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Developmental Cell Apr 2021The shoot apical meristem allows for reiterative formation of new aerial structures throughout the life cycle of a plant. We use single-cell RNA sequencing to define the...
The shoot apical meristem allows for reiterative formation of new aerial structures throughout the life cycle of a plant. We use single-cell RNA sequencing to define the cellular taxonomy of the Arabidopsis vegetative shoot apex at the transcriptome level. We find that the shoot apex is composed of highly heterogeneous cells, which can be partitioned into 7 broad populations with 23 transcriptionally distinct cell clusters. We delineate cell-cycle continuums and developmental trajectories of epidermal cells, vascular tissue, and leaf mesophyll cells and infer transcription factors and gene expression signatures associated with cell fate decisions. Integrative analysis of shoot and root apical cell populations further reveals common and distinct features of epidermal and vascular tissues. Our results, thus, offer a valuable resource for investigating the basic principles underlying cell division and differentiation in plants at single-cell resolution.
Topics: Arabidopsis; Cell Cycle; Cell Differentiation; Gravitropism; Phloem; Plant Epidermis; Plant Roots; Plant Shoots; Plant Stomata; RNA-Seq; Single-Cell Analysis; Xylem
PubMed: 33725481
DOI: 10.1016/j.devcel.2021.02.021 -
Current Opinion in Plant Biology Feb 2018While fast plant movements are spectacular but rare, almost all plants exhibit relatively slow, growth-mediated tropic movements that are key to their survival in the... (Review)
Review
While fast plant movements are spectacular but rare, almost all plants exhibit relatively slow, growth-mediated tropic movements that are key to their survival in the natural world. In this brief review, we discuss recent insights into the molecular mechanisms underlying phototropism, gravitropism, hydrotropism, and autostraightening. Careful molecular genetic and physiological studies have helped confirm the importance of lateral auxin gradients in gravitropic and phototropic responses. However, auxin signaling does not explain all tropisms: recent work has shown that abscisic acid signaling mediates root hydrotropism and has implicated mechanosensing in autostraightening, the organ straightening process recently modeled as a proprioceptive response. The interactions between distinct tropic signaling pathways and other internal and external sensory processes are also now being untangled.
Topics: Gravitropism; Light; Phototropism; Plant Development; Plant Physiological Phenomena; Plant Roots; Plants; Signal Transduction; Tropism
PubMed: 29107827
DOI: 10.1016/j.pbi.2017.10.003 -
American Journal of Botany Jan 2013Mechanical stress is a critical signal affecting morphogenesis and growth and is caused by a large variety of environmental stimuli such as touch, wind, and gravity in... (Review)
Review
Mechanical stress is a critical signal affecting morphogenesis and growth and is caused by a large variety of environmental stimuli such as touch, wind, and gravity in addition to endogenous forces generated by growth. On the basis of studies dating from the early 19th century, the plant mechanical sensors and response components related to gravity can be divided into two types in terms of their temporal character: sensors of the transient stress of reorientation (phasic signaling) and sensors capable of monitoring and responding to the extended, continuous gravitropic signal for the duration of the tropic growth response (tonic signaling). In the case of transient stress, changes in the concentrations of ions in the cytoplasm play a central role in mechanosensing and are likely a key component of initial gravisensing. Potential candidates for mechanosensitive channels have been identified in Arabidopsis thaliana and may provide clues to these rapid, ionic gravisensing mechanisms. Continuous mechanical stress, on the other hand, may be sensed by other mechanisms in addition to the rapidly adapting mechnaosensitive channels of the phasic system. Sustaining such long-term responses may be through a network of biochemical signaling cascades that would therefore need to be maintained for the many hours of the growth response once they are triggered. However, classical physiological analyses and recent simulation studies also suggest involvement of the cytoskeleton in sensing/responding to long-term mechanoresponse independently of the biochemical signaling cascades triggered by initial graviperception events.
Topics: Cytoskeleton; Gravitation; Gravitropism; Mechanotransduction, Cellular; Plants; Time Factors
PubMed: 23281392
DOI: 10.3732/ajb.1200408 -
Current Biology : CB Sep 2017Plant shoots typically grow against the gravity vector to access light, whereas roots grow downward into the soil to take up water and nutrients. These gravitropic... (Review)
Review
Plant shoots typically grow against the gravity vector to access light, whereas roots grow downward into the soil to take up water and nutrients. These gravitropic responses can be altered by developmental and environmental cues. In this review, we discuss the molecular mechanisms that govern the gravitropism of angiosperm roots, where a physical separation between sites for gravity sensing and curvature response has facilitated discovery. Gravity sensing takes place in the columella cells of the root cap, where sedimentation of starch-filled plastids (amyloplasts) triggers a pathway that results in a relocalization to the lower side of the cell of PIN proteins, which facilitate efflux of the plant hormone auxin efflux. Consequently, auxin accumulates in the lower half of the root, triggering bending of the root tip at the elongation zone. We review our understanding of the molecular mechanisms that control this process in primary roots, and discuss recent insights into the regulation of oblique growth in lateral roots and its impact on root-system architecture and soil exploration.
Topics: Gravitropism; Gravity Sensing; Indoleacetic Acids; Magnoliopsida; Plant Roots
PubMed: 28898669
DOI: 10.1016/j.cub.2017.07.015 -
Frontiers in Bioscience (Landmark... Nov 2021: Plants have evolved the dual capacity for maximizing light assimilation through stem growth (phototropism) and maximizing water and nutrient absorption through root...
: Plants have evolved the dual capacity for maximizing light assimilation through stem growth (phototropism) and maximizing water and nutrient absorption through root growth (gravitropism). Previous studies have revealed the physiological and molecular mechanisms of these two processes, but the genetic basis for how gravitropism and phototropism interact and coordinate with one another to determine plant growth remains poorly understood. : We designed a seed germination experiment using a full-sib F1 family of to simultaneously monitor the gravitropic growth of the radicle and the phototropic growth of the plumule throughout seedling ontogeny. We implemented three functional mapping models to identify quantitative trait loci (QTLs) that regulate gravitropic and phototropic growth. Univariate functional mapping dissected each growth trait separately, bivariate functional mapping mapped two growth traits simultaneously, and composite functional mapping mapped the sum of gravitropic and phototropic growth as a main axis. : Bivariate model detected 8 QTLs for gravitropism and phototropism (QWRF, GLUR, F-box, PCFS4, UBQ, TAF12, BHLH95, TMN8), composite model detected 7 QTLs for growth of main axis (ATL8, NEFH, PCFS4, UBQ, SOT16, MOR1, PCMP-H), of which, PCFS4 and UBQ were pleiotropically detected with the both model. Many of these QTLs are situated within the genomic regions of candidate genes. : The results from our models provide new insight into the mechanisms of genetic control of gravitropism and phototropism in a desert tree, and will stimulate our understanding of the relationships between gravity and light signal transduction pathways and tree adaptation to arid soil.
Topics: Gravitation; Gravitropism; Light; Phototropism; Populus; Trees
PubMed: 34856747
DOI: 10.52586/5003 -
International Journal of Molecular... Oct 2021Humans have been committed to space exploration and to find the next planet suitable for human survival. The construction of an ecosystem that adapts to the long-term... (Review)
Review
Humans have been committed to space exploration and to find the next planet suitable for human survival. The construction of an ecosystem that adapts to the long-term survival of human beings in space stations or other planets would be the first step. The space plant cultivation system is the key component of an ecosystem, which will produce food, fiber, edible oil and oxygen for future space inhabitants. Many plant experiments have been carried out under a stimulated or real environment of altered gravity, including at microgravity (0 g), Moon gravity (0.17 g) and Mars gravity (0.38 g). How plants sense gravity and change under stress environment of altered gravity were summarized in this review. However, many challenges remain regarding human missions to the Moon or Mars. Our group conducted the first plant experiment under real Moon gravity (0.17 g) in 2019. One of the cotton seeds successfully germinated and produced a green seedling, which represents the first green leaf produced by mankind on the Moon.
Topics: Gravitropism; Gravity, Altered; Humans; Plant Physiological Phenomena; Plants; Space Flight; Stress, Physiological
PubMed: 34769154
DOI: 10.3390/ijms222111723 -
The New Phytologist Dec 2022Gravity is one of the fundamental environmental cues that affect plant development. Indeed, the plant architecture in the shoots and roots is modulated by gravity. Stems... (Review)
Review
Gravity is one of the fundamental environmental cues that affect plant development. Indeed, the plant architecture in the shoots and roots is modulated by gravity. Stems grow vertically upward, whereas lateral organs, such as the lateral branches in shoots, tend to grow at a specific angle according to a gravity vector known as the gravitropic setpoint angle (GSA). During this process, gravity is sensed in specialised gravity-sensing cells named statocytes, which convert gravity information into biochemical signals, leading to asymmetric auxin distribution and driving asymmetric cell division/expansion in the organs to achieve gravitropism. As a hypothetical offset mechanism against gravitropism to determine the GSA, the anti-gravitropic offset (AGO) has been proposed. According to this concept, the GSA is a balance of two antagonistic growth components, that is gravitropism and the AGO. Although the nature of the AGO has not been clarified, studies have suggested that gravitropism and the AGO share a common gravity-sensing mechanism in statocytes. This review discusses the molecular mechanisms underlying gravitropism as well as the hypothetical AGO in the control of the GSA.
Topics: Gravity Sensing; Gravitropism; Indoleacetic Acids; Plant Development; Plant Roots
PubMed: 36089891
DOI: 10.1111/nph.18474 -
Current Biology : CB Sep 2017Plants are sessile organisms rooted in one place. The soil resources that plants require are often distributed in a highly heterogeneous pattern. To aid foraging, plants... (Review)
Review
Plants are sessile organisms rooted in one place. The soil resources that plants require are often distributed in a highly heterogeneous pattern. To aid foraging, plants have evolved roots whose growth and development are highly responsive to soil signals. As a result, 3D root architecture is shaped by myriad environmental signals to ensure resource capture is optimised and unfavourable environments are avoided. The first signals sensed by newly germinating seeds - gravity and light - direct root growth into the soil to aid seedling establishment. Heterogeneous soil resources, such as water, nitrogen and phosphate, also act as signals that shape 3D root growth to optimise uptake. Root architecture is also modified through biotic interactions that include soil fungi and neighbouring plants. This developmental plasticity results in a 'custom-made' 3D root system that is best adapted to forage for resources in each soil environment that a plant colonises.
Topics: Gravitropism; Phototropism; Plant Roots; Seedlings; Soil
PubMed: 28898665
DOI: 10.1016/j.cub.2017.06.043 -
G3 (Bethesda, Md.) Dec 2018Regulation of plant root angle is critical for obtaining nutrients and water and is an important trait for plant breeding. A plant's final, long-term root angle is the...
Regulation of plant root angle is critical for obtaining nutrients and water and is an important trait for plant breeding. A plant's final, long-term root angle is the net result of a complex series of decisions made by a root tip in response to changes in nutrient availability, impediments, the gravity vector and other stimuli. When a root tip is displaced from the gravity vector, the short-term process of gravitropism results in rapid reorientation of the root toward the vertical. Here, we explore both short- and long-term regulation of root growth angle, using natural variation in tomato to identify shared and separate genetic features of the two responses. Mapping of expression quantitative trait loci mapping and leveraging natural variation between and within species including Arabidopsis suggest a role for 27 and in determining root angle.
Topics: Acid Phosphatase; Arabidopsis; Arabidopsis Proteins; Glycoproteins; Gravitropism; Plant Roots
PubMed: 30322904
DOI: 10.1534/g3.118.200540 -
Journal of Experimental Botany Apr 2015An important feature of plants is the ability to adapt their growth towards or away from external stimuli such as light, water, temperature, and gravity. These... (Review)
Review
An important feature of plants is the ability to adapt their growth towards or away from external stimuli such as light, water, temperature, and gravity. These responsive plant growth movements are called tropisms and they contribute to the plant's survival and reproduction. Roots modulate their growth towards gravity to exploit the soil for water and nutrient uptake, and to provide anchorage. The physiological process of root gravitropism comprises gravity perception, signal transmission, growth response, and the re-establishment of normal growth. Gravity perception is best explained by the starch-statolith hypothesis that states that dense starch-filled amyloplasts or statoliths within columella cells sediment in the direction of gravity, resulting in the generation of a signal that causes asymmetric growth. Though little is known about the gravity receptor(s), the role of auxin linking gravity sensing to the response is well established. Auxin influx and efflux carriers facilitate creation of a differential auxin gradient between the upper and lower side of gravistimulated roots. This asymmetric auxin gradient causes differential growth responses in the graviresponding tissue of the elongation zone, leading to root curvature. Cell biological and mathematical modelling approaches suggest that the root gravitropic response begins within minutes of a gravity stimulus, triggering genomic and non-genomic responses. This review discusses recent advances in our understanding of root gravitropism in Arabidopsis thaliana and identifies current challenges and future perspectives.
Topics: Biological Transport; Gravitropism; Indoleacetic Acids; Models, Biological; Plant Roots; Signal Transduction
PubMed: 25547917
DOI: 10.1093/jxb/eru515