Mass spectrometry, Membrane fluidity, Phosphatidylglycerols, Stereochemistry, Thermotolerant bacteria,
• MeSH
• Bacteria MeSH
• fosfatidylglyceroly * chemie   MeSH
• horké prameny * mikrobiologie   chemie   MeSH
• stereoizomerie MeSH
• termotolerance MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fosfatidylglyceroly * MeSH

One of the most vulnerable phases in the plant life cycle is sexual reproduction, which depends on effective pollen transfer, but also on the thermotolerance of pollen grains. Pollen thermotolerance is temperature-dependent and may be reduced by increasing temperature associated with global warming. A growing body of research has focused on the effect of increased temperature on pollen thermotolerance in crops to understand the possible impact of temperature extremes on yield. Yet, little is known about the effects of temperature on pollen thermotolerance of wild plant species. To fill this gap, we selected Lotus corniculatus s.l. (Fabaceae), a species common to many European habitats and conducted laboratory experiments to test its pollen thermotolerance in response to artificial increase in temperature. To test for possible local adaptation of pollen thermal tolerance, we compared data from six lowland (389-451 m a.s.l.) and six highland (841-1,030 m a.s.l.) populations. We observed pollen germination in vitro at 15 °C, 25 °C, 30 °C, and 40 °C. While lowland plants maintained a stable germination percentage across a broad temperature range (15-30 °C) and exhibited reduced germination only at extremely high temperatures (40 °C), highland plants experienced reduced germination even at 30 °C-temperatures commonly exceeded in lowlands during warm summers. This suggests that lowland populations of L. corniculatus may be locally adapted to higher temperature for pollen germination. On the other hand, pollen tube length decreased with increasing temperature in a similar way in lowland and highland plants. The overall average pollen germination percentage significantly differed between lowland and highland populations, with highland populations displaying higher germination percentage. On the other hand, the average pollen tube length was slightly smaller in highland populations. In conclusion, we found that pollen thermotolerance of L. corniculatus is reduced at high temperature and that the germination of pollen from plant populations growing at higher elevations is more sensitive to increased temperature, which suggests possible local adaptation of pollen thermotolerance.

• Klíčová slova
• Elevational gradient, Heat stress, Local adaptation, Plant reproduction, Pollen, Pollen viability, Pollination, Thermotolerance,
• MeSH
• aklimatizace fyziologie   MeSH
• fyziologická adaptace fyziologie   MeSH
• globální oteplování MeSH
• klíčení fyziologie   MeSH
• klimatické změny MeSH
• Lotus * fyziologie   růst a vývoj   MeSH
• nadmořská výška MeSH
• pyl * fyziologie   MeSH
• teplota MeSH
• termotolerance * fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Heat stress is a frequent environmental constraint. Phytohormones can significantly affect plant thermotolerance. This study compares the effects of exogenous cytokinin meta-topolin-9-(tetrahydropyran-2-yl)purine (mT9THP) on rice (Oryza sativa) under control conditions, after acclimation by moderate temperature (A; 37 °C, 2h), heat stress (HS; 45 °C, 6h) and their combination (AHS). mT9THP is a stable cytokinin derivative that releases active meta-topolin gradually, preventing the rapid deactivation reported after exogenous cytokinin application. Under control conditions, mT9THP negatively affected jasmonic acid in leaves and abscisic and salicylic acids in crowns (meristematic tissue crucial for tillering). Exogenous cytokinin stimulated the emission of volatile organic compounds (VOC), especially 2,3-butanediol. Acclimation upregulated trans-zeatin, expression of stress- and hormone-related genes, and VOC emission. The combination of acclimation and mT9THP promoted the expression of stress markers and antioxidant enzymes and moderately increased VOC emission, including 2-ethylhexyl salicylate or furanones. AHS and HS responses shared some common features, namely, increase of ethylene precursor aminocyclopropane-1-carboxylic acid (ACC), cis-zeatin and cytokinin methylthio derivatives, as well as the expression of heat shock proteins, alternative oxidases, and superoxide dismutases. AHS specifically induced jasmonic acid and auxin indole-3-acetic acid levels, diacylglycerolipids with fewer double bonds, and VOC emissions [e.g., acetamide, lipoxygenase (LOX)-derived volatiles]. Under direct HS, exogenous cytokinin mimicked some positive acclimation effects. The combination of mT9THP and AHS had the strongest thermo-protective effect, including a strong stimulation of VOC emissions (including LOX-derived ones). These results demonstrate for the first time the crucial contribution of volatiles to the beneficial effects of cytokinin and AHS on rice thermotolerance.

• Klíčová slova
• Acclimation, Cytokinin, Heat stress, Phytohormone, Priming, Thermotolerance, Volatile organic compound,
• MeSH
• aklimatizace MeSH
• cytokininy metabolismus   MeSH
• exprese genu MeSH
• rýže (rod) * metabolismus   MeSH
• těkavé organické sloučeniny * MeSH
• termotolerance * MeSH
• zeatin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytokininy MeSH
• jasmonic acid MeSH Prohlížeč
• těkavé organické sloučeniny * MeSH
• zeatin MeSH

Being rooted in place, plants are faced with the challenge of responding to unfavourable local conditions. One such condition, heat stress, contributes massively to crop losses globally. Heatwaves are predicted to increase, and it is of vital importance to generate crops that are tolerant to not only heat stress but also to several other abiotic stresses (e.g. drought stress, salinity stress) to ensure that global food security is protected. A better understanding of the molecular mechanisms that underlie the temperature stress response in pollen will be a significant step towards developing effective breeding strategies for high and stable production in crop plants. While most studies have focused on the vegetative phase of plant growth to understand heat stress tolerance, it is the reproductive phase that requires more attention as it is more sensitive to elevated temperatures. Every phase of reproductive development is affected by environmental challenges, including pollen and ovule development, pollen tube growth, male-female cross-talk, fertilization, and embryo development. In this review we summarize how pollen is affected by heat stress and the molecular mechanisms employed during the stress period, as revealed by classical and -omics experiments.

• Klíčová slova
• heat stress (HS), heat stress response (HSR), multiomics, pollen development, thermotolerance,
• MeSH
• fyziologický stres MeSH
• pyl MeSH
• reakce na tepelný šok MeSH
• šlechtění rostlin * MeSH
• termotolerance * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

In the context of ongoing climate change, expected temperature rise may significantly limit plant growth and productivity of crop species. In this study, we investigated the effects of a sub-optimal temperature on buckwheat, a pseudocereal known for its nutraceutical advantages. Two buckwheat species differing by their reproduction method, namely Fagopyrum esculentum and Fagopyrum tataricum were grown at 21 °C and 27 °C in growth chambers. High temperature increased leaf production mainly in F. tataricum but decreased leaf area in both species. Water and photosynthesis-related parameters were affected by high temperature but our results suggested that although transpiration rate was increased, adaptive mechanisms were developed to limit the negative impact on photosynthesis. High temperature mainly affected the reproductive stage. It delayed flowering time but boosted inflorescence and flower production. Nevertheless, flower and seed abortions were observed in both species at 27 °C. Regarding flower fertility, heat affected more the female stage than the male stage and reduced the stigma receptivity. Pollen production increased with temperature in F. esculentum while it decreased in F. tataricum. Such discrepancy could be related to the self-incompatibility of F. esculentum. Both species increased their antioxidant production under high temperature to limit oxidative stress and antioxidant capacity was higher in the inflorescences than in the leaves. Total flavonoid content was particularly increased in the leaves of F. esculentum and in the inflorescences of F. tataricum. Altogether, our results showed that even if high temperature may negatively affect reproduction in buckwheat, it improves its antioxidant content.

• Klíčová slova
• Antioxidant, Common buckwheat, Flower fertility, Heat, Photosynthesis, Tartary buckwheat,
• MeSH
• antioxidancia metabolismus   MeSH
• druhová specificita MeSH
• Fagopyrum růst a vývoj   fyziologie   MeSH
• rozmnožování MeSH
• termotolerance * MeSH
• vysoká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antioxidancia MeSH

Polyhydroxyalkanoates are microbial polyesters which are considered being biological alternatives to petrochemical polymers. Extremophiles, such as thermophilic PHA producers, hold promise to improve competitiveness of PHA production process. Therefore, this work aimed at isolation of new strains, which could produce PHA under elevated temperature. Since traditional Nile red staining of colonies provided false positive results in thermophiles, we developed a novel strategy of enriching microbial consortia by PHA producers. This so called "osmoselective strategy" is based on application of osmotic challenge by sudden exposition of the mixed microbial culture to hypertonic and subsequently to hypotonic conditions; moreover, this strategy relies on the fact that PHA protect bacteria from negative effects of rapid fluctuations in osmotic pressure. In combination with fast and reliable ATR-FTIR inspection of selected colonies for presence of PHA, we were able to isolate several promising thermophilic or thermotolerant PHA producing strains belonging to the genera Bacillus, Aneurinibacillus and Chelatococcus, which indeed deserves further investigation to evaluate their potential for industrial production of PHA.

• Klíčová slova
• Enrichment, Isolation of bacteria, Osmotic challenge, Polyhydroxyalkanoates, Thermophiles,
• MeSH
• Alphaproteobacteria izolace a purifikace   MeSH
• Bacillales izolace a purifikace   MeSH
• Bacillus izolace a purifikace   MeSH
• Bacteria izolace a purifikace   MeSH
• bioreaktory MeSH
• DNA bakterií MeSH
• fermentace MeSH
• mikrobiální společenstva * MeSH
• osmóza MeSH
• polyhydroxyalkanoáty chemie   MeSH
• sekvence nukleotidů MeSH
• termotolerance MeSH
• vysoká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• DNA bakterií MeSH
• polyhydroxyalkanoáty MeSH

Targeting mutations to specific genomic loci is invaluable for assessing in vivo the effect of these changes on the biological role of the gene in study. Here, we attempted to introduce a mutation that was previously implicated in an increased heat stability of the mesophilic cyanobacterium Synechocystis sp. PCC6803 via homologous recombination to the psbA gene of Chlamydomonas reinhardtii. For that, we established a strategy for targeted mutagenesis that was derived from the efficient genome-wide homologous-recombination-based methodology that was used to target individual genes of Saccharomyces cerevisiae. While the isolated mutants did not show any benefit under elevated temperature conditions, the new strategy proved to be efficient for C. reinhardtii even in the absence of direct positive selection.

• MeSH
• Chlamydomonas reinhardtii genetika   MeSH
• fotosystém II (proteinový komplex) genetika   MeSH
• geneticky modifikované rostliny genetika   MeSH
• genom plastidový genetika   MeSH
• homologní rekombinace MeSH
• mutageneze cílená metody   MeSH
• rostlinné proteiny genetika   MeSH
• selekce (genetika) MeSH
• serin genetika   MeSH
• substituce aminokyselin MeSH
• Synechocystis genetika   MeSH
• termotolerance genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fotosystém II (proteinový komplex) MeSH
• photosystem II, psbA subunit MeSH Prohlížeč
• rostlinné proteiny MeSH
• serin MeSH

A thermotolerant bacterial strain 1D isolated from refinery oil-contaminated soil was identified as Gordonia sp. based on the analysis of 16S rRNA and gyrB gene sequences. The strain was found to utilize crude oil, diesel fuel, and a wide spectrum of alkanes at temperatures up to 50 °C. Strain 1D is the first representative of Gordonia amicalis capable of utilizing alkanes of chain length up to С36 at a temperature of 45-50 °C. The degree of crude oil degradation by Gordonia sp. 1D at 45 °C was 38% in liquid medium and 40% in soil (with regard to abiotic loss). There are no examples of so effective hydrocarbon-oxidizing thermotolerant Gordonia in the world literature. The 1D genome analysis revealed the presence of two alkane hydroxylase gene clusters, genes of dibenzothiophene cleavage, and the cleavage of salicylate and gentisate - naphthalene metabolism intermediates. The highly efficient thermotolerant strain Gordonia sp. 1D can be used in remediation of oil-contaminated soils in hot climates.

• MeSH
• bakteriální geny MeSH
• biodegradace MeSH
• fylogeneze MeSH
• genom bakteriální genetika   MeSH
• Gordonia bacterium klasifikace   genetika   metabolismus   fyziologie   MeSH
• multigenová rodina MeSH
• půdní mikrobiologie MeSH
• RNA ribozomální 16S genetika   MeSH
• ropa metabolismus   MeSH
• sekvenční analýza DNA MeSH
• substrátová specifita MeSH
• termotolerance * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• RNA ribozomální 16S MeSH
• ropa MeSH

Cytokinins are phytohormones that are involved in many processes in plants, including growth, differentiation and leaf senescence. However, they also have various activities in animals. For example, kinetin and trans-zeatin can reduce levels of several aging markers in human fibroblasts. Kinetin can also protect mice against oxidative and glyoxidative stress, and prolong fruit flies' lifespan. Additionally, several cytokinins are currently used in cosmetics. To extend knowledge of the breadth of cytokinins' activities, we examined effects of natural cytokinin bases on the model nematode Caenorhabditis elegans. We found that kinetin, para-topolin and meta-topolin prolonged the lifespan of C. elegans. Kinetin also protected the organism against oxidative and heat stress. Furthermore, our results suggest that presence of reactive oxygen species, but not DAF-16 (the main effector of the insulin/insulin-like growth factor signaling pathway), is required for the beneficial effects of kinetin. Ultra-high performance liquid chromatography-tandem mass spectrometric analysis showed that kinetin is unlikely to occur naturally in C. elegans, but the worm efficiently absorbs and metabolizes it into kinetin riboside and kinetin riboside-5'-monophosphate.

• Klíčová slova
• Aging, Caenorhabditis elegans, Cytokinin, Kinetin, Phytohormones, Topolin, Zeatin,
• MeSH
• Caenorhabditis elegans účinky léků   genetika   fyziologie   MeSH
• cytokininy farmakokinetika   farmakologie   MeSH
• dlouhověkost účinky léků   fyziologie   MeSH
• forkhead transkripční faktory genetika   metabolismus   MeSH
• inzulin metabolismus   MeSH
• kinetin farmakokinetika   farmakologie   MeSH
• mutace MeSH
• oxidační stres účinky léků   MeSH
• proteiny Caenorhabditis elegans genetika   metabolismus   MeSH
• reakce na tepelný šok účinky léků   MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• regulátory růstu rostlin farmakokinetika   farmakologie   MeSH
• signální transdukce účinky léků   MeSH
• termotolerance účinky léků   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• cytokininy MeSH
• daf-16 protein, C elegans MeSH Prohlížeč
• forkhead transkripční faktory MeSH
• inzulin MeSH
• kinetin MeSH
• proteiny Caenorhabditis elegans MeSH
• reaktivní formy kyslíku MeSH
• regulátory růstu rostlin MeSH