María Soto - Academia.edu (original) (raw)

Papers by María Soto

Frontiers in Plant Science

Editorial on the Research Topic Early signaling in the rhizobium-legume symbiosis The rhizobium-l... more Editorial on the Research Topic Early signaling in the rhizobium-legume symbiosis The rhizobium-legume symbiosis is a beneficial plant-bacteria association between soil bacteria collectively known as rhizobia and leguminous plants (Poole et al., 2018). To establish symbiosis, the rhizobia invade roots of host plants and trigger the formation of a new organ, the nodule. The rhizobia differentiate then into bacteroids and reduce atmospheric nitrogen into ammonia that will be used by the plant. The formation of nitrogen-fixing nodules is a complex process in which bacterial infection needs to be coordinated with the nodule organogenesis program. This is achieved through a continuous molecular dialogue between the host plant and rhizobia, which leads to a high degree of specificity in the interaction with even strain-and host cultivar-dependent effects (Cangioli et al., 2022). Much of that specificity is conferred by an exchange of signals that take place in the rhizosphere during the early stages of the association (Roy et al., 2020). The 10 articles hosted in the Research Topic "Early signaling in the rhizobiumlegume symbiosis", increase our knowledge on the molecular bases underlying the mutual recognition of plants and rhizobia during early stages of the interaction, i.e., before the onset of nitrogen fixation. The initiation of the rhizobium-legume symbiosis requires localization of the bacteria to potential infection sites on host roots. In this process, rhizobial chemotaxis and motility play a relevant role. The reviews by Aroney et al. and Compton and Scharf revised some important concepts related to motility and chemotaxis and the preferred attractants of several model rhizobia. Aroney et al. highlighted the importance of understanding chemotaxis and motility in legume symbionts, especially under the Frontiers in Plant Science frontiersin.org 01

Methods in Molecular Biology, 2021

In the Rhizobium-legume symbiosis, strigolactones (SLs) promote root nodule formation; however, t... more In the Rhizobium-legume symbiosis, strigolactones (SLs) promote root nodule formation; however, the exact mechanism underlying this positive effect remains unknown. The recent finding that an SL receptor legume mutant shows a wild-type nodulation phenotype suggests that SLs influence the symbiosis by acting on the bacterial partner. In agreement with this, the application of the synthetic SL analog GR24 on the alfalfa symbiont Sinorhizobium (Ensifer) meliloti has been shown to stimulate swarming, a specialized bacterial surface motility, which could influence infection of legumes by Rhizobia. Surface motility assays for many bacteria, and particularly for Rhizobia, are challenging. The establishment of protocols to study bacterial surface motility is key to decipher the role of SLs as rhizosphere cues for rhizobacteria. In this chapter, we describe a set of protocols implemented to study the different types of motility exhibited by S. meliloti.

Biogenesis of Fatty Acids, Lipids and Membranes, 2016

Bacteria produce some lipids and lipid-related compounds that function as signals for intercellul... more Bacteria produce some lipids and lipid-related compounds that function as signals for intercellular communication among prokaryotes or even in inter-kingdom communication (i.e., between prokaryotes and eukaryotes). Most of these lipidic signals participate in quorum-sensing regulation, a process that is dependent on cell density and enables a coordinated response within the population. The number and variety of bacterial non-membrane lipids that have been found to function as molecular signals is increasing and includes unsaturated fatty acids, fatty acid esters, acyl-based molecules such as N-acylhomoserine lactones and γ-butyrolactones, alkyl-based compounds such as quinolones and dialkylresorcinols, or alkane-derived signals such as α-hydroxyketones. Most of these signals are amphipathic and can diffuse through membranes and some of them are volatile. They are synthesized from common metabolites including intermediates of lipid metabolism and are recognized by membrane-bound or cytosolic receptors that trigger specific signal transduction responses. These M.J. Soto (*) • N. Calatrava-Morales Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain e-mail: mariajose.soto@eez.csic.es; nieves.calatrava@eez.csic.es I.M. López-Lara Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico e-mail: isabel@ccg.unam.mx # Springer International Publishing AG 2017 O. Geiger (ed.), Biogenesis of Fatty Acids, Lipids and Membranes, Handbook of Hydrocarbon and Lipid Microbiology , DOI 10.1007/978-3-319-43676-0_16-2 1 signals regulate important bacterial traits such as motility, production of antimicrobials, expression of virulence factors, and biofilm formation. Some of these bacterial lipids induce immune responses in eukaryotic organisms.

Molecular Plant-Microbe Interactions

Soil Biology and Biochemistry, 2010

Molecular Plant-Microbe Interactions, 1993

International Journal of Molecular Sciences

Bacteria can spread on surfaces to colonize new environments and access more resources. Rhizobia,... more Bacteria can spread on surfaces to colonize new environments and access more resources. Rhizobia, a group of α- and β-Proteobacteria, establish nitrogen-fixing symbioses with legumes that rely on a complex signal interchange between the partners. Flavonoids exuded by plant roots and the bacterial transcriptional activator NodD control the transcription of different rhizobial genes (the so-called nod regulon) and, together with additional bacterial regulatory proteins (such as TtsI, MucR or NolR), influence the production of different rhizobial molecular signals. In Sinorhizobium fredii HH103, flavonoids and NodD have a negative effect on exopolysaccharide production and biofilm production. Since biofilm formation and motility are often inversely regulated, we have analysed whether flavonoids may influence the translocation of S. fredii HH103 on surfaces. We show that the presence of nod gene-inducing flavonoids does not affect swimming but promotes a mode of surface translocation, w...

Frontiers in Plant Science, 2021

Bacteria release a wide range of volatile compounds that play important roles in intermicrobial a... more Bacteria release a wide range of volatile compounds that play important roles in intermicrobial and interkingdom communication. Volatile metabolites emitted by rhizobacteria can promote plant growth and increase plant resistance to both biotic and abiotic stresses. Rhizobia establish beneficial nitrogen-fixing symbiosis with legume plants in a process starting with a chemical dialog in the rhizosphere involving various diffusible compounds. Despite being one of the most studied plant-interacting microorganisms, very little is known about volatile compounds produced by rhizobia and their biological/ecological role. Evidence indicates that plants can perceive and respond to volatiles emitted by rhizobia. In this perspective, we present recent data that open the possibility that rhizobial volatile compounds have a role in symbiotic interactions with legumes and discuss future directions that could shed light onto this area of investigation.

Biogenesis of Fatty Acids, Lipids and Membranes, 2018

Fatty acids are the building blocks of diverse membrane lipids and therefore are essential for th... more Fatty acids are the building blocks of diverse membrane lipids and therefore are essential for the viability of bacterial cells. Fatty acids are energetically expensive to produce, and their production is highly controlled at the transcriptional and posttranscriptional level. Biosynthesis of fatty acids is catalyzed in most bacteria by a group of highly conserved proteins known as the type II fatty acid synthase (FAS II) system. This system was characterized in Escherichia coli, and a similar I. M. López-Lara (*) Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico e-mail: isabel@ccg.unam.mx M. J. Soto Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain e-mail: mariajose.soto@eez.csic.es # Springer Nature Switzerland AG 2018 O. Geiger (ed.), Biogenesis of Fatty Acids, Lipids and Membranes, Handbook of Hydrocarbon and Lipid Microbiology, https://doi.org/10.1007/978-3-319-43676-0_26-1 1 set of enzymes is present in different bacteria. Knowledge of biochemical regulation of fatty acid biosynthesis is inferred from studies in E. coli. During biosynthesis, fatty acids are esterified to the phosphopantetheine prosthetic group of the small acyl carrier protein (ACP). Long-chain acyl-ACPs, the end product of the pathway, exert feedback regulation over different key enzymes. There is a diversity of systems used for transcriptional regulation of fatty acid biosynthesis. Transcriptional regulation of fatty acid biosynthesis has been studied mainly in three model organisms, the Gram-negative E. coli and the Grampositive organisms Bacillus subtilis and Streptococcus pneumoniae. The effector molecules that modulate activity of transcription factors involved in lipid biosynthesis are either substrates (malonyl-CoA) or final products (long-chain acylACPs) of fatty acid biosynthesis. Long-chain acyl-CoAs, which are usually formed from exogenous fatty acids, are effectors of transcription factors that coordinate de novo biosynthesis with availability of fatty acids in the environment.

This article cites 45 articles, 25 of which can be accessed free

PDF corresponds to the article as it appeared upon acceptance. Fully formatted PDF and full text ... more PDF corresponds to the article as it appeared upon acceptance. Fully formatted PDF and full text (HTML) versions will be made available soon. Transcriptome profiling of a Sinorhizobium meliloti fadD mutant reveals the role of rhizobactin 1021 biosynthesis and regulation genes in the control of swarming BMC Genomics 2010, 11:157 doi:10.1186/1471-2164-11-157

Microorganisms, 2020

FadD is an acyl-coenzyme A (CoA) synthetase specific for long-chain fatty acids (LCFA). Strains m... more FadD is an acyl-coenzyme A (CoA) synthetase specific for long-chain fatty acids (LCFA). Strains mutated in fadD cannot produce acyl-CoA and thus cannot grow on exogenous LCFA as the sole carbon source. Mutants in the fadD (smc02162) of Sinorhizobium meliloti are unable to grow on oleate as the sole carbon source and present an increased surface motility and accumulation of free fatty acids at the entry of the stationary phase of growth. In this study, we found that constitutive expression of the closest FadD homologues of S. meliloti, encoded by sma0150 and smb20650, could not revert any of the mutant phenotypes. In contrast, the expression of Escherichia coli fadD could restore the same functions as S. meliloti fadD. Previously, we demonstrated that FadD is required for the degradation of endogenous fatty acids released from membrane lipids. Here, we show that absence of a functional fadD provokes a significant loss of viability in cultures of E. coli and of S. meliloti in the stat...

Environmental microbiology, Jan 28, 2018

Surface motility and biofilm formation are behaviours which enable bacteria to infect their hosts... more Surface motility and biofilm formation are behaviours which enable bacteria to infect their hosts and are controlled by different chemical signals. In the plant symbiotic alpha-proteobacterium Sinorhizobium meliloti, the lack of long-chain fatty acyl-coenzyme A synthetase activity (FadD) leads to increased surface motility, defects in biofilm development, and impaired root colonization. In this study, analyses of lipid extracts and volatiles revealed that a fadD mutant accumulates 2-tridecanone (2-TDC), a methylketone known as a natural insecticide. Application of pure 2-TDC to the wild-type strain phenocopies the free-living and symbiotic behaviours of the fadD mutant. Structural features of the methylketone determine its ability to promote S. meliloti surface translocation, which is mainly mediated by a flagella-independent motility. Transcriptomic analyses showed that 2-TDC induces differential expression of iron uptake, redox, and stress-related genes. Interestingly, this methyl...

Molecular plant-microbe interactions : MPMI, Jul 11, 2017

Sinorhizobium meliloti can translocate over surfaces. However, little is known about the regulato... more Sinorhizobium meliloti can translocate over surfaces. However, little is known about the regulatory mechanisms that control this trait and its relevance for establishing symbiosis with alfalfa plants. To gain insights into this field, we isolated Tn5 mutants of S. meliloti GR4 with impaired surface motility. In mutant strain GRS577, the transposon interrupted the ntrY gene encoding the sensor kinase of the NtrY/NtrX two-component regulatory system. GRS577 is impaired in flagella synthesis, and overproduces succinoglycan which is responsible for increased biofilm formation. The mutant also shows altered cell morphology and higher susceptibility to salt stress. GRS577 induces nitrogen-fixing nodules in alfalfa but exhibits decreased competitive nodulation. Complementation experiments indicate that both, ntrY and ntrX, account for all the phenotypes displayed by the ntrY::Tn5 mutant. Ectopic overexpression of VisNR, the motility master regulator, was sufficient to rescue motility and c...

Molecular Plant-Microbe Interactions®, 2016

Sinorhizobium fredii HH103 is a rhizobial strain showing a broad host range of nodulation. In add... more Sinorhizobium fredii HH103 is a rhizobial strain showing a broad host range of nodulation. In addition to the induction of bacterial nodulation genes, transition from a free-living to a symbiotic state requires complex genetic expression changes with the participation of global regulators. We have analyzed the role of the zinc-finger transcriptional regulator MucR1 from S. fredii HH103 under both free-living conditions and symbiosis with two HH103 host plants, Glycine max and Lotus burttii. Inactivation of HH103 mucR1 led to a severe decrease in exopolysaccharide (EPS) biosynthesis but enhanced production of external cyclic glucans (CG). This mutant also showed increased cell aggregation capacity as well as a drastic reduction in nitrogen-fixation capacity with G. max and L. burttii. However, in these two legumes, the number of nodules induced by the mucR1 mutant was significantly increased and decreased, respectively, with respect to the wild-type strain, indicating that MucR1 can ...

Plant science : an international journal of experimental plant biology, 2016

Strigolactones (SLs) are multifunctional molecules acting as modulators of plant responses under ... more Strigolactones (SLs) are multifunctional molecules acting as modulators of plant responses under nutrient deficient conditions. One of the roles of SLs is to promote beneficial association with arbuscular mycorrhizal (AM) fungi belowground under such stress conditions, mainly phosphorus shortage. Recently, a role of SLs in the Rhizobium-legume symbiosis has been also described. While SLs' function in AM symbiosis is well established, their role in the Rhizobium-legume interaction is still emerging. Recently, SLs have been suggested to stimulate surface motility of rhizobia, opening the possibility that they could also act as molecular cues. The possible effect of SLs in the motility in the alfalfa symbiont Sinorhizobium meliloti was investigated, showing that the synthetic SL analogue GR24 stimulates swarming motility in S. meliloti in a dose-dependent manner. On the other hand, it is known that SL production is regulated by nutrient deficient conditions and by AM symbiosis. Usi...

PLoS ONE, 2014

Here we report that the structure of the Sinorhizobium fredii HH103 exopolysaccharide (EPS) is co... more Here we report that the structure of the Sinorhizobium fredii HH103 exopolysaccharide (EPS) is composed of glucose, galactose, glucuronic acid, pyruvic acid, in the ratios 5:2:2:1 and is partially acetylated. A S. fredii HH103 exoA mutant (SVQ530), unable to produce EPS, not only forms nitrogen fixing nodules with soybean but also shows increased competitive capacity for nodule occupancy. Mutant SVQ530 is, however, less competitive to nodulate Vigna unguiculata. Biofilm formation was reduced in mutant SVQ530 but increased in an EPS overproducing mutant. Mutant SVQ530 was impaired in surface motility and showed higher osmosensitivity compared to its wild type strain in media containing 50 mM NaCl or 5% (w/v) sucrose. Neither S. fredii HH103 nor 41 other S. fredii strains were recognized by soybean lectin (SBL). S. fredii HH103 mutants affected in exopolysaccharides (EPS), lipopolysaccharides (LPS), cyclic glucans (CG) or capsular polysaccharides (KPS) were not significantly impaired in their soybeanroot attachment capacity, suggesting that these surface polysaccharides might not be relevant in early attachment to soybean roots. These results also indicate that the molecular mechanisms involved in S. fredii attachment to soybean roots might be different to those operating in Bradyrhizobium japonicum.