RESUMO
The plant-signaling molecule auxin triggers fast and slow cellular responses across land plants and algae. The nuclear auxin pathway mediates gene expression and controls growth and development in land plants, but this pathway is absent from algal sister groups. Several components of rapid responses have been identified in Arabidopsis, but it is unknown if these are part of a conserved mechanism. We recently identified a fast, proteome-wide phosphorylation response to auxin. Here, we show that this response occurs across 5 land plant and algal species and converges on a core group of shared targets. We found conserved rapid physiological responses to auxin in the same species and identified rapidly accelerated fibrosarcoma (RAF)-like protein kinases as central mediators of auxin-triggered phosphorylation across species. Genetic analysis connects this kinase to both auxin-triggered protein phosphorylation and rapid cellular response, thus identifying an ancient mechanism for fast auxin responses in the green lineage.
Assuntos
Embriófitas , Transdução de Sinais , Arabidopsis/genética , Arabidopsis/metabolismo , Embriófitas/metabolismo , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/metabolismo , Fosforilação , Plantas/metabolismo , Proteínas Quinases/metabolismo , Proteínas de Plantas/metabolismo , Proteínas de Algas/metabolismoRESUMO
Extracellular perception of auxin, an essential phytohormone in plants, has been debated for decades. Auxin-binding protein 1 (ABP1) physically interacts with quintessential transmembrane kinases (TMKs) and was proposed to act as an extracellular auxin receptor, but its role was disputed because abp1 knockout mutants lack obvious morphological phenotypes. Here, we identified two new auxin-binding proteins, ABL1 and ABL2, that are localized to the apoplast and directly interact with the extracellular domain of TMKs in an auxin-dependent manner. Furthermore, functionally redundant ABL1 and ABL2 genetically interact with TMKs and exhibit functions that overlap with those of ABP1 as well as being independent of ABP1. Importantly, the extracellular domain of TMK1 itself binds auxin and synergizes with either ABP1 or ABL1 in auxin binding. Thus, our findings discovered auxin receptors ABL1 and ABL2 having functions overlapping with but distinct from ABP1 and acting together with TMKs as co-receptors for extracellular auxin.
Assuntos
Arabidopsis , Ácidos Indolacéticos , Reguladores de Crescimento de Plantas , Ácidos Indolacéticos/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Arabidopsis/química , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismoRESUMO
In multicellular organisms, cells actively sense and control their own population density. Synthetic mammalian quorum-sensing circuits could provide insight into principles of population control and extend cell therapies. However, a key challenge is reducing their inherent sensitivity to "cheater" mutations that evade control. Here, we repurposed the plant hormone auxin to enable orthogonal mammalian cell-cell communication and quorum sensing. We designed a paradoxical population control circuit, termed "Paradaux," in which auxin stimulates and inhibits net cell growth at different concentrations. This circuit limited population size over extended timescales of up to 42 days of continuous culture. By contrast, when operating in a non-paradoxical regime, population control became more susceptible to mutational escape. These results establish auxin as a versatile "private" communication system and demonstrate that paradoxical circuit architectures can provide robust population control.
Assuntos
Comunicação Celular , Transdução de Sinais , Animais , Contagem de Células , Engenharia Celular , Ácidos Indolacéticos , Mamíferos , Percepção de Quorum , Biologia Sintética/métodosRESUMO
Banyan trees are distinguished by their extraordinary aerial roots. The Ficus genus includes species that have evolved a species-specific mutualism system with wasp pollinators. We sequenced genomes of the Chinese banyan tree, F. microcarpa, and a species lacking aerial roots, F. hispida, and one wasp genome coevolving with F. microcarpa, Eupristina verticillata. Comparative analysis of the two Ficus genomes revealed dynamic karyotype variation associated with adaptive evolution. Copy number expansion of auxin-related genes from duplications and elevated auxin production are associated with aerial root development in F. microcarpa. A male-specific AGAMOUS paralog, FhAG2, was identified as a candidate gene for sex determination in F. hispida. Population genomic analyses of Ficus species revealed genomic signatures of morphological and physiological coadaptation with their pollinators involving terpenoid- and benzenoid-derived compounds. These three genomes offer insights into and genomic resources for investigating the geneses of aerial roots, monoecy and dioecy, and codiversification in a symbiotic system.
Assuntos
Evolução Biológica , Ficus/genética , Genoma de Planta , Polinização/fisiologia , Árvores/genética , Vespas/fisiologia , Animais , Cromossomos de Plantas/genética , Elementos de DNA Transponíveis/genética , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Ácidos Indolacéticos/metabolismo , Anotação de Sequência Molecular , Filogenia , Raízes de Plantas/crescimento & desenvolvimento , Duplicações Segmentares Genômicas/genética , Cromossomos Sexuais/genética , Compostos Orgânicos Voláteis/análiseRESUMO
Root system architecture (RSA), the distribution of roots in soil, plays a major role in plant survival. RSA is shaped by multiple developmental processes that are largely governed by the phytohormone auxin, suggesting that auxin regulates responses of roots that are important for local adaptation. However, auxin has a central role in numerous processes, and it is unclear which molecular mechanisms contribute to the variation in RSA for environmental adaptation. Using natural variation in Arabidopsis, we identify EXOCYST70A3 as a modulator of the auxin system that causes variation in RSA by acting on PIN4 protein distribution. Allelic variation and genetic perturbation of EXOCYST70A3 lead to alteration of root gravitropic responses, resulting in a different RSA depth profile and drought resistance. Overall our findings suggest that the local modulation of the pleiotropic auxin pathway can gives rise to distinct RSAs that can be adaptive in specific environments.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Alelos , Apomorfina/análogos & derivados , Apomorfina/farmacologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Secas , Exocitose , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Estudo de Associação Genômica Ampla , Proteínas de Membrana Transportadoras/metabolismo , Mutação , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismoRESUMO
The evolution of land flora transformed the terrestrial environment. Land plants evolved from an ancestral charophycean alga from which they inherited developmental, biochemical, and cell biological attributes. Additional biochemical and physiological adaptations to land, and a life cycle with an alternation between multicellular haploid and diploid generations that facilitated efficient dispersal of desiccation tolerant spores, evolved in the ancestral land plant. We analyzed the genome of the liverwort Marchantia polymorpha, a member of a basal land plant lineage. Relative to charophycean algae, land plant genomes are characterized by genes encoding novel biochemical pathways, new phytohormone signaling pathways (notably auxin), expanded repertoires of signaling pathways, and increased diversity in some transcription factor families. Compared with other sequenced land plants, M. polymorpha exhibits low genetic redundancy in most regulatory pathways, with this portion of its genome resembling that predicted for the ancestral land plant. PAPERCLIP.
Assuntos
Evolução Biológica , Embriófitas/genética , Genoma de Planta , Marchantia/genética , Adaptação Biológica , Embriófitas/fisiologia , Regulação da Expressão Gênica de Plantas , Marchantia/fisiologia , Anotação de Sequência Molecular , Transdução de Sinais , Transcrição GênicaRESUMO
Temperature has a profound influence on plant and animal development, but its effects on stem cell behavior and activity remain poorly understood. Here, we characterize the responses of the Arabidopsis root to chilling (low but above-freezing) temperature. Chilling stress at 4°C leads to DNA damage predominantly in root stem cells and their early descendants. However, only newly generated/differentiating columella stem cell daughters (CSCDs) preferentially die in a programmed manner. Inhibition of the DNA damage response in these CSCDs prevents their death but makes the stem cell niche more vulnerable to chilling stress. Mathematical modeling and experimental validation indicate that CSCD death results in the re-establishment of the auxin maximum in the quiescent center (QC) and the maintenance of functional stem cell niche activity under chilling stress. This mechanism improves the root's ability to withstand the accompanying environmental stresses and to resume growth when optimal temperatures are restored.
Assuntos
Arabidopsis/fisiologia , Raízes de Plantas/citologia , Células-Tronco/citologia , Divisão Celular , Temperatura Baixa , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/fisiologia , Nicho de Células-Tronco , Estresse FisiológicoRESUMO
Gene transcription is a highly regulated process in all animals. In Drosophila, two major transcriptional programs, housekeeping and developmental, have promoters with distinct regulatory compatibilities and nucleosome organization. However, it remains unclear how the differences in chromatin structure relate to the distinct regulatory properties and which chromatin remodelers are required for these programs. Using rapid degradation of core remodeler subunits in Drosophila melanogaster S2 cells, we demonstrate that developmental gene transcription requires SWI/SNF-type complexes, primarily to maintain distal enhancer accessibility. In contrast, wild-type-level housekeeping gene transcription requires the Iswi and Ino80 remodelers to maintain nucleosome positioning and phasing at promoters. These differential remodeler dependencies relate to different DNA-sequence-intrinsic nucleosome affinities, which favor a default ON state for housekeeping but a default OFF state for developmental gene transcription. Overall, our results demonstrate how different transcription-regulatory strategies are implemented by DNA sequence, chromatin structure, and remodeler activity.
Assuntos
Cromatina , Nucleossomos , Animais , Cromatina/genética , Cromatina/metabolismo , Montagem e Desmontagem da Cromatina , DNA/metabolismo , Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Zeladoria , Nucleossomos/genética , Nucleossomos/metabolismoRESUMO
The Polycomb repressive complex 2 (PRC2) is an essential epigenetic regulator that deposits repressive H3K27me3. PRC2 subunits form two holocomplexes-PRC2.1 and PRC2.2-but the roles of these two PRC2 assemblies during differentiation are unclear. We employed auxin-inducible degradation to deplete PRC2.1 subunit MTF2 or PRC2.2 subunit JARID2 during differentiation of embryonic stem cells (ESCs) to neural progenitors (NPCs). Depletion of either MTF2 or JARID2 resulted in incomplete differentiation due to defects in gene regulation. Distinct sets of Polycomb target genes were derepressed in the absence of MTF2 or JARID2. MTF2-sensitive genes were marked by H3K27me3 in ESCs and remained silent during differentiation, whereas JARID2-sensitive genes were preferentially active in ESCs and became newly repressed in NPCs. Thus, MTF2 and JARID2 contribute non-redundantly to Polycomb silencing, suggesting that PRC2.1 and PRC2.2 have distinct functions in maintaining and establishing, respectively, Polycomb repression during differentiation.
Assuntos
Complexo Repressor Polycomb 2/metabolismo , Animais , Diferenciação Celular/fisiologia , Células-Tronco Embrionárias/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/genética , Histonas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Células-Tronco Neurais/metabolismo , Complexo Repressor Polycomb 2/fisiologia , Proteínas do Grupo Polycomb/metabolismo , Proteínas do Grupo Polycomb/fisiologia , Ligação Proteica/genéticaRESUMO
Based on in vitro studies, it has been demonstrated that the DSIF complex, composed of SPT4 and SPT5, regulates the elongation stage of transcription catalyzed by RNA polymerase II (RNA Pol II). The precise cellular function of SPT5 is not clear, because conventional gene depletion strategies for SPT5 result in loss of cellular viability. Using an acute inducible protein depletion strategy to circumvent this issue, we report that SPT5 loss triggers the ubiquitination and proteasomal degradation of the core RNA Pol II subunit RPB1, a process that we show to be evolutionarily conserved from yeast to human cells. RPB1 degradation requires the E3 ligase Cullin 3, the unfoldase VCP/p97, and a novel form of CDK9 kinase complex. Our study demonstrates that SPT5 stabilizes RNA Pol II specifically at promoter-proximal regions, permitting RNA Pol II release from promoters into gene bodies and providing mechanistic insight into the cellular function of SPT5 in safeguarding accurate gene expression.
Assuntos
Proteínas Culina/metabolismo , Proteínas Nucleares/metabolismo , RNA Polimerase II/química , RNA Polimerase II/metabolismo , Fatores de Elongação da Transcrição/metabolismo , Animais , Sobrevivência Celular , Proteínas Cromossômicas não Histona/metabolismo , Proteínas Culina/química , Fibroblastos/metabolismo , Humanos , Ácidos Indolacéticos/química , Camundongos , Ubiquitina-Proteína Ligases Nedd4/química , Regiões Promotoras Genéticas , Complexo de Endopeptidases do Proteassoma/química , Proteoma , Proteômica/métodos , Ubiquitina-Proteína Ligases/química , Proteína com Valosina/química , Proteína com Valosina/metabolismoRESUMO
SPT6 is a histone chaperone that tightly binds RNA polymerase II (RNAPII) during transcription elongation. However, its primary role in transcription is uncertain. We used targeted protein degradation to rapidly deplete SPT6 in human cells and analyzed defects in RNAPII behavior by a multi-omics approach and mathematical modeling. Our data indicate that SPT6 is a crucial factor for RNAPII processivity and is therefore required for the productive transcription of protein-coding genes. Unexpectedly, SPT6 also has a vital role in RNAPII termination, as acute depletion induced readthrough transcription for thousands of genes. Long-term depletion of SPT6 induced cryptic intragenic transcription, as observed earlier in yeast. However, this phenotype was not observed upon acute SPT6 depletion and therefore can be attributed to accumulated epigenetic perturbations in the prolonged absence of SPT6. In conclusion, targeted degradation of SPT6 allowed the temporal discrimination of its function as an epigenetic safeguard and RNAPII elongation factor.
Assuntos
RNA Polimerase II/metabolismo , Elongação da Transcrição Genética , Fatores de Transcrição/metabolismo , Linhagem Celular , Replicação do DNA , Humanos , Ácidos Indolacéticos/farmacologia , Poliadenilação , Proteólise/efeitos dos fármacos , RNA/biossíntese , RNA Polimerase II/genética , Fatores de Transcrição/genéticaRESUMO
The regulation of gene expression catalyzed by RNA polymerase II (Pol II) requires a host of accessory factors to ensure cell growth, differentiation, and survival under environmental stress. Here, using the auxin-inducible degradation (AID) system to study transcriptional activities of the bromodomain and extraterminal domain (BET) and super elongation complex (SEC) families, we found that the CDK9-containing BRD4 complex is required for the release of Pol II from promoter-proximal pausing for most genes, while the CDK9-containing SEC is required for activated transcription in the heat shock response. By using both the proteolysis targeting chimera (PROTAC) dBET6 and the AID system, we found that dBET6 treatment results in two major effects: increased pausing due to BRD4 loss, and reduced enhancer activity attributable to BRD2 loss. In the heat shock response, while auxin-mediated depletion of the AFF4 subunit of the SEC has a more severe defect than AFF1 depletion, simultaneous depletion of AFF1 and AFF4 leads to a stronger attenuation of the heat shock response, similar to treatment with the SEC inhibitor KL-1, suggesting a possible redundancy among SEC family members. This study highlights the usefulness of orthogonal acute depletion/inhibition strategies to identify distinct and redundant biological functions among Pol II elongation factor paralogs.
Assuntos
Expressão Gênica/genética , Fatores de Alongamento de Peptídeos/metabolismo , RNA Polimerase II/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Linhagem Celular Tumoral , Células HCT116 , Resposta ao Choque Térmico , Humanos , Fatores de Alongamento de Peptídeos/genética , Proteínas/genética , Proteínas/metabolismo , RNA Polimerase II/genética , Fatores de Transcrição/genéticaRESUMO
Increasing evidence suggests that tRNA levels are dynamically and specifically regulated in response to internal and external cues to modulate the cellular translational program. However, the molecular players and the mechanisms regulating the gene-specific expression of tRNAs are still unknown. Using an inducible auxin-degron system to rapidly deplete RPB1 (the largest subunit of RNA Pol II) in living cells, we identified Pol II as a direct gene-specific regulator of tRNA transcription. Our data suggest that Pol II transcription robustly interferes with Pol III function at specific tRNA genes. This activity was further found to be essential for MAF1-mediated repression of a large set of tRNA genes during serum starvation, indicating that repression of tRNA genes by Pol II is dynamically regulated. Hence, Pol II plays a direct and central role in the gene-specific regulation of tRNA expression.
Assuntos
Regulação da Expressão Gênica , RNA Polimerase III/metabolismo , RNA Polimerase II/metabolismo , RNA de Transferência/metabolismo , Proteínas Repressoras/metabolismo , Proteínas Celulares de Ligação ao Retinol/metabolismo , Transcrição Gênica , Células HeLa , Humanos , Processamento de Proteína Pós-Traducional , RNA Polimerase II/genética , RNA Polimerase III/genética , RNA de Transferência/genética , Proteínas Repressoras/genética , Proteínas Celulares de Ligação ao Retinol/genéticaRESUMO
In eukaryotes, three-dimensional genome organization is critical for transcriptional regulation of gene expression. Long noncoding RNAs (lncRNAs) can modulate chromatin conformation of spatially related genomic locations within the nucleus. Here, we show that the lncRNA APOLO (AUXIN-REGULATED PROMOTER LOOP) recognizes multiple distant independent loci in the Arabidopsis thaliana genome. We found that APOLO targets are not spatially associated in the nucleus and that APOLO recognizes its targets by short sequence complementarity and the formation of DNA-RNA duplexes (R-loops). The invasion of APOLO to the target DNA decoys the plant Polycomb Repressive Complex 1 component LHP1, modulating local chromatin 3D conformation. APOLO lncRNA coordinates the expression of distal unrelated auxin-responsive genes during lateral root development in Arabidopsis. Hence, R-loop formation and chromatin protein decoy mediate trans action of lncRNAs on distant loci. VIDEO ABSTRACT.
Assuntos
Arabidopsis/metabolismo , Montagem e Desmontagem da Cromatina , Cromatina/metabolismo , Regulação da Expressão Gênica de Plantas , Plantas Geneticamente Modificadas/metabolismo , RNA Longo não Codificante/metabolismo , RNA de Plantas/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Cromatina/genética , Montagem e Desmontagem da Cromatina/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Ácidos Indolacéticos/farmacologia , Modelos Genéticos , Plantas Geneticamente Modificadas/efeitos dos fármacos , Plantas Geneticamente Modificadas/genética , Estruturas R-Loop , RNA Polimerase II/genética , RNA Polimerase II/metabolismo , RNA Longo não Codificante/genética , RNA de Plantas/genética , Relação Estrutura-Atividade , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Auxins are pivotal plant hormones that regulate plant growth and transmembrane polar auxin transport (PAT) direct patterns of development. The PIN-FORMED (PIN) family of membrane transporters mediate auxin export from the plant cell and play crucial roles in PAT. Here we describe the recently solved structures of PIN transporters, PIN1, PIN3, and PIN8, and also their mechanisms of substrate recognition and transport of auxin. We compare structures of PINs in both inward- and outward-facing conformations, as well as PINs with different binding configurations for auxin. By this comparative analysis, a model emerges for an elevator transport mechanism. Central structural elements necessary for function are identified, and we show that these are shared with other distantly related protein families.
RESUMO
The plant signaling molecule auxin is present in multiple kingdoms of life. Since its discovery, a century of research has been focused on its action as a phytohormone. In land plants, auxin regulates growth and development through transcriptional and non-transcriptional programs. Some of the molecular mechanisms underlying these responses are well understood, mainly in Arabidopsis. Recently, the availability of genomic and transcriptomic data of green lineages, together with phylogenetic inference, has provided the basis to reconstruct the evolutionary history of some components involved in auxin biology. In this review, we follow the evolutionary trajectory that allowed auxin to become the "giant" of plant biology by focusing on bryophytes and streptophyte algae. We consider auxin biosynthesis, transport, physiological, and molecular responses, as well as evidence supporting the role of auxin as a chemical messenger for communication within ecosystems. Finally, we emphasize that functional validation of predicted orthologs will shed light on the conserved properties of auxin biology among streptophytes.
Assuntos
Arabidopsis , Ácidos Indolacéticos , Filogenia , Ecossistema , Evolução Molecular , Plantas , Arabidopsis/genéticaRESUMO
Roots are highly plastic organs enabling plants to adapt to a changing below-ground environment. In addition to abiotic factors like nutrients or mechanical resistance, plant roots also respond to temperature variation. Below the heat stress threshold, Arabidopsis thaliana seedlings react to elevated temperature by promoting primary root growth, possibly to reach deeper soil regions with potentially better water saturation. While above-ground thermomorphogenesis is enabled by thermo-sensitive cell elongation, it was unknown how temperature modulates root growth. We here show that roots are able to sense and respond to elevated temperature independently of shoot-derived signals. This response is mediated by a yet unknown root thermosensor that employs auxin as a messenger to relay temperature signals to the cell cycle. Growth promotion is achieved primarily by increasing cell division rates in the root apical meristem, depending on de novo local auxin biosynthesis and temperature-sensitive organization of the polar auxin transport system. Hence, the primary cellular target of elevated ambient temperature differs fundamentally between root and shoot tissues, while the messenger auxin remains the same.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Ácidos Indolacéticos/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Raízes de Plantas/metabolismo , Arabidopsis/metabolismo , Divisão Celular , Regulação da Expressão Gênica de PlantasRESUMO
Plant organogenesis requires matching the available metabolic resources to developmental programs. In Arabidopsis, the root system is determined by primary root-derived lateral roots (LRs), and adventitious roots (ARs) formed from non-root organs. Lateral root formation entails the auxin-dependent activation of transcription factors ARF7, ARF19, and LBD16. Adventitious root formation relies on LBD16 activation by auxin and WOX11. The allocation of shoot-derived sugar to the roots influences branching, but how its availability is sensed for LRs formation remains unknown. We combine metabolic profiling with cell-specific interference to show that LRs switch to glycolysis and consume carbohydrates. The target-of-rapamycin (TOR) kinase is activated in the lateral root domain. Interfering with TOR kinase blocks LR initiation while promoting AR formation. The target-of-rapamycin inhibition marginally affects the auxin-induced transcriptional response of the pericycle but attenuates the translation of ARF19, ARF7, and LBD16. TOR inhibition induces WOX11 transcription in these cells, yet no root branching occurs as TOR controls LBD16 translation. TOR is a central gatekeeper for root branching that integrates local auxin-dependent pathways with systemic metabolic signals, modulating the translation of auxin-induced genes.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Fatores de Transcrição/metabolismo , Raízes de Plantas/metabolismo , Regulação da Expressão Gênica de Plantas , Fosfatidilinositol 3-Quinases/genéticaRESUMO
In multicellular organisms, specialized tissues are generated by specific populations of stem cells through cycles of asymmetric cell divisions, where one daughter undergoes differentiation and the other maintains proliferative properties. In Arabidopsis thaliana roots, the columella - a gravity-sensing tissue that protects and defines the position of the stem cell niche - represents a typical example of a tissue whose organization is exclusively determined by the balance between proliferation and differentiation. The columella derives from a single layer of stem cells through a binary cell fate switch that is precisely controlled by multiple, independent regulatory inputs. Here, we show that the HD-Zip II transcription factors (TFs) HAT3, ATHB4 and AHTB2 redundantly regulate columella stem cell fate and patterning in the Arabidopsis root. The HD-Zip II TFs promote columella stem cell proliferation by acting as effectors of the FEZ/SMB circuit and, at the same time, by interfering with auxin signaling to counteract hormone-induced differentiation. Overall, our work shows that HD-Zip II TFs connect two opposing parallel inputs to fine-tune the balance between proliferation and differentiation in columella stem cells.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ácidos Indolacéticos/metabolismo , Células-Tronco/metabolismo , Regulação da Expressão Gênica de Plantas , Raízes de Plantas/metabolismo , Meristema/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismoRESUMO
Lateral roots (LRs) increase root surface area and allow plants greater access to soil water and nutrients. LR formation is tightly regulated by the phytohormone auxin. Whereas the transcription factor ETHYLENE-RESPONSIVE ELEMENT BINDING FACTOR13 (ERF13) prevents LR emergence in Arabidopsis (Arabidopsis thaliana), auxin activates MITOGEN-ACTIVATED PROTEIN KINASE14 (MPK14), which leads to ERF13 degradation and ultimately promotes LR emergence. In this study, we discovered interactions between ERF13 and the E3 ubiquitin ligases MOS4-ASSOCIATED COMPLEX 3A (MAC3A) and MAC3B. As MAC3A and MAC3B gradually accumulate in the LR primordium, ERF13 levels gradually decrease. We demonstrate that MAC3A and MAC3B ubiquitinate ERF13, leading to its degradation and accelerating the transition of LR primordia from stage IV to stage V. Auxin enhances the MAC3A and MAC3B interaction with ERF13 by facilitating MPK14-mediated ERF13 phosphorylation. In summary, this study reveals the molecular mechanism by which auxin eliminates the inhibitory factor ERF13 through the MPK14-MAC3A and MAC3B signaling module, thus promoting LR emergence.