搜索结果：Journal of experimental botany

The plant hormone ethylene is perceived by a small family of histidine kinase-like ethylene receptor proteins in Arabidopsis. The five receptors, considered functionally redundant, are structurally categorized into two subfamilies. Little is known about the biological importance of subfamily classification in receptor signaling or the degree of redundancy. By testing the genetic interactions of receptor genes, our results annotated differential emergent signaling of receptor isoforms. Except for the ethylene-insensitive ETR1-1 receptor, ethylene-insensitive receptors require other wild-type isoforms to convey receptor signaling. The two subfamilies are mutually required for efficient receptor signaling, and emergent receptor signaling is minimal within a subfamily. The receptor signal output was minimal for the subfamily I member ETR1, barely detectable for ERS1, and relatively strong for ETR1 and differential for ERS1 in combination with a subfamily II member. ETR1 has unique roles in receptor signaling. Together with other lines of evidence, our findings imply a low degree of functional interchangeability among receptor isoforms. The low degree of functional redundancy thus enriches the heterogeneity of receptor complexes, enabling an extended range of ethylene responsiveness. The structural features of plant ethylene receptor-like proteins were analyzed, shedding light on the evolution and emergent properties of ethylene receptor-like proteins.

The apoplast of leaves is involved in nutrient transport, microbe-host interactions, systemic signaling, cell wall dynamics, and serves as an interface for various other physiological processes. The composition of the apoplastic solute pool, which supports many of these functions, is dynamic and shaped by developmental and environmental cues. However, due to the complexity and compartmentalization of the apoplast, analysing these fluids - and thus the associated physiological processes - remains technically challenging. This study introduces a minimally invasive method for extracting apoplastic fluids from leaves of selected dicots (e.g. Arabidopsis thaliana, Vicia faba, and many more), offering two key advantages: (i) repeated extractions from the same leaves to generate time-series data, such as every 24 hours, over consecutive days, and (ii) high spatial resolution, enabling identification of macrodomains within the leaf apoplast. For example, abscisic acid macrodomains were revealed along the leaf axis, providing insight into apoplastic hormone regulation. The method also reveals other previously unrecognized aspects, such as the accumulation of kaempferol glycosides in the apoplast after plants experienced salt stress. Finally, the method addresses the distortion of apoplast compound levels caused by dilution bias that results from the inconsistent recovery of infiltration fluid. Adding pyranine enables correction, ensuring accurate and comparable data. By integrating spatial and temporal precision, this new tool will promote a deeper understanding of plant apoplastic processes and their physiological relevance in various biological contexts.

To meet the growing demand for agricultural products, optimizing photosynthesis is a promising strategy to improve the crop yields. Phenotypic variance in photosynthesis has been observed within or between species. To explore the potential of integrating photosynthetic parameters into crop breeding programs, we explored the genetic variation in photosynthesis by assessing photosynthesis-related parameters across plant development in 631 barley recombinant inbred lines (RILs) from eight HvDRR sub-populations under field conditions. The genetic complexity of these parameters was resolved by bi-parental and multi-parental quantitative trait loci (QTL) analyses. Finally, we examined the merit of integrating photosynthesis-related parameters in genomic prediction of yield and its components. Significant genotypic variations of the photosynthesis-related parameters were found among the RILs, with their heritability ranging from 0.38 to 0.54. The multiple QTL and dynamic QTL for photosynthesis observed across different developmental stages underlined the complexity of the genetics of photosynthesis in barley. The considerably higher percentage of phenotypic variance explained for genomic prediction than multi-parental QTL analysis illustrates that the photosynthesis-related parameters are inherited in a more complex way than classical agronomic traits. Notably, the prediction ability for yield was increased by integrating the photosynthesis-related parameters of some developmental stages into genomic prediction models. Therewith, our results suggest a novel perspective on increasing the efficiency of crop breeding programs by integrating photosynthesis-related parameters into prediction models.

Refilling of xylem embolism during recovery from drought has been studied for decades, although the legitimacy of supporting evidence has been debated in recent years due to potentially widespread methodological artifacts associated with destructive sampling. Evidence from multiple destructive/indirect measurements of embolism suggests sunflower can refill, but more recent evidence suggests this species is particularly susceptible to artifacts that cause the appearance of refilling. Here, we investigated drought-induced xylem embolism and its potential reversibility in intact sunflowers using low-radiation micro-computed tomography (µCT). While plants were drying, turgor loss and stomatal closure occurred at ca. -1.0 MPa, whereas comparable losses of photosystem II efficiency as well as leaf and stem xylem embolism occurred at ca. -1.5 MPa. After re-watering, xylem embolism that accumulated in stems and leaves during the drought event did not reverse despite significant recovery of transpiration and photosynthesis. We found no evidence of xylem embolism refilling in sunflowers, highlighting the potential widespread nature of methodological artifacts and the need to revisit conclusions of "refilling" in other species as well as physiological and developmental consequences of irreversible embolism.

SNAREs are important proteins that mediate the fusion of vesicles with target membranes in eukaryotic cells. The fusion of secretory vesicles with the plasma membrane is the basis of pollen tube tip growth. However, the role of Qbc SNARE SNAP30 in Arabidopsis pollen tubes has not yet been reported, and the intact SNARE complex that regulates exocytosis at the pollen tube tip has yet to be determined. Our study revealed that the deletion of SNAP30 inhibited the tip growth of Arabidopsis pollen tubes. Fluorescence recovery after photobleaching (FRAP) experiments indicated that SNAP30 plays an important role in exocytosis at the Arabidopsis pollen tube tip. Confocal microscopy revealed that SNAP30 and SYP131 or VAMP726 colocalize to the plasma membrane at the tips of Arabidopsis pollen tubes. Furthermore, we found that SNAP30 can interact with the Qa-SNARE SYP131 and R-SNARE VAMP726. In addition, SNAP30 can form a SNARE complex with VAMP726 and SYP131. These results suggest that SNAP30 forms a SNARE complex with VAMP726 and SYP131 to mediate vesicle secretion at the plasma membrane of Arabidopsis pollen tube tip. These results also indicate that the molecular mechanism of vesicle secretion may be evolutionarily conserved between animal nerve cells and plant pollen tubes.

Root hairs are specialized extensions of root epidermal cells that allow plants to explore and attach to the soil. They exhibit polar growth under the influence of isotropic turgor pressure thanks to the anisotropic nature of their cell walls. This unidirectional growth is regulated by myriad subcellular factors such as microtubule and actin dynamics, a tip-focused calcium gradient, and the interplays between gradients of apoplastic and cytosolic pH and reactive oxygen species. All these players also influence cell wall dynamics by forming feedback loops that modulate cell wall assembly and modification, which are essential processes for root hair morphogenesis. In this review we discuss the functions of cell wall polysaccharides and proteins and their impacts on the biomechanics of root hair growth at each developmental stage. We also discuss important open questions and technical advancements in studying root hair mechanobiology. Despite significant progress, many of the spatiotemporal changes that occur in the cell walls of root hairs remain undiscovered. Therefore, we highlight ongoing research and exciting future avenues that will shed light on cell wall dynamics, biomechanics, and mechanobiology of root hair morphogenesis.

C4 grasses are crucial for food and biofuel production. Originating from warm regions of the world, C4-photosynthesizing plants typically exhibit poor chilling tolerance. Some C4 grasses of Miscanthus are recognized for their exceptional chilling tolerance, however, the mechanism behind it is not fully understood. Here, we hypothesize that the rapid adjustment of leaf pigment composition contributes to mechanisms that protect photosynthesis during the initial short-term response to chilling. Miscanthus accessions with documented contrasting levels of chilling tolerance were subjected to chilling under dark and light conditions with or without nutrient limitations. The changes in pigment composition were assessed by hyperspectral indexes and molecularly validated. Our results showed that high-chilling-tolerant accession accumulates zeaxanthin and anthocyanins while reducing chlorophyll content at the end of chilling night when grown on the low-fertility soil. Interestingly, at the end of the night, low soil fertility alone was able to induce a significant difference in zeaxanthin accumulation between accessions. Night-accumulated zeaxanthin led to 38% faster NPQ following morning. Transcriptional differential regulation of enzymes involved in pigment anabolism and catabolism supports the dynamic adjustment in leaf pigment composition. The investigated changes in pigment composition can inspire new strategies to engineer crops for better stress resistance.

Stable rice production is continuously threatened by rapidly evolving, devastating rice pathogens, underscoring the need for new sources of disease resistance. Phosphoinositide 4-kinases (PI4Ks) are important in the phosphoinositide biosynthetic pathway and are classified into Type II and Type III. Type III PI4Ks have been studied for their role in plant immunity; however, the function of Type II PI4Ks remains underexplored. In this study, we investigated the role of type II PI4Ks, OsPI4Kγ2 and OsPI4Kγ6 in rice immunity. Using genome editing, we generated knockout mutants of OsPI4Kγ2 and OsPI4Kγ6, which displayed enhanced resistance to rice blast and bacterial blight as indicated by reduced disease symptoms, increased production of reactive oxygen species (ROS), and elevated defense-related gene expression. Moreover, loss of OsPI4Kγ2 or OsPI4Kγ6 significantly reduced PtdIns4P levels and biotrophic interfacial complex (BIC) formation rates, indicating that these kinases are required for maintaining normal PtdIns4P homeostasis and infection-related structure formation in rice. This study thus provides evidence that OsPI4Kγ2 and OsPI4Kγ6 act as negative regulators of rice immunity, offering new insights into their role in plant defense.

Sweet wormwood (Artemisia annua) produces and deposits artemisinin in its glandular trichomes while the molecular mechanisms of trichome development remain poorly understood. Here, we conduct single-nucleus RNA sequencing of 10-day-old A. annua seedlings, depicting the specific expression of trichome cell in leaves. The reconstruction of developmental trajectory of trichome cells not only identifies novel expressed genes, but also elucidates trichome development involved in photosynthesis, auxin biosynthesis, and cutin biosynthesis. By integrating the developmental trajectory of trichome cells with histochemical assays, we identified several genes not previously reported to be involved in trichome development, such as TOE3, MYB1, WRKY10, and ZNF. Moreover, we identified a gene in subcluster 0 encoding a previously unknown WD40 repeat nuclear protein, WDR1, potentially involved in trichome development. We showed that WDR1 not only interacts with SPL9 and enhances its ability to activate HD1 expression, but also directly binds to HD1 itself, thereby forming a regulatory feedback loop that modulates trichome development in A. annua. This study reveals a previously uncharacterized gene that regulates trichome development in A. annua based on a single-cell transcriptome analysis. The results presented here offer unprecedented insight into a new pathway for enhancing trichome density and artemisinin production.

Oxygenic photosynthesis relies on multisubunit protein complexes embedded in the thylakoid membrane, which is distinguished by its unique lipid composition consisting of galactolipids and sulfolipids together with phosphatidylglycerol rather than typical phospholipids. Emerging structural and biophysical evidence indicates that these lipids are involved in dynamic regulation of photosynthesis. Lipids act as structural cofactors to stabilize the assembly of photosystem complexes and also as modulators of membrane properties such as fluidity, polymorphism, and thickness, which directly impact photosynthetic processes. These physical properties of the thylakoid membrane are regulated according to environmental conditions. Fatty acid unsaturation modifies lipid bilayer fluidity and thereby mitigates the effects of temperature on membranes. The ratio of non-bilayer-forming to bilayer-forming lipids contributes to lipid phase transitions required for environmental responses of thylakoid proteins. Furthermore, changes in thylakoid membrane thickness regulate protein-protein assembly, such as the aggregation of light-harvesting complex II through hydrophobic mismatch, thereby modulating the light-harvesting system. In this review, we integrate recent findings to highlight the role of thylakoid lipids as modulators of photosynthetic protein interactions and their conformational and functional states, providing key insights into the functional regulation of the photosynthetic apparatus in response to environmental changes.

Seed germination is inhibited by salt stress, and this inhibition is known to be mainly mediated by the plant hormone abscisic acid (ABA). Whether and how this inhibition is fine-tuned is not fully understood. Here, we identified MODIFIER OF snc1-1 (MOS1) as an attenuator of salt-induced inhibition of seed germination. MOS1 expression was induced by salt, and this induction was partly dependent on ABA biosynthesis and signaling. The mos1 mutant showed hypersensitivity to salt stress during seed germination compared to the wild-type, accompanied by higher ABA accumulation and stronger salt-induced expression of ABA biosynthesis and signaling genes. Genetic analysis suggested that MOS1 limits both salt-induced ABA biosynthesis and ABA responsiveness. Moreover, ABI5 directly activated MOS1 expression, whereas ABI5 transcript and protein accumulated to higher levels in mos1 under salt stress. In addition, MOS1 expression was inhibited by the germination-promoting hormone gibberellin (GA), and MOS1 helped maintain GA biosynthesis. Together, these findings suggest that MOS1 attenuates salt-induced inhibition of seed germination, at least in part, through ABI5-linked negative feedback regulation of ABA signaling and modulation of GA biosynthesis.

Determining elemental concentrations in plant tissues is essential for physiological studies on abiotic stress. However, high-throughput routine analysis of light elements (sodium to calcium) in plants is challenging due to the need for complete sample dissolution and expensive and time-consuming inductively coupled plasma-mass-spectrometry (ICP-MS). Ion chromatography and ion-selective electrodes are low-cost methods but suffer from major drawbacks, including limited throughput and time-consuming sample preparation. This study reports on a new methodology for quantitative analysis of light elements in plants using monochromatic X-ray fluorescence (MXRF) analysis. We quantitatively assessed sodium and potassium uptake in Arabidopsis thaliana, Oryza sativa and Lactuca sativa in salinity treatments. The new method provides reliable results from samples as small as 1 mg, making it suitable for analysis at the seedling stage. This is enabled by the high sensitivity of the system and optimized sample preparation that ensures sufficient signal even at low sample masses. We tested the accuracy and precision of the technique for other light elements to demonstrate its broad applicability. The results show that the method delivers rapid, non-destructive, and extraction-free light element analysis on small samples highly correlating with ICP-MS. The monochromatic XRF method provides accurate measurements and reproducible results for studying salinity tolerance ideally suited for investigating elemental composition of early plant developmental stages, offering new possibilities for research into early stimuli responses.

Targeted protein degradation (TPD) has emerged as a chemical strategy to modulate proteostasis, offering important advantages over traditional small molecules. By inducing proximity between a protein of interest (POI) and the cellular degradation machinery, protein degraders enable selective and dynamic degradation of the POI. Unlike classical small molecules (i.e. inhibitors), the event-driven mode of action of chemical degraders offers new therapeutic opportunities for previously intractable diseases. Molecular glues (MGs) and proteolysis-targeting chimeras (PROTACs) can target proteins previously considered undruggable, including those lacking catalytic activity or deep binding pockets, such as transcription factors and scaffold proteins. TPD has gained substantial attention in drug discovery, with several candidates advancing in clinical trials, validating chemically induced proximity as therapeutic strategy. However, in plants, the development of synthetic degraders remains largely unexplored. Here, we review the molecular basis of TPD, with emphasis on MGs and PROTACs. We discuss critical aspects of PROTAC design, including E3 ligase suitability, target selection, and linker optimization. We also summarize engineered tag-based systems and emerging non-proteasomal modalities. Finally, we provide a critical evaluation of the opportunities and limitations of protein degraders and provide a theoretical and practical framework to facilitate the expansion of TPD in plant biology and agriculture.

Marine heatwaves (MHWs) are intensifying under climate change, yet the physiological limits that constrain seagrass resilience remain poorly defined. We experimentally tested the responses of the surfgrass Phyllospadix scouleri, a foundation species of the Northeast Pacific coast, to simulated MHWs of contrasting intensity. In a 27-day mesocosm experiment, plants were exposed to fluctuating temperatures representing a severe MHW (23.5 ± 1.5 °C) and an extreme MHW (26.5 ± 1.5 °C), while photosynthetic performance, respiration, nitrogen metabolism, oxidative stress, and growth were monitored during and after warming. Phyllospadix scouleri maintained photosynthetic capacity and carbon balance under severe warming but exhibited pronounced physiological disruption at extreme temperatures, including sustained photoinhibition, reduced nitrate assimilation, elevated respiration, and negative daily productivity. These effects persisted after heat stress, leading to reduced growth and indicating incomplete recovery. Multivariate analyses revealed a transition from tolerance to functional breakdown near 26.5 °C, suggesting a potential physiological tipping point only 5-6 °C above current summer maxima in the area of the studied population. Our findings indicate that intensifying MHWs may rapidly erode the thermal safety margin of temperate seagrasses, pushing foundational coastal ecosystems toward metabolic instability under continued ocean warming.

Pinus radiata has been characterised as strongly isohydric, which means that it tends to close stomata to maintain leaf water potential relatively constant under changing environmental conditions. However, under high temperatures, where leaf cooling may be necessary to prevent overheating, the ability to maintain this isohydric behaviour remains unexplored. Here, we examined the impact of increasing temperature (and associated needle-to-air vapor pressure deficit hereafter referred to as VPDneedle) on whole plant stomatal conductance (gc), canopy transpiration (Ec), minimal conductance (gmin) and stem water potential (Ѱstem) in well-watered Pinus radiata plants. A decline in gc was observed as temperature increased from 22°C to 32°C resulting in 27% stomatal closure, followed by levelling off at further higher temperatures. However, this stomatal closure was not enough to prevent an exponential rise in Ec and pronounced declines in Ѱstem. gmin contributed 18% of gc at 42°C and showed an exponential rise at temperatures higher than 42°C. Our findings suggests that high temperatures may lead to drop in isohydry in Pinus radiata. This shift may be crucial to avoid overheating and damage of plant tissues but at the same time leads to more negative Ѱstem, thereby increasing the chances of xylem embolism. The observed shift in stomatal response reveals that even in water conservative species like Pinus radiata, high temperatures may compromise stomatal regulation of water potential.

Avocado (Persea americana Mill.) is an economically important tree crop that exhibits a high rate of immature fruit abscission (IFA), reducing yield. As the seed coat derived from recently abscised fruitlets displays a senescence phenotype, we hypothesized that the seed coat plays a critical role in initiating IFA. Here, we show that fruitlets fated to abscise undergo growth arrest before shrinking and detaching from the tree. Comparative RNAseq analysis indicates that growth arrest is associated with a transcriptome reprogramming that is first initiated in the seed coat then transmitted to pericarp and embryo. Gene expression and hormone profiling results indicate that fruitlet growth arrest is associated with a decline in auxin activity and an increase in abscisic acid, the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid, and the bioactive jasmonate, jasmonoyl-isoleucine, in the seed coat. At a late stage of growth arrest, transcriptomic signatures further suggest that a dormancy-like program of development is induced in the seed and a senescence phenotype is activated in the seed coat. Together, our data indicate that avocado IFA is initiated by hormone-driven transcriptome reprogramming that functions to transition the seed coat to a senescence program of development, which induces growth arrest, seed dormancy and ultimately, fruitlet abscission.

Root growth angle is a key determinant of root system architecture, nutrient capture efficiency and therefore yield. Yet the mechanisms governing non-vertical growth in cereal roots remain poorly understood. Here, we investigated if cereal roots maintain Gravitropic Setpoint Angles (GSAs) and the hormonal regulatory processes underpinning GSA maintenance in cereals. Firstly, we found that both wheat seminal roots and rice crown roots actively return toward their original growth angles following displacement, consistent with true GSA maintenance. Next, we show that removal of a stable reference to gravity through clinorotation resulted in a characteristic outward curvature in all root types, indicating the presence of an antigravitropic offset similar to that described in Arabidopsis. Exogenous auxin treatment induced steeper rooting in both species, suggesting conserved hormonal regulatory mechanisms of GSA in both monocots and dicots. Interestingly, lateral root GSAs displayed species-specific differences: wheat laterals returned to their GSAs more effectively than rice laterals, which showed slower and incomplete responses. Together, these findings establish that cereal roots maintain GSAs through gravity-dependent and auxin-regulated mechanisms, providing a novel framework for understanding and manipulating root system architecture in monocot crops.

Amino acids are not only essential for plant nutrition but also serve as critical immune signaling molecules, particularly during pathogen invasion. Pathogens can manipulate amino acid metabolic pathways to counteract host immune defenses, yet the underlying mechanisms remain poorly understood. Here, we demonstrate that the Pepper mild mottle virus (PMMoV) 126 kDa protein interacts with host L-asparaginase (LA), identified as a negative regulator of antiviral defense. LA converts asparagine (Asn) to aspartic acid (Asp). Exogenous application of Asn markedly enhanced resistance to PMMoV, whereas Asp produced the opposite effect. Transcriptomic analysis revealed that Asn activates key antiviral immune pathways involving salicylic acid (SA), ethylene (Eth), and reactive oxygen species (ROS), while Asp suppresses them. Further experiments showed that the 126 kDa protein binds directly to the LA active region, enhancing its enzymatic activity and promoting Asn-to-Asp conversion, thereby weakening immune signaling. This process may also involve the VSR (viral suppressor of RNA silencing) function of the 126 kDa protein. Notably, LA also interacts with pathogenic proteins from other RNA viruses (e.g., CMV 2b, RSV NS3, TBSV P19) and facilitates Tomato bush stunt virus (TBSV) accumulation. This study elucidates how viruses exploit amino acid metabolism to promote infection and provides a novel strategy for environmentally friendly control of pepper viral diseases.

Abscission zones mediate organ separation through coordinated changes in cell wall architecture and intercellular signaling. To elucidate mechanisms of fruit abscission zone (FAZ) transitions preceding fruit detachment in the non-climacteric fruit olive (Olea europaea), we integrated physiological, transcriptomic, and cellular analyses during natural maturation and after ethylene treatment. A mesocarp-subtraction RNA-seq strategy uncovered a FAZ-enriched module of 733 genes, representing core regulators of FAZ maturation. Induction of β-1,3-glucanase genes corresponded with elevated glucanase activity and callose depletion at plasmodesmata, indicating increased symplastic signaling required to initiate the abscission. A previously undocumented rise in cytoplasmic and apoplastic pH of the olive FAZ, coupled with reduction of low-methylesterified homogalacturonan, represents a hallmark of pH-dependent wall remodeling. Transcriptomic enrichment of transporters and pH-responsive wall-modifying enzymes positions pH homeostasis as a central regulator upstream of wall reconfiguration. Concurrent activation of pectate lyases and key phenylpropanoid pathway enzymes suggests a dual remodeling trajectory involving reduction of de-methylesterified pectin, which weakens intercellular cohesion, and localized lignin deposition, defining the separation boundary. Our findings establish a conserved molecular circuit that confers ethylene competence to the FAZ and a mechanistic framework in which symplastic connectivity, pH-driven enzymatic activation, and modulation of wall polymer chemistry orchestrate FAZ maturation and fruit detachment in table olive.