RESUMO
The F-box protein MORE AXILLARY GROWTH 2 (MAX2) is a central component in the signaling cascade of strigolactones (SLs) as well as of the smoke-derived karrikins (KARs) and the so far unknown endogenous KAI2 ligand (KL). The two groups of molecules are involved in overlapping and unique developmental processes, and signal-specific outcomes are attributed to perception by the paralogous α/ß-hydrolases DWARF14 (D14) for SL and KARRIKIN INSENSITIVE 2/HYPOSENSITIVE TO LIGHT (KAI2/HTL) for KAR/KL. In addition, depending on which receptor is activated, specific members of the SUPPRESSOR OF MAX2 1 (SMAX1)-LIKE (SMXL) family control KAR/KL and SL responses. As proteins that function in the same signal transduction pathway often occur in large protein complexes, we aimed at discovering new players of the MAX2, D14, and KAI2 protein network by tandem affinity purification in Arabidopsis cell cultures. When using MAX2 as a bait, various proteins were copurified, among which were general components of the Skp1-Cullin-F-box complex and members of the CONSTITUTIVE PHOTOMORPHOGENIC 9 signalosome. Here, we report the identification of a novel interactor of MAX2, a type 5 serine/threonine protein phosphatase, designated PHYTOCHROME-ASSOCIATED PROTEIN PHOSPHATASE 5 (PAPP5). Quantitative affinity purification pointed at PAPP5 as being more present in KAI2 rather than in D14 protein complexes. In agreement, mutant analysis suggests that PAPP5 modulates KAR/KL-dependent seed germination under suboptimal conditions and seedling development. In addition, a phosphopeptide enrichment experiment revealed that PAPP5 might dephosphorylate MAX2 in vivo independently of the synthetic SL analog, rac-GR24. Together, by analyzing the protein complexes to which MAX2, D14, and KAI2 belong, we revealed a new MAX2 interactor, PAPP5, that might act through dephosphorylation of MAX2 to control mainly KAR/KL-related phenotypes and, hence, provide another link with the light pathway.
Assuntos
Proteínas de Arabidopsis/metabolismo , Proteínas de Transporte/metabolismo , Proteínas Nucleares/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Proteínas de Transporte/química , Proteínas de Transporte/genética , Germinação , Proteínas Nucleares/genética , Fosfoproteínas Fosfatases/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas/metabolismo , Plântula/genética , Plântula/crescimento & desenvolvimento , Plântula/metabolismo , Nicotiana/genéticaRESUMO
Rhodococcus fascians is currently the only phytopathogen of which the virulence genes occur on a linear plasmid. To get insight into the origin of this replicon and into the virulence strategy of this broad-spectrum phytopathogen, the sequence of the linear plasmid of strain D188, pFiD188, was determined. Analysis of the 198,917 bp revealed four syntenic regions with linear plasmids of R. erythropolis, R. jostii, and R. opacus, suggesting a common origin of these replicons. Mutational analysis of pFi_086 and pFi_102, similar to cutinases and type IV peptidases, respectively, showed that conserved region R2 was involved in plasmid dispersal and pointed toward a novel function for actinobacterial cutinases in conjugation. Additionally, pFiD188 had three regions that were unique for R. fascians. Functional analysis of the stk and nrp loci of regions U2 and U3, respectively, indicated that their role in symptom development was limited compared with that of the previously identified fas, att, and hyp virulence loci situated in region U1. Thus, pFiD188 is a typical rhodococcal linear plasmid with a composite structure that encodes core functions involved in plasmid maintenance and accessory functions, some possibly acquired through horizontal gene transfer, implicated in virulence and the interaction with the host.
Assuntos
Nicotiana/microbiologia , Doenças das Plantas/microbiologia , Plasmídeos/genética , Rhodococcus/genética , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Sequência de Bases , Biofilmes/crescimento & desenvolvimento , Conjugação Genética , Análise Mutacional de DNA , DNA Bacteriano/química , DNA Bacteriano/genética , Regulação da Expressão Gênica/genética , Genes Bacterianos/genética , Dados de Sequência Molecular , Óperon/genética , Folhas de Planta/microbiologia , Replicon/genética , Rhodococcus/enzimologia , Rhodococcus/patogenicidade , Rhodococcus/ultraestrutura , Alinhamento de Sequência , Análise de Sequência de DNA , Telômero , Virulência/genéticaRESUMO
⢠Legume roots develop two types of lateral organs, lateral roots and nodules. Nodules develop as a result of a symbiotic interaction with rhizobia and provide a niche for the bacteria to fix atmospheric nitrogen for the plant. ⢠The Arabidopsis NAC1 transcription factor is involved in lateral root formation, and is regulated post-transcriptionally by miRNA164 and by SINAT5-dependent ubiquitination. We analyzed in Medicago truncatula the role of the closest NAC1 homolog in lateral root formation and in nodulation. ⢠MtNAC1 shows a different expression pattern in response to auxin than its Arabidopsis homolog and no changes in lateral root number or nodulation were observed in plants affected in MtNAC1 expression. In addition, no interaction was found with SINA E3 ligases, suggesting that post-translational regulation of MtNAC1 does not occur in M. truncatula. Similar to what was found in Arabidopsis, a conserved miR164 target site was retrieved in MtNAC1, which reduced protein accumulation of a GFP-miR164 sensor. Furthermore, miR164 and MtNAC1 show an overlapping expression pattern in symbiotic nodules, and overexpression of this miRNA led to a reduction in nodule number. ⢠This work suggests that regulatory pathways controlling a conserved transcription factor are complex and divergent between M. truncatula and Arabidopsis.
Assuntos
Medicago truncatula/fisiologia , Proteínas de Plantas/metabolismo , Sinorhizobium meliloti/fisiologia , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Sequência de Bases , Flores/efeitos dos fármacos , Flores/genética , Flores/fisiologia , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/farmacologia , Medicago truncatula/efeitos dos fármacos , Medicago truncatula/genética , MicroRNAs/genética , Dados de Sequência Molecular , Mutação , Filogenia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/genética , Folhas de Planta/fisiologia , Proteínas de Plantas/química , Proteínas de Plantas/genética , Nodulação/genética , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Raízes de Plantas/fisiologia , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/genética , Brotos de Planta/fisiologia , Plantas Geneticamente Modificadas/efeitos dos fármacos , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/fisiologia , Estrutura Terciária de Proteína , RNA de Plantas/genética , Proteínas Recombinantes de Fusão , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Nicotiana/genética , Nicotiana/metabolismo , Transativadores/genética , Transativadores/metabolismo , Fatores de Transcrição/química , Fatores de Transcrição/genéticaRESUMO
The symbiotic interaction between legumes and rhizobia results in root nodules with nitrogen-fixing bacteroids. Throughout the lifespan of the nodules, the exchange of C sources and N compounds between the host plant and the bacteria is tightly balanced. Sucrose plays a major role in the provision of C skeletons and energy to the bacteroids. Transcription of MtATB2, encoding a bZIP transcription factor, is shown to be regulated by sucrose and is enhanced during nodule senescence. Transcripts occur in the nodule apex and in the vascular tissue of nodules and roots. Ectopic expression of the gene diminished nodule formation and affected root growth. Presumably, MtATB2 controls processes that are under sucrose homeostasis and are important for nodule and root growth.
Assuntos
Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Medicago truncatula/genética , Proteínas de Plantas/metabolismo , Nodulação/genética , Sacarose/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Fatores de Transcrição de Zíper de Leucina Básica/genética , Clonagem Molecular , Regulação da Expressão Gênica de Plantas , Medicago truncatula/metabolismo , Medicago truncatula/microbiologia , Dados de Sequência Molecular , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/microbiologia , RNA de Plantas/genética , Análise de Sequência de DNA , Simbiose , Nicotiana/genética , Nicotiana/metabolismoRESUMO
Mature indeterminate Medicago truncatula nodules are zonated with an apical meristem, an infection zone, a fixation zone with nitrogen-fixing bacteroids, and a "developmental" senescence zone that follows nodule growth with a conical front originating in the center of the fixation zone. In nitrogen-fixing cells, senescence is initiated coincidently with the expression of a family of conserved cysteine proteases that might be involved in the degradation of symbiotic structures. Environmental stress, such as prolonged dark treatment, interferes with nodule functioning and triggers a fast and global nodule senescence. Developmental and dark stress-induced senescence have several different structural and expression features, suggesting at least partly divergent underlying molecular mechanisms.