Jasmonic acid (JA) plays crucial functions during plant growth and stress response, but its roles and regulatory mechanism in plant branching remain largely unknown. Rice basal branching (tillering) ...is an essential agronomic trait that affects crop production. Here, we report that OsJAZ6, the repressor of JA signaling, negatively modulates rice tillering and drought stress tolerance. Loss-of-function mutants of OsJAZ6 exhibit a significant increase in tiller number, while OsJAZ6ΔJas-overexpression lines produce fewer tillers than wild-type plants. Further investigations show that function loss of OsJAZ6 promotes the tiller bud growth rather than formation. Mechanistic studies show that OsJAZ6 interacts with rice DELLA/SLR1 (SLENDER RICE 1), a transcription repressor of gibberellin (GA) signaling, and the interaction promotes SLR1 degradation, which further facilitates the degradation of rice tillering regulator MOC1 (MONOCULM 1), thereby inhibiting the tiller bud growth. In agreement, the slr1 mutant exhibits fewer tillers than wild type. Consistently, application of JA promotes the growth of tiller bud and thus increases the tiller number, while GA treatment results in opposite result. Meanwhile, osjaz6 mutants display enhanced drought tolerance, coupled with increased JA sensitivity, while the slr1 mutant shows the reverse behavior. Collectively, our data demonstrate that OsJAZ6 negatively modulates rice tillering as well as drought stress tolerance by destabilizing SLR1 protein. Our data shed light on the regulatory mechanism of controlling the tiller development and drought stress response in rice by the JA-OsJAZ6-SLR1 module.
•OsJAZ6 modulates rice tillering and drought response by integrating JA with GA signaling.•OsJAZ6 controls the tiller bud growth but not formation.•OsJAZ6 interacts with SLR1 to promote its degradation, which further destabilizes MOC1.•OsJAZ6 and SLR1 have opposite functions in regulating rice tiller bud growth and drought tolerance.
Proline accumulation and metabolism are associated with mechanisms of abiotic stress avoidance in plants. Proline accumulation generally improves osmotic stress tolerance whereas proline metabolism ...can have varying effects from ATP generation to the formation of reactive oxygen species. To further understand the roles of proline in stress protection, two peanut cultivars with contrasting tolerance to drought were examined by transcriptional and biochemical analyses during water stress. Plants exposed to polyethylene glycol had diminished relative water content and increased proline content; while, only the drought sensitive plants, cultivar Granoleico, showed lipid oxidative damage (measured as thiobarbituric acid reactive substances). The expression of proline biosynthesis genes (P5CS1, P5CS2a, P5CS2b, P5CR) was increased in both cultivars upon exposure to water stress. However, the relative expression of proline catabolism genes (ProDH1, ProDH2) was increased only in the sensitive cultivar during stress. Exogenous addition of proline and the proline analogue thiazolidine-4-carboxylic acid (T4C), both substrates of proline dehydrogenase, was also used to exacerbate and identify plant responses. Pretreatment of plants with T4C induced unique changes in the drought tolerant EC-98 cultivar such as higher mRNA levels of proline biosynthetic and catabolic ProDH genes, even in the absence of water stress. The increased levels of ProDH gene expression, potentially associated with higher T4C conversion to cysteine, may contribute to the tolerant phenotype.
•The drought tolerant cultivar accumulates significantly higher proline by 24 h.•Peanut cultivars exhibit differences in proline dehydrogenase (ProDH) gene expression.•The tolerant cultivar treated with thiazolidine-4-carboxylic acid (T4C) increased ProDH levels.•T4C potentially may be a cysteine precursor for specific cultivars exposed to drought stress.
Predicted changes in climate, with more severe droughts and more extreme weather variability, are gaining considerable attention from stakeholders because of the already stressed and seriously ...challenging agricultural ecosystems of the contemporary world. One of the greatest challenges faced by these unique ecosystems due to climate change is drought stress, which affects plant growth, development and metabolic processes, thus reducing production, yield, and quality of crop plants. Plants counter this stress by employing complex mechanisms through a series of physiological, cellular, and molecular processes. Among the myriad of stress tolerance mechanisms, the positive effects of Si on water status of plants have been widely appreciated. Here, we review the potential of Si supplementation in alleviating drought stress and highlight the imported mechanisms involved in Si mediated reduction of drought stress in plants. Si fertilization not only enhances the photosynthetic pigments, growth, biomass, antioxidant enzymes, gene expression, osmolyte concentrations and nutrient uptake but also improves crop production, yield and grain quality during drought stress. In addition, it provides insights on important mechanisms involved in the modification of gas exchange attributes, gene modification, nutritional homeostasis, control synthesis of compatible solutes, osmotic adjustment and stimulation of phytohormone biosynthesis and antioxidant enzymes under drought stress. We also highlight knowledge gaps and future research prospects to understand Si mediated role in alleviating drought stress.
•Drought stress induces oxidative stress which hampers many biological processes.•Si supplementation improves the biochemical, physiological, and molecular response in stressful conditions.•More knowledge about the plant gene cascade triggered by Si application is required to develop sustainable cropping systems.
HD-ZIP proteins comprise a plant-specific transcription factor family, which play pivotal roles in plant development and adaptation to ever-changing environment. Although HD-ZIP family members have ...been identified in some plant species, so far our knowledge about HD-ZIP genes in rapeseed is still limited. In this study, 178 Brassica napus HD-ZIP (BnaHDZ) family members were identified in the rapeseed genome. The phylogenetic relationship, chromosomal locations, intron-exon structures, motif composition, and expression patterns of the BnaHDZ members were analyzed. The BnaHDZ family can be phylogenetically divided into four categories (Ⅰ, Ⅱ, Ⅲ and Ⅳ). Genome-wide transcriptome analysis revealed that most of the HD-ZIP I members respond to at least one abiotic stress. Two closely homologous stress-responsive HD-ZIP Ⅰ genes, BnaHDZ22 and BnaHDZ149, were identified to be involved in drought and salt responses, and selected for further functional characterization. Overexpressing BnaHDZ149 in rapeseed increased salt sensitivity of the transgenic plants, whereas overexpressing BnaHDZ22 increased sensitivity of the transgenic plants to polyethylene glycol (PEG)-simulated drought stress. This research provides not only a comprehensive landscape of BnaHDZ genes, but also a theoretical basis for elucidating the molecular mechanism of the abiotic stress responses of the HD-ZIP family in rapeseed.
•A total of 178 HD-ZIP genes belonging to four categories (Ⅰ, Ⅱ, Ⅲ and Ⅳ) were systematically identified in B. napus.•Two closely homologous stress-responsive HD-ZIP Ⅰ genes, BnaHDZ22 and BnaHDZ149, were functionally characterized.•BnaHDZ149 was identified as a negative regulator of salt tolerance in B. napus.•Overexpression of BnaHDZ22 increased sensitivity to osmotic stress of transgenic rapeseed.
In 2018, Central Europe experienced one of the most severe and long-lasting summer drought and heat wave ever recorded. Before 2018, the 2003 millennial drought was often invoked as the example of a ...“hotter drought”, and was classified as the most severe event in Europe for the last 500 years. First insights now confirm that the 2018 drought event was climatically more extreme and had a greater impact on forest ecosystems of Austria, Germany and Switzerland than the 2003 drought. Across this region, mean growing season air temperature from April to October was more than 3.3°C above the long-term average, and 1.2°C warmer than in 2003. Here, we present a first impact assessment of the severe 2018 summer drought and heatwave on Central European forests. In response to the 2018 event, most ecologically and economically important tree species in temperate forests of Austria, Germany and Switzerland showed severe signs of drought stress. These symptoms included exceptionally low foliar water potentials crossing the threshold for xylem hydraulic failure in many species and observations of widespread leaf discoloration and premature leaf shedding. As a result of the extreme drought stress, the 2018 event caused unprecedented drought-induced tree mortality in many species throughout the region. Moreover, unexpectedly strong drought-legacy effects were detected in 2019. This implies that the physiological recovery of trees was impaired after the 2018 drought event, leaving them highly vulnerable to secondary drought impacts such as insect or fungal pathogen attacks. As a consequence, mortality of trees triggered by the 2018 events is likely to continue for several years. Our assessment indicates that many common temperate European forest tree species are more vulnerable to extreme summer drought and heat waves than previously thought. As drought and heat events are likely to occur more frequently with the progression of climate change, temperate European forests might approach the point for a substantial ecological and economic transition. Our assessment also highlights the urgent need for a pan-European ground-based monitoring network suited to track individual tree mortality, supported by remote sensing products with high spatial and temporal resolution to track, analyse and forecast these transitions.
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•Short- and long-term climate responses were investigated for mixed and pure stands.•Triplet experimental setup enables the specific analysis of mixing effects.•Douglas-fir benefits ...from mixtures, but at the expense of European beech.•Mixing effect results from complementary phenology.•Tree size, competition and limitation of the stands influence the sensitivity.
Due to possible positive and compensatory interaction between species, mixed stands are a commonly accepted silvicultural response to reduce risks arising from climate change. Nonetheless, only a few species combinations have been studied more detailed so far revealing variable mixing effects. Here, we analyze the effect of the mixture of Douglas fir and European beech with regard to the species-specific climate sensitivity of growth. We focus on three hypotheses: (i) Species-specific long term growing performance and climate sensitivity do not differ between monocultures and mixed stands, (ii) species-specific growth reactions to severe drought events do not differ between monocultures and mixed species stands and (iii) species-specific growth reactions on severe drought events are not influenced by differing ecological growing conditions.
To scrutinize the hypothesis we analyzed tree cores from both species taken from pure and mixed stands covering different site conditions and age classes. Tree ring characteristics were used to analyze the differences in climate related long-term growth responses in pure and mixed stands. Short-term responses were investigated by growth reaction indices on individual tree and stand level involving drought events during the years 1950–2010. Linear mixed models were applied to detect effects of ecological co-variables on the indices.
Results reveal that Douglas-fir in mixed stands exhibit a significant improved growing performance compared to pure stands. European beech seems to react indifferently concerning its performance in mixture compared to pure stands.
Differences in drought stress resistance and growth recovery time mainly arose between the species. Douglas-fir showed a significantly lower resistance and required more time to reach again its initial growth level compared to European beech. In mixture we found a trend that Douglas-fir growth recovery time is shortened and extended for European beech.
The analysis along the ecological gradients showed that base-limited soils systems are more drought-tolerant during drought events. Lower basal area as a proxy for reduced stand competition decreased the relative growth loss by drought.
We hypothesize that mainly spatial differentiation in height trigger enhanced diameter growth of Douglas-fir in mixture. Temporal differentiation expressed by deferred phenology attenuates climate sensitivity of this conifer. We conclude that in mixed Douglas-fir and European beech stands the former species is stabilized against climatic impacts. On the contrary, climate sensitivity of European beech is increased.
This study investigated the effect of drought stress on the amount of phenolic and flavonoid compounds as well as H2O2 and malondialdehyde (MDA) in Achillea pachycephala. The expression patterns of ...the key genes and their molecular mechanisms in the phenylpropanoid pathway (PAL, CHS, CHI, F3H, F3′H, F3′5′H, FLS) were also assessed during drought stress using quantitative real-time polymerase chain reaction (qRT-PCR). The samples were harvested at 0, 7, 14, 21 and 28 days after exposure to drought stress. High-performance liquid chromatography (HPLC) analysis was performed to determine the changes of phenolic and flavonoid compounds – chlorogenic acid, caffeic acid, rutin, luteolin-7-O-glycoside, 1,3-dicaffeoylquinic acid, apigenin-7-O-glycoside, luteolin, apigenin and kaempferol – during stress conditions. Concentrations of most of the compounds increased with increasing drought stress duration. Most of the phenolic acids continued to accumulate with increasing duration of stress, while flavonoids dramatically decreased at day 28 of stress. Chlorogenic acid was the most abundant phenolic acid (4.97 mg/100 g dry weight DW) at the beginning of the experiment, while it decreased at day 7 and increased again at day 21. However, different trends were observed for some flavonoids, such as luteolin and apigenin. At the beginning of stress treatment, high accumulation of free radicals (H2O2) and lipid peroxidation (MDA) led to elevated expression of most of the flavonoid genes. MDA increased from 22.66 to 43.28 μmol g−1 DW at day 28. CHS gene expression was elevated at day 7, while chi gene expression remained unchanged. At the end of the stress period, most of the flavonoid concentrations and expression of the relevant genes also increased. The results can facilitate selection of appropriate drought conditions to obtain the highest levels of flavonoids such as luteolin and apigenin and phenolic compounds such as chlorogenic acid for improved health benefits.
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•The effect of drought on flavonoid genes and metabolites were assessed in Achillea pachycephalla.•The concentration of the phenolics and flavonoids showed different trends in response to drought.•H2O2 and MDA were elevated at the beginning of drought stress.•Most of the genes were upregulated at the beginning and end days of the stress.
Due to global climate change, abiotic stresses are affecting plant growth, productivity, and the quality of cultivated crops. Stressful conditions disrupt physiological activities and suppress ...defensive mechanisms, resulting in stress-sensitive plants. Consequently, plants implement various endogenous strategies, including plant hormone biosynthesis (e.g., abscisic acid, jasmonic acid, salicylic acid, brassinosteroids, indole-3-acetic acid, cytokinins, ethylene, gibberellic acid, and strigolactones) to withstand stress conditions. Combined or single abiotic stress disrupts the normal transportation of solutes, causes electron leakage, and triggers reactive oxygen species (ROS) production, creating oxidative stress in plants. Several enzymatic and non-enzymatic defense systems marshal a plant’s antioxidant defenses. While stress responses and the protective role of the antioxidant defense system have been well-documented in recent investigations, the interrelationships among plant hormones, plant neurotransmitters (NTs, such as serotonin, melatonin, dopamine, acetylcholine, and γ-aminobutyric acid), and antioxidant defenses are not well explained. Thus, this review discusses recent advances in plant hormones, transgenic and metabolic developments, and the potential interaction of plant hormones with NTs in plant stress response and tolerance mechanisms. Furthermore, we discuss current challenges and future directions (transgenic breeding and genome editing) for metabolic improvement in plants using modern molecular tools. The interaction of plant hormones and NTs involved in regulating antioxidant defense systems, molecular hormone networks, and abiotic-induced oxidative stress tolerance in plants are also discussed.
Calcium-dependent protein kinase (CDPK) as one of calcium sensors were play important roles in stress responses. CDPK-related protein kinase (CRK) was identified as subgroup III of CDPK has been ...characterized in many plants, but the members and functions of CRK genes in hulless barley (Hordeum vulgare L.) has not been clarified. Here, we identified four HvCRK genes and named HvCRK1-4 according to chromosomes localization. Moreover, the physiological function of highly induced genes of HvCRK2 and HvCRK4 were investigated in drought stress tolerance by examining their overexpression transgenic lines functions generated in Arabidopsis thaliana. Under drought stress, both overexpression HvCRK2 and HvCRK4 displayed reduced drought resistance, and accompanied by higher accumulation levels of ROS. Notably, overexpression of HvCRK2 and HvCRK4 reduced sensitivity to exogenous ABA, meanwhile the expression of ABA-responsive genes in transgenic plants were down-regulated compared to the wild type in response to drought stress. Furthermore, the physically interaction of HvCRK2 and HvCRK4 with calmodulin (CaM) and calmodulin-like (CML) proteins were determined in vivo, the further results showed that HvCML32 binds to HvCRK2/4 S_TKC structural domains and negatively regulates drought tolerance. In summary, this study identified HvCRK members and indicated that HvCRK2 and HvCRK4 genes play negative roles in drought tolerance, and provide insight into potential molecular mechanism of HvCRK2 and HvCRK4 in response to drought stress.
•Four HvCRK genes were identified in hulless barley (Hordeum vulgare L.).•Two members of HvCRK2/CRK4 were negatively regulated drought tolerance in transgenic Arabidopsis thaliana.•The calcium sensor of calmodulin-like protein HvCML32 interacted with HvCRK2/CRK4 and negatively regulated drought tolerance in transgenic Arabidopsis thaliana.•This work provide insights into the mechanism of HvCRK2/4 in drought tolerance.
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