RESUMEN
Hybrid sterility restricts the utilization of superior heterosis of indica-japonica inter-subspecific hybrids. In this study, we report the identification of RHS12, a major locus controlling male gamete sterility in indica-japonica hybrid rice. We show that RHS12 consists of two genes (iORF3/DUYAO and iORF4/JIEYAO) that confer preferential transmission of the RHS12-i type male gamete into the progeny, thereby forming a natural gene drive. DUYAO encodes a mitochondrion-targeted protein that interacts with OsCOX11 to trigger cytotoxicity and cell death, whereas JIEYAO encodes a protein that reroutes DUYAO to the autophagosome for degradation via direct physical interaction, thereby detoxifying DUYAO. Evolutionary trajectory analysis reveals that this system likely formed de novo in the AA genome Oryza clade and contributed to reproductive isolation (RI) between different lineages of rice. Our combined results provide mechanistic insights into the genetic basis of RI as well as insights for strategic designs of hybrid rice breeding.
Asunto(s)
Tecnología de Genética Dirigida , Oryza , Hibridación Genética , Oryza/genética , Fitomejoramiento/métodos , Aislamiento Reproductivo , Infertilidad VegetalRESUMEN
The extracellular pH is a vital regulator of various biological processes in plants. However, how plants perceive extracellular pH remains obscure. Here, we report that plant cell-surface peptide-receptor complexes can function as extracellular pH sensors. We found that pattern-triggered immunity (PTI) dramatically alkalinizes the acidic extracellular pH in root apical meristem (RAM) region, which is essential for root meristem growth factor 1 (RGF1)-mediated RAM growth. The extracellular alkalinization progressively inhibits the acidic-dependent interaction between RGF1 and its receptors (RGFRs) through the pH sensor sulfotyrosine. Conversely, extracellular alkalinization promotes the alkaline-dependent binding of plant elicitor peptides (Peps) to its receptors (PEPRs) through the pH sensor Glu/Asp, thereby promoting immunity. A domain swap between RGFR and PEPR switches the pH dependency of RAM growth. Thus, our results reveal a mechanism of extracellular pH sensing by plant peptide-receptor complexes and provide insights into the extracellular pH-mediated regulation of growth and immunity in the RAM.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Concentración de Iones de Hidrógeno , Meristema/metabolismo , Péptidos/metabolismo , Células Vegetales , Raíces de Plantas/metabolismo , Plantas/metabolismo , Receptores de Superficie Celular/metabolismo , Transducción de SeñalRESUMEN
2',3'-cAMP is a positional isomer of the well-established second messenger 3',5'-cAMP, but little is known about the biology of this noncanonical cyclic nucleotide monophosphate (cNMP). Toll/interleukin-1 receptor (TIR) domains of nucleotide-binding leucine-rich repeat (NLR) immune receptors have the NADase function necessary but insufficient to activate plant immune responses. Here, we show that plant TIR proteins, besides being NADases, act as 2',3'-cAMP/cGMP synthetases by hydrolyzing RNA/DNA. Structural data show that a TIR domain adopts distinct oligomers with mutually exclusive NADase and synthetase activity. Mutations specifically disrupting the synthetase activity abrogate TIR-mediated cell death in Nicotiana benthamiana (Nb), supporting an important role for these cNMPs in TIR signaling. Furthermore, the Arabidopsis negative regulator of TIR-NLR signaling, NUDT7, displays 2',3'-cAMP/cGMP but not 3',5'-cAMP/cGMP phosphodiesterase activity and suppresses cell death activity of TIRs in Nb. Our study identifies a family of 2',3'-cAMP/cGMP synthetases and establishes a critical role for them in plant immune responses.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Muerte Celular/genética , AMP Cíclico/biosíntesis , GMP Cíclico/biosíntesis , Ligasas/metabolismo , NAD+ Nucleosidasa/metabolismo , Enfermedades de las Plantas , Inmunidad de la Planta/fisiología , Proteínas de Plantas/metabolismo , Receptores Inmunológicos/metabolismo , Receptores de Interleucina-1/metabolismo , Nicotiana/genética , Nicotiana/metabolismoRESUMEN
Nucleotide-binding, leucine-rich repeat receptors (NLRs) are major immune receptors in plants and animals. Upon activation, the Arabidopsis NLR protein ZAR1 forms a pentameric resistosome in vitro and triggers immune responses and cell death in plants. In this study, we employed single-molecule imaging to show that the activated ZAR1 protein can form pentameric complexes in the plasma membrane. The ZAR1 resistosome displayed ion channel activity in Xenopus oocytes in a manner dependent on a conserved acidic residue Glu11 situated in the channel pore. Pre-assembled ZAR1 resistosome was readily incorporated into planar lipid-bilayers and displayed calcium-permeable cation-selective channel activity. Furthermore, we show that activation of ZAR1 in the plant cell led to Glu11-dependent Ca2+ influx, perturbation of subcellular structures, production of reactive oxygen species, and cell death. The results thus support that the ZAR1 resistosome acts as a calcium-permeable cation channel to trigger immunity and cell death.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/inmunología , Arabidopsis/metabolismo , Calcio/metabolismo , Proteínas Portadoras/metabolismo , Resistencia a la Enfermedad/inmunología , Inmunidad de la Planta , Transducción de Señal , Animales , Muerte Celular , Membrana Celular/metabolismo , Permeabilidad de la Membrana Celular , Ácido Glutámico/metabolismo , Membrana Dobles de Lípidos/metabolismo , Oocitos/metabolismo , Células Vegetales/metabolismo , Multimerización de Proteína , Protoplastos/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Imagen Individual de Molécula , Vacuolas/metabolismo , XenopusRESUMEN
Nucleotide-binding leucine-rich repeat (NLR) proteins play a pivotal role in plant immunity by recognizing pathogen effectors1,2. Maintaining a balanced immune response is crucial, as excessive NLR expression can lead to unintended autoimmunity3,4. Unlike most NLRs, the plant NLR required for cell death 2 (NRC2) belongs to a small NLR group characterized by constitutively high expression without self-activation5. The mechanisms underlying NRC2 autoinhibition and activation are not yet understood. Here we show that Solanum lycopersicum (tomato) NRC2 (SlNRC2) forms dimers and tetramers and higher-order oligomers at elevated concentrations. Cryo-electron microscopy shows an inactive conformation of SlNRC2 in these oligomers. Dimerization and oligomerization not only stabilize the inactive state but also sequester SlNRC2 from assembling into an active form. Mutations at the dimeric or interdimeric interfaces enhance pathogen-induced cell death and immunity in Nicotiana benthamiana. The cryo-electron microscopy structures unexpectedly show inositol hexakisphosphate (IP6) or pentakisphosphate (IP5) bound to the inner surface of the C-terminal leucine-rich repeat domain of SlNRC2, as confirmed by mass spectrometry. Mutations at the inositol phosphate-binding site impair inositol phosphate binding of SlNRC2 and pathogen-induced SlNRC2-mediated cell death in N. benthamiana. Our study indicates a negative regulatory mechanism of NLR activation and suggests inositol phosphates as cofactors of NRCs.
RESUMEN
Plant nucleotide-binding leucine-rich repeat (NLR) immune receptors with an N-terminal Toll/interleukin-1 receptor (TIR) domain mediate recognition of strain-specific pathogen effectors, typically via their C-terminal ligand-sensing domains1. Effector binding enables TIR-encoded enzymatic activities that are required for TIR-NLR (TNL)-mediated immunity2,3. Many truncated TNL proteins lack effector-sensing domains but retain similar enzymatic and immune activities4,5. The mechanism underlying the activation of these TIR domain proteins remain unclear. Here we show that binding of the TIR substrates NAD+ and ATP induces phase separation of TIR domain proteins in vitro. A similar condensation occurs with a TIR domain protein expressed via its native promoter in response to pathogen inoculation in planta. The formation of TIR condensates is mediated by conserved self-association interfaces and a predicted intrinsically disordered loop region of TIRs. Mutations that disrupt TIR condensates impair the cell death activity of TIR domain proteins. Our data reveal phase separation as a mechanism for the activation of TIR domain proteins and provide insight into substrate-induced autonomous activation of TIR signalling to confer plant immunity.
Asunto(s)
Adenosina Trifosfato , Arabidopsis , NAD , Nicotiana , Separación de Fases , Proteínas de Plantas , Dominios Proteicos , Adenosina Trifosfato/metabolismo , Arabidopsis/genética , Arabidopsis/inmunología , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/inmunología , Proteínas de Arabidopsis/metabolismo , Muerte Celular , Mutación , NAD/metabolismo , Nicotiana/genética , Nicotiana/inmunología , Nicotiana/metabolismo , Proteínas NLR/química , Proteínas NLR/genética , Proteínas NLR/inmunología , Proteínas NLR/metabolismo , Enfermedades de las Plantas/inmunología , Inmunidad de la Planta/genética , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/inmunología , Proteínas de Plantas/metabolismo , Regiones Promotoras Genéticas , Dominios Proteicos/genética , Receptores Inmunológicos/química , Receptores Inmunológicos/genética , Receptores Inmunológicos/inmunología , Receptores Inmunológicos/metabolismo , Transducción de Señal , Receptores Toll-Like/química , Receptores de Interleucina-1/químicaRESUMEN
Plants rely on cell-surface-localized pattern recognition receptors to detect pathogen- or host-derived danger signals and trigger an immune response1-6. Receptor-like proteins (RLPs) with a leucine-rich repeat (LRR) ectodomain constitute a subgroup of pattern recognition receptors and play a critical role in plant immunity1-3. Mechanisms underlying ligand recognition and activation of LRR-RLPs remain elusive. Here we report a crystal structure of the LRR-RLP RXEG1 from Nicotiana benthamiana that recognizes XEG1 xyloglucanase from the pathogen Phytophthora sojae. The structure reveals that specific XEG1 recognition is predominantly mediated by an amino-terminal and a carboxy-terminal loop-out region (RXEG1(ID)) of RXEG1. The two loops bind to the active-site groove of XEG1, inhibiting its enzymatic activity and suppressing Phytophthora infection of N. benthamiana. Binding of XEG1 promotes association of RXEG1(LRR) with the LRR-type co-receptor BAK1 through RXEG1(ID) and the last four conserved LRRs to trigger RXEG1-mediated immune responses. Comparison of the structures of apo-RXEG1(LRR), XEG1-RXEG1(LRR) and XEG1-BAK1-RXEG1(LRR) shows that binding of XEG1 induces conformational changes in the N-terminal region of RXEG1(ID) and enhances structural flexibility of the BAK1-associating regions of RXEG1(LRR). These changes allow fold switching of RXEG1(ID) for recruitment of BAK1(LRR). Our data reveal a conserved mechanism of ligand-induced heterodimerization of an LRR-RLP with BAK1 and suggest a dual function for the LRR-RLP in plant immunity.
Asunto(s)
Glicósido Hidrolasas , Phytophthora , Inmunidad de la Planta , Proteínas de Plantas , Receptores de Reconocimiento de Patrones , Secuencias de Aminoácidos , Sitios de Unión , Cristalografía por Rayos X , Glicósido Hidrolasas/metabolismo , Leucina/metabolismo , Ligandos , Phytophthora/enzimología , Phytophthora/inmunología , Phytophthora/fisiología , Proteínas de Plantas/química , Proteínas de Plantas/inmunología , Proteínas de Plantas/metabolismo , Multimerización de Proteína , Receptores de Reconocimiento de Patrones/química , Receptores de Reconocimiento de Patrones/inmunología , Receptores de Reconocimiento de Patrones/metabolismo , Nicotiana/química , Nicotiana/metabolismoRESUMEN
Plant intracellular nucleotide-binding leucine-rich repeat receptors (NLRs) detect pathogen effectors to trigger immune responses1. Indirect recognition of a pathogen effector by the dicotyledonous Arabidopsis thaliana coiled-coil domain containing NLR (CNL) ZAR1 induces the formation of a large hetero-oligomeric protein complex, termed the ZAR1 resistosome, which functions as a calcium channel required for ZAR1-mediated immunity2-4. Whether the resistosome and channel activities are conserved among plant CNLs remains unknown. Here we report the cryo-electron microscopy structure of the wheat CNL Sr355 in complex with the effector AvrSr356 of the wheat stem rust pathogen. Direct effector binding to the leucine-rich repeats of Sr35 results in the formation of a pentameric Sr35-AvrSr35 complex, which we term the Sr35 resistosome. Wheat Sr35 and Arabidopsis ZAR1 resistosomes bear striking structural similarities, including an arginine cluster in the leucine-rich repeats domain not previously recognized as conserved, which co-occurs and forms intramolecular interactions with the 'EDVID' motif in the coiled-coil domain. Electrophysiological measurements show that the Sr35 resistosome exhibits non-selective cation channel activity. These structural insights allowed us to generate new variants of closely related wheat and barley orphan NLRs that recognize AvrSr35. Our data support the evolutionary conservation of CNL resistosomes in plants and demonstrate proof of principle for structure-based engineering of NLRs for crop improvement.
Asunto(s)
Canales de Calcio , Microscopía por Crioelectrón , Proteínas NLR , Proteínas de Plantas , Receptores Inmunológicos , Triticum , Arabidopsis/inmunología , Arabidopsis/metabolismo , Arginina , Canales de Calcio/química , Canales de Calcio/inmunología , Canales de Calcio/metabolismo , Cationes/metabolismo , Leucina , Proteínas NLR/química , Proteínas NLR/inmunología , Proteínas NLR/metabolismo , Enfermedades de las Plantas/inmunología , Enfermedades de las Plantas/microbiología , Inmunidad de la Planta , Proteínas de Plantas/química , Proteínas de Plantas/inmunología , Proteínas de Plantas/metabolismo , Receptores Inmunológicos/química , Receptores Inmunológicos/inmunología , Receptores Inmunológicos/metabolismo , Triticum/inmunología , Triticum/metabolismo , Secuencias de Aminoácidos , Secuencia Conservada , ElectrofisiologíaRESUMEN
Nucleotide binding and leucine-rich repeat-containing receptors (NLRs) have a critical role in plant immunity through direct or indirect recognition of pathogen effectors. Recent studies have demonstrated that such recognition induces formation of large protein complexes called resistosomes to mediate NLR immune signaling. Some NLR resistosomes activate Ca2+ influx by acting as Ca2+-permeable channels, whereas others function as active NADases to catalyze the production of nucleotide-derived second messengers. In this review we summarize these studies on pathogen effector-induced assembly of NLR resistosomes and resistosome-mediated production of the second messengers of Ca2+ and nucleotide derivatives. We also discuss downstream events and regulation of resistosome signaling.
Asunto(s)
Proteínas NLR , Plantas , Proteínas NLR/química , Proteínas NLR/metabolismo , Transducción de Señal , Sistemas de Mensajero Secundario , Nucleótidos/metabolismoRESUMEN
Plants must make decisions to balance their growth versus defense against pathogens. Signaling of the plant peptide hormone phytosulfokine (PSK) has emerged as a critical stimulus for growth promotion. In this issue of The EMBO Journal, Ding et al (2022) show that PSK signaling promotes nitrogen assimilation via phosphorylation of glutamate synthase 2 (GS2). In the absence of PSK signaling, the plants growth is stunted, but its resistance to disease is reinforced.
Asunto(s)
Hormonas Peptídicas , Proteínas de Plantas , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transducción de Señal , Reguladores del Crecimiento de las Plantas , Plantas Modificadas Genéticamente/metabolismoRESUMEN
Nucleotide-binding domain, leucine-rich repeat receptors (NLRs) mediate innate immunity by forming inflammasomes. Activation of the NLR protein NLRP1 requires autocleavage within its function-to-find domain (FIIND)1-7. In resting cells, the dipeptidyl peptidases DPP8 and DPP9 interact with the FIIND of NLRP1 and suppress spontaneous NLRP1 activation8,9; however, the mechanisms through which this occurs remain unknown. Here we present structural and biochemical evidence that full-length rat NLRP1 (rNLRP1) and rat DPP9 (rDPP9) form a 2:1 complex that contains an autoinhibited rNLRP1 molecule and an active UPA-CARD fragment of rNLRP1. The ZU5 domain is required not only for autoinhibition of rNLRP1 but also for assembly of the 2:1 complex. Formation of the complex prevents UPA-mediated higher-order oligomerization of UPA-CARD fragments and strengthens ZU5-mediated NLRP1 autoinhibition. Structure-guided biochemical and functional assays show that both NLRP1 binding and enzymatic activity are required for DPP9 to suppress NLRP1 in human cells. Together, our data reveal the mechanism of DPP9-mediated inhibition of NLRP1 and shed light on the activation of the NLRP1 inflammasome.
Asunto(s)
Dipeptidil-Peptidasas y Tripeptidil-Peptidasas/química , Proteínas NLR/química , Animales , Proteínas Adaptadoras de Señalización CARD , Células HEK293 , Humanos , Péptidos y Proteínas de Señalización Intracelular , Proteínas del Tejido Nervioso , Unión Proteica , Dominios Proteicos , Estructura Secundaria de Proteína , RatasRESUMEN
In plants, host-pathogen coevolution often manifests in reciprocal, adaptive genetic changes through variations in host nucleotide-binding leucine-rich repeat immune receptors (NLRs) and virulence-promoting pathogen effectors. In grass powdery mildew (PM) fungi, an extreme expansion of a RNase-like effector family, termed RALPH, dominates the effector repertoire, with some members recognized as avirulence (AVR) effectors by cereal NLR receptors. We report the structures of the sequence-unrelated barley PM effectors AVRA6, AVRA7, and allelic AVRA10/AVRA22 variants, which are detected by highly sequence-related barley NLRs MLA6, MLA7, MLA10, and MLA22 and of wheat PM AVRPM2 detected by the unrelated wheat NLR PM2. The AVR effectors adopt a common scaffold, which is shared with the RNase T1/F1 family. We found striking variations in the number, position, and length of individual structural elements between RALPH AVRs, which is associated with a differentiation of RALPH effector subfamilies. We show that all RALPH AVRs tested have lost nuclease and synthetase activities of the RNase T1/F1 family and lack significant binding to RNA, implying that their virulence activities are associated with neo-functionalization events. Structure-guided mutagenesis identified six AVRA6 residues that are sufficient to turn a sequence-diverged member of the same RALPH subfamily into an effector specifically detected by MLA6. Similar structure-guided information for AVRA10 and AVRA22 indicates that MLA receptors detect largely distinct effector surface patches. Thus, coupling of sequence and structural polymorphisms within the RALPH scaffold of PMs facilitated escape from NLR recognition and potential acquisition of diverse virulence functions.
Asunto(s)
Ascomicetos , Ascomicetos/metabolismo , Grano Comestible/genética , Grano Comestible/metabolismo , Ribonucleasa T1/genética , Ribonucleasa T1/metabolismo , Polimorfismo Genético , Enfermedades de las Plantas/microbiología , Proteínas de Plantas/metabolismoRESUMEN
Receptor kinases of the Catharanthus roseus RLK1-like (CrRLK1L) family have emerged as important regulators of plant reproduction, growth and responses to the environment1. Endogenous RAPID ALKALINIZATION FACTOR (RALF) peptides2 have previously been proposed as ligands for several members of the CrRLK1L family1. However, the mechanistic basis of this perception is unknown. Here we report that RALF23 induces a complex between the CrRLK1L FERONIA (FER) and LORELEI (LRE)-LIKE GLYCOSYLPHOSPHATIDYLINOSITOL (GPI)-ANCHORED PROTEIN 1 (LLG1) to regulate immune signalling. Structural and biochemical data indicate that LLG1 (which is genetically important for RALF23 responses) and the related LLG2 directly bind RALF23 to nucleate the assembly of RALF23-LLG1-FER and RALF23-LLG2-FER heterocomplexes, respectively. A conserved N-terminal region of RALF23 is sufficient for the biochemical recognition of RALF23 by LLG1, LLG2 or LLG3, and binding assays suggest that other RALF peptides that share this conserved N-terminal region may be perceived by LLG proteins in a similar manner. Structural data also show that RALF23 recognition is governed by the conformationally flexible C-terminal sides of LLG1, LLG2 and LLG3. Our work reveals a mechanism of peptide perception in plants by GPI-anchored proteins that act together with a phylogenetically unrelated receptor kinase. This provides a molecular framework for understanding how diverse RALF peptides may regulate multiple processes, through perception by distinct heterocomplexes of CrRLK1L receptor kinases and GPI-anchored proteins of the LRE and LLG family.
Asunto(s)
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Arabidopsis/inmunología , Arabidopsis/metabolismo , Proteínas Ligadas a GPI/metabolismo , Péptidos y Proteínas de Señalización Intercelular/química , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Fragmentos de Péptidos/metabolismo , Fosfotransferasas/metabolismo , Proteínas de Arabidopsis/genética , Péptidos y Proteínas de Señalización Intercelular/genética , Modelos Moleculares , Mutagénesis , Proteínas Mutantes/química , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Mutación , Fragmentos de Péptidos/química , Fragmentos de Péptidos/genética , Fosfotransferasas/genética , Docilidad , Unión Proteica/genética , Conformación Proteica , Multimerización de ProteínaRESUMEN
Stomata are microscopic openings that allow for the exchange of gases between plants and the environment. In Arabidopsis, stomatal patterning is specified by the ERECTA family (ERf) receptor kinases (RKs), the receptor-like protein (RLP) TOO MANY MOUTHS (TMM), and EPIDERMAL PATTERNING FACTOR (EPF) peptides. Here we show that TMM and ER or ER-LIKE1 (ERL1) form constitutive complexes, which recognize EPF1 and EPF2, but the single ERfs do not. TMM interaction with ERL1 creates a binding pocket for recognition of EPF1 and EPF2, indicating that the constitutive TMM-ERf complexes function as the receptors of EPF1 and EPF2. EPFL9 competes with EPF1 and EPF2 for binding to the ERf-TMM complex. EPFL4 and EPFL6, however, are recognized by the single ERfs without the requirement of TMM. In contrast to EPF1,2, the interaction of EPFL4,6 with an ERf is greatly reduced in the presence of TMM. Taken together, our data demonstrate that TMM dictates the specificity of ERfs for the perception of different EPFs, thus functioning as a specificity switch for the regulation of the activities of ERfs.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Proteínas de Unión al ADN/metabolismo , Regulación de la Expresión Génica de las Plantas , Estomas de Plantas/crecimiento & desarrollo , Arabidopsis/metabolismo , Estomas de Plantas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores de Superficie Celular/metabolismo , Transducción de Señal , Especificidad por SustratoRESUMEN
The shoot apical meristem (SAM) is a reservoir of stem cells that gives rise to all post-embryonic above-ground plant organs. The size of the SAM remains stable over time owing to a precise balance of stem cell replenishment versus cell incorporation into organ primordia. The WUSCHEL (WUS)/CLAVATA (CLV) negative feedback loop is central to SAM size regulation. Its correct function depends on accurate spatial expression of WUS and CLV3 A signaling pathway, consisting of ERECTA family (ERf) receptors and EPIDERMAL PATTERNING FACTOR LIKE (EPFL) ligands, restricts SAM width and promotes leaf initiation. Although ERf receptors are expressed throughout the SAM, EPFL ligands are expressed in its periphery. Our genetic analysis of Arabidopsis demonstrated that ERfs and CLV3 synergistically regulate the size of the SAM, and wus is epistatic to ERf genes. Furthermore, activation of ERf signaling with exogenous EPFLs resulted in a rapid decrease of CLV3 and WUS expression. ERf-EPFL signaling inhibits expression of WUS and CLV3 in the periphery of the SAM, confining them to the center. These findings establish the molecular mechanism for stem cell positioning along the radial axis.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas de Homeodominio/metabolismo , Transducción de Señal/fisiología , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/farmacología , Cicloheximida/farmacología , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Proteínas de Homeodominio/genética , Meristema/fisiología , Mutagénesis , Hojas de la Planta/metabolismoRESUMEN
DNA methylation directed by 24-nucleotide (nt) small interfering RNAs (siRNAs) plays critical roles in gene regulation and transposon silencing in Arabidopsis. 24-nt siRNAs are known to be processed from double-stranded RNAs by Dicer-like 3 (DCL3) and loaded into the effector Argonaute 4 (AGO4). Here we report a distinct class of siRNAs independent of DCLs (sidRNAs). sidRNAs are present as ladders of â¼ 20-60 nt in length, often having the same 5' ends but differing in 3' ends by 1-nt steps. We further show that sidRNAs are associated with AGO4 and capable of directing DNA methylation. Finally we show that sidRNA production depends on distributive 3'-5' exonucleases. Our findings suggest an alternative route for siRNA biogenesis. Precursor transcripts are bound by AGO4 and subsequently subjected to 3'-5' exonucleolytic trimming for maturation. We propose that sidRNAs generated through this route are the initial triggers of de novo DNA methylation.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Metilación de ADN , ARN Interferente Pequeño/biosíntesis , Proteínas de Arabidopsis/genética , Proteínas Argonautas/metabolismo , Secuencia de Bases , Genoma de Planta , Datos de Secuencia Molecular , Mutación/genética , ARN de Planta/genética , ARN Polimerasa Dependiente del ARN/genética , Plantones/genéticaRESUMEN
While working for the United States Department of Agriculture on the North Dakota Agricultural College campus in Fargo, North Dakota, in the 1940s and 1950s, Harold H. Flor formulated the genetic principles for coevolving plant host-pathogen interactions that govern disease resistance or susceptibility. His 'gene-for-gene' legacy runs deep in modern plant pathology and continues to inform molecular models of plant immune recognition and signaling. In this review, we discuss recent biochemical insights to plant immunity conferred by nucleotide-binding domain/leucine-rich-repeat (NLR) receptors, which are major gene-for-gene resistance determinants in nature and cultivated crops. Structural and biochemical analyses of pathogen-activated NLR oligomers (resistosomes) reveal how different NLR subtypes converge in various ways on calcium (Ca2+) signaling to promote pathogen immunity and host cell death. Especially striking is the identification of nucleotide-based signals generated enzymatically by plant toll-interleukin 1 receptor (TIR) domain NLRs. These small molecules are part of an emerging family of TIR-produced cyclic and noncyclic nucleotide signals that steer immune and cell-death responses in bacteria, mammals, and plants. A combined genetic, molecular, and biochemical understanding of plant NLR activation and signaling provides exciting new opportunities for combatting diseases in crops. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Asunto(s)
Agricultura , Productos Agrícolas , Estados Unidos , Animales , Productos Agrícolas/genética , Calcio , Muerte Celular , Nucleótidos , MamíferosRESUMEN
Nucleotide-binding domain leucine-rich repeat-containing receptors (NLRs) in plants can detect avirulence (AVR) effectors of pathogenic microbes. The Mildew locus a (Mla) NLR gene has been shown to confer resistance against diverse fungal pathogens in cereal crops. In barley, Mla has undergone allelic diversification in the host population and confers isolate-specific immunity against the powdery mildew-causing fungal pathogen Blumeria graminis forma specialis hordei (Bgh). We previously isolated the Bgh effectors AVRA1, AVRA7, AVRA9, AVRA13, and allelic AVRA10/AVRA22, which are recognized by matching MLA1, MLA7, MLA9, MLA13, MLA10 and MLA22, respectively. Here, we extend our knowledge of the Bgh effector repertoire by isolating the AVRA6 effector, which belongs to the family of catalytically inactive RNase-Like Proteins expressed in Haustoria (RALPHs). Using structural prediction, we also identified RNase-like folds in AVRA1, AVRA7, AVRA10/AVRA22, and AVRA13, suggesting that allelic MLA recognition specificities could detect structurally related avirulence effectors. To better understand the mechanism underlying the recognition of effectors by MLAs, we deployed chimeric MLA1 and MLA6, as well as chimeric MLA10 and MLA22 receptors in plant co-expression assays, which showed that the recognition specificity for AVRA1 and AVRA6 as well as allelic AVRA10 and AVRA22 is largely determined by the receptors' C-terminal leucine-rich repeats (LRRs). The design of avirulence effector hybrids allowed us to identify four specific AVRA10 and five specific AVRA22 aa residues that are necessary to confer MLA10- and MLA22-specific recognition, respectively. This suggests that the MLA LRR mediates isolate-specific recognition of structurally related AVRA effectors. Thus, functional diversification of multi-allelic MLA receptors may be driven by a common structural effector scaffold, which could be facilitated by proliferation of the RALPH effector family in the pathogen genome.
Asunto(s)
Ascomicetos/fisiología , Hordeum/genética , Leucina/química , Enfermedades de las Plantas/genética , Proteínas de Plantas/genética , Receptores Inmunológicos/genética , Ribonucleasas/química , Alelos , Secuencia de Aminoácidos , Regulación de la Expresión Génica de las Plantas , Variación Genética , Hordeum/inmunología , Hordeum/microbiología , Inmunidad Innata , Leucina/genética , Enfermedades de las Plantas/inmunología , Enfermedades de las Plantas/microbiología , Proteínas de Plantas/metabolismo , Receptores Inmunológicos/metabolismo , Ribonucleasas/metabolismo , Homología de SecuenciaRESUMEN
Plants have developed innate immune systems to fight against pathogenic fungi by monitoring pathogenic signals known as pathogen-associated molecular patterns (PAMP) and have established endo symbiosis with arbuscular mycorrhizal (AM) fungi through recognition of mycorrhizal (Myc) factors. Chitin elicitor receptor kinase 1 of Oryza sativa subsp. Japonica (OsCERK1) plays a bifunctional role in mediating both chitin-triggered immunity and symbiotic relationships with AM fungi. However, it remains unclear whether OsCERK1 can directly recognize chitin molecules. In this study, we show that OsCERK1 binds to the chitin hexamer ((NAG)6 ) and tetramer ((NAG)4 ) directly and determine the crystal structure of the OsCERK1-(NAG)6 complex at 2 Å. The structure shows that one OsCERK1 is associated with one (NAG)6 . Upon recognition, chitin hexamer binds OsCERK1 by interacting with the shallow groove on the surface of LysM2. These structural findings, complemented by mutational analyses, demonstrate that LysM2 is crucial for recognition of both (NAG)6 and (NAG)4 . Altogether, these findings provide structural insights into the ability of OsCERK1 in chitin perception, which will lead to a better understanding of the role of OsCERK1 in mediating both immunity and symbiosis in rice.
Asunto(s)
Micorrizas , Oryza , Quitina/metabolismo , Oryza/metabolismo , Transducción de Señal , Micorrizas/fisiología , Simbiosis , Percepción , Proteínas de Plantas/metabolismoRESUMEN
Post-translational modifications of histones are significant regulators of replication, transcription, and DNA repair. Particularly, newly synthesized histone H4 in H3/H4 heterodimers becomes acetylated on N-terminal lysine residues prior to its incorporation into chromatin. Previous studies have established that the histone acetyltransferase (HAT) complex Hat1p/Hat2p medicates this modification. However, the mechanism of how Hat1p/Hat2p recognizes and facilitates the enzymatic activities on the newly assembled H3/H4 heterodimer remains unknown. Furthermore, Hat2p is a WD40 repeat protein, which is found in many histone modifier complexes. However, how the WD40 repeat proteins facilitate enzymatic activities of histone modification enzymes is unclear. In this study, we first solved the high-resolution crystal structure of a Hat1p/Hat2p/CoA/H4 peptide complex and found that the H4 tail interacts with both Hat1p and Hat2p, by which substrate recruitment is facilitated. We further discovered that H3 N-terminal peptides can bind to the Hat2p WD40 domain and solved the structure of the Hat1p/Hat2p/CoA/H4/H3 peptide complex. Moreover, the interaction with Hat2p requires unmodified Arg2/Lys4 and Lys9 on the H3 tail, suggesting a novel model to specify the activity of Hat1p/Hat2p toward newly synthesized H3/H4 heterodimers. Together, our study demonstrated the substrate recognition mechanism by the Hat1p/Hat2p complex, which is critical for DNA replication and other chromatin remodeling processes.