Journal of Experimental Botany最新文献

Within plant cell walls, plasmodesmal channels harbour unique collections of proteins to maintain their structure and facilitate dynamic regulation of cell-to-cell connectivity. Proteomic surveys, combined with evidence from confocal microscopy, have identified heavy metal-associated (HMA) domain-containing proteins as residents at plasmodesmata; however, the functional relevance of this localization is currently unknown. Although HMA domains themselves are present in all kingdoms of life, in plants they can be found in three main families: HPPs, HIPPs, and P1B-type ATPases. Within the last decade, HPPs and HIPPs have emerged as frequent host targets of pathogen-derived molecules, including secreted effectors from bacteria, fungi, and oomycetes, and a viral movement protein. The seemingly conserved targeting of HMA domains throughout distantly related pathosystems suggests that these proteins could play integral roles in plant immunity. This is corroborated by observations of HMA-like domains being integrated into plant immune receptors, enabling direct binding of effectors to activate downstream signalling, as well as genetic evidence highlighting the influence of HPPs and HIPPs on disease susceptibility. Drawing especially from plant pathology studies, we speculate about the potential metallochaperone and signalling functions of these enigmatic plasmodesmal components.

Lipids have long been recognized as essential components of plant cells, providing structural integrity, and serving as reservoirs of metabolic energy. However, the last decade has transformed our understanding of lipids, revealing their critical and dynamic roles in plant immunity. Far from being passive molecules, lipids and lipid-derived signals orchestrate diverse immune responses, bridging structural defense mechanisms with complex biochemical signaling networks. In this review, we delve into the roles of the cuticle, sterols, sphingolipids, and glycerolipids in plant defense. We explore how these lipid classes work individually and synergistically to fortify local barriers and facilitate systemic immune responses. We aim to shed light on the interconnectedness of these lipid types, identify emerging trends, and propose future directions to uncover their full potential in plant immunity. This focused perspective underscores the transformative impact of lipids on our understanding of plant-pathogen interactions and highlights their promise in improving crop disease resistance.

In plant RNA silencing, siRNAs and miRNAs guide ARGONAUTE (AGO) effector proteins to silence sequence-complementary RNA/DNA. This helps regulate developmental patterning, adaptation to stress, antiviral defense, or genome integrity/maintenance. Remarkably, these regulations not only occur intracellularly, but may also manifest in remote tissues. Here, I summarize the evidence that RNA silencing moves from cell to cell and via the phloem, the long-distance extension of the symplasm-the cytosolic connection network between cells through plasmodesmata (PDs). I then illustrate several biological functions linked to movement of RNA silencing. Besides a still largely putative role for mobile virus-derived (v)siRNAs in conferring immunity, several endogenous small RNAs (sRNAs) act as systemic signals orchestrating organismal responses to abiotic stress or symbiosis. Other mobile sRNAs act as morphogens and generate gene expression gradients by moving from cell to cell. If RNA silencing indeed moves symplasmically via PDs, then various processes probably regulate its transport; discovering these processes was expected to shed light on macromolecular trafficking in general. In a final part of this perspective, I describe several forward genetic systems set in Arabidopsis to specifically tackle the above issue. Some were instrumental in revealing hitherto unknown AGO-mediated mechanisms that modulate movement of silencing within silencing-incipient, traversed, or recipient cells. Somewhat disappointingly, however, the systems fell short of identifying factors impacting the silencing cell-to cell-trafficking channels or their regulation. I discuss here plausible reasons for these shortcomings, what could be learnt from them, how they could be remedied, and how a better understanding of their physiological foundations might shed light on so far overlooked aspects of movement of plant RNA silencing.

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.