Plant Direct最新文献

Adopting crops and agricultural practices that help sustain yield under abiotic stress will be a major element of future food security under climate change. However, little of the intensive research into the mechanisms of plant abiotic stress response has translated into improved yield stability. A suspected obstacle to translatability of research findings in this area is artificial experimental conditions, but we lack evidence to support this explanation. Here, we combined a meta-analysis and an experimental approach to compare the effect of salt stress on wheat yield, growth, and physiology across four distinct experimental settings: field/field-like conditions, potted plants in a climate chamber, in a greenhouse, and outdoors. The meta-analysis, comparing responses relative to control conditions over similar ranges of salt stress intensity, confirmed that field conditions led to more limited impact on yield than in the other three experimental settings and uncovered differences in how shoot and root biomass are relatively affected by salt stress between greenhouse and outdoors pot experiments. In our experiment, we identified very distinct responses for each of the four experimental settings, with plants outdoors accumulating more Na⁺ and proline than plants indoors, and shoot growth and yield were least affected by stress in field-like conditions and most affected in the climate chambers. Together, these results suggest that the nature of the acclimation mechanisms used by wheat to face salt stress can depend on the experimental setting. While our findings need confirmation for other crops and abiotic stresses, we recommend renewed attention to the conditions under which experiments are carried out and to favor more realistic growth conditions when possible.

Contamination of farmland with heavy metals (HMs), particularly arsenic, cadmium, and lead, poses significant risks to human health and food security, especially through HM bioaccumulation in rice (Oryza Sativa). Current methods of detection for HMs, such as ICP-MS, provide accurate measurements but are destructive and labor-intensive, limiting their feasibility for widespread agricultural use. In this study, we investigated the potential of Raman spectroscopy (RS) as a nondestructive, cost-effective alternative for the detection of HM stress and thereby uptake in rice. Using a dose-response experimental design, we examined the sensitivity of RS for detecting varying levels of arsenic, cadmium, and lead-induced stress. Our analyses revealed several dose-dependent changes in Raman peaks associated with carotenoid and phenylpropanoid abundance. We found these changes were specific to each HM, reflecting the activation of distinct stress-response mechanisms. We also performed ICP-MS of harvested rice tissue, allowing us to build Raman-based calibration curves for predicting the HM concentration within rice. Lastly, we built a machine-learning algorithm that could interpret the Raman spectra to diagnose the specific type of HM toxicity with an average of 84.5% accuracy after only 1 week of HM stress. These findings highlight the promise of RS as a valuable tool for real-time, nondestructive monitoring of HM contamination in rice crops. Notably, the dose-response experimental design demonstrated RS's ability to detect HM stress levels that aligned with typical environmental contamination.

Plants respond to attack by chewing insects through the recognition of herbivore-associated molecular patterns (HAMPs) that are present in oral secretions (OS) and released at the wound site, leading to appropriate deployment of plant immune responses. Because insect feeding is accompanied by severe wounding of the leaf tissue, the specific contribution of HAMPs to defense is not well characterized. Also, OS contain effectors that interfere with the activation of defenses, but the underlying downregulated genes are poorly studied. Here, we analyzed the transcriptome of Arabidopsis thaliana leaves in response to wounding alone or to wounding and application of OS from Spodoptera littoralis or Pieris brassicae. For both insects, OS amplified wound-induced responses and specifically promoted the activation of stress and hormonal pathways, as well as pathogen-related responses. In contrast, OS inhibited the expression of genes involved in the regulation and biosynthesis of aliphatic glucosinolates (GS), and cell wall strengthening. In addition, OS-mediated suppression of wound-induced ERF114 and wound healing-related genes uncovered a novel strategy to impair defenses. In support of these findings, we observed an increased performance of S. littoralis and P. brassicae larvae feeding on OS-treated Arabidopsis plants. Altogether, we highlight a major contribution of OS components to plant response to herbivory and unveil the potential role of conserved OS-derived effector(s) in inhibiting defenses.

Magnesium deficiency is a major nutritional constraint that limits the growth and yield of crops and has not generated the necessary attention. In addition, the solution commonly proposed to solve the nutritional problems of crops was using chemical fertilizers. In contrast, other approaches that are more practical, quick to apply, less expensive, and have no impact on the environment and human health are now proposed. Accordingly, we have placed a primary emphasis on the common bean response to magnesium deficiency (Mg-D), with particular attention to the genotypic differences (using two cultivars: coco blanc [CB] and coco nain [CN]), and the use of melatonin (Mlt) as a seed priming agent to identify some traits of tolerance and assess the value of Mlt as a biostimulant of plant tolerance to Mg deficiency. The experiment was conducted hydroponically in a greenhouse, with a factorial completely randomized design. Obtained results showed specific Mg chlorosis in mature leaves more severe and precocious in CB than CN. Mg-D significantly hindered chlorophyll pigments, SPAD index, shoot and root biomass, Mg content, maximum quantum yield of PSII (Fv/Fm), and the photochemically converted energy fraction in PSII (YII). The photochemical quenching (qP) and electron transfer rate (ETR) decreased also, against an increase in nonphotochemical quenching (qNP). Seed priming with Mlt efficiently alleviated these multiple effects, and CN responded better to Mlt treatment. CN is more tolerant than CB due to its better management of Mg nutrition and the related Mg-dependent functions. Melatonin significantly improves the tolerance of common bean to Mg deficiency through an efficient management of energy in the electron transfer chain.

Tea plants (Camellia sinensis L.) use ammonium and nitrate as the main sources of nitrogen (N), but they respond differently to these two compounds. In this study, we investigated the effect of the ammonium:nitrate ratio on tea plant growth as well as N uptake and metabolism. A kinetics analysis showed that both ammonium and nitrate were absorbed, with no major differences within the concentration range 0.71-2.86 mM. Additionally, growth peaked when the ammonium:nitrate ratio was 25:75. The concentrations of several free amino acids, including theanine, in new leaves and roots increased as the proportion of ammonium increased. Glutamine concentrations in new leaves and roots were highest at ammonium:nitrate ratio of 25:75. Moreover, the transcription of key genes involved in theanine and glutamine biosynthesis was differentially affected by changes in N ratios, which explained the differences in metabolic changes. The glutamine:theanine ratio was higher at an ammonium:nitrate ratio of 25:75 than at 100:0 and 75:25, suggesting that the ammonium:nitrate ratio may affect the ratio of glutamine synthesis activity to theanine synthesis activity. We examined N metabolism regulatory genes and identified candidate genes, including SENSITIVE TO PROTON RHIZOTOXICITY 3.1 and NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1.2, in tea plants. These transcription factor genes are involved in the regulation of nitrate absorption and metabolism. Identifying genes that regulate N metabolism is essential for improving N use efficiency. The study findings will be useful for optimizing N fertilization management practices to control tea growth and quality.

An efficient nitrate uptake system contributes to the improvement of crop nitrogen use efficiency under low nitrogen availability. The High Affinity nitrate Transport System (HATS) in plants is active in low range of external nitrate and is mediated by a two-component system (high affinity transporters NRT2 associated to a partner protein NRT3 (NAR2)). In Brachypodium, the model plant for C3 cereals, we investigated the role of BdNRT2A and BdNRT3.2 through various experimental approaches. Expression profile of BdNRT2.A and BdNRT3.2 genes in response to nitrate availability fits perfectly with the characteristics of the HATS components. ¹⁵Nitrate influx measurements decreased in bdnrt2a mutants (one NaN₃ induced mutant with a truncated NRT2A protein and two amiRNA mutants). In addition, the N limited phenotype of the mutant with a truncated NRT2A protein confirmed that BdNRT2A is a major contributor of the HATS in Brachypodium. An effective nitrate transport in the heterologous expression system Xenopus oocytes required the coexpression of BdNRT2A and BdNRT3.2 that characterizes two-component system of the HATS. Functional interaction between BdNRT2A-GFP and BdNRT3.2-RFP fusion proteins was observed at the plasma membrane in Arabidopsis protoplasts in transient expression experiments with BdNRT3.2 being necessary for the plasma membrane localization of BdNRT2A. The role of a conserved Ser residue in BdNRT2A (S461) specific to monocotyledons was evaluated in the BdNRT2A and BdNRT3.2 interaction leading to plasma membrane targeting. Assuming that S461 could be regulated by phosphorylation, a directed mutagenesis was performed to mimic a nonphosphorylated (S461A) or a constitutively phosphorylated (S461D), However, the mimicking the phosphorylation status of S461 by mutagenesis did not modify the BdNRT2A and BdNRT3.2 interaction, suggesting a more complex regulating mechanism. In conclusion, our data show that BdNRT2A and BdNRT3.2 are the main components of the nitrate HATS activity in Brachypodium (Bd21-3) and allow an optimal growth in low N conditions.

Cucurbits are cultivated worldwide in regions with high concentrations of arsenic (As), a hazardous metalloid, affecting produce quality and increasing the consumer exposure. Cucurbitacins are herbivore-deterrent secondary metabolites that contribute to the plant defense response. The impact of As exposure on phenotypic and metabolic traits has not been studied in members of the Cucurbitaceae family, such as squash (Cucurbita pepo L.). To comprehend the effects of As on the root system of C. pepo, we assessed phenotype, cucurbitacin content, and transcriptome under low and high As concentrations. We report that at low dosages, cucurbitacins are decreased, while growth is not significantly affected. Conversely, high dosages impact growth and development altering root phenotype but cucurbitacin content is not significantly different from untreated plants. Furthermore, gene ontology enrichment on results of the RNA-seq analysis indicate that high dosages of As affect cellular regulatory processes, with genes related to glutathione metabolism being of the most upregulated. Additionally, an in-depth analysis of orthologs members of the heavy metal-associated (HMA)-domain superfamily and As-related transporters suggest a dosage-dependent participation of key members. WGCNA analysis reveals As-specific gene co-expression modules, indicating that low As levels induce adaptive responses in energy and allantoin metabolism, while higher levels trigger intensified oxidative stress responses, including upregulation of MYB transcription factors and heat shock proteins, which may support tolerance to the metalloid. Overall, As influences the root system physiology and metabolism in a concentration-specific manner, highlighting key defense systems and genes involved in C. pepo response to As exposure.

Iron-sulfur clusters are involved in many biological processes, including photosynthetic electron transport in the chloroplast and respiratory electron transport in the mitochondrion. Iron-sulfur cluster biosynthesis requires iron-sulfur carriers such as nitrogen-fixation-subunit-U [NFU]-type proteins. The Arabidopsis thaliana nuclear genome encodes two mitochondrion-targeted NFU proteins: NFU4 and NFU5, previously reported to have a primary role in the biosynthesis of the lipoate cofactor, mediated by the 4Fe-4S enzyme lipoyl synthase. Through in vitro reconstitution and spectroscopic analysis, we found that recombinant NFU4 and NFU5 proteins had UV-visible features characteristic of 4Fe-4S clusters. In addition, we confirmed that double homozygous, complete loss-of-function nfu4 nfu5 mutants had an embryo-lethal phenotype. To investigate the functional relationship between NFU4 and NFU5, we generated sesquimutants that were homozygous loss-of-function for one gene and heterozygous for the other, which appeared slightly smaller than nfu4-2, nfu4-4, and nfu5-1 single mutants. This suggests that the simultaneous decrease in levels of NFU4 and NFU5 proteins may have an additive effect on plant growth. Quantitative reverse transcription PCR showed that the NFU4 transcript was absent in mutants homozygous for nfu4-2 and nfu4-4 and that the NFU5 transcript level was substantially reduced in the nfu5-1 single mutant or sesquimutants. Consistent with the transcript data, the abundances of NFU4 and NFU5 proteins were either virtually absent or substantially reduced in the corresponding single mutants and sesquimutants. Immunoblot analysis showed that most nfu4 and nfu5-1 single, double, and sesquimutants had significant reductions in the levels of mitochondrial 4Fe-4S proteins, such as aconitase (ACO) and biotin synthase 2 (BIO2; note that BIO2 also contains a 2Fe-2S cluster). In addition, nfu4 nfu5 sesquimutants showed substantial reductions in the protein level of the 75-kDa subunit of respiratory complex I (CI75), which contains one 2Fe-2S cluster and two 4Fe-4S clusters. These observations indicate that NFU4 and NFU5 are important in maintaining the levels of mitochondrial 4Fe-4S proteins. Such observations are also consistent with the hypothesis that NFU4 and NFU5 may serve as iron-sulfur carriers and may play a role in the transfer of 4Fe-4S clusters to recipient apoproteins, such as ACO and CI75, during the biogenesis and maturation of mitochondrial 4Fe-4S clusters.

Balance among the sequential photophysical, photochemical, and biochemical reactions of photosynthesis is needed for converting fleeting energy in light to stable energy in chemical bonds. Any imbalance acts as either a bottleneck for limiting photosynthetic efficiency or an agent for inducing structural and functional damage to photosynthetic apparatus. Not only must each reaction be carefully regulated, but regulatory processes must also be coordinated across the reactions. However, regulations of different stages of photosynthesis have rarely been studied jointly. Non-photochemical quenching (NPQ) and stomatal conductance (g _s) are key regulators of photophysical and biochemical reactions, respectively. Existing evidence suggests that the redox state of plastoquinone regulates g _s and that the photochemical reactions are partially regulated by the ultrastructural dynamics of thylakoids induced by osmotic water fluxes in chloroplasts of land plants. To examine how these regulations are coordinated and feedback to each other, we simultaneously measured NPQ and g _s and inferred the redox state of plastoquinone and the light-induced thylakoid swelling/shrinking on numerous C₃ and C₄ species. For all species measured, NPQ and g _s covary with the redox states of the electron transport chain, particularly plastoquinone, and increase as thylakoid swelling is inferred. NPQ has the maximal sensitivity at the light intensity at which thylakoid is inferred to be fully swollen. Our findings suggest that plant energy and water use strategies are intimately linked by evolution, and studying the regulations of different photosynthetic stages as a whole can lead to new insights of the functioning of photosynthetic machinery in dynamic environments.

As photoautotrophs, plants use light not only as a source of energy but also as cues for directing growth and development. Phytochromes comprise a small gene family of plant specific light receptors that absorb mostly in the red/far-red portion of the electromagnetic spectrum. These light receptors are well-studied in the model species Arabidopsis thaliana, yet much less is known about their functions in other species. We have generated CRISPR-induced mutations in SlPHYTOCHROME E (SlPHYE) and SlPHYF, produced higher order mutants, and characterized some of their physiological functions in tomato (Solanum lycopersicum). We report that SlphyE plays a major role in detecting far-red light, repressing germination when light conditions are unfavorable for establishing a new seedling. While SlphyE functions on its own, it also synergistically works with another phytochrome, SlphyB1, which by itself only plays a minor role in germination control. Aside from its role in far-red light detection, SlPhyE is also involved in perceiving red light, leading to the repression of hypocotyl elongation and the promotion of light avoidance growth in the roots. SlPhyF acts synergistically with phyB1 during photomorphogenesis but it is not involved in far-red light detection during germination.