Summary Understanding photosynthesis in natural, dynamic light environments requires knowledge of... more Summary Understanding photosynthesis in natural, dynamic light environments requires knowledge of long‐term acclimation, short‐term responses, and their mechanistic interactions. To approach the latter, we systematically determined and characterized light‐environmental effects on thylakoid ion transport‐mediated short‐term responses during light fluctuations. For this, Arabidopsis thaliana wild‐type and mutants of the Cl− channel VCCN1 and the K+ exchange antiporter KEA3 were grown under eight different light environments and characterized for photosynthesis‐associated parameters and factors in steady state and during light fluctuations. For a detailed characterization of selected light conditions, we monitored ion flux dynamics at unprecedented high temporal resolution by a modified spectroscopy approach. Our analyses reveal that daily light intensity sculpts photosynthetic capacity as a main acclimatory driver with positive and negative effects on the function of KEA3 and VCCN1 du...
As climate changes, maintenance of yield stability requires efficient selection for drought toler... more As climate changes, maintenance of yield stability requires efficient selection for drought tolerance. Drought-tolerant cultivars have been successfully but slowly bred by yield-based selection in arid environments. Marker-assisted selection accelerates breeding but is less effective for polygenic traits. Therefore, we investigated a selection based on phenotypic markers derived from automatic phenotyping systems. Our trial comprised 64 potato genotypes previously characterised for drought tolerance in ten trials representing Central European drought stress scenarios. In two trials, an automobile LIDAR system continuously monitored shoot development under optimal (C) and reduced (S) water supply. Six 3D images per day provided time courses of plant height (PH), leaf area (A3D), projected leaf area (A2D) and leaf angle (LA). The evaluation workflow employed logistic regression to estimate initial slope (k), inflection point (Tm) and maximum (Mx) for the growth curves of PH and A2D. G...
Main conclusion Higher acclimated freezing tolerance improved winter survival, but reduced reprod... more Main conclusion Higher acclimated freezing tolerance improved winter survival, but reduced reproductive fitness of Arabidopsis thaliana accessions under field and controlled conditions. Abstract Low temperature is one of the most important abiotic factors influencing plant fitness and geographical distribution. In addition, cold stress is known to influence crop yield and is therefore of great economic importance. Increased freezing tolerance can be acquired by the process of cold acclimation, but this may be associated with a fitness cost. To assess the influence of cold stress on the fitness of plants, long-term field trials over 5 years were performed with six natural accessions of Arabidopsis thaliana ranging from very tolerant to very sensitive to freezing. Fitness parameters, as seed yield and 1000 seed mass, were measured and correlation analyses with temperature and freezing tolerance data performed. The results were compared with fitness parameters from controlled chamber e...
Drought represents a major abiotic stress factor negatively affecting growth, yield and tuber qua... more Drought represents a major abiotic stress factor negatively affecting growth, yield and tuber quality of potatoes. Quantitative trait locus (QTL) analyses were performed in cultivated potatoes for drought tolerance index DRYM (deviation of relative starch yield from the experimental median), tuber starch content, tuber starch yield, tuber fresh weight, selected transcripts and metabolites under control and drought stress conditions. Eight genomic regions of major interest for drought tolerance were identified, three representing standalone DRYM QTL. Candidate genes, e.g., from signaling pathways for ethylene, abscisic acid and brassinosteroids, and genes encoding cell wall remodeling enzymes were identified within DRYM QTL. Co-localizations of DRYM QTL and QTL for tuber starch content, tuber starch yield and tuber fresh weight with underlying genes of the carbohydrate metabolism were observed. Overlaps of DRYM QTL with metabolite QTL for ribitol or galactinol may indicate trade-offs...
Metabolite profiling techniques based on the mass-spectrometer allow a comprehensive overview ove... more Metabolite profiling techniques based on the mass-spectrometer allow a comprehensive overview over the plant’s metabolism to the combination of drought with co-occurring abiotic stresses. The picture obtained will be affected by the decisions on sampling and the interaction between stress and the plant, which can range from a priming effect of the stress to the death of the plant. Metabolite profiling is predominantly performed on plant leaves or fruits due to their easy accessibility and their crucial role for plant production, fitness, and yield. Roots and tubers are studied less although they encounter soilborne stresses, especially salt stress, first. Metabolite profiles are highly affected by the timing of the sampling with respect to the plant’s diurnal rhythm, its developmental stage, and the combination of duration and extent of stress. Mild, short-term stress may act as a signal triggering adjustments in the plant’s metabolism, thus priming the organism to encounter later, ...
Understanding photosynthesis in natural, dynamic light environments requires knowledge of long-te... more Understanding photosynthesis in natural, dynamic light environments requires knowledge of long-term acclimation, short-term responses, and their mechanistic interactions. However, the latter is poorly understood. We systematically determined light-environment effects on the thylakoid ion transport-mediated responses of photosynthesis during light fluctuations. Our analyses reveal daily light intensity as the main acclimatory driver that sculps photosynthetic capacity and thereby governs the activities of the thylakoid Cl- channel VCCN1 and the H+/K+ exchanger KEA3 during high light phases. We uncover high zeaxanthin accumulation as a response to fluctuating light environments, which delays the relaxation of energy dependent quenching (qE). KEA3 partly suppresses zeaxanthin accumulation over the day and thereby further accelerates the response of photosynthesis to low light periods. In summary, both light-environment factors, intensity and variability, modulate the function of thylak...
Potato is regarded as drought sensitive and most vulnerable to climate changes. Its cultivation i... more Potato is regarded as drought sensitive and most vulnerable to climate changes. Its cultivation in drought prone regions or under conditions of more frequent drought periods, especially in subtropical areas, requires intensive research to improve drought tolerance in order to guarantee high yields under limited water supplies. A candidate gene approach was used to develop functional simple sequence repeat (SSR) markers for association studies in potato with the aim to enhance breeding for drought tolerance. SSR primer combinations, mostly surrounding interrupted complex and compound repeats, were derived from 103 candidate genes for drought tolerance. Validation of the SSRs was performed in an association panel representing 34 mainly starch potato cultivars. Seventy-five out of 154 SSR primer combinations (49%) resulted in polymorphic, highly reproducible banding patterns with polymorphic information content (PIC) values between 0.11 and 0.90. Five SSR markers identified allelic dif...
SummaryPotato (Solanum tuberosum L.) is one of the most important food crops worldwide. Current p... more SummaryPotato (Solanum tuberosum L.) is one of the most important food crops worldwide. Current potato varieties are highly susceptible to drought stress. In view of global climate change, selection of cultivars with improved drought tolerance and high yield potential is of paramount importance. Drought tolerance breeding of potato is currently based on direct selection according to yield and phenotypic traits and requires multiple trials under drought conditions. Marker‐assisted selection (MAS) is cheaper, faster and reduces classification errors caused by noncontrolled environmental effects. We analysed 31 potato cultivars grown under optimal and reduced water supply in six independent field trials. Drought tolerance was determined as tuber starch yield. Leaf samples from young plants were screened for preselected transcript and nontargeted metabolite abundance using qRT‐PCR and GC‐MS profiling, respectively. Transcript marker candidates were selected from a published RNA‐Seq data...
Systems responses to drought stress of four potato reference cultivars with differential drought ... more Systems responses to drought stress of four potato reference cultivars with differential drought tolerance (Solanum tuberosum L.) were investigated by metabolome profiling and RNA-Sequencing. Systems analysis was based on independent field and greenhouse trials. Robust differential drought responses across all cultivars under both conditions comprised changes proline, raffinose, galactinol, arabitol, arabinonic acid, chlorogenic acid, and 102 transcript levels. The encoded genes contained a high proportion of heat shock proteins and proteins with signaling or regulatory functions, e.g. a homolog of abscisic acid receptor PYL4. Constitutive differences of the tolerant compared to the sensitive cultivars included arbutin, octopamine, ribitol, and 248 transcripts. The gene products of many of these transcripts were pathogen response related, such as receptor kinases, or regulatory proteins e.g. a homolog of the Arabidopsis FOUR LIPS MYB-regulator of stomatal cell proliferation. Functio...
ABSTRACT Rice (Oryza sativa) is less frequently used in basic research than Arabidopsis, although... more ABSTRACT Rice (Oryza sativa) is less frequently used in basic research than Arabidopsis, although rice is a valuable model system for many monocot crops and possesses a high genetic variability in physiologically as well as agriculturally relevant features such as abiotic stress tolerance, nutrient efficiency and flower time control. A reason is the seemingly difficult cultivation of rice outside the rice production area. This review aims to assist newcomers to the field to develop cultivation protocols for their local controlled environment. The main challenges are high light demands, photoperiodicity and low micronutrient efficiency. The nutrient efficiency problem can be overcome by adding micronutrient fertiliser to potting substrates and keeping the soil waterlogged to increase micronutrient availability and mobility. Cultivation of rice on adjusted hydroponic solutions with high iron concentration provides the basis for successful heavy isotope labelling. Many rice cultivars need high light intensities in combination with short-day conditions to complete their life cycle. However, some photoperiod-insensitive cultivars will flower even under relatively low light intensities. In highly photoperiod-sensitive cultivars, like Nipponbare, flowering can be induced by a limited period of short-day treatment in the sensitive period, after which the cultivation can be continued in long-day conditions. The life cycle of many cultivars is completed in 90 to 120 days, its length being thus comparable to Arabidopsis and shorter than in other cereals. In conclusion, with the right cultivation technique, rice is an amiable model species for researchers beyond the rice area too.
Climate models predict an increased likelihood of seasonal droughts for many areas of the world. ... more Climate models predict an increased likelihood of seasonal droughts for many areas of the world. Breeding for drought tolerance could be accelerated by marker-assisted selection. As a basis for marker identification, we studied the genetic variance, predictability of field performance and potential costs of tolerance in potato (Solanum tuberosum L.). Potato produces high calories per unit of water invested, but is drought-sensitive. In 14 independent pot or field trials, 34 potato cultivars were grown under optimal and reduced water supply to determine starch yield. In an artificial dataset, we tested several stress indices for their power to distinguish tolerant and sensitive genotypes independent of their yield potential. We identified the deviation of relative starch yield from the experimental median (DRYM) as the most efficient index. DRYM corresponded qualitatively to the partial least square model-based metric of drought stress tolerance in a stress effect model. The DRYM ide...
Quantitative proteomics by metabolic labeling has a high impact on the growing field of plant sys... more Quantitative proteomics by metabolic labeling has a high impact on the growing field of plant systems biology. SILAC has been pioneered and optimized for plant cell culture systems allowing for SILAC-based quantitative experiments in specialized experimental setups. In comparison to other model organisms, the application of SILAC to whole plants is challenging. As autotrophic organisms, plants under their natural growth conditions can hardly be fully labeled with stable isotope-coded amino acids. The metabolic labeling with inorganic nitrogen is therefore the method of choice for most whole-plant physiological questions. Plants can easily metabolize different inorganic nitrogen isotopes. The incorporation of the labeled inorganic nitrogen then results in proteins and metabolites with distinct molecular mass, which can be detected on a mass spectrometer. In comparative quantitative experiments, similarly as in SILAC experiments, treated and untreated samples are differentially labeled by nitrogen isotopes and jointly processed, thereby minimizing sample-to-sample variation. In recent years, heavy nitrogen labeling has become a widely used strategy in quantitative proteomics and novel approaches were developed for metabolite identification. Here we present a typical hydroponics setup, the workflow for processing of samples, mass spectrometry and data analysis for large-scale metabolic labeling experiments of whole plants.
Summary Understanding photosynthesis in natural, dynamic light environments requires knowledge of... more Summary Understanding photosynthesis in natural, dynamic light environments requires knowledge of long‐term acclimation, short‐term responses, and their mechanistic interactions. To approach the latter, we systematically determined and characterized light‐environmental effects on thylakoid ion transport‐mediated short‐term responses during light fluctuations. For this, Arabidopsis thaliana wild‐type and mutants of the Cl− channel VCCN1 and the K+ exchange antiporter KEA3 were grown under eight different light environments and characterized for photosynthesis‐associated parameters and factors in steady state and during light fluctuations. For a detailed characterization of selected light conditions, we monitored ion flux dynamics at unprecedented high temporal resolution by a modified spectroscopy approach. Our analyses reveal that daily light intensity sculpts photosynthetic capacity as a main acclimatory driver with positive and negative effects on the function of KEA3 and VCCN1 du...
As climate changes, maintenance of yield stability requires efficient selection for drought toler... more As climate changes, maintenance of yield stability requires efficient selection for drought tolerance. Drought-tolerant cultivars have been successfully but slowly bred by yield-based selection in arid environments. Marker-assisted selection accelerates breeding but is less effective for polygenic traits. Therefore, we investigated a selection based on phenotypic markers derived from automatic phenotyping systems. Our trial comprised 64 potato genotypes previously characterised for drought tolerance in ten trials representing Central European drought stress scenarios. In two trials, an automobile LIDAR system continuously monitored shoot development under optimal (C) and reduced (S) water supply. Six 3D images per day provided time courses of plant height (PH), leaf area (A3D), projected leaf area (A2D) and leaf angle (LA). The evaluation workflow employed logistic regression to estimate initial slope (k), inflection point (Tm) and maximum (Mx) for the growth curves of PH and A2D. G...
Main conclusion Higher acclimated freezing tolerance improved winter survival, but reduced reprod... more Main conclusion Higher acclimated freezing tolerance improved winter survival, but reduced reproductive fitness of Arabidopsis thaliana accessions under field and controlled conditions. Abstract Low temperature is one of the most important abiotic factors influencing plant fitness and geographical distribution. In addition, cold stress is known to influence crop yield and is therefore of great economic importance. Increased freezing tolerance can be acquired by the process of cold acclimation, but this may be associated with a fitness cost. To assess the influence of cold stress on the fitness of plants, long-term field trials over 5 years were performed with six natural accessions of Arabidopsis thaliana ranging from very tolerant to very sensitive to freezing. Fitness parameters, as seed yield and 1000 seed mass, were measured and correlation analyses with temperature and freezing tolerance data performed. The results were compared with fitness parameters from controlled chamber e...
Drought represents a major abiotic stress factor negatively affecting growth, yield and tuber qua... more Drought represents a major abiotic stress factor negatively affecting growth, yield and tuber quality of potatoes. Quantitative trait locus (QTL) analyses were performed in cultivated potatoes for drought tolerance index DRYM (deviation of relative starch yield from the experimental median), tuber starch content, tuber starch yield, tuber fresh weight, selected transcripts and metabolites under control and drought stress conditions. Eight genomic regions of major interest for drought tolerance were identified, three representing standalone DRYM QTL. Candidate genes, e.g., from signaling pathways for ethylene, abscisic acid and brassinosteroids, and genes encoding cell wall remodeling enzymes were identified within DRYM QTL. Co-localizations of DRYM QTL and QTL for tuber starch content, tuber starch yield and tuber fresh weight with underlying genes of the carbohydrate metabolism were observed. Overlaps of DRYM QTL with metabolite QTL for ribitol or galactinol may indicate trade-offs...
Metabolite profiling techniques based on the mass-spectrometer allow a comprehensive overview ove... more Metabolite profiling techniques based on the mass-spectrometer allow a comprehensive overview over the plant’s metabolism to the combination of drought with co-occurring abiotic stresses. The picture obtained will be affected by the decisions on sampling and the interaction between stress and the plant, which can range from a priming effect of the stress to the death of the plant. Metabolite profiling is predominantly performed on plant leaves or fruits due to their easy accessibility and their crucial role for plant production, fitness, and yield. Roots and tubers are studied less although they encounter soilborne stresses, especially salt stress, first. Metabolite profiles are highly affected by the timing of the sampling with respect to the plant’s diurnal rhythm, its developmental stage, and the combination of duration and extent of stress. Mild, short-term stress may act as a signal triggering adjustments in the plant’s metabolism, thus priming the organism to encounter later, ...
Understanding photosynthesis in natural, dynamic light environments requires knowledge of long-te... more Understanding photosynthesis in natural, dynamic light environments requires knowledge of long-term acclimation, short-term responses, and their mechanistic interactions. However, the latter is poorly understood. We systematically determined light-environment effects on the thylakoid ion transport-mediated responses of photosynthesis during light fluctuations. Our analyses reveal daily light intensity as the main acclimatory driver that sculps photosynthetic capacity and thereby governs the activities of the thylakoid Cl- channel VCCN1 and the H+/K+ exchanger KEA3 during high light phases. We uncover high zeaxanthin accumulation as a response to fluctuating light environments, which delays the relaxation of energy dependent quenching (qE). KEA3 partly suppresses zeaxanthin accumulation over the day and thereby further accelerates the response of photosynthesis to low light periods. In summary, both light-environment factors, intensity and variability, modulate the function of thylak...
Potato is regarded as drought sensitive and most vulnerable to climate changes. Its cultivation i... more Potato is regarded as drought sensitive and most vulnerable to climate changes. Its cultivation in drought prone regions or under conditions of more frequent drought periods, especially in subtropical areas, requires intensive research to improve drought tolerance in order to guarantee high yields under limited water supplies. A candidate gene approach was used to develop functional simple sequence repeat (SSR) markers for association studies in potato with the aim to enhance breeding for drought tolerance. SSR primer combinations, mostly surrounding interrupted complex and compound repeats, were derived from 103 candidate genes for drought tolerance. Validation of the SSRs was performed in an association panel representing 34 mainly starch potato cultivars. Seventy-five out of 154 SSR primer combinations (49%) resulted in polymorphic, highly reproducible banding patterns with polymorphic information content (PIC) values between 0.11 and 0.90. Five SSR markers identified allelic dif...
SummaryPotato (Solanum tuberosum L.) is one of the most important food crops worldwide. Current p... more SummaryPotato (Solanum tuberosum L.) is one of the most important food crops worldwide. Current potato varieties are highly susceptible to drought stress. In view of global climate change, selection of cultivars with improved drought tolerance and high yield potential is of paramount importance. Drought tolerance breeding of potato is currently based on direct selection according to yield and phenotypic traits and requires multiple trials under drought conditions. Marker‐assisted selection (MAS) is cheaper, faster and reduces classification errors caused by noncontrolled environmental effects. We analysed 31 potato cultivars grown under optimal and reduced water supply in six independent field trials. Drought tolerance was determined as tuber starch yield. Leaf samples from young plants were screened for preselected transcript and nontargeted metabolite abundance using qRT‐PCR and GC‐MS profiling, respectively. Transcript marker candidates were selected from a published RNA‐Seq data...
Systems responses to drought stress of four potato reference cultivars with differential drought ... more Systems responses to drought stress of four potato reference cultivars with differential drought tolerance (Solanum tuberosum L.) were investigated by metabolome profiling and RNA-Sequencing. Systems analysis was based on independent field and greenhouse trials. Robust differential drought responses across all cultivars under both conditions comprised changes proline, raffinose, galactinol, arabitol, arabinonic acid, chlorogenic acid, and 102 transcript levels. The encoded genes contained a high proportion of heat shock proteins and proteins with signaling or regulatory functions, e.g. a homolog of abscisic acid receptor PYL4. Constitutive differences of the tolerant compared to the sensitive cultivars included arbutin, octopamine, ribitol, and 248 transcripts. The gene products of many of these transcripts were pathogen response related, such as receptor kinases, or regulatory proteins e.g. a homolog of the Arabidopsis FOUR LIPS MYB-regulator of stomatal cell proliferation. Functio...
ABSTRACT Rice (Oryza sativa) is less frequently used in basic research than Arabidopsis, although... more ABSTRACT Rice (Oryza sativa) is less frequently used in basic research than Arabidopsis, although rice is a valuable model system for many monocot crops and possesses a high genetic variability in physiologically as well as agriculturally relevant features such as abiotic stress tolerance, nutrient efficiency and flower time control. A reason is the seemingly difficult cultivation of rice outside the rice production area. This review aims to assist newcomers to the field to develop cultivation protocols for their local controlled environment. The main challenges are high light demands, photoperiodicity and low micronutrient efficiency. The nutrient efficiency problem can be overcome by adding micronutrient fertiliser to potting substrates and keeping the soil waterlogged to increase micronutrient availability and mobility. Cultivation of rice on adjusted hydroponic solutions with high iron concentration provides the basis for successful heavy isotope labelling. Many rice cultivars need high light intensities in combination with short-day conditions to complete their life cycle. However, some photoperiod-insensitive cultivars will flower even under relatively low light intensities. In highly photoperiod-sensitive cultivars, like Nipponbare, flowering can be induced by a limited period of short-day treatment in the sensitive period, after which the cultivation can be continued in long-day conditions. The life cycle of many cultivars is completed in 90 to 120 days, its length being thus comparable to Arabidopsis and shorter than in other cereals. In conclusion, with the right cultivation technique, rice is an amiable model species for researchers beyond the rice area too.
Climate models predict an increased likelihood of seasonal droughts for many areas of the world. ... more Climate models predict an increased likelihood of seasonal droughts for many areas of the world. Breeding for drought tolerance could be accelerated by marker-assisted selection. As a basis for marker identification, we studied the genetic variance, predictability of field performance and potential costs of tolerance in potato (Solanum tuberosum L.). Potato produces high calories per unit of water invested, but is drought-sensitive. In 14 independent pot or field trials, 34 potato cultivars were grown under optimal and reduced water supply to determine starch yield. In an artificial dataset, we tested several stress indices for their power to distinguish tolerant and sensitive genotypes independent of their yield potential. We identified the deviation of relative starch yield from the experimental median (DRYM) as the most efficient index. DRYM corresponded qualitatively to the partial least square model-based metric of drought stress tolerance in a stress effect model. The DRYM ide...
Quantitative proteomics by metabolic labeling has a high impact on the growing field of plant sys... more Quantitative proteomics by metabolic labeling has a high impact on the growing field of plant systems biology. SILAC has been pioneered and optimized for plant cell culture systems allowing for SILAC-based quantitative experiments in specialized experimental setups. In comparison to other model organisms, the application of SILAC to whole plants is challenging. As autotrophic organisms, plants under their natural growth conditions can hardly be fully labeled with stable isotope-coded amino acids. The metabolic labeling with inorganic nitrogen is therefore the method of choice for most whole-plant physiological questions. Plants can easily metabolize different inorganic nitrogen isotopes. The incorporation of the labeled inorganic nitrogen then results in proteins and metabolites with distinct molecular mass, which can be detected on a mass spectrometer. In comparative quantitative experiments, similarly as in SILAC experiments, treated and untreated samples are differentially labeled by nitrogen isotopes and jointly processed, thereby minimizing sample-to-sample variation. In recent years, heavy nitrogen labeling has become a widely used strategy in quantitative proteomics and novel approaches were developed for metabolite identification. Here we present a typical hydroponics setup, the workflow for processing of samples, mass spectrometry and data analysis for large-scale metabolic labeling experiments of whole plants.
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Papers by Karin Köhl