Journal of Experimental Botany最新文献

Plants optimize carbon partitioning in response to heterogeneous nutrient availability to enhance resource acquisition. However, the structural and molecular mechanisms underlying this plasticity remain poorly understood. Here, we combined histology, fluorescent tracing, and single-cell RNA sequencing to investigate how maize basal nodes mediate asymmetric carbon allocation under split-root heterogeneous phosphorus (P) supply. We found that the P-supplied side exhibited significant increases in the number and cross-sectional area of vascular bundles, particularly small vascular bundles and phloem, accompanied by elevated non-structural carbohydrate levels and enhanced photoassimilate allocation. Single-cell transcriptomics identified 13 cell types and revealed cell-type-specific transcriptional reprogramming, including upregulation of carbohydrate metabolism (e.g., incw1, invan5) and transport genes (e.g., sweet13a, stp2, stp4). Pseudotime analysis indicated a differentiation bias toward xylem parenchyma under local P supply. Additionally, downregulation of trpp14 in procambial cells suggests a potential role for trehalose-6-phosphate in regulating sink strength. Our study establishes vascular bundle plasticity and cellular functional heterogeneity as key mechanisms for spatially programmed carbon partitioning in response to P heterogeneity, providing insights for improving nutrient use efficiency in crops.

C4 plants have traditionally been classified into NADP-malic enzyme (NADP-ME), NAD-malic enzyme (NAD-ME) and PEP carboxykinase (PEPCK) subtypes based on the predominant C4-acid decarboxylating enzyme. To investigate the relative contributions of malate and aspartate to C4-pathway fluxes in each subtype, we performed 13CO2 pulse-chase labelling experiments on four C4 grass species: Zea mays and Setaria viridis (NADP-ME), Panicum miliaceum (NAD-ME) and Megathyrsus maximus (PEPCK). Only a proportion (8-50%) of the total malate pool in the leaves is photosynthetically active whereas essentially all of the aspartate pool is photosynthetically active. Estimates of metabolic fluxes indicate that approximately two thirds of the C4 pathway flux is via malate in Z. mays and the remaining third via aspartate, while in S. viridis 50% of the flux is via malate and 50% via aspartate. In P. miliaceum and M. maximus, 91% and 85% of the flux is via aspartate and the remaining 5% and 15% via malate, respectively. The results demonstrate the feasibility of using non-radioactive 13CO2 in pulse-chase labelling experiments to study C4 photosynthesis and to detect C4 pathway fluxes in C3 plants engineered to perform C4 photosynthesis.

Target of Rapamycin (TOR) is an evolutionarily conserved protein kinase that serves as a crucial signalling hub, seamlessly integrating a wide range of internal and external signals to meticulously regulate cellular and organismal physiology. TOR is crucial in regulating the different phases of the lifecycle in plants including embryogenesis, seed germination, meristem activation, root and leaf development, flowering, and senescence. Beyond its central role in growth and development, emerging research has revealed its significant involvement in the response to environmental stresses. Even though plant growth regulators such as auxin, cytokinin (CK), brassinosteroids (BR), gibberellin (GA), abscisic acid (ABA), ethylene (ET), salicylic acid (SA), jasmonic acid (JA), and nitric oxide (NO) function as pivotal signalling molecules in modulating plant development and stress responses, how they coordinate with the energy status still remains obscure. Here we summarize the current findings on the dynamic interconnection between TOR and these discrete phytoregulators, and their potential role in executing diverse biological processes in plants.

Plant sucrose transporters of the SUT and SWEET family are essential for phloem loading and unloading in higher plants. Members of both families are able to form homo- and hetero-oligomers, thereby changing their subcellular localization and functionality. Not only oligomerization, but also interaction with other proteinaceous interaction partners might affect the subcellular localization and thereby the functionality of plant sucrose and glucose transporters. Identification of individual interactomes of different sucrose or glucose transporters helped to assign different functions to each of the transporters since the population of protein-protein interaction partners varies considerably. Nevertheless, several common interaction partners could be identified for SUT1, SUT2, and SUT4 from Solanaceae, suggesting common regulatory mechanisms, although individual physiological functions are fulfilled. This review will focus on recent advances in the field of sugar transporter dynamics within and between cells, their targeting, and their functional regulation by direct physical contact with other proteins. Elucidation of the individual interactomes of sugar transporters of the SUT or SWEET family will help to understand their regulatory network and impact on the whole plant physiology, thereby opening up new strategies for crop plant adaptation to appropriate environmental conditions or climate change.

Lactate dehydrogenases are oxidoreductases present in almost all living organisms. They catalyze the interconversion of pyruvate and L-lactate with simultaneous oxidation of NADH and reduction of NAD+. Since their function remains largely unexplored in rice, in this study we deciphered the role of the rice lactate dehydrogenase, OsLdh3. OsLdh3 showed optimum enzyme activity at pH 6.6 for the forward reaction (pyruvate to L-lactate) and pH 9 for the reverse reaction (L-lactate to pyruvate). Protein-protein interaction studies revealed that OsLdh3 interacts with the glycolytic enzymes glyceraldehyde 3-phosphate dehydrogenaseC3 (OsGAPC3) and Enolase2 (OsLos2), suggesting its role in regulating glycolytic flux. Further, overexpression of OsLdh3 in rice showed enhanced abiotic stress tolerance by exhibiting elevated NAD+ levels and OsGAPC3 activity, thereby facilitating an improved glycolytic continuum and higher pyruvate accumulation. Consequently, these lines also showed increased mitochondrial respiration and ATP synthesis, and reduced reactive oxygen species (ROS) accumulation. Further, enhanced photosynthetic efficiency and reduced yield penalty of the stress-imposed OsLdh3 overexpression lines underscore its importance in crop productivity under adverse climatic conditions. Thus, our findings show that OsLdh3 enhances stress tolerance in rice by regulating redox homeostasis and respiration, reducing ROS levels, and maintaining energy balance. This makes OsLdh3 a promising candidate gene for developing climate-resilient rice cultivars with reduced yield gap.

Plant leaves provide a source of organic carbon for distribution to non-photosynthetic sink organs, transported as sugars in the phloem. Besides terminal sinks at the ends of the phloem, carbon is also delivered laterally to axial sinks such as stems, petioles, or taproots, which surround phloem conduits. Here, we review the current understanding of the mechanisms involved in allocating sugars to axial sinks. Sugar unloading can occur via apoplastic or symplastic cellular paths, depending on species and development. We highlight the roles of sugar transporters, as well as sugar-cleaving enzymes, which contribute to maintaining sink strength by modulating local sugar gradients. Although the underlying transport machinery is broadly similar to that in terminal sinks, axial sinks may require specific regulatory mechanisms to balance competition with downstream terminal sinks, as well as solutions for storing high levels of sucrose effectively-mechanisms that remain largely uncharacterized. We highlight major knowledge gaps and challenges in research on axial sinks. Given the economic importance of axial sink crops (e.g. sugarcane, cassava), a better understanding of resource allocation has a large potential for improving yield through targeted manipulation of sugar transport.

Nutrients not only provide energy and structural components but also play essential roles as regulatory molecules to control plant growth and development. Flowering is a key developmental phase transition (from vegetative to reproductive growth), and its precise timing determines reproductive fitness and crop yield. This requires coordination of metabolism, partitioning between source and sink tissues, and apical meristem activity with nutrient supplies. Here we summarize recent advances in our understanding of nutrient-regulated flowering, focusing on sugars and the three primary (soil-supplied) macronutrients nitrogen, phosphorus, and potassium, also considering drought stress as a highly relevant condition affecting nutrient availability. Most notably, recent evidence indicates that the evolutionarily conserved SNF1-RELATED KINASE 1 (SnRK1), a key metabolic sensor, serves as an integrator of nutrient status to control flowering. However, the combined effects of multiple nutrients on flowering and differences in responses between plant species remain underexplored and are an important topic for future research.

Plants maintain internal stability even amid fluctuating external conditions. For energy, nutrients, and fixed carbon, this relies on the dynamic coordination between resource acquisition and allocation to maintenance, growth, and development. However, individual cellular changes in activity are limited in their impact. Instead, systems-level adaptation in multicellular organisms requires collective action and coordination of how resources are used in the rate of formation, precise anatomy, and physiological activity of newly formed organs. This further requires intricate linking between established energy and nutrient signalling pathways and development mechanisms that integrate responses over space and time. Developmental pace and resource homeostasis represent two sides of the same coin and are facilitated by coupled feedback between resource uptake and morphological efficiency. The trilateral framework between availability, developmental pace, and morphology determines resource management, and as such whole-plant resilience and climate adaptation strategies. We explore how feedback mechanisms mediate local resource acquisition of carbon, nitrogen, and phosphorus, how developmental programs such as organogenesis, root foraging response, and branching match resource availability over space and time, and how architectural and morphological efficiency of roots and shoots minimize investment costs and maintain development acquisition potential to facilitate high demands for growth.

Plants face diverse abiotic and biotic stresses, including drought, heat, salinity, herbivory, pathogens, and competition. To mitigate the fitness costs of these threats, they have evolved immediate compensatory mechanisms and immune responses, such as phytohormone signaling, secondary metabolite production, and the hypersensitive response. However, activating these stress-response programs often comes at the expense of optimal growth. This shift in cellular energy and resource allocation underpins the classical 'growth-defense trade-off'. Beyond short-term metabolic reprogramming, plants also engage developmental switches that alter broader growth patterns to compensate for or avoid stress. In this review, we explore how maize, a longstanding model for plant development, rewires growth in response to stress. We highlight key developmental genes that maintain homeostatic growth or trigger major morphological changes in coordination with stress signals. We also examine recent insights into how plants rebalance energy under stress, with a focus on the TOR-sensitive hormone networks. Finally, we discuss how maize-specific innovations in growth-stress integration could inform efforts to enhance resilience in other crops. These strategies are essential for developing more sustainable agriculture, where crops can endure transient stress without initiating permanent developmental shifts that reduce yield.