Environmental and Experimental Botany最新文献

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.

This study investigates how the absence of trichomes and variations in stomatal properties affect the quantum efficiency of photosynthesis in Arabidopsis thaliana during drought stress. We analyzed three genotypes: Col-8 (with trichomes and lower stomatal density), epf1epf2 (with higher stomatal density), and tmm-1 (lacking trichomes and altered stomatal characteristics) to determine the influence of these anatomical traits on photosynthetic performance. Under well-watered conditions, epf1epf2 and tmm-1 exhibited higher photosynthetic efficiency (Fv´/Fm´) compared to Col-8. During drought stress, Col-8 maintained stable Fv´/Fm´, while epf1epf2 and tmm-1 experienced significant reductions. Our findings indicate that the presence of trichomes and higher stomatal density positively impacts photosynthetic efficiency under optimal watering while the presence of trichomes becomes less crucial under drought stress. Efficient adjustment of stomatal density and size under drought conditions plays a more significant role. These insights emphasize the importance of considering anatomical traits in breeding programs to enhance drought resistance and photosynthetic performance in plants.

Rapeseed (Brassica napus L.) is a globally significant overwintering oilseed crop. Polyamine oxidase (PAO), an evolutionarily conserved family of FAD-binding proteins, plays crucial roles in plant growth, development, and response to abiotic stress. However, there is a scarcity of systematic identification and functional analysis of the PAO gene family in rapeseed. In this study, we identified 8, 7, 9, 16, 14 and 13 PAO genes in the genomes of B. rapa, B. nigra, B. oleracea, B. napus, B. juncea and B. carinata, respectively, which can be categorized into three subgroups: PAO1, PAO2/3/4, and PAO5. Molecular evolutionary analyses revealed a high conservation of PAO genes in Brassicaceae plants. RNA-seq and RT-qPCR analyses demonstrated the different expression patterns of different subgroups of BnaPAO genes in various tissues and under different treatments in rapeseed. Remarkably, among those PAO genes, only BnaPAO1 genes (BnaA.PAO1.a and BnaC.PAO1.a) were strongly induced by freezing stress. Further analysis confirmed that overexpression of BnaC.PAO1.a significantly improved the freezing tolerance of rapeseed by scavenging ROS. These findings provide a foundation for understanding the biological functions of PAO genes in response to freezing stress in rapeseed.

Banana (Musa spp.) is a vital tropical fruit crop cultivated worldwide and is known for its nutritional value. The cultivation of bananas is often challenged by environmental stresses such as cold and drought, which can adversely affect plant productivity. In response to these challenges, plants deploy adaptive mechanisms to mitigate the impacts of environmental stresses. Calcium (Ca²⁺), recognized as a universal second messenger, is pivotal in cellular responses to hormones, pathogens, and stress factors. This study explores the potential of exogenous calcium supplementation as a cost-effective and promising solution, influencing metabolic activities and signal transductions in plants. To investigate the defensive role of Ca²⁺ supplementation in banana plants subjected to drought (200 mM Mannitol) and cold (14 °C) stress, comprehensive analyses were conducted to elucidate the mechanism underlying Ca²⁺-mediated stress tolerance. The plants were treated with mannitol, cold or Hoagland, and then supplemented with CaCl₂ (15 mM). Exogenous Ca²⁺ treatment significantly increased the proline content and maintained water balance and cellular stability. Additionally, it enhanced the production of protective secondary metabolites and activated key antioxidant enzymes, countering oxidative stress. Molecular analysis revealed an upregulation of calcium-binding proteins involved in stress response, while Ca²⁺ treatment reduced lipid peroxidation, as indicated by lower malondialdehyde (MDA) levels, signifying improved membrane integrity and reduced oxidative damage. These findings underscore the protective impact of exogenously supplied calcium, offering insights for sustainable strategies to enhance banana resilience in the face of environmental challenges and climate change.

Invasive plants commonly compete with native plants in the introduced range; however, how leaf litter and rhizosphere soil microbes influence the competition between invasive and native plants with varying microbial sources and seedling densities remains to be characterized. In this study, the invasive plant Ageratina adenophora (Asteraceae) and two cooccurring native plant species, Senecio scandens (Asteraceae) and Achyranthes bidentata (Amaranthaceae), were used as experimental plants to test their impacts in a greenhouse. We observed that leaf litter and rhizosphere soil microbes negatively or neutrally impacted invasive or native plant growth when competing. However, microbes enhanced the competitive dominance of A. adenophora over S. scandens but weakened its competitiveness over A. bidentata. Leaf litter microbes were more beneficial for A. adenophora growth and thus made it more competitive than rhizosphere soil microbes when competing with S. scandens. Regardless of the presence or absence of microbes, conspecific inoculation was better for A. adenophora growth and thus enhanced competition dominance more than heterospecific inoculation when competing with A. bidentata. A high seedling density was more beneficial for A. adenophora competition dominance than a low density was when A. adenophora was competing with S. scandens. Nonetheless, the relative competitiveness of A. adenophora was greater than that of the two native species; in particular, A. adenophora had stronger competitive dominance over A. bidentata than over S. scandens. Our data confirmed that the important role of leaf litter microbes in the competition between invasive and native plants cannot be ignored.