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"Plant cells"
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Plant cells and life processes
Explores the features of the plant cell and their life processes.
Book
Plant cell wall integrity maintenance in model plants and crop species-relevant cell wall components and underlying guiding principles
The walls surrounding the cells of all land-based plants provide mechanical support essential for growth and development as well as protection from adverse environmental conditions like biotic and abiotic stress. Composition and structure of plant cell walls can differ markedly between cell types, developmental stages and species. This implies that wall composition and structure are actively modified during biological processes and in response to specific functional requirements. Despite extensive research in the area, our understanding of the regulatory processes controlling active and adaptive modifications of cell wall composition and structure is still limited. One of these regulatory processes is the cell wall integrity maintenance mechanism, which monitors and maintains the functional integrity of the plant cell wall during development and interaction with environment. It is an important element in plant pathogen interaction and cell wall plasticity, which seems at least partially responsible for the limited success that targeted manipulation of cell wall metabolism has achieved so far. Here, we provide an overview of the cell wall polysaccharides forming the bulk of plant cell walls in both monocotyledonous and dicotyledonous plants and the effects their impairment can have. We summarize our current knowledge regarding the cell wall integrity maintenance mechanism and discuss that it could be responsible for several of the mutant phenotypes observed.
Journal Article
A phase-separated nuclear GBPL circuit controls immunity in plants
Liquid–liquid phase separation (LLPS) has emerged as a central paradigm for understanding how membraneless organelles compartmentalize diverse cellular activities in eukaryotes
1
–
3
. Here we identify a superfamily of plant guanylate-binding protein (GBP)-like GTPases (GBPLs) that assemble LLPS-driven condensates within the nucleus to protect against infection and autoimmunity. In
Arabidopsis thaliana
, two members of this family—GBPL1 and GBPL3—undergo phase-transition behaviour to control transcriptional responses as part of an allosteric switch that is triggered by exposure to biotic stress. GBPL1, a pseudo-GTPase, sequesters catalytically active GBPL3 under basal conditions but is displaced by GBPL3 LLPS when it enters the nucleus following immune cues to drive the formation of unique membraneless organelles termed GBPL defence-activated condensates (GDACs) that we visualized by in situ cryo-electron tomography. Within these mesoscale GDAC structures, native GBPL3 directly bound defence-gene promoters and recruited specific transcriptional coactivators of the Mediator complex and RNA polymerase II machinery to massively reprogram host gene expression for disease resistance. Together, our study identifies a GBPL circuit that reinforces the biological importance of phase-separated condensates, in this case, as indispensable players in plant defence.
A family of plant guanylate-binding protein-like GTPases controls phase separation and assembly of condensates, thereby forming a circuit that regulates transcriptional responses to biotic stress.
Journal Article
Structure and growth of plant cell walls
Plant cells build nanofibrillar walls that are central to plant growth, morphogenesis and mechanics. Starting from simple sugars, three groups of polysaccharides, namely, cellulose, hemicelluloses and pectins, with very different physical properties are assembled by the cell to make a strong yet extensible wall. This Review describes the physics of wall growth and its regulation by cellular processes such as cellulose production by cellulose synthase, modulation of wall pH by plasma membrane H+-ATPase, wall loosening by expansin and signalling by plant hormones such as auxin and brassinosteroid. In addition, this Review discusses the nuanced roles, properties and interactions of cellulose, matrix polysaccharides and cell wall proteins and describes how wall stress and wall loosening cooperatively result in cell wall growth.Plant cells assemble a strong yet extensible primary cell wall consisting largely of polysaccharides. Emerging models of wall growth integrate physical properties such as mechanical strength and tension with cellular processes that govern wall loosening and expansion.
Journal Article
The Arabidopsis MicroRNA396-GRF1/GRF3 Regulatory Module Acts as a Developmental Regulator in the Reprogramming of Root Cells during Cyst Nematode Infection
The syncytium is a unique plant root organ whose differentiation is induced by plant-parasitic cyst nematodes to create a source of nourishment. Syncytium formation involves the redifferentiation and fusion of hundreds of root cells. The underlying regulatory networks that control this unique change of plant cell fate are not understood. Here, we report that a strong downregulation of Arabidopsis (Arabidopsis thaliana) microRNA396 (miR396) in cells giving rise to the syncytium coincides with the initiation of the syncytial induction/formation phase and that specific miR396 up-regulation in the developed syncytium marks the beginning of the maintenance phase, when no new cells are incorporated into the syncytium. In addition, our results show that miR396 in fact has a role in the transition from one phase to the other. Expression modulations of miR396 and its Growth-Regulating Factor (GRF) target genes resulted in reduced syncytium size and arrested nematode development. Furthermore, genome-wide expression profiling revealed that the miR396-GRF regulatory system can alter the expression of 44% of the more than 7,000 genes reported to change expression in the Arabidopsis syncytium. Thus, miR396 represents a key regulator for the reprogramming of root cells. As such, this regulatory unit represents a powerful molecular target for the parasitic animal to modulate plant cells and force them into novel developmental pathways.
Journal Article
A Peptide Hormone and Its Receptor Protein Kinase Regulate Plant Cell Expansion
Plant cells are immobile; thus, plant growth and development depend on cell expansion rather than cell migration. The molecular mechanism by which the plasma membrane initiates changes in the cell expansion rate remains elusive. We found that a secreted peptide, RALF (rapid alkalinization factor), suppresses cell elongation of the primary root by activating the cell surface receptor FERONIA in Arabidopsis thaliana. A direct peptide-receptor interaction is supported by specific binding of RALF to FERONIA and reduced binding and insensitivity to RALF-induced growth inhibition in feronia mutants. Phosphoproteome measurements demonstrate that the RALF-FERONIA interaction causes phosphorylation of plasma membrane H+–adenosine triphosphatase 2 at Ser899, mediating the inhibition of proton transport. The results reveal a molecular mechanism for RALF-induced extracellular alkalinization and a signaling pathway that regulates cell expansion.
Journal Article
Vision, challenges and opportunities for a Plant Cell Atlas
With growing populations and pressing environmental problems, future economies will be increasingly plant-based. Now is the time to reimagine plant science as a critical component of fundamental science, agriculture, environmental stewardship, energy, technology and healthcare. This effort requires a conceptual and technological framework to identify and map all cell types, and to comprehensively annotate the localization and organization of molecules at cellular and tissue levels. This framework, called the Plant Cell Atlas (PCA), will be critical for understanding and engineering plant development, physiology and environmental responses. A workshop was convened to discuss the purpose and utility of such an initiative, resulting in a roadmap that acknowledges the current knowledge gaps and technical challenges, and underscores how the PCA initiative can help to overcome them.
Journal Article
hemicellulose‐bound form of silicon inhibits cadmium ion uptake in rice (Oryza sativa) cells
Silicon (Si) alleviates cadmium (Cd) toxicity in rice (Oryza sativa). However, the chemical mechanisms at the single‐cell level are poorly understood. Here, a suspension of rice cells exposed to Cd and/or Si treatments was investigated using a combination of plant cell nutritional, molecular biological, and physical techniques including in situ noninvasive microtest technology (NMT), polymerase chain reaction (PCR), inductively coupled plasma mass spectroscopy (ICP‐MS), and atomic force microscopy (AFM) in Kelvin probe mode (KPFM). We found that Si‐accumulating cells had a significantly reduced net Cd²⁺influx, compared with that in Si‐limited cells. PCR analyses of the expression levels of Cd and Si transporters in rice cells showed that, when the Si concentration in the medium was increased, expression of the Si transporter gene Low silicon rice 1 (Lsi1) was up‐regulated, whereas expression of the gene encoding the transporter involved in the transport of Cd, Natural resistance‐associated macrophage protein 5 (Nramp5), was down‐regulated. ICP‐MS results revealed that 64% of the total Si in the cell walls was bound to hemicellulose constituents following the fractionation of the cell walls, and consequently inhibited Cd uptake. Furthermore, AFM in KPFM demonstrated that the heterogeneity of the wall surface potential was higher in cells cultured in the presence of Si than in those cultured in its absence, and was homogenized after the addition of Cd. These results suggest that a hemicellulose‐bound form of Si with net negative charges is responsible for inhibition of Cd uptake in rice cells by a mechanism of [Si‐hemicellulose matrix]Cd complexation and subsequent co‐deposition.
Journal Article