Journal of Experimental Botany最新文献

Maize is among the most commonly grown crops worldwide. Infections with Ustilago maydis, causing corn smut disease and leading to loss of biomass, yield, and silage quality, occur in all major growing regions. Rising global temperatures are predicted to reshape crop-pathogen interactions and subsequently threaten yield. However, the impact of minimal temperature changes resulting from climate change, and the molecular basis of temperature-modulated susceptibility, remain poorly understood. To investigate these, U. maydis infection trials and RNA-seq profiling across multiple maize cultivars grown under distinct temperature regimes based on the evaluation of climate data for Bavaria (Germany) were conducted. Even a minimal temperature change enhanced disease symptoms, while a brief heatwave greatly increased tumor formation and accelerated disease development. The observed phenotypic changes were accompanied by broad temperature- and cultivar-defined alterations in the host's transcriptional response. Expression-phenotype correlations, followed by in vivo testing, revealed factors contributing to variation in resistance. GIBBERELLIC ACID STIMULATED TRANSCRIPT-LIKE 4 is a broad resistance factor with implications of germplasm-specific variations in expression. The expression of γ-aminobutyric acid (GABA) transaminases, which cleave GABA, which acts as a susceptibility metabolite during U. maydis infection, is regulated in a temperature- and cultivar-dependent manner and correlated with fewer infections.

Allelic variations in BnaFLC.A10, BnaFLC.A2, and BnaFT.A2 have been associated with flowering time regulation in Brassica napus. However, the effects of their interactions remain insufficiently understood. In this study, we investigated the genetic basis underlying flowering time differences between the winter-type Tapidor and the spring-type Westar. Utilizing quantitative trait locus sequencing (QTL-seq) and transcriptome analysis, BnaFLC.A10, BnaFLC.A2, and BnaFT.A2 were identified as candidate genes associated with flowering time variation. Functional evidence from transgenic ectopic expression and CRISPR/Cas9-mediated genome editing supports their involvement in flowering time regulation. Genotypic and phenotypic analysis of 248 individuals from an (Westar×Tapidor) F2 population, along with 226 B. napus accessions, indicated additive effects of BnaFLC.A10 and BnaFLC.A2 in vernalization requirements and potential epistatic interactions with different BnaFT.A2 alleles. These results provide insights into the genetic interactions underlying flowering time variation and may assist in optimizing allele combinations for enhanced adaptation in B. napus breeding.

Water moves through trees pulled under tension through a series of dead tubes called xylem. During drought, conduits can be invaded by air, causing an embolism, leading to tissue or whole-plant death. Fagus sylvatica is the most abundant European broadleaf forest tree, and is currently under threat due to an increasing frequency and severity of drought, resulting in xylem embolism, dieback, and death. Here, we investigated the variation in embolism resistance across globally distributed individuals of F. sylvatica f. purpurea receiving between 563 mm and 1362 mm of rainfall per year, as well as variation in embolism resistance across the canopy. We found no difference in the water potential when 50% of the stem xylem was embolized (P50) across locations in this clonal form of F. sylvatica but we did find variation in P50 across the canopy driven by light, with shade branches being significantly more vulnerable than part or full sun-adapted branches. The lack of variation in response to annual rainfall in a globally distributed clone has implications for predicting the risk of mortality driven by periodic droughts and long-term shifts in rainfall patterns due to climate change in F. sylvatica. Our work also highlights the importance of horticultural resources such as globally distributed clones as a model system for examining plant responses to the environment.

Drought-induced depletion of non-structural carbohydrates has been reported to affect xylem hydraulic vulnerability, which in turn is frequently correlated with water potential at turgor-loss point. Given that non-structural carbohydrate depletion can impair osmoregulation, we hypothesised that vessel-associated parenchyma cells (VACs) that undergo drought-induced turgor loss and plasmolysis could facilitate gas movement and the formation of xylem embolism. Plasmolysis was induced in wood parenchyma of Populus nigra stems of mature trees and potted plants by radial injection or axial perfusion with a polyethylene glycol solution at low osmotic potential. The effect of polyethylene glycol on embolism resistance was assessed using the gas injection technique followed by classic hydraulic quantification of embolism, as well as with flow-centrifuge measurements. Light and transmission electron microscopy confirmed the occurrence of plasmolysis of VACs in osmotically treated samples, while hydraulic measurements revealed an increase in xylem vulnerability to embolism upon induction of plasmolysis, raising the loss of hydraulic conductivity by ∼20-40%. The results therefore support the hypothesis that the maintenance of cell turgor in VACs is critical for xylem hydraulic integrity under drought. We speculate that plasmolysis of VACs could promote gas movement to functional vessels via vessel-parenchyma pits, increasing the likelihood of embolism propagation.

Cotton fiber elongation is a complex developmental process regulated by hormonal and metabolic signals. Auxin (indole-3-acetic acid, IAA) and brassinosteroid (BR) play crucial roles in cotton fiber development, but the mechanism by which they coordinate to regulate fiber elongation remains unclear. In this study, we determined that IAA levels gradually increase during fiber development and are higher in long-fiber varieties. In vitro ovule culture experiments revealed that IAA promotes fiber elongation in a dose-dependent manner. Transcriptome analysis showed that IAA activates BR biosynthesis and the BR signaling pathway, implying crosstalk between the two hormones. Interestingly, IAA could partially rescue fiber elongation caused by BR deficiency due to brassinazole treatment and in pag1 mutants, and BR supplementation partially alleviated fiber inhibition resulting from impaired IAA transport or IAA deficiency. However, neither hormone fully compensated for the absence of the other, indicating that both serve non-redundant roles in fiber elongation. Additionally, inhibiting glucose signaling by suppressing hexokinase activity through N-acetylglucosamine impaired fiber growth, but this could be rescued by exogenous application of either IAA or BR, suggesting that glucose acts upstream of IAA and BR, which cooperatively regulate the elongation of cotton fibers.

Hybridization and polyploidization combine divergent nuclear genomes with maternally inherited organelles, often disrupting cytonuclear coadaptation critical for respiration and photosynthesis. This review examines the mechanisms, outcomes, and evolutionary significance of cytonuclear incompatibility in plants. We focus on how divergence in nuclear-encoded, organelle-targeted proteins and organelle genomes leads to mismatched interactions in protein import, folding, and assembly of multi-subunit enzyme complexes. The evidence highlights taxon- and complex-specific responses that mitigate incompatibilities, including the biased retention and expression of maternal alleles, gene conversions, and regulatory adjustments. We highlight how cytonuclear compatibility in hybrid lineages entails responses at multiple levels of regulation, including methylation/chromatin accessibility, gene expression, alternative splicing, translation rates, organelle import, protein-folding and assembly, and protein degradation pathways. Manifestations such as chlorosis, seed sterility, or hybrid breakdown underscore their role in shaping reproductive barriers. Conversely, maternal bias and compensatory mechanisms often act to restore functional integration of parental genomes, allowing hybrid and polyploid persistence. Beyond their evolutionary role in speciation and adaptation, cytonuclear incompatibilities underpin key practical applications, notably cytoplasmic male sterility, a cornerstone of hybrid crop breeding. We conclude that cytonuclear dynamics reveal both constraints and opportunities, illuminating plant diversification, hybrid resilience, and agricultural innovation.

The aleurone in cereal grains is an outer cell layer enriched with multiple nutrients important for human health. Enhancing the thickness of the aleurone layer through breeding could improve the nutritional value of rice. In this study, we characterized OsABCB24, a member of the ABCB transporter gene subfamily in rice, and its role in regulating aleurone development. Expression profiling revealed that OsABCB24 is predominantly expressed in seedling leaves and developing caryopsis, particularly in aleurone layer cells during grain filling. Subcellular localization analyses via protoplast transfection and immunogold labeling demonstrated that OsABCB24 is localized to the chloroplast. Knockout of OsABCB24 significantly increased the thickness of the aleurone cells and elevated the concentrations of minerals such as phosphorus, potassium, zinc, magnesium, and copper in brown rice. Knockout of OsABCB24 also decreased the concentrations of free and conjugated indole-3-acetic acid (IAA) in developing caryopsis and increased the leaf angle by influencing cell proliferation and elongation on the adaxial side of the lamina joint at the seedling stage. Leaf angle was less sensitive to exogenous IAA in osabcb24 mutants than in the wild type. Taken together, these findings suggest that OsABCB24 is a negative regulator of aleurone cell expansion possibly by modulating auxin homeostasis. OsABCB24 is a promising genetic target for breeding rice with increased aleurone thickness and nutrient concentrations without yield penalty.

The importance of the vascular network for transporting water, carbohydrates, and nutrients for sustaining plant growth and development in the vegetative body of plants is well known. Nevertheless, the vascular network within a fruit is still inadequately understood. Here, we characterized the vascular network in the fruit pericarp of 10 tomato genotypes varying in fruit size from 20 to 287 g (fresh mass) and investigated its relationships with typical hydraulic and anatomical traits under well-watered and water deficit conditions. We found that larger fruits had lower vein length density, accompanied by a larger number of xylem vessels within a vascular bundle and lower water uptake capacity per fresh mass. Vein length density was positively correlated with total soluble solids, while negatively correlated with mesocarp cell size. This study highlights the association between the hydraulic function of the fruit peripheral vascular network and fruit size, likely opening up a new research avenue for understanding fruit evolution, aiding in the selection of drought-tolerant genotypes, and encouraging the integration of fruit venation patterns into research.

The transition from vegetative to reproductive growth is a critical phase in the life cycle of a plant, directly affecting fecundity and overall crop productivity. This phase change is regulated by both endogenous genetic programs and environmental cues, including photoperiod, ambient temperature, abiotic stress, and nutrient availability. Among essential macronutrients, nitrogen (N), phosphorus (P), and potassium (K) support fundamental plant growth processes and actively regulate flowering time through distinct physiological and molecular mechanisms. Many studies have shown that both deficiency and excess of N, P, or K can either accelerate or delay flowering, depending on the species, developmental stage, and environmental context. In this review, we summarize the current knowledge on how N, P, and K affect flowering time in various plant species, including model and crop plants. We highlight the nutrient-responsive regulatory pathways and key genes involved in floral transition. By integrating recent findings in molecular genetics, physiology, and agronomy, we provide insights into how precise nutrient management can optimize flowering schedules, improve yield stability, and reduce fertilizer dependency. These insights, along with understanding macronutrient use efficiency, are essential for developing sustainable agricultural strategies that can adapt to changing environmental conditions, while ensuring food security and productivity.

Increases in global temperature and drought are negatively impacting the yields of major crops. Therefore, targeted improvements to intrinsic water use efficiency (WUEi) are needed to reduce the water required for agricultural production. While it is very time-consuming to directly measure WUEi, stable carbon isotope ratios (δ13C) are a reliable high throughput proxy trait for quantifying WUEi in C3 species. While genetic studies have improved our understanding of the relationship between WUEi and δ13C in C4 species, the knowledge needed to implement δ13C in breeding schemes is incomplete. Using a maize line with an extremely negative δ13C value, a quantitative genetics approach was used to identify a large deletion in carbonic anhydrase1 (cah1). Carbonic anhydrase is the first enzymatic step of the C4 photosynthetic pathway and is known to affect δ13C. Surprisingly, the line with the mutant allele had significantly higher carbonic anhydrase activity with a concurrent reduction in δ13C, the opposite of what would be expected based on C4 carbon isotope fractionation theory. These observations decouple δ13C and WUEi, which calls for further investigation into carbon isotope discrimination in C4 species.