RESUMEN
Certain obligate parasites induce complex and substantial phenotypic changes in their hosts in ways that favor their transmission to other trophic levels. However, the mechanisms underlying these changes remain largely unknown. Here we demonstrate how SAP05 protein effectors from insect-vectored plant pathogenic phytoplasmas take control of several plant developmental processes. These effectors simultaneously prolong the host lifespan and induce witches' broom-like proliferations of leaf and sterile shoots, organs colonized by phytoplasmas and vectors. SAP05 acts by mediating the concurrent degradation of SPL and GATA developmental regulators via a process that relies on hijacking the plant ubiquitin receptor RPN10 independent of substrate ubiquitination. RPN10 is highly conserved among eukaryotes, but SAP05 does not bind insect vector RPN10. A two-amino-acid substitution within plant RPN10 generates a functional variant that is resistant to SAP05 activities. Therefore, one effector protein enables obligate parasitic phytoplasmas to induce a plethora of developmental phenotypes in their hosts.
Asunto(s)
Arabidopsis/crecimiento & desarrollo , Arabidopsis/parasitología , Interacciones Huésped-Parásitos/fisiología , Parásitos/fisiología , Proteolisis , Ubiquitinas/metabolismo , Secuencia de Aminoácidos , Animales , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Ingeniería Genética , Humanos , Insectos/fisiología , Modelos Biológicos , Fenotipo , Fotoperiodo , Filogenia , Phytoplasma/fisiología , Desarrollo de la Planta , Brotes de la Planta/crecimiento & desarrollo , Plantas Modificadas Genéticamente , Complejo de la Endopetidasa Proteasomal/metabolismo , Estabilidad Proteica , Reproducción , Nicotiana , Factores de Transcripción/metabolismo , Transcripción GenéticaRESUMEN
Many organisms evolved strategies to survive desiccation. Plant seeds protect dehydrated embryos from various stressors and can lay dormant for millennia. Hydration is the key trigger to initiate germination, but the mechanism by which seeds sense water remains unresolved. We identified an uncharacterized Arabidopsis thaliana prion-like protein we named FLOE1, which phase separates upon hydration and allows the embryo to sense water stress. We demonstrate that biophysical states of FLOE1 condensates modulate its biological function in vivo in suppressing seed germination under unfavorable environments. We find intragenic, intraspecific, and interspecific natural variation in FLOE1 expression and phase separation and show that intragenic variation is associated with adaptive germination strategies in natural populations. This combination of molecular, organismal, and ecological studies uncovers FLOE1 as a tunable environmental sensor with direct implications for the design of drought-resistant crops, in the face of climate change.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Germinación , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Priones/metabolismo , Semillas/crecimiento & desarrollo , Agua/metabolismo , Arabidopsis/genética , Arabidopsis/ultraestructura , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/ultraestructura , Deshidratación , Imagenología Tridimensional , Péptidos y Proteínas de Señalización Intercelular/química , Mutación/genética , Latencia en las Plantas , Plantas Modificadas Genéticamente , Dominios Proteicos , Isoformas de Proteínas/metabolismo , Semillas/ultraestructuraRESUMEN
Recognition of microbe-associated molecular patterns (MAMPs) is crucial for the plant's immune response. How this sophisticated perception system can be usefully deployed in roots, continuously exposed to microbes, remains a mystery. By analyzing MAMP receptor expression and response at cellular resolution in Arabidopsis, we observed that differentiated outer cell layers show low expression of pattern-recognition receptors (PRRs) and lack MAMP responsiveness. Yet, these cells can be gated to become responsive by neighbor cell damage. Laser ablation of small cell clusters strongly upregulates PRR expression in their vicinity, and elevated receptor expression is sufficient to induce responsiveness in non-responsive cells. Finally, localized damage also leads to immune responses to otherwise non-immunogenic, beneficial bacteria. Damage-gating is overridden by receptor overexpression, which antagonizes colonization. Our findings that cellular damage can "switch on" local immune responses helps to conceptualize how MAMP perception can be used despite the presence of microbial patterns in the soil.
Asunto(s)
Arabidopsis/inmunología , Enfermedades de las Plantas/inmunología , Enfermedades de las Plantas/microbiología , Raíces de Plantas/inmunología , Receptores de Reconocimiento de Patrones/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/microbiología , Arabidopsis/efectos de la radiación , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/efectos de la radiación , Ascorbato Peroxidasas/metabolismo , Ascorbato Peroxidasas/efectos de la radiación , Flagelina/farmacología , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Terapia por Láser/métodos , Proteínas de la Membrana/metabolismo , Proteínas de la Membrana/efectos de la radiación , Microscopía Confocal , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/microbiología , Raíces de Plantas/efectos de la radiación , Proteínas Quinasas/metabolismo , Proteínas Quinasas/efectos de la radiación , Receptores de Reconocimiento de Patrones/efectos de la radiación , Transducción de Señal/efectos de los fármacos , Transducción de Señal/efectos de la radiación , Imagen de Lapso de TiempoRESUMEN
Cell polarity is fundamental for tissue morphogenesis in multicellular organisms. Plants and animals evolved multicellularity independently, and it is unknown whether their polarity systems are derived from a single-celled ancestor. Planar polarity in animals is conferred by Wnt signaling, an ancient signaling pathway transduced by Dishevelled, which assembles signalosomes by dynamic head-to-tail DIX domain polymerization. In contrast, polarity-determining pathways in plants are elusive. We recently discovered Arabidopsis SOSEKI proteins, which exhibit polar localization throughout development. Here, we identify SOSEKI as ancient polar proteins across land plants. Concentration-dependent polymerization via a bona fide DIX domain allows these to recruit ANGUSTIFOLIA to polar sites, similar to the polymerization-dependent recruitment of signaling effectors by Dishevelled. Cross-kingdom domain swaps reveal functional equivalence of animal and plant DIX domains. We trace DIX domains to unicellular eukaryotes and thus show that DIX-dependent polymerization is an ancient mechanism conserved between kingdoms and central to polarity proteins.
Asunto(s)
Arabidopsis/química , Arabidopsis/citología , Polaridad Celular/fisiología , Células Vegetales/fisiología , Polimerizacion , Dominios Proteicos , Animales , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Proteína Axina/química , Proteína Axina/metabolismo , Bryopsida/química , Bryopsida/citología , Bryopsida/genética , Bryopsida/crecimiento & desarrollo , Células COS , Chlorocebus aethiops , Proteínas Dishevelled/metabolismo , Células HEK293 , Humanos , Marchantia/química , Marchantia/citología , Marchantia/genética , Marchantia/crecimiento & desarrollo , Proteínas de la Membrana/química , Proteínas de la Membrana/metabolismo , Plantas Modificadas Genéticamente , Proteínas Represoras/metabolismo , Vía de Señalización WntRESUMEN
How do genes modify cellular growth to create morphological diversity? We study this problem in two related plants with differently shaped leaves: Arabidopsis thaliana (simple leaf shape) and Cardamine hirsuta (complex shape with leaflets). We use live imaging, modeling, and genetics to deconstruct these organ-level differences into their cell-level constituents: growth amount, direction, and differentiation. We show that leaf shape depends on the interplay of two growth modes: a conserved organ-wide growth mode that reflects differentiation; and a local, directional mode that involves the patterning of growth foci along the leaf edge. Shape diversity results from the distinct effects of two homeobox genes on these growth modes: SHOOTMERISTEMLESS broadens organ-wide growth relative to edge-patterning, enabling leaflet emergence, while REDUCED COMPLEXITY inhibits growth locally around emerging leaflets, accentuating shape differences created by patterning. We demonstrate the predictivity of our findings by reconstructing key features of C. hirsuta leaf morphology in A. thaliana. VIDEO ABSTRACT.
Asunto(s)
Arabidopsis/crecimiento & desarrollo , Cardamine/crecimiento & desarrollo , Hojas de la Planta/crecimiento & desarrollo , Arabidopsis/genética , Cardamine/genética , Linaje de la Célula/genética , Biología Computacional/métodos , Regulación de la Expresión Génica de las Plantas/genética , Hojas de la Planta/genética , Proteínas de Plantas/metabolismoRESUMEN
The root cap surrounding the tip of plant roots is thought to protect the delicate stem cells in the root meristem. We discovered that the first layer of root cap cells is covered by an electron-opaque cell wall modification resembling a plant cuticle. Cuticles are polyester-based protective structures considered exclusive to aerial plant organs. Mutations in cutin biosynthesis genes affect the composition and ultrastructure of this cuticular structure, confirming its cutin-like characteristics. Strikingly, targeted degradation of the root cap cuticle causes a hypersensitivity to abiotic stresses during seedling establishment. Furthermore, lateral root primordia also display a cuticle that, when defective, causes delayed outgrowth and organ deformations, suggesting that it facilitates lateral root emergence. Our results show that the previously unrecognized root cap cuticle protects the root meristem during the critical phase of seedling establishment and promotes the efficient formation of lateral roots.
Asunto(s)
Arabidopsis/crecimiento & desarrollo , Cápsula de Raíz de Planta/metabolismo , Cápsula de Raíz de Planta/fisiología , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Pared Celular/metabolismo , Regulación de la Expresión Génica de las Plantas/genética , Lípidos de la Membrana/biosíntesis , Lípidos de la Membrana/metabolismo , Meristema/metabolismo , Mutación , Raíces de Plantas/citología , Plantones/genética , Plantones/crecimiento & desarrolloRESUMEN
Sun-loving plants have the ability to detect and avoid shading through sensing of both blue and red light wavelengths. Higher plant cryptochromes (CRYs) control how plants modulate growth in response to changes in blue light. For growth under a canopy, where blue light is diminished, CRY1 and CRY2 perceive this change and respond by directly contacting two bHLH transcription factors, PIF4 and PIF5. These factors are also known to be controlled by phytochromes, the red/far-red photoreceptors; however, transcriptome analyses indicate that the gene regulatory programs induced by the different light wavelengths are distinct. Our results indicate that CRYs signal by modulating PIF activity genome wide and that these factors integrate binding of different plant photoreceptors to facilitate growth changes under different light conditions.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Criptocromos/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/efectos de la radiación , Expresión Génica , Hipocótilo/crecimiento & desarrollo , Luz , Fitocromo B/metabolismoRESUMEN
A staggering diversity of endophytic fungi associate with healthy plants in nature, but it is usually unclear whether these represent stochastic encounters or provide host fitness benefits. Although most characterized species of the fungal genus Colletotrichum are destructive pathogens, we show here that C. tofieldiae (Ct) is an endemic endophyte in natural Arabidopsis thaliana populations in central Spain. Colonization by Ct initiates in roots but can also spread systemically into shoots. Ct transfers the macronutrient phosphorus to shoots, promotes plant growth, and increases fertility only under phosphorus-deficient conditions, a nutrient status that might have facilitated the transition from pathogenic to beneficial lifestyles. The host's phosphate starvation response (PSR) system controls Ct root colonization and is needed for plant growth promotion (PGP). PGP also requires PEN2-dependent indole glucosinolate metabolism, a component of innate immune responses, indicating a functional link between innate immunity and the PSR system during beneficial interactions with Ct.
Asunto(s)
Arabidopsis/microbiología , Colletotrichum/aislamiento & purificación , Fosfatos/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/fisiología , Proteínas de Arabidopsis/metabolismo , Colletotrichum/fisiología , Endófitos , Proteínas de Transporte de Fosfato/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Raíces de Plantas/microbiología , España , SimbiosisRESUMEN
DNA methylation is a conserved epigenetic modification that is important for gene regulation and genome stability. Aberrant patterns of DNA methylation can lead to plant developmental abnormalities. A specific DNA methylation state is an outcome of dynamic regulation by de novo methylation, maintenance of methylation and active demethylation, which are catalysed by various enzymes that are targeted by distinct regulatory pathways. In this Review, we discuss DNA methylation in plants, including methylating and demethylating enzymes and regulatory factors, and the coordination of methylation and demethylation activities by a so-called methylstat mechanism; the functions of DNA methylation in regulating transposon silencing, gene expression and chromosome interactions; the roles of DNA methylation in plant development; and the involvement of DNA methylation in plant responses to biotic and abiotic stress conditions.
Asunto(s)
Arabidopsis/genética , Metilación de ADN/genética , Epigénesis Genética/genética , Regulación de la Expresión Génica de las Plantas/genética , Animales , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/metabolismo , ADN de Plantas/genética , Humanos , Proteínas Nucleares/metabolismo , Plantas/genéticaRESUMEN
Precise control of cell division is essential for proper patterning and growth during the development of multicellular organisms. Coordination of formative divisions that generate new tissue patterns with proliferative divisions that promote growth is poorly understood. SHORTROOT (SHR) and SCARECROW (SCR) are transcription factors that are required for formative divisions in the stem cell niche of Arabidopsis roots1,2. Here we show that levels of SHR and SCR early in the cell cycle determine the orientation of the division plane, resulting in either formative or proliferative cell division. We used 4D quantitative, long-term and frequent (every 15 min for up to 48 h) light sheet and confocal microscopy to probe the dynamics of SHR and SCR in tandem within single cells of living roots. Directly controlling their dynamics with an SHR induction system enabled us to challenge an existing bistable model3 of the SHR-SCR gene-regulatory network and to identify key features that are essential for rescue of formative divisions in shr mutants. SHR and SCR kinetics do not align with the expected behaviour of a bistable system, and only low transient levels, present early in the cell cycle, are required for formative divisions. These results reveal an uncharacterized mechanism by which developmental regulators directly coordinate patterning and growth.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Ciclo Celular , Raíces de Plantas , Arabidopsis/citología , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ciclo Celular/genética , División Celular/genética , Regulación de la Expresión Génica de las Plantas , Raíces de Plantas/citología , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Microscopía Confocal , MutaciónRESUMEN
Calcium (Ca2+) is an essential nutrient for plants and a cellular signal, but excessive levels can be toxic and inhibit growth1,2. To thrive in dynamic environments, plants must monitor and maintain cytosolic Ca2+ homeostasis by regulating numerous Ca2+ transporters3. Here we report two signalling pathways in Arabidopsis thaliana that converge on the activation of vacuolar Ca2+/H+ exchangers (CAXs) to scavenge excess cytosolic Ca2+ in plants. One mechanism, activated in response to an elevated external Ca2+ level, entails calcineurin B-like (CBL) Ca2+ sensors and CBL-interacting protein kinases (CIPKs), which activate CAXs by phosphorylating a serine (S) cluster in the auto-inhibitory domain. The second pathway, triggered by molecular patterns associated with microorganisms, engages the immune receptor complex FLS2-BAK1 and the associated cytoplasmic kinases BIK1 and PBL1, which phosphorylate the same S-cluster in CAXs to modulate Ca2+ signals in immunity. These Ca2+-dependent (CBL-CIPK) and Ca2+-independent (FLS2-BAK1-BIK1/PBL1) mechanisms combine to balance plant growth and immunity by regulating cytosolic Ca2+ homeostasis.
Asunto(s)
Arabidopsis , Calcio , Homeostasis , Inmunidad de la Planta , Arabidopsis/citología , Arabidopsis/crecimiento & desarrollo , Arabidopsis/inmunología , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Calcio/metabolismo , Proteínas de Unión al Calcio/metabolismo , Citosol/metabolismo , Fosforilación , Fosfoserina/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas de Transporte de Catión/metabolismo , Antiportadores/metabolismoRESUMEN
Plant membrane transporters controlling metabolite distribution contribute key agronomic traits1-6. To eliminate anti-nutritional factors in edible parts of crops, the mutation of importers can block the accumulation of these factors in sink tissues7. However, this often results in a substantially altered distribution pattern within the plant8-12, whereas engineering of exporters may prevent such changes in distribution. In brassicaceous oilseed crops, anti-nutritional glucosinolate defence compounds are translocated to the seeds. However, the molecular targets for export engineering of glucosinolates remain unclear. Here we identify and characterize members of the USUALLY MULTIPLE AMINO ACIDS MOVE IN AND OUT TRANSPORTER (UMAMIT) family-UMAMIT29, UMAMIT30 and UMAMIT31-in Arabidopsis thaliana as glucosinolate exporters with a uniport mechanism. Loss-of-function umamit29 umamit30 umamit31 triple mutants have a very low level of seed glucosinolates, demonstrating a key role for these transporters in translocating glucosinolates into seeds. We propose a model in which the UMAMIT uniporters facilitate glucosinolate efflux from biosynthetic cells along the electrochemical gradient into the apoplast, where the high-affinity H+-coupled glucosinolate importers GLUCOSINOLATE TRANSPORTERS (GTRs) load them into the phloem for translocation to the seeds. Our findings validate the theory that two differently energized transporter types are required for cellular nutrient homeostasis13. The UMAMIT exporters are new molecular targets to improve nutritional value of seeds of brassicaceous oilseed crops without altering the distribution of the defence compounds in the whole plant.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Glucosinolatos , Proteínas de Transporte de Membrana , Semillas , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Glucosinolatos/metabolismo , Homeostasis , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/metabolismo , Floema/metabolismo , Reproducibilidad de los Resultados , Semillas/metabolismoRESUMEN
Organ morphogenesis depends on mechanical interactions between cells and tissues. These interactions generate forces that can be sensed by cells and affect key cellular processes. However, how mechanical forces, together with biochemical signals, contribute to the shaping of complex organs is still largely unclear. We address this question using the seed of Arabidopsis as a model system. We show that seeds first experience a phase of rapid anisotropic growth that is dependent on the response of cortical microtubule (CMT) to forces, which guide cellulose deposition according to shape-driven stresses in the outermost layer of the seed coat. However, at later stages of development, we show that seed growth is isotropic and depends on the properties of an inner layer of the seed coat that stiffens its walls in response to tension but has isotropic material properties. Finally, we show that the transition from anisotropic to isotropic growth is due to the dampening of cortical microtubule responses to shape-driven stresses. Altogether, our work supports a model in which spatiotemporally distinct mechanical responses control the shape of developing seeds in Arabidopsis.
Asunto(s)
Arabidopsis , Microtúbulos , Semillas , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Arabidopsis/genética , Semillas/crecimiento & desarrollo , Semillas/metabolismo , Microtúbulos/metabolismo , Fenómenos Biomecánicos , Estrés Mecánico , Anisotropía , Celulosa/metabolismoRESUMEN
The Casparian strip is a barrier in the endodermal cell walls of plants that allows the selective uptake of nutrients and water. In the model plant Arabidopsis thaliana, its development and establishment are under the control of a receptor-ligand mechanism termed the Schengen pathway. This pathway facilitates barrier formation and activates downstream compensatory responses in case of dysfunction. However, due to a very tight functional association with the Casparian strip, other potential signaling functions of the Schengen pathway remain obscure. In this work, we created a MYB36-dependent synthetic positive feedback loop that drives Casparian strip formation independently of Schengen-induced signaling. We evaluated this by subjecting plants in which the Schengen pathway has been uncoupled from barrier formation, as well as a number of established barrier-mutant plants, to agar-based and soil conditions that mimic agricultural settings. Under the latter conditions, the Schengen pathway is necessary for the establishment of nitrogen-deficiency responses in shoots. These data highlight Schengen signaling as an essential hub for the adaptive integration of signaling from the rhizosphere to aboveground tissues.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Nitrógeno , Brotes de la Planta , Transducción de Señal , Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Nitrógeno/metabolismo , Brotes de la Planta/metabolismo , Brotes de la Planta/crecimiento & desarrollo , Suelo/química , Regulación de la Expresión Génica de las Plantas , Proteínas Quinasas/metabolismo , Proteínas Quinasas/genética , Pared Celular/metabolismo , Factores de Transcripción/metabolismo , Factores de Transcripción/genéticaRESUMEN
A key question in plant biology is how oriented cell divisions are integrated with patterning mechanisms to generate organs with adequate cell type allocation. In the root vasculature, a gradient of miRNA165/6 controls the abundance of HD-ZIP III transcription factors, which in turn control cell fate and spatially restrict vascular cell proliferation to specific cells. Here, we show that vascular development requires the presence of ARGONAUTE10, which is thought to sequester miRNA165/6 and protect HD-ZIP III transcripts from degradation. Our results suggest that the miR165/6-AGO10-HDZIP III module acts by buffering cytokinin responses and restricting xylem differentiation. Mutants of AGO10 show faster growth rates and strongly enhanced survival under severe drought conditions. However, this superior performance is offset by markedly increased variation and phenotypic plasticity in sub-optimal carbon supply conditions. Thus, AGO10 is required for the control of formative cell division and coordination of robust cell fate specification of the vasculature, while altering its expression provides a means to adjust phenotypic plasticity.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Proteínas Argonautas , División Celular , Regulación de la Expresión Génica de las Plantas , MicroARNs , Raíces de Plantas , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/citología , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas Argonautas/metabolismo , Proteínas Argonautas/genética , División Celular/genética , Raíces de Plantas/citología , Raíces de Plantas/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/genética , MicroARNs/genética , MicroARNs/metabolismo , Diferenciación Celular , Xilema/citología , Xilema/metabolismo , Xilema/crecimiento & desarrollo , Xilema/genéticaRESUMEN
The RNA-silencing effector ARGONAUTE10 influences cell fate in plant shoot and floral meristems. ARGONAUTE10 also accumulates in the root apical meristem (RAM), yet its function(s) therein remain elusive. Here, we show that ARGONAUTE10 is expressed in the root cell initials where it controls overall RAM activity and length. ARGONAUTE10 is also expressed in the stele, where post-transcriptional regulation confines it to the root tip's pro-vascular region. There, variations in ARGONAUTE10 levels modulate metaxylem-vs-protoxylem specification. Both ARGONAUTE10 functions entail its selective, high-affinity binding to mobile miR165/166 transcribed in the neighboring endodermis. ARGONAUTE10-bound miR165/166 is degraded, likely via SMALL-RNA-DEGRADING-NUCLEASES1/2, thus reducing miR165/166 ability to silence, via ARGONAUTE1, the transcripts of cell fate-influencing transcription factors. These include PHABULOSA (PHB), which controls meristem activity in the initials and xylem differentiation in the pro-vasculature. During early germination, PHB transcription increases while dynamic, spatially-restricted transcriptional and post-transcriptional mechanisms reduce and confine ARGONAUTE10 accumulation to the provascular cells surrounding the newly-forming xylem axis. Adequate miR165/166 concentrations are thereby channeled along the ARGONAUTE10-deficient yet ARGONAUTE1-proficient axis. Consequently, inversely-correlated miR165/166 and PHB gradients form preferentially along the axis despite ubiquitous PHB transcription and widespread miR165/166 delivery inside the whole vascular cylinder.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Proteínas Argonautas , Regulación de la Expresión Génica de las Plantas , Meristema , MicroARNs , Raíces de Plantas , Xilema , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , MicroARNs/metabolismo , MicroARNs/genética , Meristema/metabolismo , Meristema/crecimiento & desarrollo , Meristema/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas Argonautas/metabolismo , Proteínas Argonautas/genética , Xilema/metabolismo , Xilema/crecimiento & desarrollo , Xilema/genética , Raíces de Plantas/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/genéticaRESUMEN
Translation inhibition is a major but poorly understood mode of action of microRNAs (miRNAs) in plants and animals. In particular, the subcellular location where this process takes place is unknown. Here, we show that the translation inhibition, but not the mRNA cleavage activity, of Arabidopsis miRNAs requires ALTERED MERISTEM PROGRAM1 (AMP1). AMP1 encodes an integral membrane protein associated with endoplasmic reticulum (ER) and ARGONAUTE1, the miRNA effector and a peripheral ER membrane protein. Large differences in polysome association of miRNA target RNAs are found between wild-type and the amp1 mutant for membrane-bound, but not total, polysomes. This, together with AMP1-independent recruitment of miRNA target transcripts to membrane fractions, shows that miRNAs inhibit the translation of target RNAs on the ER. This study demonstrates that translation inhibition is an important activity of plant miRNAs, reveals the subcellular location of this activity, and uncovers a previously unknown function of the ER.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Carboxipeptidasas/metabolismo , Retículo Endoplásmico/metabolismo , MicroARNs/metabolismo , ARN de Planta/metabolismo , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/genética , Carboxipeptidasas/genética , Pleiotropía Genética , Mutación , Polirribosomas/metabolismo , Biosíntesis de Proteínas , ARN Mensajero/metabolismoRESUMEN
Extreme weather conditions associated with climate change affect many aspects of plant and animal life, including the response to infectious diseases. Production of salicylic acid (SA), a central plant defence hormone1-3, is particularly vulnerable to suppression by short periods of hot weather above the normal plant growth temperature range via an unknown mechanism4-7. Here we show that suppression of SA production in Arabidopsis thaliana at 28 °C is independent of PHYTOCHROME B8,9 (phyB) and EARLY FLOWERING 310 (ELF3), which regulate thermo-responsive plant growth and development. Instead, we found that formation of GUANYLATE BINDING PROTEIN-LIKE 3 (GBPL3) defence-activated biomolecular condensates11 (GDACs) was reduced at the higher growth temperature. The altered GDAC formation in vivo is linked to impaired recruitment of GBPL3 and SA-associated Mediator subunits to the promoters of CBP60g and SARD1, which encode master immune transcription factors. Unlike many other SA signalling components, including the SA receptor and biosynthetic genes, optimized CBP60g expression was sufficient to broadly restore SA production, basal immunity and effector-triggered immunity at the elevated growth temperature without significant growth trade-offs. CBP60g family transcription factors are widely conserved in plants12. These results have implications for safeguarding the plant immune system as well as understanding the concept of the plant-pathogen-environment disease triangle and the emergence of new disease epidemics in a warming climate.
Asunto(s)
Aclimatación , Proteínas de Arabidopsis , Arabidopsis , Ambiente , Calentamiento Global , Inmunidad de la Planta , Temperatura , Arabidopsis/crecimiento & desarrollo , Arabidopsis/inmunología , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Unión a Calmodulina/genética , Regulación de la Expresión Génica de las Plantas , Calentamiento Global/estadística & datos numéricos , Interacciones Huésped-Patógeno , Fitocromo B , Enfermedades de las Plantas/genética , Inmunidad de la Planta/genética , Ácido Salicílico/metabolismo , Factores de TranscripciónRESUMEN
The shoot apical meristem is a key stem cell niche in plants, and proper stem cell maintenance is partly regulated by CLAVATA3 (CLV3). Without CLV3 meristems overgrow, but the mechanistic basis of this phenotype was unclear. A new paper in Development suggests that CLV3 modulates the physical properties of meristematic stem cells, and that these properties help shape meristem morphology. To learn more about the story behind the paper, we caught up with first author Léa Rambaud-Lavigne and corresponding authors Namrata Gundiah, Arezki Boudaoud and Pradeep Das.
Asunto(s)
Meristema , Meristema/crecimiento & desarrollo , Meristema/citología , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Historia del Siglo XXI , Biología Evolutiva/historia , Historia del Siglo XXRESUMEN
Tissue morphogenesis remains poorly understood. In plants, a central problem is how the 3D cellular architecture of a developing organ contributes to its final shape. We address this question through a comparative analysis of ovule morphogenesis, taking advantage of the diversity in ovule shape across angiosperms. Here, we provide a 3D digital atlas of Cardamine hirsuta ovule development at single cell resolution and compare it with an equivalent atlas of Arabidopsis thaliana. We introduce nerve-based topological analysis as a tool for unbiased detection of differences in cellular architectures and corroborate identified topological differences between two homologous tissues by comparative morphometrics and visual inspection. We find that differences in topology, cell volume variation and tissue growth patterns in the sheet-like integuments and the bulbous chalaza are associated with differences in ovule curvature. In contrast, the radialized conical ovule primordia and nucelli exhibit similar shapes, despite differences in internal cellular topology and tissue growth patterns. Our results support the notion that the structural organization of a tissue is associated with its susceptibility to shape changes during evolutionary shifts in 3D cellular architecture.