Journal of Experimental Botany最新文献

Proteostasis relies on the coordinated control of protein synthesis, folding, modification and degradation, and an increasingly clear picture is emerging that many important decisions governing protein fate occur co-translationally. As nascent chains first appear at the ribosome exit tunnel, they encounter a suite of ribosome-associated enzymes that begin to shape whether proteins fold productively, acquire the correct N-terminal imprinting modifications, or require surveillance and removal. This review focuses on two major facets of co-translational control that determine protein and proteome stability, with particular attention to recent advances in plants. First, N-terminal (Nt-) methionine excision, Nt- acetylation and Nt-myristoylation are examined as early imprinting steps that define the chemical identity and regulatory trajectories of newly synthesized proteins, including how they influence targeting to N-degron pathways of proteolysis. Second, ribosome-associated quality control (RQC) pathways that sense ribosome stalling or collision are outlined, along with their roles in directing aberrant nascent chains towards ubiquitylation, extraction and degradation before they can accumulate and trigger proteotoxic stress. Together, these modification and surveillance mechanisms form an integrated decision-making network that establishes protein stability at the earliest stages of synthesis, contributing to proteostasis and impacting plant growth, development, and stress adaptation.

Numerous studies have reported disease suppression in intercropping systems, attributing it to mechanisms such as host dilution, microclimate modification, barrier effect, and induced resistance. However, the relative contributions of mechanisms to altered disease dynamics remains unclear. We combined field experiments and mechanistic modelling to quantify the importance of these mechanisms in suppressing Phytophthora infestans in potato intercropped with faba bean, ryegrass, or maize. Field data was used to estimate effects of disease-suppressive mechanisms on various disease processes. These were integrated into a dynamic microclimate-dependent epidemiological simulation model of late blight to predict the progression of disease severity, and the individual contribution of mechanisms. Even small differences (1-3%) in relative humidity accumulated to significantly impact disease severity. The model most accurately predicted disease suppression only when host dilution, microclimate modification and barrier effect were combined, suggesting that each contributes substantially. Individual mechanisms varied in strength across companion crops and sometimes counteracted (particularly microclimate modification and barrier effect), but their combined effects consistently reduced disease. This study provides a novel framework to disentangle and quantify the contribution of disease-suppressive mechanisms in intercropping systems, enhancing our understanding of disease suppression in species mixtures, to help design cropping systems less reliant on chemical protection.

The ripening behavior of blueberries (Vaccinium corymbosum) remains debated, with classifications ranging from climacteric to non-climacteric or atypical climacteric. While ethylene's role in blueberry ripening has been primarily studied through postharvest ethephon treatments, its endogenous function and the presence of system II ethylene biosynthesis remain unclear. This study aimed to evaluate ethylene's role in blueberry fruit ripening and determine the presence or absence of system II ethylene biosynthesis for fruit ripening classification. Highbush blueberries exhibited low ethylene emissions, which increased at the fruit coloring and pink stages, coinciding with an increase in ethylene's precursors SAM and ACC, increased respiration rate, acidity loss, sugar accumulation, anthocyanin synthesis, and fruit pigmentation. Genome-wide analysis identified two putative ethylene biosynthetic genes, VcACS3 and VcACO6, which were expressed during ripening and functionally validated via transient overexpression in 'O'Neal' fruit. However, in planta and postharvest propylene treatment, which mimics ethylene's effects, failed to induce autocatalytic ethylene biosynthesis across cultivars. Additionally, in planta and postharvest 1-MCP treatment in all genotypes, and transient overexpression of Atetr1-1 in 'O'Neal' fruit, inhibited ripening without reducing ethylene emission. These findings indicate that while ethylene modulates blueberry ripening, its biosynthesis is not autocatalytically controlled. Thus, blueberries are best classified as non-climacteric fruit with ethylene-dependent ripening characteristics.

Dehydration tolerance and embolism resistance contribute to plant drought survival, but their limits and combinations in perennial grasses remain unexplored. We investigated four grasses (Stipa species and Dactylis subspecies) from Mediterranean sites prone to intense summer drought. Plant tolerance to soil water deficit and tissue dehydration, embolism resistance (P50), and water-soluble carbohydrates (WSCs) were measured under severe drought. Dactylis were more dehydration tolerant, reaching 50% survival at a lower soil water potential (-6.07 MPa) than Stipa (-2.64 MPa), and at a lower leaf base water content (32.8%) than Stipa (50.0%). Dactylis accumulated higher WSCs in leaf bases [479 mg g-1 dry mass (DM), high fructan concentration] than Stipa (17 mg g-1 DM, high sucrose concentration). WSCs contributed 47% (Dactylis) and 29% (Stipa) to osmotic adjustment. However, Stipa had higher embolism resistance (P50= -8.7 MPa) than Dactylis (-2.9 MPa). Plants from the most arid sites had the highest dehydration tolerance, while embolism resistance was uncorrelated with aridity of the sites of origin. We found the highest embolism resistance and dehydration tolerance reported for herbaceous species. We showed that semi-arid grasses combine contrasting strategies to survive drought. Assessing these strategy combinations is crucial to predicting plant resilience under climate change.

Flavonoids are a diverse group of secondary metabolites or specialized metabolites that play crucial roles in plant defense against insect herbivores, linking biochemical, physiological, and ecological processes. This review provides a comprehensive overview of flavonoid biosynthesis, classification, and regulatory mechanisms, emphasizing their direct and indirect roles in deterring insect attacks. Also, the structural modifications in flavonoid classes can strongly alter their bioactivity across insect orders. We explore how insect-derived cues dynamically influence flavonoid production, highlighting their importance in signal transduction and the coevolution of plant-insect interactions. In addition, we discuss the multifunctional nature of flavonoids in responding to both biotic and abiotic stresses, and how these defense layers interact to shape complex plant responses. The review also examines emerging genetic and molecular approaches that harness flavonoid pathways for enhanced pest resistance, with consideration of recent biotechnological advances, environmental impacts, and their potential applications as biopesticides and biostimulants. By integrating these perspectives, we highlight the promise of flavonoid-based strategies in developing sustainable, ecosystem-specific pest management solutions.

Hypoxia significantly impacts plant metabolism and growth by disrupting mitochondrial respiration, and oxygen sensing plays a vital role in regulating responses to low-oxygen conditions. Plants sense oxygen through the N-degron pathway, involving Plant Cysteine Oxidases (PCOs) that oxidize the Ethylene Response Factors belonging to group VII (ERF-VII), leading to their degradation under normoxia. Under hypoxic conditions, PCO activity decreases, stabilizing ERF-VII proteins and activating the transcription of Hypoxia-Responsive Genes (HRGs) to adapt to oxygen limitation. Recent research highlights additional factors, including the MBR1/MED25 complex, ERF-VII phosphorylation, and the integration of energy and oxygen signals via the Target of Rapamicin (TOR) pathway, which fine-tune the hypoxic response. Upon reoxygenation, PCOs restore activity and degrade ERF-VII, but this degradation is delayed, possibly due to reactive oxygen species (ROS) inhibiting PCO function. Repressive factors such as HRA1 and ORA59 also modulate ERF-VII activity to suppress HRG expression. The plant's response to hypoxia also involves a sophisticated network of molecular signals, including calcium signaling and the redox-modulatory role of phytoglobins and nitric oxide. Despite significant progress, much remains unknown about plant hypoxia, as its complex, spatiotemporal nature affects not only environmental adaptation but also development and plant-microbe interactions, necessitating intricate regulatory mechanisms.

Stomatal closure regulated by abscisic acid (ABA) is a critical plant response to drought, with reactive oxygen species (ROS), playing a central signaling role. However, the involvement of antioxidant enzymes and their regulators in this process remains insufficiently understood. Here, we investigate the role of miR398 and its target gene SlCSD1, which encodes a Cu/Zn superoxide dismutase, in ABA-induced stomatal closure and drought tolerance in tomato (Solanum lycopersicum). Overexpression of sly-miR398b or knockout of SlCSD1 resulted in elevated O₂•⁻ levels, enhanced stomatal closure, and improved drought tolerance. In contrast, sly-miR398b mutants showed diminished O₂•⁻ accumulation, reduced stomatal closure, and increased sensitivity to drought. Pharmacological assays confirmed that miR398b-mediated stomatal responses depend on O₂•⁻ signaling. Further analysis revealed that ABA-responsive element binding factor (SlABF2) directly binds to an ABA-responsive element (ABRE) in the sly-miR398b promoter and activates its expression. Overexpression of SlABF2 upregulated expression of sly-miR398b, increased O₂•⁻ production, and promoted stomatal closure and drought tolerance. Moreover, SlABF2 activity is regulated by Sucrose Nonfermenting Related Kinase 2.6 (SlSnRK2.6), a core component of the ABA signaling pathway. Together, these findings identify a regulatory cascade in which the SnRK2.6-ABF2-miR398b-CSD1 module fine-tunes O₂•⁻ levels to control stomatal aperture, thereby enhancing drought tolerance in tomato.

Pathogen and pest effectors play a crucial role in manipulating plant biological processes, facilitating infection and infestation. While pathogens and pests secrete repertoires of effectors into host plants, most effector function studies focus on characterising individual proteins. Our previous work identified a genetically linked and co-regulated gene pair in the aphid pest Myzus persicae encoding effectors Mp1 and Mp58. Here, we explored the functional link between these two effectors. We revealed that effectors Mp1 and Mp58 interact in planta and in vitro and form an oligomeric complex. The putative orthologs of the Mp1-Mp58 pair in the aphid species Rhopalosiphum padi, Rp1 and Rp58 also interact, but members of the pair cannot interact across aphid species, suggesting that effector pairs have co-evolved within each aphid species but diversified across species. Both Mp1 and Mp58 associate with the host Vacuolar Protein Sorting associated Protein 52 (VPS52) to form an Mp1-Mp58-VPS52 complex which localises at vesicle-like structures. Our findings point to effector complex formation in plant-insect interactions and highlight a further layer of complexity in the molecular dialogue between insects and their host plants. Our work highlights the importance of considering the context in which effectors may function within a larger effector repertoire.

Apple is an important economic species, and it always suffered by biotic stress during its growth and development. Fungi and pests are two types of biotic stress that have significant destructive effects on apples. Besides, the LRR-RLKs family play a key role in regulating plant responses to biotic stress. In this study, overexpressing MdLRR-RLK1 enhanced apple resistance to Colletotrichum fructicola and aphids by promoting the expression of resistance genes such as WRKYs, PRs and JA-pathway genes, as well as increasing the content of antioxidant enzymes and secondary metabolites. Additionally, MdLRR-RLK1 could interact with MdGRP1-LIKE in vivo and in vitro, and MdLRR-RLK1 could phosphorylate MdGRP1-LIKE in vitro. Overexpressing MdGRP1-LIKE enhanced apple resistance to C. fructicola by increasing the expression of resistance genes such as WRKYs and PRs and the content of antioxidant enzymes. However, overexpressing MdGRP1-LIKE did not enhance the apple resistance to aphids. These findings reveal the mechanism of the MdLRR-RLK1-MdGRP1-LIKE module regulated apple resistance to Colletotrichum fructicola stress.

Hypoxic conditions in waterlogged or flooded soils results in massive penalties to crop production and food security, and the problem is only going to increase under current climate scenarios. While the number of papers dealing with plants adaptive responses to flooding is increasing exponentially, most staple crops remain highly sensitive to excessive water in the soil. In this work, we analyze the likely reason for this discrepancy. We argue that the current focus on traits aimed to increase oxygen level in plant tissues under conditions of soil flooding (such as aerenchyma formation; developing of adventitious roots; or formation of radial oxygen loss barrier) is not sufficient to account for all constraints affecting crop performance under stress conditions. By conducting a bioinformatic analysis of a large number of wetland and dryland species we show that the former species possess much larger number of gene copies that allow plants to improve acquisition of essential nutrients (such as N and P) as well as effectively deal with elemental toxicities (e.g. Mn and Fe) originating from changes in redox potential in flooded soils. We then call for a major paradigm shift in our approach for breeding for improved waterlogging stress tolerance by complementing oxygen supply-related traits to those related to vacuolar sequestration of heavy metals and improved nutrient use efficiency. The likely trade-offs of this approach for crop growth under normoxic conditions are discussed.