Reduced height (Rht) genes have revolutionised wheat cultivation, but they can compromise freezing tolerance, and only a few alleles are in use. Thus, evaluating the role of other Rht alleles in stress responses is crucial. Far-red supplementation of white light (W+FR) can induce pre-hardening in cereals at 15°C. However, the relevant effect of blue light enrichment (W+B) is poorly described. This study investigates the influence of W+FR or W+B exposure in young winter wheat leaves of a tall (wild-type, rht12) and a dwarf, gibberellin-deficient (near-isogenic line, Rht12) genotype in cv. Maris Huntsman background over 10 days at 15°C. The main objectives were to investigate the relationship between light quality, gibberellin homeostasis, and freezing tolerance. Key parameters such as frost injury, hormonal pools and the expression of relevant genes were examined. Results provided evidence about the involvement of Rht alleles in the basal freezing tolerance of wheat leaves from the side of gibberellin availability. It was revealed that W+FR and W+B treatments partially rescued the freezing-sensitive phenotype of Rht12 leaves, suggesting a potential compensatory mechanism. Analysis of gibberellic acid (GA) metabolism indicated differential responses to light treatments between the Rht12 and wild-type leaves, with implications for freezing tolerance. Moreover, alterations in hormone levels, including jasmonic acid (JA) and salicylic acid (SA), were observed, highlighting the complex interplay between light signalling and hormonal regulation in wheat. Overall, these findings suggest that manipulating light responses may offer a strategy to enhance freezing tolerance in gibberellin-deficient dwarf wheat genotypes.

• MeSH
• Red Light MeSH
• Genotype MeSH
• Gibberellins metabolism   MeSH
• Plant Leaves * radiation effects   physiology   metabolism   MeSH
• Triticum * physiology   radiation effects   genetics   metabolism   MeSH
• Gene Expression Regulation, Plant radiation effects   MeSH
• Plant Growth Regulators * metabolism   MeSH
• Light * MeSH
• Freezing MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Cyclopentanes MeSH
• Gibberellins MeSH
• jasmonic acid MeSH Browser
• Oxylipins MeSH
• Plant Growth Regulators * MeSH

Winter oilseed rape (Brassica napus L.), the principal oilseed crop in Europe, is notably vulnerable to spring frosts that can drastically reduce yields in ways that are challenging to predict with standard techniques. Our research focused on evaluating the efficacy of photosynthetic efficiency analysis in this crop and identifying specific chlorophyll fluorescence parameters severely impacted by frost, which could serve as noninvasive biomarkers for yield decline. The experiments were carried out in semi-controlled conditions with several treatments: a control, one day at -3°C, three days at -3°C, one day at -6°C, and three days at -6°C. We employed continuous-excitation and pulse-amplitude-modulation chlorophyll fluorescence measurements to assess plant sensitivity to frost. Also, plant gas exchange and chlorophyll content index measurements were performed. Certain parameters strongly correlated with final yield losses, thereby establishing a basis for developing new agricultural protocols to predict and mitigate frost damage in rapeseed crops accurately.

• Keywords
• abiotic stresses, bioindicator, chlorophyll a fluorescence, noninvasive biomarkers, plant gas exchange, plant traits,
• Publication type
• Journal Article MeSH

Winter plants acclimate to frost mainly during the autumn months, through the process of cold acclimation. Global climate change is causing changes in weather patterns such as the occurrence of warmer periods during late autumn or in winter. An increase in temperature after cold acclimation can decrease frost tolerance, which is particularly dangerous for winter crops. The aim of this study was to investigate the role of brassinosteroids (BRs) and BR analogues as protective agents against the negative results of deacclimation. Plants were cold-acclimated (3 weeks, 4 °C) and deacclimated (1 week, 16/9 °C d/n). Deacclimation generally reversed the cold-induced changes in the level of the putative brassinosteroid receptor protein (BRI1), the expression of BR-induced COR, and the expression of SERK1, which is involved in BR signal transduction. The deacclimation-induced decrease in frost tolerance in oilseed rape could to some extent be limited by applying steroid regulators. The deacclimation in plants could be detected using non-invasive measurements such as leaf reflectance, chlorophyll a fluorescence, and gas exchange monitoring.

• Keywords
• 24-epibrassinolide, 28-homocastasterone, BRI1, CO2 assimilation, COR, SERK, brassinosteroid analogues, chlorophyll a fluorescence, frost tolerance, leaf reflectance,
• MeSH
• Acclimatization * MeSH
• Brassica napus * physiology   metabolism   MeSH
• Brassinosteroids * metabolism   MeSH
• Plant Leaves metabolism   physiology   MeSH
• Cold Temperature * MeSH
• Gene Expression Regulation, Plant * MeSH
• Seasons MeSH
• Plant Proteins metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Brassinosteroids * MeSH
• Plant Proteins MeSH

It is well established that cold acclimation processes are highly influenced, apart from cold ambient temperatures, by light-dependent environmental factors. In this study we investigated whether an extra blue (B) light supplementation would be able to further improve the well-documented freezing tolerance enhancing effect of far-red (FR) enriched white (W) light. The impact of B and FR light supplementation to white light (WFRB) on hormone levels and lipid contents were determined in winter barley at moderate (15 °C) and low (5 °C) temperatures. Low R:FR ratio effectively induced frost tolerance in barley plantlets, but additional B light further enhanced frost hardiness at both temperatures. Supplementation of WFR (white light enriched with FR light) with B had a strong positive effect on abscisic acid accumulation while the suppression of salicylic acid and jasmonic acid levels were observed at low temperature which resembles the shade avoidance syndrome. We also observed clear lipidomic differences between the individual light and temperature treatments. WFRB light changed the total lipid content negatively, but monogalactosyldiacylglycerol (MGDG) content was increased, nonetheless. Our results prove that WFRB light can greatly influence phytohormone dynamics and lipid contents, which eventually leads to more efficient pre-hardening to avoid frost damage.

• Keywords
• barley, cold acclimation, light regulation, light-emitting diode (LED) lighting, lipidome, phytohormones,
• Publication type
• Journal Article MeSH

Acclimation to salt stress in plants is regulated by complex signaling pathways involving endogenous phytohormones. The signaling role of salicylic acid (SA) in regulating crosstalk between endogenous plant growth regulators' levels was investigated in barley (Hordeum vulgare L. 'Ince'; 2n = 14) leaves and roots under salt stress. Salinity (150 and 300 mM NaCl) markedly reduced leaf relative water content (RWC), growth parameters, and leaf water potential (LWP), but increased proline levels in both vegetative organs. Exogenous SA treatment did not significantly affect salt-induced negative effects on RWC, LWP, and growth parameters but increased the leaf proline content of plants under 150 mM salt stress by 23.1%, suggesting that SA enhances the accumulation of proline, which acts as a compatible solute that helps preserve the leaf's water status under salt stress. Changes in endogenous phytohormone levels were also investigated to identify agents that may be involved in responses to increased salinity and exogenous SA. Salt stress strongly affected endogenous cytokinin (CK) levels in both vegetative organs, increasing the concentrations of CK free bases, ribosides, and nucleotides. Indole-3-acetic acid (IAA, auxin) levels were largely unaffected by salinity alone, especially in barley leaves, but SA strongly increased IAA levels in leaves at high salt concentration and suppressed salinity-induced reductions in IAA levels in roots. Salt stress also significantly increased abscisic acid (ABA) and ethylene levels; the magnitude of this increase was reduced by treatment with exogenous SA. Both salinity and SA treatment reduced jasmonic acid (JA) levels at 300 mM NaCl but had little effect at 150 mM NaCl, especially in leaves. These results indicate that under high salinity, SA has antagonistic effects on levels of ABA, JA, ethylene, and most CKs, as well as basic morphological and physiological parameters, but has a synergistic effect on IAA, which was well exhibited by principal component analysis (PCA).

• Keywords
• Hordeum vulgare, barley, phytohormones, salicylic acid, salt stress,
• Publication type
• Journal Article MeSH

Low temperatures in the autumn induce enhanced expression/relative accumulation of several cold-inducible transcripts/proteins with protective functions from Late-embryogenesis-abundant (LEA) superfamily including dehydrins. Several studies dealing with plants grown under controlled conditions revealed a correlation (significant quantitative relationship) between dehydrin transcript/protein relative accumulation and plant frost tolerance. However, to apply these results in breeding, field experiments are necessary. The aim of the review is to provide a summary of the studies dealing with the relationships between plant acquired frost tolerance and COR/LEA transcripts/proteins relative accumulation in cereals grown in controlled and field conditions. The impacts of cold acclimation and vernalisation processes on the ability of winter-type Triticeae to accumulate COR/LEA proteins are discussed. The factors determining dehydrin relative accumulation under controlled cold acclimation treatments versus field trials during winter seasons are discussed. In conclusion, it can be stated that dehydrins could be used as suitable indicators of winter survival in field-grown winter cereals but only in plant prior to the fulfilment of vernalisation requirement.

• Keywords
• COR14b, cold acclimation, dehydrins, field trials, frost tolerance, growth chambers, vernalisation,
• Publication type
• Journal Article MeSH
• Review MeSH

Cold acclimation, the necessary prerequisite for promotion of freezing tolerance, is affected by both low temperature and enhanced far-red/red light (FR/R) ratio. The impact of FR supplementation to white light, created by artificial LED light sources, on the hormone levels, metabolism, and expression of the key hormone metabolism-related genes was determined in winter barley at moderate (15 °C) and low (5 °C) temperature. FR-enhanced freezing tolerance at 15 °C was associated with promotion of abscisic acid (ABA) levels, and accompanied by a moderate increase in indole-3-acetic acid (IAA) and cis-zeatin levels. The most prominent impact on the plants' freezing tolerance was found after FR pre-treatment at 15 °C (for 10 days) followed by cold treatment at FR supplementation (7 days). The response of ABA was diminished in comparison with white light treatment, probably due to the elevation of stress tolerance during FR pre-treatment. Jasmonic acid (JA) and salicylic acid (SA) were transiently reduced. When the plants were exposed directly to a combination of cold (5 °C) and FR supplementation, ABA increase was higher than in white light, and was associated with enhanced elevation of JA and, in the longer term (after 7 days), with IAA and cis-zeatin increase, which indicates a stronger stress response and better acclimation. Cold hardening was more efficient when FR light was applied in the early developmental stage of the barley plants (three-leaf stage, 18 days), rather than in later stages (28-days). The dynamics of the phytohormone changes are well supported by the expression profiles of the key hormone metabolism-related genes. This series of treatments serves as evidence for the close relationship between plant hormones, light quality, and low temperature at the beginning of cold acclimation. Besides the timing of the FR treatments, plant age also represents a key factor during light spectrum-dependent cold acclimation.

• Keywords
• LED lighting, barley, frost-tolerance, low R/FR ratio, phytohormones,
• MeSH
• Acclimatization physiology   MeSH
• Hordeum genetics   metabolism   radiation effects   MeSH
• Abscisic Acid metabolism   MeSH
• Indoleacetic Acids metabolism   MeSH
• Plant Leaves genetics   metabolism   radiation effects   MeSH
• Cold Temperature * MeSH
• Reverse Transcriptase Polymerase Chain Reaction MeSH
• Gene Expression Regulation, Plant radiation effects   MeSH
• Plant Growth Regulators metabolism   MeSH
• Gene Expression Profiling methods   MeSH
• Light * MeSH
• Freezing MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• indoleacetic acid MeSH Browser
• Abscisic Acid MeSH
• Indoleacetic Acids MeSH
• Plant Growth Regulators MeSH

Plant survival in temperate zones requires efficient cold acclimation, which is strongly affected by light and temperature signal crosstalk, which converge in modulation of hormonal responses. Cold under low light conditions affected Arabidopsis responses predominantly in apices, possibly because energy supplies were too limited for requirements of these meristematic tissues, despite a relatively high steady-state quantum yield. Comparing cold responses at optimal light intensity and low light, we found activation of similar defence mechanisms-apart from CBF1-3 and CRF3-4 pathways, also transient stimulation of cytokinin type-A response regulators, accompanied by fast transient increase of trans-zeatin in roots. Upregulated expression of components of strigolactone (and karrikin) signalling pathway indicated involvement of these phytohormones in cold responses. Impaired response of phyA, phyB, cry1 and cry2 mutants reflected participation of these photoreceptors in acquiring freezing tolerance (especially cryptochrome CRY1 at optimal light intensity and phytochrome PHYA at low light). Efficient cold acclimation at optimal light was associated with upregulation of trans-zeatin in leaves and roots, while at low light, cytokinin (except cis-zeatin) content remained diminished. Cold stresses induced elevation of jasmonic acid and salicylic acid (in roots). Low light at optimal conditions resulted in strong suppression of cytokinins, jasmonic and salicylic acid.

• Keywords
• auxin, combined stress, cryptochrome, cytokinin, gene expression, gibberellin, phytochrome, plant hormones,
• MeSH
• Acclimatization * MeSH
• Arabidopsis * genetics   metabolism   MeSH
• Arabidopsis Proteins * biosynthesis   genetics   MeSH
• Gene Expression Regulation, Plant * MeSH
• Light * MeSH
• Freezing * MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Arabidopsis Proteins * MeSH

BACKGROUND: Over the life cycle of perennial trees, the dormant state enables the avoidance of abiotic stress conditions. The growth cycle can be partitioned into induction, maintenance and release and is controlled by complex interactions between many endogenous and environmental factors. While phytohormones have long been linked with dormancy, there is increasing evidence of regulation by DAM and CBF genes. To reveal whether the expression kinetics of CBFs and their target PtDAM1 is related to growth cessation and endodormancy induction in Populus, two hybrid poplar cultivars were studied which had known differential responses to dormancy inducing conditions. RESULTS: Growth cessation, dormancy status and expression of six PtCBFs and PtDAM1 were analyzed. The 'Okanese' hybrid cultivar ceased growth rapidly, was able to reach endodormancy, and exhibited a significant increase of several PtCBF transcripts in the buds on the 10th day. The 'Walker' cultivar had delayed growth cessation, was unable to enter endodormancy, and showed much lower CBF expression in buds. Expression of PtDAM1 peaked on the 10th day only in the buds of 'Okanese'. In addition, PtDAM1 was not expressed in the leaves of either cultivar while leaf CBFs expression pattern was several fold higher in 'Walker', peaking at day 1. Leaf phytohormones in both cultivars followed similar profiles during growth cessation but differentiated based on cytokinins which were largely reduced, while the Ox-IAA and iP7G increased in 'Okanese' compared to 'Walker'. Surprisingly, ABA concentration was reduced in leaves of both cultivars. However, the metabolic deactivation product of ABA, phaseic acid, exhibited an early peak on the first day in 'Okanese'. CONCLUSIONS: Our results indicate that PtCBFs and PtDAM1 have differential kinetics and spatial localization which may be related to early growth cessation and endodormancy induction under the regime of low night temperature and short photoperiod in poplar. Unlike buds, PtCBFs and PtDAM1 expression levels in leaves were not associated with early growth cessation and dormancy induction under these conditions. Our study provides new evidence that the degradation of auxin and cytokinins in leaves may be an important regulatory point in a CBF-DAM induced endodormancy. Further investigation of other PtDAMs in bud tissue and a study of both growth-inhibiting and the degradation of growth-promoting phytohormones is warranted.

• Keywords
• Endodormancy, Gene expression, Growth cessation, Plant hormone, Populus, PtCBFs, PtDAM1,
• MeSH
• Chimera growth & development   MeSH
• Genetic Variation MeSH
• Populus genetics   growth & development   MeSH
• Gene Expression Regulation, Plant MeSH
• Plant Growth Regulators genetics   MeSH
• Genes, Plant MeSH
• Gene Expression Profiling MeSH
• Plant Dormancy genetics   MeSH
• Plant Development genetics   MeSH
• Publication type
• Journal Article MeSH
• Comparative Study MeSH
• Names of Substances
• Plant Growth Regulators MeSH

Plants growing in any particular geographical location are exposed to variable and diverse environmental conditions throughout their lifespan. The multifactorial environmental pressure resulted into evolution of plant adaptation and survival strategies requiring ability to integrate multiple signals that combine to yield specific responses. These adaptive responses enable plants to maintain their growth and development while acquiring tolerance to a variety of environmental conditions. An essential signaling cascade that incorporates a wide range of exogenous as well as endogenous stimuli is multistep phosphorelay (MSP). MSP mediates the signaling of essential plant hormones that balance growth, development, and environmental adaptation. Nevertheless, the mechanisms by which specific signals are recognized by a commonly-occurring pathway are not yet clearly understood. Here we summarize our knowledge on the latest model of multistep phosphorelay signaling in plants and the molecular mechanisms underlying the integration of multiple inputs including both hormonal (cytokinins, ethylene and abscisic acid) and environmental (light and temperature) signals into a common pathway. We provide an overview of abiotic stress responses mediated via MSP signaling that are both hormone-dependent and independent. We highlight the mutual interactions of key players such as sensor kinases of various substrate specificities including their downstream targets. These constitute a tightly interconnected signaling network, enabling timely adaptation by the plant to an ever-changing environment. Finally, we propose possible future directions in stress-oriented research on MSP signaling and highlight its potential importance for targeted crop breeding.

• Keywords
• Arabidopsis, abiotic stress, abscisic acid, cytokinin, ethylene, light signaling, multistep phosphorelay (MSP), temperature,
• Publication type
• Journal Article MeSH
• Review MeSH