Non-host and induced resistance in the Taphrina-Arabidopsis model system

Plant pathology is an important area of research for maintaining food security and ecosystem services. Many model systems have been developed to study plant diseases in a more practical environment such as in Arabidopsis thaliana. However, among the ten most important pathogens for research or economy, dimorphic plantassociated yeasts and pathogens of trees are missing. Plants are constantly challenged with a huge number of potential pathogens but the development of disease remains the exception. This complete resistance against a pathogen is termed non-host resistance. Some yeasts are capable to induce resistance in plants against other pathogens. This has potential for biological control measures. Our aim was to develop a model system for studying non-host and induced resistance with the dimorphic birch pathogen Taphrina betulina in Arabidopsis. We studied the mechanistic details conferring non-host resistance to T. betulina by challenging stress signalling mutants with the pathogen and observing symptom development, root growth, fungal establishment in planta and phototoxic stress. The results suggest that type I non-host resistance protects Arabidopsis against Taphrina. This is dependent on the EIN2 protein and mediated through an antagonism between the salicylic acid and jasmonic acid defence signalling pathways. Pre-inoculation with Taphrina betulina surprisingly increased growth of Pseudomonas syringae. We suggest that this is due to the activation of jasmonic acid and ethylene signalling which antagonise the salicylic acid defences required for Pseudomonas resistance. In this study, we showed that Arabidopsis is a non-host for Taphrina betulina and that this pathosystem can be used as a model for studying the mechanisms of nonhost resistance. These insights can give information about possible properties leading to susceptibility in the host. There is a large scope of opportunities for further study into this model

Onset of autumn senescence in High Arctic plants shows similar patterns in natural and experimental snow depth gradients

Predicted changes in snow cover and temperature raise uncertainties about how the beginning and the end of the growing season will shift for Arctic plants. Snowmelt timing and temperature are known to affect the timing of bud burst, but their effects on autumn senescence are less clear. To address this, researchers have examined senescence under natural and experimental environmental gradients. However, these approaches address different aspects of plant responses and the extent to which they can be compared is poorly understood. In this study, we show that the effect of snowmelt timing on the timing of autumn senescence in High Arctic plants is the same between a natural and an experimental gradient in three out of four studied species. While the two approaches mostly produce comparable results, they give in combination greater insight into the phenological responses to predicted climate changes. We also showed that a short warming treatment in autumn delayed senescence by 3.5 days in Dryas octopetala L., which is a 10% extension of the growing season end for this species. Warming treatments have commonly been applied to the whole growing season, but here we show that even isolated autumn warming can be sufficient to affect plant senescence.Peer reviewe

Sub-Arctic alpine Vaccinium vitis-idaea exhibits resistance to strong variation in snowmelt timing and frost exposure, suggesting high resilience under climatic change

In tundra ecosystems, snow cover protects plants from low temperatures in winter and buffers temperature fluctuations in spring. Climate change may lead to reduced snowfall and earlier snowmelt, potentially exposing plants to more frequent and more severe frosts in the future. Frost can cause cell damage and, in combination with high solar irradiance, reduce the photochemical yield of photosystem II (phi(PSII)). Little is known about the natural variation in frost exposure within individual habitats of tundra plant populations and the populations' resilience to this climatic variation. Here, we assessed how natural differences in snowmelt timing affect microclimatic variability of frost exposure in habitats of the evergreenVaccinium vitis-idaeain sub-Arctic alpine Finland and whether this variability affects the extent of cell damage and reduction in phi(PSII). Plants in early melting plots were exposed to more frequent and more severe frost events, and exhibited a more pronounced decrease in phi(PSII), during winter and spring compared to plants in late-melting plots. Snowmelt timing did not have a clear effect on the degree of cell damage as assessed by relative electrolyte leakage. Our results show that sub-Arctic alpineV. vitis-idaeais currently exposed to strong climatic variation on a small spatial scale, similar to that projected to be caused by climate change, without significant resultant damage. We conclude thatV. vitis-idaeais effective in mitigating the effects of large variations in frost exposure caused by differences in snowmelt timing. This suggests thatV. vitis-idaeawill be resilient to the ongoing climate change.Peer reviewe

Effects of Microclimatic Variation of Snowmelt and Temperature on Subarctic-Alpine and Arctic Plants

Climate change will be most pronounced at high latitudes where it will affect autumn, winter and spring disproportionally more than the growing season. Increasing or decreasing precipitation as snow, rising temperature and more frequent freeze-thaw cycles raise uncertainties about how the timing of snowmelt and the length of the growing season will change for northern plants. The timing of plant developmental stages (phenophases) in relation to snowmelt timing is important for avoiding harsh weather conditions in spring and ensuring a long growing season. In this doctoral dissertation, I investigate the effect of snowmelt timing and temperature conditions on plant phenology and plant stress. The first objective was to determine the natural variation in snowmelt timing on a small spatial scale in subarctic-alpine Finland. Such variation in the microclimate is created by the landscape topography and show the range of conditions plant populations are currently adapted to. Snowmelt timing varied by up to seven weeks within a few metres distance, so that early-melting plots were exposed to more frequent and more severe spring freezing events. This implies that plant populations are already exposed to the kind of climatic conditions which would be predicted from climate change. Secondly, I studied how the physiology of Vaccinium vitis-idaea and the phenology of seven subarctic-alpine plant species are affected by this natural variation in microclimate. The higher numbers of freezing events in early-melting plots were related to a higher reduction in the quantum yield of photosystem II (ΦPSII) in V. vitis-idaea, but not to increases in frost damage. This species therefore does not suffer substantial damage from the natural climatic variation in this habitat, implying that in this location it is likely highly resistant to the predicted changes in climate. Differences in snowmelt timing also led to three distinct patterns of phenological timing in subarctic-alpine plant species along the snowmelt gradient. These patterns can raise ideas about the mechanisms underlying the rate of plant development and can help researchers classify past and future phenological responses. Lastly, I compare the effect of natural versus experimental gradients of snowmelt timing on the timing of autumn senescence in High Arctic plants. The results show that the two gradients lead to different conclusions regarding the effect of snowmelt timing on the timing of autumn senescence. Selective warming only in the beginning of autumn had a delaying effect on autumn senescence in Dryas octopetala, despite the short duration of the warming treatment. Previous studies have commonly employed a warming treatment over the entire growing season. The results of this dissertation highlight that we need to integrate different approaches to studying climate change effects on plants. Natural gradients, although often disregarded, can give additional insight into plants’ adaptation to climate variation and therefore complement experiments. Experimental treatments simulating climate change need to be very selective in which period of the plant life cycle they are applied as expected changes in climate strongly depend on the season. Due to the variable sensitivity of different phenophases and plant species to climate and the importance of plants in the ecosystem carbon balance, further detailed research is needed to understand the drivers and mechanisms underlying plant phenology.Ilmastonmuutos vaikuttaa erityisen voimakkaasti arktisiin ja subarktisiin alueisiin maapallolla. Vaikutukset kohdistuvat voimakkaammin syksyyn, talveen ja kevääseen kuin kesään, joka on kasvien kasvukautta. Kohoavan lämpötilan sekä vesi- ja lumisateen muutoksien ja sään vaihteluiden vaikutukset lumen sulamisen ajoittumiseen ja pohjoisten kasvien kasvukauteen tunnetaan puutteellisesti. Kasvien vuodenaikaisten kehitysvaiheiden (silmujen puhkeaminen, lehtien kehittyminen, kukkiminen ja siementen kypsyminen sekä ruskan alkaminen) ajoittuminen suhteessa lumen sulamisen ajankohtaan on kriittistä pohjoisilla alueilla, missä kasvukausi on lyhyt ja ilmasto on äärevä. Tässä väitöstutkimuksessa tarkastelin lumen sulamisen ajankohdan ja lämpötilan vaihtelun vaikutuksia kasvien vuodenaikaiseen kehittymiseen ja kasveille aiheutuvaan stressiin. Tutkin lumen sulamisen ajoittumisen ja lämpötilan pienen mittakaavan vaihtelua metsänrajan yläpuolella Saanatunturilla Pohjois-Suomessa. Lumen sulamisen ajankohta vaihteli seitsemän viikon verran vain muutaman metrin sisällä. Koska lumi suojaa kasveja alhaisilta lämpötiloilta, kasvit altistuivat useammin pakkasille varhain keväällä sulavilla kuin myöhään sulavilla kasvupaikoilla. Siten kasvit ovat jo nykyisin alttiina sellaiselle pienilmaston vaihtelulle, joka vastaa ilmastonmuutoksen seurauksena odotettavia olosuhteita. Tutkin myös, onko lumen varhainen sulaminen stressitekijä puolukalle, ja kuinka lumen sulamisen ajankohta vaikuttaa pohjoisten kasvien vuodenaikaiseen kehitykseen. Tulokset osoittavat, että puolukan fotosynteesikapasiteetti (kyky tuottaa auringon säteilyenergian avulla vedestä ja hiilidioksidista sokereita) laskee keväällä lumen sulamisen voimakkaammin varhain kuin myöhään sulavilla paikoilla. Pakkasvaurioiden esiintymiseen lumen sulamisen ajankohdan ei havaittu vaikuttavan. Tämä osoittaa, että puolukka on hyvin sopeutunut monenlaisiin ilmastollisiin olosuhteisiin. Joillakin lajeilla kasvukauden aikaisten kehitysvaiheiden ajoittumisen huomattiin riippuvan lumen sulamisen ajankohdasta, toisilla lajeilla tätä riippuvuutta sitä vastoin ei havaittu. Eri kasvilajeilla on siten erilaisia mekanismeja sopeutua ilmaston vaihteluun. Kokeellisesti kohetun ilman lämpötilan todettiin vaikuttavan ruskan ajoittumiseen: jo lyhytkestoinen (muutaman viikon kestänyt) lämpötilan kohottaminen viivästytti kellastumisen alkamista lapinvuokon lehdissä

Effects of Microclimatic Variation of Snowmelt and Temperature on Subarctic-Alpine and Arctic Plants

Climate change will be most pronounced at high latitudes where it will affect autumn, winter and spring disproportionally more than the growing season. Increasing or decreasing precipitation as snow, rising temperature and more frequent freeze-thaw cycles raise uncertainties about how the timing of snowmelt and the length of the growing season will change for northern plants. The timing of plant developmental stages (phenophases) in relation to snowmelt timing is important for avoiding harsh weather conditions in spring and ensuring a long growing season. In this doctoral dissertation, I investigate the effect of snowmelt timing and temperature conditions on plant phenology and plant stress. The first objective was to determine the natural variation in snowmelt timing on a small spatial scale in subarctic-alpine Finland. Such variation in the microclimate is created by the landscape topography and show the range of conditions plant populations are currently adapted to. Snowmelt timing varied by up to seven weeks within a few metres distance, so that early-melting plots were exposed to more frequent and more severe spring freezing events. This implies that plant populations are already exposed to the kind of climatic conditions which would be predicted from climate change. Secondly, I studied how the physiology of Vaccinium vitis-idaea and the phenology of seven subarctic-alpine plant species are affected by this natural variation in microclimate. The higher numbers of freezing events in early-melting plots were related to a higher reduction in the quantum yield of photosystem II (ΦPSII) in V. vitis-idaea, but not to increases in frost damage. This species therefore does not suffer substantial damage from the natural climatic variation in this habitat, implying that in this location it is likely highly resistant to the predicted changes in climate. Differences in snowmelt timing also led to three distinct patterns of phenological timing in subarctic-alpine plant species along the snowmelt gradient. These patterns can raise ideas about the mechanisms underlying the rate of plant development and can help researchers classify past and future phenological responses. Lastly, I compare the effect of natural versus experimental gradients of snowmelt timing on the timing of autumn senescence in High Arctic plants. The results show that the two gradients lead to different conclusions regarding the effect of snowmelt timing on the timing of autumn senescence. Selective warming only in the beginning of autumn had a delaying effect on autumn senescence in Dryas octopetala, despite the short duration of the warming treatment. Previous studies have commonly employed a warming treatment over the entire growing season. The results of this dissertation highlight that we need to integrate different approaches to studying climate change effects on plants. Natural gradients, although often disregarded, can give additional insight into plants’ adaptation to climate variation and therefore complement experiments. Experimental treatments simulating climate change need to be very selective in which period of the plant life cycle they are applied as expected changes in climate strongly depend on the season. Due to the variable sensitivity of different phenophases and plant species to climate and the importance of plants in the ecosystem carbon balance, further detailed research is needed to understand the drivers and mechanisms underlying plant phenology.Ilmastonmuutos vaikuttaa erityisen voimakkaasti arktisiin ja subarktisiin alueisiin maapallolla. Vaikutukset kohdistuvat voimakkaammin syksyyn, talveen ja kevääseen kuin kesään, joka on kasvien kasvukautta. Kohoavan lämpötilan sekä vesi- ja lumisateen muutoksien ja sään vaihteluiden vaikutukset lumen sulamisen ajoittumiseen ja pohjoisten kasvien kasvukauteen tunnetaan puutteellisesti. Kasvien vuodenaikaisten kehitysvaiheiden (silmujen puhkeaminen, lehtien kehittyminen, kukkiminen ja siementen kypsyminen sekä ruskan alkaminen) ajoittuminen suhteessa lumen sulamisen ajankohtaan on kriittistä pohjoisilla alueilla, missä kasvukausi on lyhyt ja ilmasto on äärevä. Tässä väitöstutkimuksessa tarkastelin lumen sulamisen ajankohdan ja lämpötilan vaihtelun vaikutuksia kasvien vuodenaikaiseen kehittymiseen ja kasveille aiheutuvaan stressiin. Tutkin lumen sulamisen ajoittumisen ja lämpötilan pienen mittakaavan vaihtelua metsänrajan yläpuolella Saanatunturilla Pohjois-Suomessa. Lumen sulamisen ajankohta vaihteli seitsemän viikon verran vain muutaman metrin sisällä. Koska lumi suojaa kasveja alhaisilta lämpötiloilta, kasvit altistuivat useammin pakkasille varhain keväällä sulavilla kuin myöhään sulavilla kasvupaikoilla. Siten kasvit ovat jo nykyisin alttiina sellaiselle pienilmaston vaihtelulle, joka vastaa ilmastonmuutoksen seurauksena odotettavia olosuhteita. Tutkin myös, onko lumen varhainen sulaminen stressitekijä puolukalle, ja kuinka lumen sulamisen ajankohta vaikuttaa pohjoisten kasvien vuodenaikaiseen kehitykseen. Tulokset osoittavat, että puolukan fotosynteesikapasiteetti (kyky tuottaa auringon säteilyenergian avulla vedestä ja hiilidioksidista sokereita) laskee keväällä lumen sulamisen voimakkaammin varhain kuin myöhään sulavilla paikoilla. Pakkasvaurioiden esiintymiseen lumen sulamisen ajankohdan ei havaittu vaikuttavan. Tämä osoittaa, että puolukka on hyvin sopeutunut monenlaisiin ilmastollisiin olosuhteisiin. Joillakin lajeilla kasvukauden aikaisten kehitysvaiheiden ajoittumisen huomattiin riippuvan lumen sulamisen ajankohdasta, toisilla lajeilla tätä riippuvuutta sitä vastoin ei havaittu. Eri kasvilajeilla on siten erilaisia mekanismeja sopeutua ilmaston vaihteluun. Kokeellisesti kohetun ilman lämpötilan todettiin vaikuttavan ruskan ajoittumiseen: jo lyhytkestoinen (muutaman viikon kestänyt) lämpötilan kohottaminen viivästytti kellastumisen alkamista lapinvuokon lehdissä

Phenological responses to small-scale spatial variation in snowmelt timing reveal compensatory and conservative strategies in subarctic-alpine plants

Background: In tundra ecosystems, the adjustment of phenological events, such as bud burst, to snowmelt timing is crucial to the climatic adaptation of plants. Natural small-scale variations in microclimate potentially enable plant populations to persist in a changing climate.Aims: To assess how plant phenology responds to natural differences in snowmelt timing.Methods: We observed the timing of eight vegetative and reproductive phenophases in seven dwarf-shrub species in relation to differences in snowmelt timing on a small spatial scale in an alpine environment in subarctic Finland.Results: Some species and phenophases showed accelerated development with later snowmelt, thus providing full or partial compensation for the shorter snow-free period. Full compensation resulted in synchronous occurrence of phenophases across the snowmelt gradient. In other species, there was no acceleration of development. The timing of phenophases varied between two consecutive years and two opposing mountain slope aspects.Conclusions: The results have shown three distinct patterns in the timing of phenophases in relation to snowmelt and suggest alternative strategies for adaptation to snowmelt timing. These strategies potentially apply to other species and tundra ecosystems and provide a framework, enabling one to compare and generalise phenological responses to snowmelt timing under different future climate scenarios.Peer reviewe

Soziale Ungleichheit als Schwerpunkt in der Lehrer*innenbildung. Fachdidaktische Überlegungen und Konzepte

Kern F, Gehrmann S, Kastrup V, et al. Soziale Ungleichheit als Schwerpunkt in der Lehrer*innenbildung. Fachdidaktische Überlegungen und Konzepte. PraxisForschungLehrer*innenbildung. Zeitschrift für Schul- und Professionsentwicklung. 2024;6(1):1-30.Im Mittelpunkt des Teilprojekts 3 „Fachdidaktische Professionalisierung unter Berücksichtigung sozialer Ungleichheit und Inklusion“ des Bielefelder Projekts BiProfessional der Qualitätsoffensive Lehrerbildung (Förderkennzeichen: 01JA1908) stand die Frage, wie die Produktion und Reproduktion sozialer Ungleichheit durch Lehrer*innenhandeln und institutionelle Diskriminierung in universitären Veranstaltungen verschiedener Fachdidaktiken in den Blick genommen werden kann, um bei Studierenden durch transdisziplinäre und phasenübergreifende Formate des Forschende Lernens ein reflexiv-kritischen Praxisverständnis zu entwickeln. Dieser Beitrag stellt die Ergebnisse des Projekts dar, indem er zunächst grundlegende Begriffe klärt und in den Kontext allgemeiner sowie fachspezifischer Ungleichheitsphänomene setzt. Anschließend werden Konzepte aus den einzelnen Fachdidaktiken dargestellt, durch die angehende Lehrkräfte eine kritisch-reflexive Distanzierung zu ihren eigenen Wahrnehmungsmustern anstreben und deren potenziellen Zusammenhang mit einer möglichen Reproduktion sozialer Ungleichheit erkennen sollen. Die Ausführungen zeigen, wie Lehramtsstudierenden bewusst gemacht werden kann, auf welche Weise Schule und Unterricht als (Re-)Produktionsort und sie selbst als Lehrkräfte als Reproduktionsagent*innen von Ungleichheit eine zentrale Rolle spielen und dass eine entsprechend kritisch-reflexive Distanzierung gegenüber den eigenen Wahrnehmungsmustern eine notwendige Ressource zu deren Bearbeitung darstellt

Soziale Ungleichheit als Schwerpunkt in der Lehrer*innenbildung: Fachdidaktische Überlegungen und Konzepte

Im Mittelpunkt des Teilprojekts 3 „Fachdidaktische Professionalisierung unter Berücksichtigung sozialer Ungleichheit und Inklusion“ des Bielefelder Projekts BiProfessional der Qualitätsoffensive Lehrerbildung (Förderkennzeichen: 01JA1908) stand die Frage, wie die Produktion und Reproduktion sozialer Ungleichheit durch Lehrer*innenhandeln und institutionelle Diskriminierung in universitären Veranstaltungen verschiedener Fachdidaktiken in den Blick genommen werden kann, um bei Studierenden durch transdisziplinäre und phasenübergreifende Formate des Forschende Lernens ein reflexiv-kritischen Praxisverständnis zu entwickeln. Dieser Beitrag stellt die Ergebnisse des Projekts dar, indem er zunächst grundlegende Begriffe klärt und in den Kontext allgemeiner sowie fachspezifischer Ungleichheitsphänomene setzt. Anschließend werden Konzepte aus den einzelnen Fachdidaktiken dargestellt, durch die angehende Lehrkräfte eine kritisch-reflexive Distanzierung zu ihren eigenen Wahrnehmungsmustern anstreben und deren potenziellen Zusammenhang mit einer möglichen Reproduktion sozialer Ungleichheit erkennen sollen. Die Ausführungen zeigen, wie Lehramtsstudierenden bewusst gemacht werden kann, auf welche Weise Schule und Unterricht als (Re-)Produktionsort und sie selbst als Lehrkräfte als Reproduktionsagent*innen von Ungleichheit eine zentrale Rolle spielen und dass eine entsprechend kritisch-reflexive Distanzierung gegenüber den eigenen Wahrnehmungsmustern eine notwendige Ressource zu deren Bearbeitung darstellt