Explore the vast range of titles available.

Background Plants are continuously exposed to changing environmental conditions and biotic attacks that affect plant growth. In crops, the inability to respond appropriately to stress has strong detrimental effects on agricultural production and yield. Ca 2+ signalling plays a fundamental role in the response of plants to most abiotic and biotic stresses. However, research on stimulus-specific Ca 2+ signals has mostly been pursued in Arabidopsis thaliana , while in other species these events are little investigated . Results In this study, we introduced the Ca 2+ reporter-encoding gene APOAEQUORIN into the crop species barley ( Hordeum vulgare ). Measurements of the dynamic changes in [Ca 2+ ] cyt in response to various stimuli such as NaCl, mannitol, H 2 O 2 , and flagellin 22 (flg22) revealed the occurrence of dose- as well as tissue-dependent [Ca 2+ ] cyt transients. Moreover, the Ca 2+ signatures were unique for each stimulus, suggesting the involvement of different Ca 2+ signalling components in the corresponding stress response. Alongside, the barley Ca 2+ signatures were compared to those produced by the phylogenetically distant model plant Arabidopsis. Notable differences in temporal kinetics and dose responses were observed, implying species-specific differences in stress response mechanisms. The plasma membrane Ca 2+ channel blocker La 3+ strongly inhibited the [Ca 2+ ] cyt response to all tested stimuli, indicating a critical role of extracellular Ca 2+ in the induction of stress-associated Ca 2+ signatures in barley. Moreover, by analysing spatio-temporal dynamics of the [Ca 2+ ] cyt transients along the developmental gradient of the barley leaf blade we demonstrate that different parts of the barley leaf show quantitative differences in [Ca 2+ ] cyt transients in response to NaCl and H 2 O 2 . There were only marginal differences in the response to flg22, indicative of developmental stage-dependent Ca 2+ responses specifically to NaCl and H 2 O 2 . Conclusion This study reveals tissue-specific Ca 2+ signals with stimulus-specific kinetics in the crop species barley, as well as quantitative differences along the barley leaf blade. A number of notable differences to the model plants Arabidopsis may be linked to different stimulus sensitivity. These transgenic barley reporter lines thus present a valuable tool to further analyse mechanisms of Ca 2+ signalling in this crop and to gain insights into the variation of Ca 2+ -dependent stress responses between stress-susceptible and -resistant species.

Background Ca 2+ and H 2 O 2 are second messengers that regulate a wide range of cellular events in response to different environmental and developmental cues. In plants, stress-induced H 2 O 2 has been shown to initiate characteristic Ca 2+ signatures; however, a clear picture of the molecular connection between H 2 O 2 -induced Ca 2+ signals and H 2 O 2 -induced cellular responses is missing, particularly in cereal crops such as barley. Here, we employed RNA-seq analyses to identify transcriptome changes in roots and leaves of barley after H 2 O 2 treatment under conditions that inhibited the formation of cytosolic Ca 2+ transients. To that end, plasma membrane Ca 2+ channels were blocked by LaCl 3 application prior to stimulation of barley tissues with H 2 O 2 . Results We examined the expression patterns of 4246 genes that had previously been shown to be differentially expressed upon H 2 O 2 application. Here, we further compared their expression between H 2 O 2 and LaCl 3  + H 2 O 2 treatment. Genes showing expression patterns different to the previous study were considered to be Ca 2+ -dependent H 2 O 2 -responsive genes. These genes, numbering 331 in leaves and 1320 in roots, could be classified in five and four clusters, respectively. Expression patterns of several genes from each cluster were confirmed by RT-qPCR. We furthermore performed a network analysis to identify potential regulatory paths from known Ca 2+ -related genes to the newly identified Ca 2+ -dependent H 2 O 2 responsive genes, using the recently described Stress Knowledge Map. This analysis indicated several transcription factors as key points of the responses mediated by the cross-talk between H 2 O 2 and Ca 2+ . Conclusion Our study indicates that about 70% of the H 2 O 2 -responsive genes in barley roots require a transient increase in cytosolic Ca 2+ concentrations for alteration in their transcript abundance, whereas in leaves, the Ca 2+ dependency was much lower at about 33%. Targeted gene analysis and pathway modeling identified not only known components of the Ca 2+ signaling cascade in plants but also genes that are not yet connected to stimuli-associated signaling. Potential key transcription factors identified in this study can be further analyzed in barley and other crops to ultimately disentangle the underlying mechanisms of H 2 O 2 -associated signal transduction mechanisms. This could aid breeding for improved stress resistance to optimize performance and productivity under increasing climate challenges.

In cereal crops, such as barley ( Hordeum vulgare L.), the ability to appropriately respond to environmental cues is an important factor for yield stability and thus for agricultural production. Reactive oxygen species (ROS), such as hydrogen peroxide (H 2 O 2 ), are key components of signal transduction cascades involved in plant adaptation to changing environmental conditions. H 2 O 2 -mediated stress responses include the modulation of expression of stress-responsive genes required to cope with different abiotic and biotic stresses. Despite its importance, knowledge of the effects of H 2 O 2 on the barley transcriptome is still scarce. In this study, we identified global transcriptomic changes induced after application of 10 mM H 2 O 2 to five-day-old barley plants. In total, 1883 and 1001 differentially expressed genes (DEGs) were identified in roots and leaves, respectively. Most of these DEGs were organ-specific, with only 209 DEGs commonly regulated and 37 counter-regulated between both plant parts. A GO term analysis further confirmed that different processes were affected in roots and leaves. It revealed that DEGs in leaves mostly comprised genes associated with hormone signaling, response to H 2 O 2 and abiotic stresses. This includes many transcriptions factors and small heat shock proteins. DEGs in roots mostly comprised genes linked to crucial aspects of H 2 O 2 catabolism and oxidant detoxification, glutathione metabolism, as well as cell wall modulation. These categories include many peroxidases and glutathione transferases. As with leaves, the H 2 O 2 response category in roots contains small heat shock proteins, however, mostly different members of this family were affected and they were all regulated in the opposite direction in the two plant parts. Validation of the expression of the selected commonly regulated DEGs by qRT-PCR was consistent with the RNA-seq data. The data obtained in this study provide an insight into the molecular mechanisms of oxidative stress responses in barley, which might also play a role upon other stresses that induce oxidative bursts.

Calmodulin (CaM) is a ubiquitous sensor/transducer of calcium signals in eukaryotic organisms. While CaM mediated calcium regulation of cytosolic processes is well established, there is growing evidence for the inclusion of organelles such as chloroplasts, mitochondria and peroxisomes into the calcium/calmodulin regulation network. A number of CaM-binding proteins have been identified in these organelles and processes such as protein import into chloroplasts and mitochondria have been shown to be governed by CaM regulation. What have been missing to date are the mediators of this regulation since no CaM or calmodulin-like protein (CML) has been identified in any of these organelles. Here we show that two Arabidopsis CMLs, AtCML3 and AtCML30, are localized in peroxisomes and mitochondria, respectively. AtCML3 is targeted via an unusual C-terminal PTS1-like tripeptide while AtCML30 utilizes an N-terminal, non-cleavable transit peptide. Both proteins possess the typical structure of CaMs, with two pairs of EF-hand motifs separated by a short linker domain. They furthermore display common characteristics, such as calcium-dependent alteration of gel mobility and calcium-dependent exposure of a hydrophobic surface. This indicates that they can function in a similar manner as canonical CaMs. The presence of close homologues to AtCML3 and AtCML30 in other plants further indicates that organellar targeting of these CMLs is not a specific feature of Arabidopsis . The identification of peroxisomal and mitochondrial CMLs is an important step in the understanding how these organelles are integrated into the cellular calcium/calmodulin signaling pathways.

The import of nuclear-encoded proteins into chloroplasts is tightly controlled on both sides of the envelope membranes. Regulatory circuits include redox-control as well as calcium-regulation, with calmodulin being the likely mediator of the latter. Using affinity-chromatography on calmodulin-agarose, we could identify the inner envelope translocon component Tic32 as the predominant calmodulin-binding protein of this membrane. Calmodulin-binding assays corroborate the interaction for heterologously expressed as well as native Tic32. The interaction is calcium-dependent and is mediated by a calmodulin-binding domain between Leu-296 and Leu-314 close to the C-proximal end of the pea Tic32. We furthermore could establish Tic32 as a bona fide NADPH-dependent dehydrogenase. NADPH but not NADH or NADP⁺ affects the interaction of Tic110 with Tic32 as well as Tic62. At the same time, dehydrogenase activity of Tic32 is affected by calmodulin. In particular, binding of NADPH and calmodulin to Tic32 appear to be mutually exclusive. These results suggest that redox modulation and calcium regulation of chloroplast protein import convene at the Tic translocon and that both could be mediated by Tic32.

Plants are continuously exposed to changing environmental conditions and biotic attacks that affect plant growth. In crops, the inability to respond appropriately to stress has strong detrimental effects on agricultural production and yield. Ca.sup.2+ signalling plays a fundamental role in the response of plants to most abiotic and biotic stresses. However, research on stimulus-specific Ca.sup.2+ signals has mostly been pursued in Arabidopsis thaliana, while in other species these events are little investigated . In this study, we introduced the Ca.sup.2+ reporter-encoding gene APOAEQUORIN into the crop species barley (Hordeum vulgare). Measurements of the dynamic changes in [Ca.sup.2+].sub.cyt in response to various stimuli such as NaCl, mannitol, H.sub.2O.sub.2, and flagellin 22 (flg22) revealed the occurrence of dose- as well as tissue-dependent [Ca.sup.2+].sub.cyt transients. Moreover, the Ca.sup.2+ signatures were unique for each stimulus, suggesting the involvement of different Ca.sup.2+ signalling components in the corresponding stress response. Alongside, the barley Ca.sup.2+ signatures were compared to those produced by the phylogenetically distant model plant Arabidopsis. Notable differences in temporal kinetics and dose responses were observed, implying species-specific differences in stress response mechanisms. The plasma membrane Ca.sup.2+ channel blocker La.sup.3+ strongly inhibited the [Ca.sup.2+].sub.cyt response to all tested stimuli, indicating a critical role of extracellular Ca.sup.2+ in the induction of stress-associated Ca.sup.2+ signatures in barley. Moreover, by analysing spatio-temporal dynamics of the [Ca.sup.2+].sub.cyt transients along the developmental gradient of the barley leaf blade we demonstrate that different parts of the barley leaf show quantitative differences in [Ca.sup.2+].sub.cyt transients in response to NaCl and H.sub.2O.sub.2. There were only marginal differences in the response to flg22, indicative of developmental stage-dependent Ca.sup.2+ responses specifically to NaCl and H.sub.2O.sub.2. This study reveals tissue-specific Ca.sup.2+ signals with stimulus-specific kinetics in the crop species barley, as well as quantitative differences along the barley leaf blade. A number of notable differences to the model plants Arabidopsis may be linked to different stimulus sensitivity. These transgenic barley reporter lines thus present a valuable tool to further analyse mechanisms of Ca.sup.2+ signalling in this crop and to gain insights into the variation of Ca.sup.2+-dependent stress responses between stress-susceptible and -resistant species.

Plants are continuously exposed to changing environmental conditions and biotic attacks that affect plant growth. In crops, the inability to respond appropriately to stress has strong detrimental effects on agricultural production and yield. Ca.sup.2+ signalling plays a fundamental role in the response of plants to most abiotic and biotic stresses. However, research on stimulus-specific Ca.sup.2+ signals has mostly been pursued in Arabidopsis thaliana, while in other species these events are little investigated . In this study, we introduced the Ca.sup.2+ reporter-encoding gene APOAEQUORIN into the crop species barley (Hordeum vulgare). Measurements of the dynamic changes in [Ca.sup.2+].sub.cyt in response to various stimuli such as NaCl, mannitol, H.sub.2O.sub.2, and flagellin 22 (flg22) revealed the occurrence of dose- as well as tissue-dependent [Ca.sup.2+].sub.cyt transients. Moreover, the Ca.sup.2+ signatures were unique for each stimulus, suggesting the involvement of different Ca.sup.2+ signalling components in the corresponding stress response. Alongside, the barley Ca.sup.2+ signatures were compared to those produced by the phylogenetically distant model plant Arabidopsis. Notable differences in temporal kinetics and dose responses were observed, implying species-specific differences in stress response mechanisms. The plasma membrane Ca.sup.2+ channel blocker La.sup.3+ strongly inhibited the [Ca.sup.2+].sub.cyt response to all tested stimuli, indicating a critical role of extracellular Ca.sup.2+ in the induction of stress-associated Ca.sup.2+ signatures in barley. Moreover, by analysing spatio-temporal dynamics of the [Ca.sup.2+].sub.cyt transients along the developmental gradient of the barley leaf blade we demonstrate that different parts of the barley leaf show quantitative differences in [Ca.sup.2+].sub.cyt transients in response to NaCl and H.sub.2O.sub.2. There were only marginal differences in the response to flg22, indicative of developmental stage-dependent Ca.sup.2+ responses specifically to NaCl and H.sub.2O.sub.2. This study reveals tissue-specific Ca.sup.2+ signals with stimulus-specific kinetics in the crop species barley, as well as quantitative differences along the barley leaf blade. A number of notable differences to the model plants Arabidopsis may be linked to different stimulus sensitivity. These transgenic barley reporter lines thus present a valuable tool to further analyse mechanisms of Ca.sup.2+ signalling in this crop and to gain insights into the variation of Ca.sup.2+-dependent stress responses between stress-susceptible and -resistant species.

Plants are continuously exposed to changing environmental conditions and biotic attacks that affect plant growth. In crops, the inability to respond appropriately to stress has strong detrimental effects on agricultural production and yield. Ca.sup.2+ signalling plays a fundamental role in the response of plants to most abiotic and biotic stresses. However, research on stimulus-specific Ca.sup.2+ signals has mostly been pursued in Arabidopsis thaliana, while in other species these events are little investigated . In this study, we introduced the Ca.sup.2+ reporter-encoding gene APOAEQUORIN into the crop species barley (Hordeum vulgare). Measurements of the dynamic changes in [Ca.sup.2+].sub.cyt in response to various stimuli such as NaCl, mannitol, H.sub.2O.sub.2, and flagellin 22 (flg22) revealed the occurrence of dose- as well as tissue-dependent [Ca.sup.2+].sub.cyt transients. Moreover, the Ca.sup.2+ signatures were unique for each stimulus, suggesting the involvement of different Ca.sup.2+ signalling components in the corresponding stress response. Alongside, the barley Ca.sup.2+ signatures were compared to those produced by the phylogenetically distant model plant Arabidopsis. Notable differences in temporal kinetics and dose responses were observed, implying species-specific differences in stress response mechanisms. The plasma membrane Ca.sup.2+ channel blocker La.sup.3+ strongly inhibited the [Ca.sup.2+].sub.cyt response to all tested stimuli, indicating a critical role of extracellular Ca.sup.2+ in the induction of stress-associated Ca.sup.2+ signatures in barley. Moreover, by analysing spatio-temporal dynamics of the [Ca.sup.2+].sub.cyt transients along the developmental gradient of the barley leaf blade we demonstrate that different parts of the barley leaf show quantitative differences in [Ca.sup.2+].sub.cyt transients in response to NaCl and H.sub.2O.sub.2. There were only marginal differences in the response to flg22, indicative of developmental stage-dependent Ca.sup.2+ responses specifically to NaCl and H.sub.2O.sub.2. This study reveals tissue-specific Ca.sup.2+ signals with stimulus-specific kinetics in the crop species barley, as well as quantitative differences along the barley leaf blade. A number of notable differences to the model plants Arabidopsis may be linked to different stimulus sensitivity. These transgenic barley reporter lines thus present a valuable tool to further analyse mechanisms of Ca.sup.2+ signalling in this crop and to gain insights into the variation of Ca.sup.2+-dependent stress responses between stress-susceptible and -resistant species.

Plants are continuously exposed to changing environmental conditions and biotic attacks that affect plant growth. In crops, the inability to respond appropriately to stress has strong detrimental effects on agricultural production and yield. Ca.sup.2+ signalling plays a fundamental role in the response of plants to most abiotic and biotic stresses. However, research on stimulus-specific Ca.sup.2+ signals has mostly been pursued in Arabidopsis thaliana, while in other species these events are little investigated . In this study, we introduced the Ca.sup.2+ reporter-encoding gene APOAEQUORIN into the crop species barley (Hordeum vulgare). Measurements of the dynamic changes in [Ca.sup.2+].sub.cyt in response to various stimuli such as NaCl, mannitol, H.sub.2O.sub.2, and flagellin 22 (flg22) revealed the occurrence of dose- as well as tissue-dependent [Ca.sup.2+].sub.cyt transients. Moreover, the Ca.sup.2+ signatures were unique for each stimulus, suggesting the involvement of different Ca.sup.2+ signalling components in the corresponding stress response. Alongside, the barley Ca.sup.2+ signatures were compared to those produced by the phylogenetically distant model plant Arabidopsis. Notable differences in temporal kinetics and dose responses were observed, implying species-specific differences in stress response mechanisms. The plasma membrane Ca.sup.2+ channel blocker La.sup.3+ strongly inhibited the [Ca.sup.2+].sub.cyt response to all tested stimuli, indicating a critical role of extracellular Ca.sup.2+ in the induction of stress-associated Ca.sup.2+ signatures in barley. Moreover, by analysing spatio-temporal dynamics of the [Ca.sup.2+].sub.cyt transients along the developmental gradient of the barley leaf blade we demonstrate that different parts of the barley leaf show quantitative differences in [Ca.sup.2+].sub.cyt transients in response to NaCl and H.sub.2O.sub.2. There were only marginal differences in the response to flg22, indicative of developmental stage-dependent Ca.sup.2+ responses specifically to NaCl and H.sub.2O.sub.2. This study reveals tissue-specific Ca.sup.2+ signals with stimulus-specific kinetics in the crop species barley, as well as quantitative differences along the barley leaf blade. A number of notable differences to the model plants Arabidopsis may be linked to different stimulus sensitivity. These transgenic barley reporter lines thus present a valuable tool to further analyse mechanisms of Ca.sup.2+ signalling in this crop and to gain insights into the variation of Ca.sup.2+-dependent stress responses between stress-susceptible and -resistant species.

Ca.sup.2+ and H.sub.2O.sub.2 are second messengers that regulate a wide range of cellular events in response to different environmental and developmental cues. In plants, stress-induced H.sub.2O.sub.2 has been shown to initiate characteristic Ca.sup.2+ signatures; however, a clear picture of the molecular connection between H.sub.2O.sub.2-induced Ca.sup.2+ signals and H.sub.2O.sub.2-induced cellular responses is missing, particularly in cereal crops such as barley. Here, we employed RNA-seq analyses to identify transcriptome changes in roots and leaves of barley after H.sub.2O.sub.2 treatment under conditions that inhibited the formation of cytosolic Ca.sup.2+ transients. To that end, plasma membrane Ca.sup.2+ channels were blocked by LaCl.sub.3 application prior to stimulation of barley tissues with H.sub.2O.sub.2. We examined the expression patterns of 4246 genes that had previously been shown to be differentially expressed upon H.sub.2O.sub.2 application. Here, we further compared their expression between H.sub.2O.sub.2 and LaCl.sub.3 + H.sub.2O.sub.2 treatment. Genes showing expression patterns different to the previous study were considered to be Ca.sup.2+-dependent H.sub.2O.sub.2-responsive genes. These genes, numbering 331 in leaves and 1320 in roots, could be classified in five and four clusters, respectively. Expression patterns of several genes from each cluster were confirmed by RT-qPCR. We furthermore performed a network analysis to identify potential regulatory paths from known Ca.sup.2+-related genes to the newly identified Ca.sup.2+-dependent H.sub.2O.sub.2 responsive genes, using the recently described Stress Knowledge Map. This analysis indicated several transcription factors as key points of the responses mediated by the cross-talk between H.sub.2O.sub.2 and Ca.sup.2+. Our study indicates that about 70% of the H.sub.2O.sub.2-responsive genes in barley roots require a transient increase in cytosolic Ca.sup.2+ concentrations for alteration in their transcript abundance, whereas in leaves, the Ca.sup.2+ dependency was much lower at about 33%. Targeted gene analysis and pathway modeling identified not only known components of the Ca.sup.2+ signaling cascade in plants but also genes that are not yet connected to stimuli-associated signaling. Potential key transcription factors identified in this study can be further analyzed in barley and other crops to ultimately disentangle the underlying mechanisms of H.sub.2O.sub.2-associated signal transduction mechanisms. This could aid breeding for improved stress resistance to optimize performance and productivity under increasing climate challenges.