Environmental and Experimental Botany最新文献

Brassinosteroid (BR) plays a crucial role in plant growth, development and response to abiotic stress. However, the mechanism by which BR regulates the response of potato plants to phosphorus deficiency stress is still largely unknown. In this work, the effects of BR on the growth of potato plants under phosphorus deficient condition were investigated. Exogenous BR application mitigated the growth inhibition caused by phosphorus deficiency stress. Transcriptomic analyses revealed that BR application altered the expression of genes involved in mitogen-activated protein kinase (MAPK) signaling pathway, plant hormone signal transduction, and nitrogen and phosphorus metabolisms under phosphorus deficient condition. Further gene ontology (GO) analysis indicated a significant enrichment of genes associated with reactive oxygen species scavenging process. Ectopic expression of potato brassinosteroid synthesis gene StCYP85A1 in Arabidopsis improved the resistance of transgenic plants to phosphorus deficiency stress, as indicated by the increased germination greening ratio and root growth. Quantitative real time PCR and antioxidant enzyme activity analysis revealed that ectopic expression of StCYP85A1 altered the expression of genes related to nitrogen and phosphorus metabolism, and promoted antioxidant enzyme activity in transgenic plants. These findings indicated that BR improved the tolerance of potato plants to phosphorus deficiency stress by regulating nutrient homeostasis and reactive oxygen species scavenging.

This study provided evidence at the first time showing that root inoculation with the plant growth-promoting rhizobacteria Paraburkholderia sp. GD17 improved the growth and tolerance to Cd stress in Chinese cabbage seedlings. Under normal conditions, the shoot fresh and dry weight of GD17-inoculated 30-day-old plants increased by about 29 % and 33 %, and their root fresh and dry weight by 104 % and 67 %, respectively, compared with their non-inoculated partners. The GD17-mediated growth promotion could be attributed to its facilitating influence on plant acquisition of nutrient elements and photosynthetic efficiency, and decreasing abscisic acid production. Under Cd stress, an effective alleviation in Cd-induced growth inhibition was observed in GD17 plants relative to non-inoculated control, suggesting that the root inoculation with GD17 played a systemic protective role. The Cd concentration in plant aerial tissues was comparable between GD17 plants and non-inoculated ones, but it was substantially decreased in GD17 plant roots. In response to Cd, GD17-inoculated plants generally showed a stronger ability to absorb and transport nutrient elements to shoots. The GD17-conferred plant tolerance to Cd was also associated with an increased antioxidative capacity companied by declined oxidative damage, optimal levels of phytohormones, increased flavonoid synthesis as indicated by significantly upregulated expression of related genes and activity of phenylalanine ammonia-lyase. Additionally, root inoculation with GD17 effectively mitigated the Cd-induced decline in photosynthetic efficiency. Collectively, this study firstly showed that GD17-conferred growth-promotion and Cd-tolerance in Chinese cabbage was correlated with multiple regulatory roles in plant metabolism, which, in most cases, was involved in the regulation at the transcription levels of relevant genes.

In the cold acclimated (CA) state, a reduced tissue water content is considered important to survive subzero temperatures. However, the causal relationship between the reduced water content and increased frost hardiness is unclear. Our aim was to assess whether the seasonally reduced water content affects the freezing dynamics and the amount of ice formed in evergreen leaves: Xeromorph leaves of the woody species Buxus sempervirens and Hedera helix were compared with the herbaceous, soft-leaved Bellis perennis in the non-acclimated (NA) state in summer, during cold acclimation, and in the fully CA state in winter. Freezing dynamics were studied using differential scanning calorimetry in addition to the volume fraction of ice and related to water content, osmotic potential, and frost hardiness. In the CA state, freezing dynamics were slower than in NA state. In xeromorph leaves, displacement from ideal equilibrium freezing was higher than in B. perennis. Freeze dehydration was lower in CA state. In the CA state, water content and osmotic potential were reduced, except for B. sempervirens, where the water content remained unchanged. Active osmoregulation and controlled dehydration (only found in two species), are supporting cellular water retention against the dehydrative force of extracellular ice. B. perennis had the highest water content and the least negative osmotic potential and was the most frost susceptible species (LT₁₀: 8.4 °C CA). The leaves froze at ideal equilibrium. 83 % of the total water froze, occupying more than 60 vol%. H. helix (LT₁₀: 18.4 °C CA) was frost hardier and B. sempervirens (LT₁₀: 28.8 °C CA) the frost hardiest species, but in contrast to the other species tested got frost killed by intracellular freezing. The xeromorph leaves froze at non-ideal equilibrium and had lesser ice masses. Despite an increase in frost hardiness with CA, the volume fraction of ice at LT₁₀ was the same (30–40 vol%). In the CA state, slower freeze dehydration and at the same subzero temperature lesser ice masses appeared to be important for higher frost hardiness. Overall, an important component of cold acclimation in evergreen leaves was the slowing of freezing dynamics, which, depending on the species, involved a specific cell architecture, osmoregulation, and a reduction in water content.

Vapor pressure deficit (VPD) directly affects the driving force of plant water movement by altering the water potential gradient between the atmosphere and plants and indirectly influences the resistance to water movement by regulating plant structure. Concurrently, light intensity modulates both the driving force and resistance to water movement by regulating plant morphology and nonstructural carbohydrate synthesis. Despite significant advances in the understanding of the regulatory effects of VPD on water absorption and transport in tomatoes, the effect of light intensity regulation under varying VPDs on water transport and homeostasis remains to be clarified. Here, we investigated the effects of two light intensities (L300; 300 µmol m^–2 s^–1, L600; 600 µmol m^–2 s^–1) on plant anatomy, physiological traits, hydraulic properties, and expression of plasma membrane intrinsic proteins (PIPs) and tonoplast intrinsic proteins (TIPs) in tomatoes subjected to long-term high and low VPDs. In addition, we analysed the correlations and path coefficients of these indicators. These results indicate that higher light intensity reduces resistance to water movement by enhancing root morphology, vessel parameters in roots and stems, leaf vein density, stomatal morphology, physiological traits, and expression of SlTIPs and SlPIPs in both roots and leaves. Concurrently, increased light intensity boosts the driving force of water movement by amplifying the water potential difference and transpiration under low VPD. However, under high VPD, elevated light intensities create a larger water potential difference, prompting plants to reduce this excessive force by decreasing transpiration and stomatal conductance, thereby maintaining water homeostasis. These findings suggest that light intensity can effectively regulate water homeostasis by dynamically optimising plant structure, hydraulic properties, and the expression of SlTIPs and SlPIPs across different VPDs, providing a theoretical foundation for practical light intensity management in agriculture.

Ammopiptanthus mongolicus is an evergreen broad-leaved shrub growing in temperate regions. Plant defensins, a type of cysteine-rich small peptides, contribute to plant defense as antimicrobial peptides. In this study, we analyzed the evolution and expression patterns of the defensin gene family in A. mongolicus, and explored the function and regulatory mechanisms of the AmDEF2.7 gene in response to abiotic stress. Seven out of ten defensin genes had undergone segmental duplication and tandem duplication, especially, AmDEF2.6, AmDEF2.7, and AmDEF2.8, which were clustered on chromosome 9. The expression of multiple defensin genes was responsive to abiotic stress, with three defensin genes, including AmDEF2.7, showing significant induction during winter. Yeast expressing AmDEF2.7 gene exhibited increased resistance to freeze-thaw cycles and osmotic stress, while transgenic Arabidopsis overexpressing the AmDEF2.7 showed improved tolerance to both freezing and drought conditions. Furthermore, AmWRKY14 bound to the AmDEF2.7 gene promoter, and activated the expression of AmDEF2.7. These results highlighted the role of defensin AmDEF2.7 in the adaptation of A. mongolicus to temperate winter climate. This study expands our knowledge of plant defensin and provides support for clarifying the molecular mechanism of the adaptation of A. mongolicus to winter climate.

Epichloë infection can affect the fungal disease resistance of host grasses. However, few studies have been reported on the effects of endophyte infection on non-symbiotic neighbours. We surveyed the plant diseases in natural grassland, and compared differences of total disease index between neighboring and non-neighboring plants of Achnatherum sibiricum. Then laboratory experiments were conducted to investigate the effects of endophyte on the growth of four pathogen species as well as the brown patch of the host and its neighboring plants. The results of plant disease investigation in natural grassland showed that the major epidemic diseases of grasses were spot blight, rust disease and powdery mildew in Hulunbuir natural grassland. Among common herbages, the total disease index of endophyte-infected A. sibiricum was the lowest. Compared with non-neighboring plants, the brown patch disease index of Leymus chinensis, Stipa baicalensis and Agropyron cristatum was significantly reduced when neighbouring with A. sibiricum. The laboratory experiments results showed that the culture filtration of both Epichloë gansuensis and Epichloë sibiricum significantly restrained the growth of Curvularia lunata, Bipolaris sorokiniana, Sclerotinia sclerotiorum and Sclerotinia trifoliorum. The two species of endophytes could reduce lesion area of detached host leaves. In vivo plant experiments, the endophyte reduced the disease resistance of both the host and its neighbor grasses L. chinensis to C. lunata and B. sorokiniana. This study first verified that the endophytes in A. sibiricum have a positive effect on disease resistance of neighbor grasses to brown patch. The study contributes to the understanding of endophyte-host interactions and suggests potential applications of endophytes in biological control strategies for grassland management.

Application of beneficial microbial consortia for improving plant growth and productivity is considered a major approach to attain sustainable crop production. The construction of plant growth promoting (PGP) bacterial consortia (BC) is reliant on the design of microbial systems based on tuned inter-species interactions with known ecological functions. In this study, maize rhizoplane-associated bacteria were isolated from seven distinct agricultural regions in Morocco. Taxonomic and functional (related to phosphorus “P” use) diversity of 107 rhizoplane bacterial isolates were explored to construct BC while preserving the diversity of the niche they were isolated from. Thirty-six BC were generated, including 28 intra-zone consortia, seven intra-region consortia and one global BC. Quantification of three functional genes: glucose dehydrogenase encoding gene (gcd), pyrroloquinoline quinone (pqqC), and alkaline phosphatase encoding gene (phoD), involved in P cycling, confirmed the presence of gcd in nineteen BC, pqqC in eight BC and phoD in only one BC. In vitro functional characterization revealed that all BC were able to solubilize/mineralize P (50–88 ppm) through the production of organic acids and acid phosphatase (25 – 280 nmol.h⁻¹). Assessment of above- and below-ground parameters of 45-day old maize plants identified five potential niche-constructed “intra-zone” BC (BC_-6, _-11, _-12, _-14, and _-18) notably in terms of plant biomass, shoot nutrient (N, P, K) uptake and induced root morphological and physiological traits. These BC were associated with increased rhizosphere available P (80 ppm) and decreased microbial biomass P (17 ppm) while the remaining BC significantly increased microbial biomass P (30 ppm) at the expense of a decreased rhizosphere available P (35 ppm) with no significant effect on plant nutrient uptake and biomass. These findings demonstrate that intra-zone BC constructed from the same niche outperformed the intra- and inter-region consortia, supporting the niche-conservatism approach to construct P-efficient BC. This study lays a technical foundation for the construction of synthetic microbial consortia for plant growth and nutrient acquisition, through the optimization of inter-species bacterial interactions.

The growth-defense tradeoff is a central mechanism for plants to cope with environmental challenges. Soil contamination with heavy metals, especially cadmium (Cd), can strongly influence the adaptive capacity of plants by modulating both growth and defense. However, how the growth-defense tradeoff adaptive to Cd stress and its dynamic patterns are not yet known. To elucidate these patterns, we conducted an experiment with the pioneer plant Miscanthus floridulus by subjecting it to a gradient of exogenous Cd concentrations, and calculated root mean square deviation based on 12 traits to decipher the direction and intensity of the growth-defense tradeoff. We observed that growth traits such as photosynthetic rate, chlorophyll content, above- and belowground biomass, root surface area and root diameter decreased under Cd stress, while the antioxidative compounds increased. Notably, both above- and belowground parts showed a preference for growth in the absence of Cd stress (tradeoff intensity= 0.013 and 0.013, respectively, unitless). However, under the high Cd stress (40 mg/kg), the aboveground tradeoff remained towards growth (tradeoff intensity= 0.024), while the belowground tradeoff shifted towards defense (tradeoff intensity= −0.046). Under 10 and 20 mg/kg Cd stress, the shifts were uncertain towards either growth or defense for above and belowground parts, suggesting a complex above-belowground interplay. The belowground tradeoff was mainly influenced by plant Cd accumulation, soil fluorescein diacetate hydrolase (S.FDA), and soil available potassium. In contrast, the aboveground tradeoff was primarily driven by plant hydrogen peroxide (H₂O₂) accumulation, S.FDA, and soil alkaline phosphomonoesterase. Overall, Cd in soil altered physicochemical properties and Cd accumulation, which in turn had a significant impact on belowground defense mechanisms. We revealed that the shifts in growth-defense tradeoff differed between aboveground and belowground under Cd stress. Our results provided a new insight into the physiological and biochemical mechanisms underlying plant adaptation to Cd stress from the perspective of the growth-defense tradeoff.

Pteris vittata is the first reported arsenic (As) hyperaccumulator, which is also a calcium (Ca) indicator and adapts to calcareous environment. Therefore, it is hypothesized that Ca plays a role in As accumulation but detail effects and mechanisms are unclear. Typical Ca-compounds (CaCO₃, Ca₃(PO₄)₂ and CaSO₄) were added to hydroponics. CaCO₃ and Ca₃(PO₄)₂ increased pH by 0.75 and 0.31, while CaSO₄ decreased it by 0.26. Besides, CaCO₃ increased As concentration in P. vittata frond by 25.8 % from 65.4 to 82.3 mg kg^–1, while Ca₃(PO₄)₂ and CaSO₄ decreased it by 15.1–38.2 % to 40.4–55.5 mg kg^–1. So the effect of CaCO₃ on soil pH, As bioavailability and As-transformation bacterial community was further examined. In pots, CaCO₃ increased soil pH by 0.57 and increased bioavailable As concentration by 6.2 μg kg^–1, thereby induced 27.3–28.5 % promotion in As plant accumulation. Rhizosphere bacterial community variance can be explained by soil pH and bioavailable As changes at 49–66 %. P. vittata frond As concentration was negatively correlated with rhizosphere As-transformation bacterial diversity (arrA and arsM) (R=-0.57 and -0.66), and positively correlated with the relative abundance of Geobacter (R=0.66) and Pseudomanas (R=0.48), which mediating As mobilization and transformation. This indicated that CaCO₃ can enhance As uptake by P. vittata via increasing soil pH, As bioavailability and mediating As-transformation bacterial community in the rhizosphere. The information helps to better understand how calcareous environment-adaptation benefits P. vittata to uptake and accumulate As. This helps to strategize more efficient processes for As-contaminated soils remediation using the hyperaccumulating plants.

Silicon (Si) accumulation by grasses is a key mechanism for alleviating biotic and abiotic stresses, including insect herbivory. In addition to conferring physical resistance, tissue silicification may enhance anti-herbivore phytohormone production, such as the jasmonic and salicylic (JA and SA) acid pathways, and downstream regulation of defence genes, although this is poorly understood. Elevated atmospheric carbon dioxide (eCO₂) concentrations predicted by climate models are reported to reduce Si accumulation in several plant taxa and may therefore compromise Si-augmented resistance. We investigated how Si enrichment and eCO₂ regulate the JA and SA pathways and expression of defence genes in wheat (Triticum aestivum) challenged by a global insect pest (Helicoverpa armigera). Si treatments increased JA production and expression of β-1,3-ENDOGLUCANASE (GNS), and MITOGEN-ACTIVATED PROTEIN KINASE (MAPK; WCK-1) defence genes, while suppressing SA production, resulting in reduced feeding and growth of H. armigera. In contrast, under eCO₂ conditions, Si accumulation was reduced, GNS downregulated, but SA production was upregulated. Despite compromised plant defences, H. armigera growth rates were reduced under eCO₂. We conclude that eCO₂ and Si supplementation contrastingly regulate anti-herbivore defences in wheat; these important drivers operate independently and may influence future patterns of pest resistance in wheat under projected rises in atmospheric CO₂.