Viability of Embryo Sacs and Fruit Set in Different Plum (Prunus domestica L.) Cultivars Grown under Norwegian Climatic Conditions

Compatibility and synchrony between specialized tissues of the pistil, female gametophytes and male gametophytes, are necessary for successful pollination, fertilization, and fruit set in angiosperms. The aim of the present work was to study the development and viability of embryo sacs, as well as fertilization success, in relation to the fruit set of the cultivars ‘Mallard’, ‘Edda’, ‘Jubileum’, and ‘Reeves’, under specific Norwegian climatic conditions. Emasculated, unpollinated, and open-pollinated flowers were collected at the beginning of flowering, and on the 3rd, 6th, 9th, and 12th days after flowering, from all four plum cultivars over two years (2018/2019). Ovaries were dehydrated, embedded in paraffin wax, sectioned, stained, and observed under a light microscope. Results showed the existence of synchronization between successive phases in the development of the embryo sac and individual phases of flowering. All plum cultivars had higher percentages of viable embryo sacs, fertilized embryo sacs, and fruit set in 2018 than in 2019. These differences may be related to the very low temperatures during the post-full-flowering period in 2019, and to the low adaptation of some studied cultivars to unfavorable conditions. In our study, the cultivar ‘Jubileum’ showed the highest percentage of viable embryo sacs, fertilized embryo sacs, and fruit set compared to other cultivars, i.e., the best low-temperature adaptation.

Systematic investigation of the link between enzyme catalysis and cold adaptation

Cold temperature is prevalent across the biosphere and slows the rates of chemical reactions. Increased catalysis has been predicted to be a dominant adaptive trait of enzymes to reduced temperature, and this expectation has informed physical models for enzyme catalysis and influenced bioprospecting strategies. To systematically test rate enhancement as an adaptive trait to cold, we paired kinetic constants of 2223 enzyme reactions with their organism’s optimal growth temperature (TGrowth) and analyzed trends of rate constants as a function of TGrowth. These data do not support a general increase in rate enhancement in cold adaptation. In the model enzyme ketosteroid isomerase (KSI), there is prior evidence for temperature adaptation from a change in an active site residue that results in a tradeoff between activity and stability. Nevertheless, we found that little of the rate constant variation for 20 KSI variants was accounted for by TGrowth. In contrast, and consistent with prior expectations, we observed a correlation between stability and TGrowth across 433 proteins. These results suggest that temperature exerts a weaker selection pressure on enzyme rate constants than stability and that evolutionary forces other than temperature are responsible for the majority of enzymatic rate constant variation.

Comparative Transcriptome Analysis of Two Populations of Dastarcus helophoroides (Fairmaire) under High Temperature Stress

The differentially expressed genes (DEGs), key genes and metabolic pathways of the parasitic beetle, Dastarcus helophoroides (Fairmaire), were compared between the fiftieth commercially reared population and the first natural population to reveal the adaptive mechanism in response to high temperature stress. The high-throughput sequencing technique was employed for transcriptome sequencing of two populations of D. helophoroides. In total, 47,763 non-redundant transcripts with the average length of 989.31 bp and the N50 of 1607 bp were obtained. Under high temperature stress, 1108 DEGs were found in the commercial population; while there were 3946 DEGs in the natural population, which were higher than those in the commercial population (3.56 times). High temperature stress of D. helophoroides promoted the expression of heat shock proteins (HSPs) and metabolism-related genes in both populations, but metabolism synthesis and hydrolysis of natural population was much higher, allowing them to produce more resistant substances (such as HSPs, superoxide dismutase (SOD), peroxiredoxin (Prx), etc.). Therefore, HSPs may play a major role in the high temperature adaptation of a commercial population, while the natural population probably respond to heat stress with more resistant substances (such as HSPs, SOD, Prx, etc.). These results provide a reference to select and domesticate a specific ecotype with stronger adaptability to the high temperature weather in the forest and further improve the efficiency of D. helophoroides as a bio-control factor.

The population genetics of adaptation through copy-number variation in a fungal plant pathogen

ABSTRACTMicrobial pathogens can rapidly adapt to changing environments such as the application of pesticides or host resistance. Copy number variations (CNV) are a major source of adaptive genetic variation for recent adaptation. Here, we analyze how a major fungal pathogen of barley, Rhynchosporium commune, has adapted to host environment, fungicide and temperature challenges. We screen the genomes of 126 isolates sampled across a worldwide set of populations and identify a total of 7’879 gene duplications and 116 gene deletions. Most gene duplications result from segmental chromosomal duplications. We find that genes showing recent gains or losses are enriched in functions related to host exploitation (i.e. effectors and cell wall degrading enzymes). We perform a phylogeny-informed genome-wide association study (GWAS) and identify 191 copy-number variants associated with different pathogenesis and temperature related traits, including a large segmental duplication of CYP51A that has contributed to the emergence of azole resistance. Additionally, we use a genome-wide SNP dataset to replicate the GWAS and contrast it with the CNV-focused analysis. We find that frequencies of adaptive CNV alleles show high variation among populations for traits under strong selection such as fungicide resistance. In contrast, adaptive CNV alleles underpinning temperature adaptation tend to be near fixation. Finally, we show that transposable elements are important drivers of recent gene copy-number variation. Loci showing signatures of recent positive selection are enriched in miniature inverted repeat transposons. Our findings show how extensive segmental duplications create the raw material for recent adaptation in global populations of a fungal pathogen.

The Role of Cytochrome P450 4C1 and Carbonic Anhydrase 3 in Response to Temperature Stress in Bemisia tabaci

The position of the chromatin opening of Bemisia tabaci undergoes significant changes under different temperature stresses, and numerous regulatory factors have been found. In this study, we verified two key factors, cytochrome P450 4C1 and carbonic anhydrase 3. The results showed that invasive whiteflies had a significantly lower heat resistance after silencing BtCYP 4C1 and BtCar3. In addition, whiteflies had a higher cold tolerance after silencing BtCYP 4C1. These results indicate that BtCYP 4C1 and BtCar3 are key regulators in the temperature adaptation of B. tabaci. Moreover, they may be key factors in influencing the geographical distribution and dispersal of B. tabaci as an invasive species in China.

The Genetic and Physiological Characteristics of the Symbiodinium spp. in the Endemic Anemone Anthopleura Aureoradiata

<p>Photosynthetic dinoflagellates of the genus Symbiodinium form symbiotic relationships with many marine hosts, including cnidarian corals and sea anemones. This partnership is extremely successful in tropical waters leading to a great diversity of coral species and Symbiodinium types. Environmental condition in the tropics are stable, changes to which can lead to destabilization of the symbiotic interactions between the host and symbiont, which in turn can lead to total breakdown of the partnership and expulsion of the symbiont. Temperate symbiotic cnidarian species, especially sea anemones, are less common but locally abundant. Environmental conditions are highly variable with extreme differences in light and temperature. Adaptation to these conditions has led to the success of resilient partnerships, but also to less diversity of Symbiodinium types. This study looked at the relationship between the endemic New Zealand anemone, Anthopleura aureoradiata, and its symbiotic relationship with the Symbiodinium cells it harbours. The aim was to determine why and how this symbiotic relationship is so resilient to the temperate conditions by 1) determining the molecular identity of the Symbiodinium spp. within the anemone, throughout its latitudinal range and through the seasons, and whether any seasonal changes differed between two habitats, the rocky shore and mudflats; 2) comparing the identity of the Symbiodinium spp. in New Zealand with those from four species of anemones from Europe (Cereus pedunculatus, Anthopleura ballii and Anemonia viridis from the south-west of England and Aiptasia mutabilis from Brittany (France)) to establish any differences or similarities between the northern and southern hemispheres; 3) determining whether resilience to environmental conditions is attributed to the Symbiodinium photoprotective mechanisms. A. aureoradiata were collected in early autumn in five sites from the top (Parengarenga Harbour) to the bottom (Stewart Island) of New Zealand for the latitudinal study. Seasonal anemones were collected from a rocky shore in Wellington Harbour (Point Halswell, Kau Bay) and a mudflat at Pauatahanui Inlet. Symbiodinium types were identified to subcladal level using ITS2 sequencing. A low diversity of types was found, with all anemones harbouring algal cells identified as being similar, or identical to, Symbiodinium sp. Mediterranean clade A (Med clade A) and Symbiodinium sp. Amed (Amed). 96.55% of the anemones from the latitudinal study, all the winter anemones, 87.50% of the summer anemones and almost 78% of the autumn anemones harboured Symbiodinium cells most similar or identical to Med clade A. All Symbiodinium sequences from the European anemones also were identified as being similar or identical to Med clade A or Amed, suggesting that the Symbiodinium in A. aureoradiata are likely not endemic. It is not known whether anemones harbour both types simultaneously and whether a change in dominant symbiont type occurs with seasons within anemones by “shuffling”. The photophysiology of the Symbiodinium cells isolated from the anemones was studied using an Imaging-PAM fluorometer whilst being maintained in six light and temperature treatments. The photosynthetic rate of PSII, energy quenching by NPQ, and photosystem recovery were measured to determine whether the Symbiodinium cells had a strong capacity for photoprotection and were able to down-regulate quickly to reduce photodamage to the chloroplast. The main outcome of this study is that the Symbiodinium cells within A. aureoradiata are very effective in protecting themselves against photo-damage by activating an efficient NPQ system. Down-regulation of the quantum efficiency of PSII under high light conditions appeared to cease altogether. Whether this was a true measurement of down-regulation to stop photodamage, or whether these clade A types use an alternative electron transport that bypasses PSII, and can therefore not be measured with the I-PAM fluorometer technique used, needs to be addressed in future studies.</p>

The Genetic and Physiological Characteristics of the Symbiodinium spp. in the Endemic Anemone Anthopleura Aureoradiata

<p>Photosynthetic dinoflagellates of the genus Symbiodinium form symbiotic relationships with many marine hosts, including cnidarian corals and sea anemones. This partnership is extremely successful in tropical waters leading to a great diversity of coral species and Symbiodinium types. Environmental condition in the tropics are stable, changes to which can lead to destabilization of the symbiotic interactions between the host and symbiont, which in turn can lead to total breakdown of the partnership and expulsion of the symbiont. Temperate symbiotic cnidarian species, especially sea anemones, are less common but locally abundant. Environmental conditions are highly variable with extreme differences in light and temperature. Adaptation to these conditions has led to the success of resilient partnerships, but also to less diversity of Symbiodinium types. This study looked at the relationship between the endemic New Zealand anemone, Anthopleura aureoradiata, and its symbiotic relationship with the Symbiodinium cells it harbours. The aim was to determine why and how this symbiotic relationship is so resilient to the temperate conditions by 1) determining the molecular identity of the Symbiodinium spp. within the anemone, throughout its latitudinal range and through the seasons, and whether any seasonal changes differed between two habitats, the rocky shore and mudflats; 2) comparing the identity of the Symbiodinium spp. in New Zealand with those from four species of anemones from Europe (Cereus pedunculatus, Anthopleura ballii and Anemonia viridis from the south-west of England and Aiptasia mutabilis from Brittany (France)) to establish any differences or similarities between the northern and southern hemispheres; 3) determining whether resilience to environmental conditions is attributed to the Symbiodinium photoprotective mechanisms. A. aureoradiata were collected in early autumn in five sites from the top (Parengarenga Harbour) to the bottom (Stewart Island) of New Zealand for the latitudinal study. Seasonal anemones were collected from a rocky shore in Wellington Harbour (Point Halswell, Kau Bay) and a mudflat at Pauatahanui Inlet. Symbiodinium types were identified to subcladal level using ITS2 sequencing. A low diversity of types was found, with all anemones harbouring algal cells identified as being similar, or identical to, Symbiodinium sp. Mediterranean clade A (Med clade A) and Symbiodinium sp. Amed (Amed). 96.55% of the anemones from the latitudinal study, all the winter anemones, 87.50% of the summer anemones and almost 78% of the autumn anemones harboured Symbiodinium cells most similar or identical to Med clade A. All Symbiodinium sequences from the European anemones also were identified as being similar or identical to Med clade A or Amed, suggesting that the Symbiodinium in A. aureoradiata are likely not endemic. It is not known whether anemones harbour both types simultaneously and whether a change in dominant symbiont type occurs with seasons within anemones by “shuffling”. The photophysiology of the Symbiodinium cells isolated from the anemones was studied using an Imaging-PAM fluorometer whilst being maintained in six light and temperature treatments. The photosynthetic rate of PSII, energy quenching by NPQ, and photosystem recovery were measured to determine whether the Symbiodinium cells had a strong capacity for photoprotection and were able to down-regulate quickly to reduce photodamage to the chloroplast. The main outcome of this study is that the Symbiodinium cells within A. aureoradiata are very effective in protecting themselves against photo-damage by activating an efficient NPQ system. Down-regulation of the quantum efficiency of PSII under high light conditions appeared to cease altogether. Whether this was a true measurement of down-regulation to stop photodamage, or whether these clade A types use an alternative electron transport that bypasses PSII, and can therefore not be measured with the I-PAM fluorometer technique used, needs to be addressed in future studies.</p>

Pre- and post-mating reproductive isolation evolve independently during rapid adaptation to high temperature

Ambient temperature is one major ecological factor driving adaptation in natural populations, but its impact on the emergence of new species is not yet clear. Here, we explored the evolution of reproductive isolation during temperature adaptation by exposing 10 replicate Drosophila simulans populations to a hot temperature regime. Within less than 200 generations, both pre- and post-mating reproductive isolation evolved. The altered lipid metabolism of evolved flies also affected the cuticular hydrocarbon (CHCs) profiles. Different CHC profiles could explain the emerged assortative mating between ancestral and evolved populations. Hence, we identified the hallmark of ecological speciation driven by temperature adaptation. While this pre-mating isolation occurred only between ancestral and evolved replicate populations, post-mating reproductive isolation was observed among evolved replicate populations. We propose that epistatic interactions of reproduction-related genes between males and females resulted in adaptive co-evolution. Incompatibilities between different gene combinations favored in each replicate could explain the observed post-mating reproductive isolation. We anticipate that this mutation-order-like speciation from standing genetic variation, a new speciation process, is widespread in nature when highly polygenic traits are involved in adaptation.

Overexpression of the ZmSAMDC Enhances Cold Tolerance in Transgenic Maize (Zea Mays L.)

Maize (Zea mays L.) is a food crop sensitive to low temperatures. Low temperature, as one of the abiotic stress hazards, seriously affects the yield of corn. However, the genetic basis of low-temperature adaptation in maize is still poorly understood. In this study, maize S-adenosylmethionine decarboxylase (SAMDC) was localized on the nucleus. We introduced the SAMDC gene into the excellent maize inbred line variety GSH9901 and used Agrobacterium-mediated transformation to produce cold-tolerant transgenic maize lines. After a 3-year single-location field trial, the contents of polyamine (PA), proline, malondialdehyde, an antioxidant enzyme, and APX in the leaves of transgenic maize plants overexpressing SAMDC were significantly increased, and the introduction of the SAMDC gene was significantly increased the expression of CBFs and cold-related genes.The agronomic traits of overexpression maize changed and the yield traits were significantly improved, but no significant changes were found in plant height, ear length, and shaft thickness.Thus, engineering the SAMDC enzyme is an effective strategy to improve the cold tolerance and value of maize.

Effects of different colorants on service performance for colored asphalt pavement in cold regions

Purpose The service performance for colored asphalt pavement is inevitably affected by the addition of different colorants, especially the challenge of low temperature environment in cold regions. Therefore, the purpose of study is to explore the effects of different colorants on the service performance for colored asphalt pavement and to provide a foundation for improving the applicability of colored asphalt pavement in cold regions. Design/methodology/approach In the study, three kinds of colorants (iron oxide red, iron oxide yellow, iron oxide green) were used to compare the influence of different colorants amounts and different colorants kinds on the service performance for colored asphalt pavement in cold regions. According to the characteristics of low temperature in cold regions, the effects of different colorants on the low temperature performance for colored asphalt pavement were studied. Findings The study shows that different colorants have different effects on the service performance of colored asphalt pavement. The high temperature performance increases with the increase of the colorants amount, but the low temperature performance is opposite. Additionally, the yellow colored asphalt pavement has more advantages of low temperature adaptation than the red and green colored asphalt pavement. Originality/value The study results provide a certain theoretical foundation for the application of colored asphalt pavement in cold regions and have certain value and significance for the further development of colored asphalt pavement.