Journal of Experimental Botany最新文献

Demand for rice is rapidly increasing in sub-Saharan Africa; however, its productivity is constrained by nutrient-poor paddy soils, particularly those deficient in N and P. Improving root system architecture offers potential to enhance nutrient uptake efficiency and increase yield under such conditions. This study aimed to identify the most effective root phenotype for enhancing grain yield under the nutrient-deficient soil conditions in Madagascar. A high-yielding indica cultivar-IR64-and 12 near-isogenic and pyramiding lines carrying single or multiple quantitative trait loci for root growth angle, length, volume, and thickness were evaluated across several nutrient-deficient paddy fields with varying nutrient gradients with depth. A pyramiding line combining DRO1 and qsor1, which confer deeper and shallower rooting traits, respectively, exhibited significantly higher grain yield than IR64 at the yield levels of 2.7-5.1 t ha-1. This dimorphic root system expanded root distribution into both topsoil and subsoil, enhanced N and P uptake, and increased overall grain yield by 16-23% relative to IR64. These findings suggest that root system architecture expansion into multiple soil layers represents a promising ideotype for improving rice performance in nutrient-deficient paddy fields and may serve as a key breeding target to boost rice production in sub-Saharan Africa.

Plasmodesmata (PD) are essential cellular structures that facilitate intercellular communication in plants, enabling the transport of nutrients and signaling molecules. Over the past decades, significant strides have been made in unraveling the formation, function, and regulation of PD. Identification and functional characterization of PD-associated proteins have greatly advanced our understanding of PD. This review discusses past efforts in uncovering PD proteomes and highlights recent breakthroughs in applying proximity labeling (PL) assays to map plant protein interactomes. Special attention is given to using PL assays in studying PD biology, emphasizing their potential to drive future advancements and deepen our understanding of PD function and regulation. By integrating PL technologies with established methodologies, researchers can gain comprehensive insights into the dynamic composition and roles of PD.

Plant cell walls exist as a complex and varied blend of polysaccharides and proteins; the combination of which has evolved over millions of years. Research on how these components interact is key to understanding a plant's mechanical, structural, communicative, and biological traits. However, knowledge on cell wall components, its biophysical properties and cellular functions, remains sparse. Particularly challenging is the analysis of cell wall microdomains such as plasmodesmata. Plasmodesmata are membranous bridges embedded in cell walls facilitating cytoplasm-to-cytoplasm (i.e. symplasmic) transport of diverse factors, including proteins and signalling molecules that control plant development. Here, we review recent research on plasmodesmata cell walls connecting structural and mechanical properties of their components and evidence of their function at plasmodesmata. Most work in this area focuses on callose (a β-1,3-glucan that accumulates at plasmodesmata), but compositional and proteomic analysis indicate interplay with wall pectins, xyloglucans, and cellulose structures that remains under-investigated. We discuss the importance of understanding polymer interactions at the molecular and biophysical level, and their relevance for plasmodesmata biomechanics. We also highlight new techniques and outstanding questions and reflect on the opportunities for translation of knowledge in the improvement of plant traits and in biomaterial design.

Eukaryotes developed a separate compartment for transcription, the nucleus (karyon), which is protected by a double membrane with micropores that enable the exchange of solutes between cytoplasm and nucleoplasm, in particular the exchange of RNAs and proteins. The composition and structure of the nuclear pore core scaffold have been resolved at the atomic level. The core of the transport mechanism is generated by intrinsically disordered phenylalanine-glycine (FG)-repeat proteins, the FG-nucleoporins. The in vivo state of the FG barrier in native nuclear pore complexes (NPCs) remains a topic of debate, with polymer brushes, liquid state, or bimolecular condensates (also termed hydrogels) discussed as barriers in the pore. Purified FG domains can reproduce many of the features of nuclear transport, such as the dependence of cargo transport on size and certain surface features. This review provides an overview of the composition, structure, and transport mechanism of NPCs and the role of phase separation. Due to analogous functions in protein and RNA transport and similarities of transport properties through NPCs and plasmodesmata, the summary provided here for the NPCs may be instructive for studies on the structure and function of plasmodesmata.

The movement of molecules through plasmodesmata (PD) is a fundamentally important process in plant tissues. Several decades of investigations have provided deeper insights into the basics of diffusive and advective flow through PD. However, PD still represent one of the least understood plant structures of major importance. This is based on their complex variable shape-composed of proteins, membranes, and wall material at nanoscale. We critically discuss approaches to study movement through PD, including microinjection/microdiffusion, expression of fluorescent proteins and photoactivatable probes. In addition, we highlight physical principles that form the basis for movement through PD.

Chloroplast is a major sink for copper (Cu), where it plays a crucial role in photosynthesis and oxidative stress protection. The molecular mechanisms controlling Cu homeostasis in the chloroplast in rice remain unclear. Here, we identify OsHMA7, a P1B-type ATPase, as a chloroplast envelope-localized Cu transporter necessary for transporting Cu into the chloroplast. Temporal expression analysis revealed that OsHMA7 is expressed in both roots and leaves with a diurnal rhythmicity in the latter. Subcellular fractionation and confocal microscopy confirmed its exclusive localization to the leaf chloroplast envelope membrane and likely in plastids of roots. Heterologous expression in yeast demonstrated the Cu transport activity of OsHMA7. Knockout of OsHMA7 by CRISPR-Cas9 significantly decreased the concentration of Cu in the chloroplasts, resulting in large decreases in the abundance of the Cu-containing proteins plastocyanin and Cu/Zn-superoxide dismutase 2. Consequently, photosynthetic electron transfer efficiency and phytosynthesis rate were reduced and the production of reactive oxygen species was enhanced. The oshma7 mutants displayed severe growth impairments, with a 76-78% decrease in the tiller number and an 81-96% loss in grain yield. Our findings establish OsHMA7 as an important Cu transporter in chloroplasts in rice, directly linking Cu homeostasis to photosynthetic efficiency and crop productivity.

Floral nectar-living microbes contribute to flower protection and pollinator health, and are primarily determined by nectar chemical composition. Microbial communities in non-hexose-rich nectars, as well as their ability to inhibit pathogens and modulate plant development, have been poorly explored. Here, we used metabarcoding to examine the richness and relative abundance of bacteria and fungi from avocado, a globally important crop with a unique nectar chemical composition, whose production is severely affected by the incidence of diseases and by low pollination rates. We also explored the antagonistic activity of the nectar microbial culturable fraction and their volatile organic compounds (VOCs) against avocado pathogens Phytophthora cinnamomi and Colletotrichum gloeosporioides, and against the most devastating honeybee pathogens Ascosphaera apis and Paenibacillus larvae. Furthermore, we experimentally analyzed the effects of microbial isolates and their emitted VOCs on plant growth and the activation of the jasmonic acid (JA) defense-responses in the model plant Arabidopsis thaliana. Pseudomonas, Acinetobacter, Protomyces and Vishniacozyma were the dominant microbial genera inhabiting avocado nectar. From 43 evaluated isolates, 17 bacteria and three yeasts inhibited the plant and honeybee pathogens, promoted the growth of A. thaliana seedlings and induced JA signaling. The effect of microbial VOCs in promoting plant growth was noteworthy as VOCs emitted by all tested isolates promoted lateral root formation and increased plant biomass. Collectively, our findings highlight the selectivity of avocado nectar over its microbiota, which could directly impact the plant fitness and contribute to its pollinators´ health.

The gravitropic set-point angle (GSA) defines the orientation of roots relative to gravity and is a central determinant of root system architecture (RSA). By shaping soil exploration patterns, GSA influences plant anchorage, water and nutrient uptake, stress resilience, and rhizosphere interactions. While dicots and monocots differ fundamentally in RSA, recent studies described that core regulators of GSA, including gravity sensing, auxin transport, and hormonal crosstalk are conserved. Arabidopsis thaliana has served as a model plant to uncover the molecular basis of GSA. Integrating discoveries from multiple model and crop systems now provides a systems-level view of how plants regulate root distribution. Beyond hormonal networks, GSA integrates mechanical cues, cytoskeletal dynamics, calcium and pH gradients, and environmental inputs, providing plants with remarkable developmental plasticity. This review compares conserved and lineage-specific mechanisms across plant groups. Finally, we outline molecular targets of GSA as breeding traits to optimize RSA for resource efficiency and climate-resilient agriculture.