Myosin XI, a model of its conserved role in plant cell tip growth.

In eukaryotic cells, organelle and vesicle transport, positioning, and interactions play crucial roles in cytoplasmic organization and function. These processes are governed by intracellular trafficking mechanisms. At the core of that trafficking, the cytoskeleton and directional transport by motor proteins stand out as its key regulators. Plant cell tip growth is a well-studied example of cytoplasm organization by polarization. This polarization, essential for the cell's function, is driven by the cytoskeleton and its associated motors. This review will focus on myosin XI, a molecular motor critical for vesicle trafficking and polarized plant cell growth. We will center our discussion on recent data from the moss Physcomitrium patens and the liverwort Marchantia polymorpha. The biochemical properties and structure of myosin XI in various plant species are discussed, highlighting functional conservation across species. We further explore this conservation of myosin XI function in the process of vesicle transport in tip-growing cells. Existing evidence indicates that myosin XI actively organizes actin filaments in tip-growing cells by a mechanism based on vesicle clustering at their tips. A hypothetical model is presented to explain the essential function of myosin XI in polarized plant cell growth based on vesicle clustering at the tip. The review also provides insight into the in vivo localization and dynamics of myosin XI, emphasizing its role in cytosolic calcium regulation, which influences the polymerization of F-actin. Lastly, we touch upon the need for additional research to elucidate the regulation of myosin function.

Extending cognition: a vegetal rejoinder to extensionless thought and to extended cognition.

In this paper, we propose a crucial supplement to the framework of plant cognition, namely extending cognition. We argue that plants and other organisms with an open-ended body plan actively extend their cognition when growing tissues or organs. Their cognition expands with their body expansion. After considering the defining features of extending cognition, we present a model where growth, along with aspects of plant physiology (e.g. biochemical exudates), as well as the "negative extension" of growing away from obstacles or stressful environments, are the building blocks for a more refined understanding of plant cognition. We conclude by outlining the general implications of the theory of extending cognition and indicating directions for future research.

Impact of the TOR pathway on plant growth via cell wall remodeling.

Plant growth is intimately linked to the availability of carbon and energy status. The Target of rapamycin (TOR) pathway is a highly relevant metabolic sensor and integrator of plant-assimilated C into development and growth. The cell wall accounts for around a third of the cell biomass, and the investment of C into this structure should be finely tuned for optimal growth. The plant C status plays a significant role in controlling the rate of cell wall synthesis. TOR signaling regulates cell growth and expansion, which are fundamental processes for plant development. The availability of nutrients and energy, sensed and integrated by TOR, influences cell division and elongation, ultimately impacting the synthesis and deposition of cell wall components. The plant cell wall is crucial in environmental adaptation and stress responses. TOR senses and internalizes various environmental cues, such as nutrient availability and stresses. These environmental factors influence TOR activity, which modulates cell wall remodeling to cope with changing conditions. Plant hormones, including auxins, gibberellins, and brassinosteroids, also regulate TOR signaling and cell wall-related processes. The connection between nutrients and cell wall pathways modulated by TOR are discussed.

Diverse roles played by "Pseudomonas fluorescens complex" volatile compounds in their interaction with phytopathogenic microrganims, pests and plants.

Pseudomonas fluorescens complex consists of environmental and some human opportunistic pathogenic bacteria. It includes mainly beneficial and few phytopathogenic species that are common inhabitants of soil and plant rhizosphere. Many members of the group are in fact known as effective biocontrol agents of plant pathogens and as plant growth promoters and for these attitudes they are of great interest for biotechnological applications. The antagonistic activity of fluorescent Pseudomonas is mainly related to the production of several antibiotic compounds, lytic enzymes, lipopeptides and siderophores. Several volatile organic compounds are also synthesized by fluorescent Pseudomonas including different kinds of molecules that are involved in antagonistic interactions with other organisms and in the induction of systemic responses in plants. This review will mainly focus on the volatile compounds emitted by some members of P. fluorescens complex so far identified, with the aim to highlight the role played by these molecules in the interaction of the bacteria with phytopathogenic micro and macro-organisms and plants.

Potencial dendrocronológico de tres especies de Podocarpáceas de la Cordillera de los Andes / Dendrochronological potential of three Podocarpaceae species from the Andean Cordillera

Resumen Introducción: Poco se conoce del potencial dendrocronológico de las Podocarpáceas en el trópico. Objetivo: Explorar el potencial dendrocronológico de tres especies de podocarpáceas: Retrophyllum rospigliosii, Podocarpus oleifolius y Prumnopitys harmsiana. Métodos: De plantaciones no manejadas localizadas en los Andes colombianos, se muestrearon y analizaron 88 árboles: 30 muestras de R. rospigliosii provenientes de secciones transversales, 30 y 28 muestras de P. oleifolius y P. harmsiana, respectivamente, provenientes de núcleos de madera extraídos con barreno de incrementos. Las muestras se procesaron siguiendo las técnicas dendrocronológicas estándar. Resultados: En general, las características anatómicas de los anillos de crecimiento son similares para las tres especies, con una anatomía simple de traqueidas alineadas radialmente por tratarse de coníferas. Dado que la edad conocida de la plantación coincide con el número de anillos se considera una fuerte evidencia de la frecuencia anual de su formación en R. rospigliosii y P. oleifolius, las cuales presentaron buena sincronización (cofechado) con una inter-correlación promedio de 0.55 (r-Pearson). Para P. harmsiana no fue posible concretar series de ancho de anillos de las muestras recolectadas. Las series estandarizadas de R. rospigliosii y P. oleifolius mostraron una relación con los registros instrumentales de precipitación y temperatura, indicando que estas especies pueden ser promisorias para estudios adicionales. Conclusión: La investigación dendrocronología con especies de Podocarpáceas podría realizarse exitosamente con R. rospigliosii y P. oleifolius, pero no con P. harmsiana.

Abstract Introduction: Little is known about the dendrochronological potential of Podocarpaceaes in the tropics. Objective: To explore the dendrochronological potential of three Podocarpaceae species: Retrophyllum rospigliosii, Podocarpus oleifolius, and Prumnopitys harmsiana. Methods: From a non-managed plantation in the Andean cordillera in Colombia, a total of 88 trees were analyzed: 30 samples of cross-sections of R. rospigliosii, and 30 and 28 samples of P. oleifolius and P. harmsiana, respectively, obtained with an increment borer. Samples were processed according to standard dendrochronological methods. Results: The anatomical characteristics of the growth rings of the three species are similar, with a simple conifer anatomy with radially oriented tracheids. Since the known age of the plantation coincides with the number of tree rings this is strong evidence of annual tree-ring frequency of R. rospigliosii and P. oleifolius which also showed a satisfactory cross-dating with an average inter-correlation of 0.55 (r-Pearson). For P. harmsiana, it was not possible to build a tree-ring series from the collected samples. R. rospigliosii and P. oleifolius standardized ring-width chronologies showed a relationship with the instrumental records of rainfall and temperature, indicating these species may be promising further studies. Conclusions: Dendrochronological research with Podocarpaceae species could be carried out successfully with R. rospigliosii and P. oleifolius but not with P. harmsiana.

Plant and microbial features governing an endophytic lifestyle.

Beneficial microorganisms colonizing internal plant tissues, the endophytes, support their host through plant growth promotion, pathogen protection, and abiotic stress alleviation. Their efficient application in agriculture requires the understanding of the molecular mechanisms and environmental conditions that facilitate in planta accommodation. Accumulating evidence reveals that commensal microorganisms employ similar colonization strategies as their pathogenic counterparts. Fine-tuning of immune response, motility, and metabolic crosstalk accounts for their differentiation. For a holistic perspective, in planta experiments with microbial collections and comprehensive genome data exploration are crucial. This review describes the most recent findings on factors involved in endophytic colonization processes, focusing on bacteria and fungi, and discusses required methodological approaches to unravel their relevance within a community context.

A 2D model to study how secondary growth affects the self-supporting behaviour of climbing plants.

Climbing plants exhibit specialized shoots, called "searchers", to cross spaces and alternate between spatially discontinuous supports in their natural habitats. To achieve this task, searcher shoots combine both primary and secondary growth processes of their stems in order to support, orientate and explore their extensional growth into the environment. Currently, there is an increasing interest in developing models to describe plant growth and posture. However, the interactions between the sensing activity (e.g. photo-, gravi-, proprioceptive sensing) and the elastic responses are not yet fully understood. Here, we aim to model the extension and rigidification of searcher shoots. Our model defines variations in the radius (and consequently in mass distribution) along the shoot based on experimental data collected in natural habitats of two climbing species: Trachelospermum jasminoides (Lindl.) Lem. and Condylocarpon guianense Desf.. Using this framework, we predicted the sensory aspect of a plant, that is, the plant's response to external stimuli, and the plant's proprioception, that is, the plant's "self-awareness". The results suggest that the inclusion of the secondary growth in a model is fundamental to predict the postural development and self-supporting growth phase of shoots in climbing plants.

Membrane vesicle engineering with "à la carte" bacterial-immunogenic molecules for organism-free plant vaccination.

The United Nations heralds a world population exponential increase exceeding 9.7 billion by 2050. This poses the challenge of covering the nutritional needs of an overpopulated world by the hand of preserving the environment. Extensive agriculture practices harnessed the employment of fertilizers and pesticides to boost crop productivity and prevent economic and harvest yield losses attributed to plagues and diseases. Unfortunately, the concomitant hazardous effects stemmed from such agriculture techniques are cumbersome, that is, biodiversity loss, soils and waters contaminations, and human and animal poisoning. Hence, the so-called 'green agriculture' research revolves around designing novel biopesticides and plant growth-promoting bio-agents to the end of curbing the detrimental effects. In this field, microbe-plant interactions studies offer multiple possibilities for reshaping the plant holobiont physiology to its benefit. Along these lines, bacterial extracellular membrane vesicles emerge as an appealing molecular tool to capitalize on. These nanoparticles convey a manifold of molecules that mediate intricate bacteria-plant interactions including plant immunomodulation. Herein, we bring into the spotlight bacterial extracellular membrane vesicle engineering to encase immunomodulatory effectors into their cargo for their application as biocontrol agents. The overarching goal is achieving plant priming by deploying its innate immune responses thereby preventing upcoming infections.

Functions of silicon and phytolith in higher plants.

Silicon (Si) is abundant in the lithosphere, and previous studies have confirmed that silicon plays an important role in plant growth. Higher plants absorb soluble silicon from soil through roots which is deposited in plant tissues mainly in the form of phytoliths. Based on previous studies, the research progress in silicon and phytoliths in the structural protection, enhancement on photosynthesis and transpiration of plants and plant growth and stress resistance was reviewed. Meanwhile, gaps in phytolith research, including phytolith morphology and function, impact of diverse environmental factors coupling with phytoliths, phytolith characteristics at different stages of plant development and phytoliths in regional vegetation are identified. The paper intends to promote the wider application of phytolith research findings and provides reference for further research on phytoliths.

Plants use molecular mechanisms mediated by biomolecular condensates to integrate environmental cues with development.

This review highlights recent literature on biomolecular condensates in plant development and discusses challenges for fully dissecting their functional roles. Plant developmental biology has been inundated with descriptive examples of biomolecular condensate formation, but it is only recently that mechanistic understanding has been forthcoming. Here, we discuss recent examples of potential roles biomolecular condensates play at different stages of the plant life cycle. We group these examples based on putative molecular functions, including sequestering interacting components, enhancing dwell time, and interacting with cytoplasmic biophysical properties in response to environmental change. We explore how these mechanisms could modulate plant development in response to environmental inputs and discuss challenges and opportunities for further research into deciphering molecular mechanisms to better understand the diverse roles that biomolecular condensates exert on life.

Insights on Phytohormonal Crosstalk in Plant Response to Nitrogen Stress: A Focus on Plant Root Growth and Development.

Nitrogen (N) is a vital mineral component that can restrict the growth and development of plants if supplied inappropriately. In order to benefit their growth and development, plants have complex physiological and structural responses to changes in their nitrogen supply. As higher plants have multiple organs with varying functions and nutritional requirements, they coordinate their responses at the whole-plant level based on local and long-distance signaling pathways. It has been suggested that phytohormones are signaling substances in such pathways. The nitrogen signaling pathway is closely associated with phytohormones such as auxin (AUX), abscisic acid (ABA), cytokinins (CKs), ethylene (ETH), brassinosteroid (BR), strigolactones (SLs), jasmonic acid (JA), and salicylic acid (SA). Recent research has shed light on how nitrogen and phytohormones interact to modulate physiology and morphology. This review provides a summary of the research on how phytohormone signaling affects root system architecture (RSA) in response to nitrogen availability. Overall, this review contributes to identifying recent developments in the interaction between phytohormones and N, as well as serving as a foundation for further study.

Nuclear redox processes in land plant development and stress adaptation.

Recent findings expanded our knowledge about plant redox regulation in stress responses by demonstrating that redox processes exert crucial nuclear regulatory functions in meristems and other developmental processes. Analyses of redox-modulated transcription factor functions and coregulatory ROXYs, CC-type land-plant specific glutaredoxins, reveal new insights into the redox control of plant transcription factors and participation of ROXYs in plant development. The role for ROS and redox signaling in response to low-oxygen conditions further strengthens the importance of redox processes in meristems and tissue differentiation as well as for adaptation to changing environments effecting food crop productivity.

Streptomyces can be an excellent plant growth manager.

Streptomyces, the most abundant and arguably the most important genus of actinomycetes, is an important source of biologically active compounds such as antibiotics, and extracellular hydrolytic enzymes. Since Streptomyces can have a beneficial symbiotic relationship with plants they can contribute to nutrition, health and fitness of the latter. This review article summarizes recent research contributions on the ability of Streptomyces to promote plant growth and improve plant tolerance to biotic and abiotic stress responses, as well as on the consequences, on plant health, of the enrichment of rhizospheric soils in Streptomyces species. This review summarizes the most recent reports of the contribution of Streptomyces to plant growth, health and fitness and suggests future research directions to promote the use of these bacteria for the development of a cleaner agriculture.

TOR kinase, a GPS in the complex nutrient and hormonal signaling networks to guide plant growth and development.

To survive and sustain growth, sessile plants have developed sophisticated internal signalling networks that respond to various external and internal cues. Despite the central roles of nutrient and hormone signaling in plant growth and development, how hormone-driven processes coordinate with metabolic status remains largely enigmatic. Target of rapamycin (TOR) kinase is an evolutionarily conserved master regulator that integrates energy, nutrients, growth factors, hormones, and stress signals to promote growth in all eukaryotes. Inspired by recent comprehensive systems, chemical, genetic, and genomic studies on TOR in plants, this review discusses a potential role of TOR as a 'global positioning system' that directs plant growth and developmental programs both temporally and spatially by integrating dynamic information in the complex nutrient and hormonal signaling networks. We further evaluate and depict the possible functional and mechanistic models for how a single protein kinase, TOR, is able to recognize, integrate, and even distinguish a plethora of positive and negative input signals to execute appropriate and distinct downstream biological processes via multiple partners and effectors.

Estimation of Leaf Area Index with a Multi-Channel Spectral Micro-Sensor for Wireless Sensing Networks.

The leaf area index (LAI) is a key parameter in the context of monitoring the development of tree crowns and plants in general. As parameters such as carbon assimilation, environmental stress on carbon, and the water fluxes within tree canopies are correlated to the leaves surface, this parameter is essential for understanding and modeling ecological processes. However, its continuous monitoring using manual state-of-the-art measurement instruments is still challenging. To address this challenge, we present an innovative sensor concept to obtain the LAI based on the cheap and easy to integrate multi-channel spectral sensor AS7341. Additionally, we present a method for processing and filtering the gathered data, which enables very high accuracy measurements with an nRMSE of only 0.098, compared to the manually-operated state-of-the-art instrument LAI-2200C (LiCor). The sensor that is embedded on a sensor node has been tested in long-term experiments, proving its suitability for continuous deployment over an entire season. It permits the estimation of both the plant area index (PAI) and leaf area index (LAI) and provides the first wireless system that obtains the LAI solely powered by solar cells. Its energy autonomy and wireless connectivity make it suitable for a massive deployment over large areas and at different levels of the tree crown. It may be upgraded to allow the parallel measurement of photosynthetic active radiation (PAR) and light quality, relevant parameters for monitoring processes within tree canopies.

Growth-defense trade-offs in plants.

Walking through a garden or a crop field, you may notice that plants damaged by pests (insects or pathogens) look smaller than the same kind of plants nearby that are not damaged. An obvious explanation would be that damaged plants may have lost substantial photosynthetic tissue due to insect and pathogen activities. As such, plants may have a reduced ability to capture light and perform photosynthesis, which fuels the growth of plants. While this is likely part of the reason why damaged plants look smaller, there is also another and perhaps more fascinating explanation that we would like to discuss here in this primer. It turns out that plants attacked by insects, pathogens and other biotic stressors may 'purposely' slow down their growth and that this response is often systemic, meaning that it occurs throughout the plant and beyond the tissue that is damaged by pests. Interestingly, some chemicals or plant genetic mutations that simulate insect or pathogen attacks without causing a loss of photosynthetic tissue can also slow plant growth, suggesting the physical loss of photosynthetic tissue per se is not always a prerequisite for slowing down plant growth. In contrast, there are conditions under which plants need to grow rapidly. For example, plants grow quickly when searching for light during germination or under a shaded canopy due to crowding from neighboring plants. Under these conditions, rapid plant growth is often accompanied by increased susceptibility to pests, presumably because growth is prioritized over defense. This inverse growth-defense relationship is commonly known as the 'growth-defense trade-off' and may be considered one of the most fundamental principles of 'plant economics' that allows plants to adjust growth and defense based on external conditions (Figure 1). As plants must both grow and defend in order to reproduce and survive in the natural world, growth-defense trade-offs have important ecological consequences. In agricultural settings, crops have often been bred to maximize growth-related traits, which could inadvertently result in the loss of useful genetic traits for biotic defenses. Thus, deciphering the molecular mechanisms underlying growth-defense trade-off phenomena could impact future crop breeding strategies aimed at designing superior crop plants with high yields as well as the ability to defend against biotic stressors. Here, we discuss some of the prevailing hypotheses about growth-defense trade-offs, our current understanding of the underlying mechanisms, and the ongoing efforts to optimize growth-defense trade-offs in crop plants.

Is it best to add native shrubs to a coastal sage scrub restoration project as seeds or as seedlings?

Ecological restoration frequently involves the addition of native plants, but the effectiveness (in terms of plant growth, plant survival, and cost) of using seeds versus container plants has not been studied in many plant communities. It is also not known if plant success would vary by species or based on functional traits. To answer these questions, we added several shrub species to a coastal sage scrub restoration site as seeds or as seedlings in a randomized block design. We measured percent cover, density, species richness, size, survival, and costs. Over the two years of the study, shrubs added to the site as seeds grew more and continued to have greater density than plants added from containers. Seeded plots also had greater native species richness than planted plots. However, shrubs from containers had higher survival rates, and percent cover was comparable between the planted and seeded treatments. Responses varied by species depending on functional traits, with deep-rooted evergreen species establishing better from container plants. Our cost analysis showed that it is more expensive to use container plants than seed, with most of the costs attributed to labor and supplies needed to grow plants. Our measurements of shrub density, survival, species richness, and growth in two years in our experimental plots lead us to conclude that coastal sage scrub restoration with seeds is optimal for increasing density and species richness with limited funds, yet the addition of some species from container plants may be necessary if key species are desired as part of the project objectives.

The people behind the papers - Ya Min, Stephanie Conway and Elena Kramer.

Organogenesis in plants is a dynamic process that occurs in meristems, where stem cells are maintained. A new paper in Development characterises the real-time dynamics of floral organ primordia initiation and floral meristem termination. We caught up with the authors, Ya Min, Stephanie Conway and Elena Kramer, to find out more about the paper and the story behind the research.

Heat Stress Reduces Root Meristem Size via Induction of Plasmodesmal Callose Accumulation Inhibiting Phloem Unloading in Arabidopsis.

The intercellular transport of sugars, nutrients, and small molecules is essential for plant growth, development, and adaptation to environmental changes. Various stresses are known to affect the cell-to-cell molecular trafficking modulated by plasmodesmal permeability. However, the mechanisms of plasmodesmata modification and molecules involved in the phloem unloading process under stress are still not well understood. Here, we show that heat stress reduces the root meristem size and inhibits phloem unloading by inducing callose accumulation at plasmodesmata that connect the sieve element and phloem pole pericycle. Furthermore, we identify the loss-of-function of CALLOSE SYNTHASE 8 (CalS8), which is expressed specifically in the phloem pole pericycle, decreasing the plasmodesmal callose deposition at the interface between the sieve element and phloem pole pericycle and alleviating the suppression at root meristem size by heat stress. Our studies indicate the involvement of callose in the interaction between root meristem growth and heat stress and show that CalS8 negatively regulates the thermotolerance of Arabidopsis roots.

Salicylic Acid in Root Growth and Development.

In plants, salicylic acid (SA) is a hormone that mediates a plant's defense against pathogens. SA also takes an active role in a plant's response to various abiotic stresses, including chilling, drought, salinity, and heavy metals. In addition, in recent years, numerous studies have confirmed the important role of SA in plant morphogenesis. In this review, we summarize data on changes in root morphology following SA treatments under both normal and stress conditions. Finally, we provide evidence for the role of SA in maintaining the balance between stress responses and morphogenesis in plant development, and also for the presence of SA crosstalk with other plant hormones during this process.