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The recognition of different microbe-associated molecular patterns in the rhizosphere triggers in the plant root the activation of either an immune response or an accommodation program. In both types of responses, Ca2+is a crucial intracellular messenger, mediating the early stages of the respective signalling pathways. In this work, we analysed the cytosolic and nuclear Ca2+changes activated by a set of chitin-related oligomers in different genetic backgrounds ofLotus japonicusroots by using specifically targeted aequorin-based Ca2+reporters. By means of pharmacological and genetic approaches, we dissected the Ca2+signal into two temporally distinct components: a rapid initial transient, followed by a longer and milder elevation in Ca2+concentration. Taking advantage of a complementary analysis using a cameleon-based bioassay inMedicago truncatularoot organ cultures, we showed that the second phase can be interpreted as the Ca2+spiking that is widely described in response to the perception of symbiotic signals. By contrast, the rapid first phase, critically dependent on elicitor concentration, was found to correlate with the activation of plant immunity marker genes. Overall, our study provides novel clues to a better understanding of the subtle boundaries between symbiotic and immunity responses in root-fungus interactions.HighlightIntracellular calcium changes induced inLotus japonicusroots by fungal signals were dissected in two separate phases, relying on distinct genetic programs and differentially mediating plant symbiotic or immunity responses.

Iron is critical for host-pathogen interactions. While pathogens seek to scavenge iron to spread, the host aims at decreasing iron availability to reduce pathogen virulence. Thus, iron sensing and homeostasis are of particular importance to prevent host infection and part of nutritional immunity. While the link between iron homeostasis and immunity pathways is well established in plants, how iron levels are sensed and integrated with immune response pathways remain unknown. We identified a receptor kinase, SRF3 coordinating root growth, iron homeostasis and immunity pathways via regulation of callose synthase activity. These processes are modulated by iron levels and rely on SRF3 extracellular and kinase domain which tune its accumulation and partitioning at the cell surface. Mimicking bacterial elicitation with the flagellin peptide flg22 phenocopies SRF3 regulation upon low iron levels and subsequent SRF3-dependent responses. We propose that SRF3 is part of nutritional immunity responses involved in sensing external iron levels.

Iron is critical for host–pathogen interactions. While pathogens seek to scavenge iron to spread, the host aims at decreasing iron availability to reduce pathogen virulence. Thus, iron sensing and homeostasis are of particular importance to prevent host infection and part of nutritional immunity. While the link between iron homeostasis and immunity pathways is well established in plants, how iron levels are sensed and integrated with immune response pathways remains unknown. Here we report a receptor kinase SRF3, with a role in coordinating root growth, iron homeostasis and immunity pathways via regulation of callose synthases. These processes are modulated by iron levels and rely on SRF3 extracellular and kinase domains which tune its accumulation and partitioning at the cell surface. Mimicking bacterial elicitation with the flagellin peptide flg22 phenocopies SRF3 regulation upon low iron levels and subsequent SRF3-dependent responses. We propose that SRF3 is part of nutritional immunity responses involved in sensing external iron levels.

SummaryIron is critical for host-pathogen interactions. While pathogens seek to scavenge iron to spread, the host aims at decreasing iron availability to reduce pathogen virulence. Thus, iron sensing and homeostasis are of particular importance to prevent host infection and part of nutritional immunity. While the link between iron homeostasis and immunity pathways is well established in plants, how iron levels are sensed and integrated with immune response pathways remain unknown. We identified a receptor kinase, SRF3 coordinating root growth, iron homeostasis and immunity pathways via regulation of callose synthase activity. These processes are modulated by iron levels and rely on SRF3 extracellular and kinase domain which tune its accumulation and partitioning at the cell surface. Mimicking bacterial elicitation with the flagellin peptide flg22 phenocopies SRF3 regulation upon low iron levels and subsequent SRF3-dependent responses. We propose that SRF3 is part of nutritional immunity responses involved in sensing external iron levels.

En este trabajo se propone a través de una doble aproximación etnográfica y arqueológica comprender lógicas de la sacralización del espacio andino. Sin pretender realizar analogías directas, fundamentándonos en las discusiones críticas de la arqueología etnográfica, se busca mediante ejemplos de ceremonias realizada por cusqueños migrantes en la ciudad de La Plata (nucleados en la Academia Mayor de la Lengua Quechua) entender ciertos modos de la estructuración del espacio en el sitio inkaico El Shincal de Quimivil en la provincia de Catamarca. Se toman como referencias teóricas los postulados de las ontologías relacionales para interpelar el registro arqueológico inka a partir de los juegos de conformación del espacio segmentado, ordenado y jerarquizado mediante reglas de oposición y complementariedad traducidas en dualidad, tripartición y cuatripartición y esquemas de inclusión fractal. A partir del análisis de diferentes planos empíricos de El Shincal se propone interpretar la posible intención inka de construir un espacio sacralizado como forma de expandir la conquista de nuevos territorios apelando a la búsqueda de alianzas con agentes no humanos dotados de poder. In this work, it is proposed through a double ethnographic and archaeological approach, understand logics of sacralization of the Andean space. Without pretending to make direct analogies, basing on the critical discussions of ethnographic archaeology, is sought through examples of ceremonies performed by migrant Cusqueños in the city of La Plata (nucleated in the Academia Mayor de la Lengua Quechua) understand certain ways of structuring the space in the Inka site El Shincal de Quimivil in the province of Catamarca. They are taken as theoretical references the postulates of relational ontologies to interpellate the Inka archaeological record from the games of conformation of the segmented, ordered and nested space through rules of opposition and complementarity translated into duality, tripartition and quadripartition, and fractal inclusion schemes. From the analysis of different empirical planes of El Shincal, it is proposed to interpret the possible Inka intention to construct a sacred space as a way to expand the conquest of new territories appealing to the search for alliances with non-human agents endowed with power. Fil: Giovannetti, Marco Antonio. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Arqueología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina

Phosphate represents a major limiting factor for plant productivity. Plants have evolved different solutions to adapt to phosphate limitation ranging from a profound tuning of their root system architecture and metabolic profile to the evolution of widespread mutualistic interactions. Here we elucidated plant responses and their genetic basis to different phosphate levels in a plant species that is widely used as a model for AM symbiosis: Lotus japonicus. Rather than focussing on a single model strain, we measured root growth and anion content in response to different levels of phosphate in 130 Lotus natural accessions. This allowed us not only to uncover common as well as divergent responses within this species, but also enabled Genome Wide Association Studies by which we identified new genes regulating phosphate homeostasis in Lotus. Among them, we showed that insertional mutants of a cytochrome B5 reductase and a Leucine-Rich-Repeat receptor showed different phosphate concentration in plants grown under phosphate sufficient condition. Under low phosphate conditions, we found a correlation between plant biomass and the decrease of plant phosphate concentration in plant tissues, representing a dilution effect. Altogether our data of the genetic and phenotypic variation within a species capable of AM complements studies that have been conducted in Arabidopsis, and advances our understanding of the continuum of genotype by phosphate level interaction existing throughout dicot plants., Author summary Phosphate is one of the main limiting factors for plant growth. Plants have evolved different strategies to face phosphate limitation ranging from a profound tuning of their root system architecture and metabolic profile to the evolution of widespread mutualistic interactions, such as arbuscular mycorrhizal symbiosis. Here we investigate plant responses and their genetic basis to different phosphate levels in a model legume plant species, Lotus japonicus, a plant commonly used for studying root endosymbioses. We combine high throughput root phenotyping and nutrient measurements with a natural variation approach. With this approach, we elucidate relations between root phenotypic responses and nutrient accumulation and we uncover, under low phosphate conditions, a correlation between plant biomass and the decrease of plant phosphate concentration in plant tissues. Using Genome Wide Association mapping and integration of multiple traits, we identified new genes regulating phosphate homeostasis in Lotus and confirmed their functions using multiple independent insertion mutant lines.

Arbuscular mycorrhizal (AM) symbiosis improves host plant phosphorous (P) status and elicits the expression of AM-inducible phosphate transporters (PTs) in arbuscule-containing cells, where they control arbuscule morphogenesis and P release. We confirmed such functions for LjPT4 in mycorrhizal Lotus japonicus. Promoter-GUS experiments showed LjPT4 transcription not only in arbusculated cells but also in root tips, in the absence of the fungus: here LjPT4 transcription profile depended on the phosphate level. In addition, quantitative RT-PCR confirmed the expression of Lotus and Medicago truncatula PT4 in the tips of non-mycorrhizal roots. Starting from these observations, we hypothesized that AM-inducible PTs may have a regulatory role in plant development, irrespective of the fungal presence. Firstly, we focused on root development responses to different phosphate treatments in both plants demonstrating that phosphate starvation induced a higher number of lateral roots. By contrast, Lotus PT4i plants and Medicago mtpt4 mutants did not show any differential response to phosphate levels, suggesting that PT4 genes affect early root branching. Phosphate starvation-induced genes and a key auxin receptor, MtTIR1, showed an impaired expression in mtpt4 plants. We suggest PT4 genes as novel components of the P-sensing machinery at the root tip level, independently of AM fungi.

Plants are sessile organisms that can tune their body architecture to the environment. This is very pronounced in their root system. In particular, nutrient availability strongly influences the architecture of the root system; depending on the abundance of specific nutrients, root growth rates and lateral root number are modulated. The extent of these effects is important for plant adaptation and has a major impact on plant fitness. However, the assessment of quantitative effects on a scale large enough for identifying genes and variants using quantitative genetics is difficult, and well-developed methods have been largely restricted to the model species Arabidopsis thaliana. In this chapter, we present a protocol for high-throughput phenotyping of early root traits in the model legume plant Lotus japonicus. This species allows for the study of important root-associated traits that are not present in Arabidopsis, such as symbioses with nitrogen-fixing Rhizobia and arbuscular mycorrhizal fungi. The methods described in this chapter can be used in the context of reverse and forward genetics approaches to dissect the genetic basis of root growth in legumes.

The symbiosis established with arbuscular mycorrhizal (AM) fungi is one of the main and long-lasting strategies that plants have adopted to improve their nutrient uptake capacities. Carbon for mineral exchange between the two symbionts is regulated by the activities of fine-tuned plant and fungal transporter genes, some of which have been described in the last 15 years. In this chapter we specifically focus on the effects and functioning of arbuscular mycorrhizas in the context of nitrogen, phosphorus, and sulfur nutrition and specifically on the molecular mechanisms of such exchanges. We also introduced the recent concept of transceptor, emphasizing the importance of genetic determinants as key components of nutrient sensing and signaling pathways. At the same time, because the effect of AM symbiosis is not limited to changes in plant nutrient homeostasis at a local root level, we also describe plant responses at a systemic level.

Plants are sessile organisms that can tune their body architecture to the environment. This is very pronounced in their root system. In particular, nutrient availability strongly influences the architecture of the root system; depending on the abundance of specific nutrients, root growth rates and lateral root number are modulated. The extent of these effects is important for plant adaptation and has a major impact on plant fitness. However, the assessment of quantitative effects on a scale large enough for identifying genes and variants using quantitative genetics is difficult, and well-developed methods have been largely restricted to the model species Arabidopsis thaliana. In this chapter, we present a protocol for high-throughput phenotyping of early root traits in the model legume plant Lotus japonicus. This species allows for the study of important root-associated traits that are not present in Arabidopsis, such as symbioses with nitrogen-fixing Rhizobia and arbuscular mycorrhizal fungi. The methods described in this chapter can be used in the context of reverse and forward genetics approaches to dissect the genetic basis of root growth in legumes.

The interaction between legumes and arbuscular mycorrhizal (AM) fungi is vital to the development of sustainable plant production systems. Here, we focus on a putative MYB-like (LjMAMI) transcription factor (TF) previously reported to be highly upregulated in Lotus japonicus mycorrhizal roots. Phylogenetic analyses revealed that the protein is related to a group of TFs involved in phosphate (Pi) starvation responses, the expression of which is independent of the Pi level, such as PHR1. GUS transformed plants and quantitative reverse transcription PCR revealed strong gene induction in arbusculated cells, as well as the presence of LjMAMI transcripts in lateral root primordia and root meristems, even in the absence of the fungus, and independently of Pi concentration. In agreement with its putative identification as a TF, an eGFP-LjMAMI chimera was localized to the nuclei of plant protoplasts, whereas in transgenic Lotus roots expressing the eGFP-LjMAMI fusion protein under the control of the native promoter, the protein was located in the nuclei of the arbusculated cells. Further expression analyses revealed a correlation between LjMAMI and LjPT4, a marker gene for mycorrhizal function. To elucidate the role of the LjMAMI gene in the mycorrhizal process, RNAi and overexpressing root lines were generated. All the lines retained their symbiotic capacity; however, RNAi root lines and composite plants showed an important reduction in root elongation and branching in the absence of the symbiont. The results support the involvement of the AM-responsive LjMAMI in non-symbiotic functions: i.e. root growth.

El tráfico de objetos arqueológicos representa desde hace décadas uno de los grandes flagelos difíciles de controlar por parte de las políticas para la protección del Patrimonio Cultural. El mercado negro funciona con la transformación de estos bienes públicos en propiedades individuales, mercancías que circulan en una cadena capitalista institucionalizada donde el mayor beneficio recae en los últimos eslabones. La penalización de estos delitos como parte de las políticas proteccionistas recae generalmente en quienes, desfavorecidos por las leyes de un mercado capitalista, inician el circuito. Sin embargo, los museos –en su mayoría primer mundistas-, así como los coleccionistas privados, incentivan el movimiento ilegal; ambos resguardados por las concesiones de un sistema que protege la propiedad privada.La relación Estado-mercado que se instaura a partir de las políticas neoliberales de los países latinoamericanos es un terreno que necesita ser explorado y analizado si se pretende desenmascarar la realidad del tráfico ilegal.

Enzymes of the sulfur assimilation pathway are potential targets for improving nutrient content and environmental stress responses in plants. The committed step in this pathway is catalyzed by ATP sulfurylase, which synthesizes adenosine 5′-phosphosulfate (APS) from sulfate and ATP. To better understand the molecular basis of this energetically unfavorable reaction, the x-ray crystal structure of ATP sulfurylase isoform 1 from soybean (Glycine max ATP sulfurylase) in complex with APS was determined. This structure revealed several highly conserved substrate-binding motifs in the active site and a distinct dimerization interface compared with other ATP sulfurylases but was similar to mammalian 3′-phosphoadenosine 5′-phosphosulfate synthetase. Steady-state kinetic analysis of 20 G. max ATP sulfurylase point mutants suggests a reaction mechanism in which nucleophilic attack by sulfate on the α-phosphate of ATP involves transition state stabilization by Arg-248, Asn-249, His-255, and Arg-349. The structure and kinetic analysis suggest that ATP sulfurylase overcomes the energetic barrier of APS synthesis by distorting nucleotide structure and identifies critical residues for catalysis. Mutations that alter sulfate assimilation in Arabidopsis were mapped to the structure, which provides a molecular basis for understanding their effects on the sulfur assimilation pathway.

Summary Arbuscular mycorrhizas (AMs) are one of the most widespread symbioses in the world. They allow plants to receive mineral nutrients from the symbiotic fungus which in turn gets back up to 20% of plant carbon and completes its life cycle. Especially in low-nutrient conditions, AM fungi are capable of significantly improving plant phosphate and nitrogen acquisition, but fewer data are available about sulfur (S) nutrition. We focused on S metabolism in Lotus japonicus upon mycorrhizal colonization under sulfur starvation or repletion. We investigated both tissue sulfate concentrations and S-related gene expression, at cell-type or whole-organ level. Gene expression and sulfate tissue concentration showed that Rhizophagus irregularis colonization can improve plant S nutritional status under S starvation. A group 1 sulfate transporter, LjSultr1;2, induced by both S starvation and mycorrhiza formation, was identified. Its transcript was localized in arbuscule-containing cells, which was confirmed with a promoter-GUS assay, and its function was verified through phenotyping of TILLING mutants in nonmycorrhizal seedlings. LjSultr1;2 thus appears to encode a key protein involved in plant sulfate uptake. In contrast to phosphate transporters, a single gene, LjSultr1;2, seems to mediate both direct and symbiotic pathways of S uptake in L. japonicus.

Sulfur is an essential macronutrient for all living organisms. Plants take up inorganic sulfate from the soil, reduce it, and assimilate it into bioorganic compounds, but part of this sulfate is stored in the vacuoles. In our first attempt to identify genes involved in the control of sulfate content in the leaves, we reported that a quantitative trait locus (QTL) for sulfate content in Arabidopsis (Arabidopsis thaliana) was underlain by the APR2 isoform of the key enzyme of sulfate assimilation, adenosine 5'-phosphosulfate reductase. To increase the knowledge of the control of this trait, we cloned a second QTL from the same analysis. Surprisingly, the gene underlying this QTL encodes the ATPS1 isoform of the enzyme ATP sulfurylase, which precedes adenosine 5'-phosphosulfate reductase in the sulfate assimilation pathway. Plants with the Bay allele of ATPS1 accumulate lower steady-state levels of ATPS1 transcript than those with the Sha allele, which leads to lower enzyme activity and, ultimately, the accumulation of sulfate. Our results show that the transcript variation is controlled in cis. Examination of ATPS1 sequences of Bay-0 and Shahdara identified two deletions in the first intron and immediately downstream the gene in Bay-0 shared with multiple other Arabidopsis accessions. The average ATPS1 transcript levels are lower in these accessions than in those without the deletions, while sulfate levels are significantly higher. Thus, sulfate content in Arabidopsis is controlled by two genes encoding subsequent enzymes in the sulfate assimilation pathway but using different mechanisms, variation in amino acid sequence and variation in expression levels.

Background Arbuscular mycorrhizas (AM) are widespread symbioses that provide great advantages to the plant, improving its nutritional status and allowing the fungus to complete its life cycle. Nevertheless, molecular mechanisms that lead to the development of AM symbiosis are not yet fully deciphered. Here, we have focused on two putative aquaporin genes, LjNIP1 and LjXIP1, which resulted to be upregulated in a transcriptomic analysis performed on mycorrhizal roots of Lotus japonicus. Results A phylogenetic analysis has shown that the two putative aquaporins belong to different functional families: NIPs and XIPs. Transcriptomic experiments have shown the independence of their expression from their nutritional status but also a close correlation with mycorrhizal and rhizobial interaction. Further transcript quantification has revealed a good correlation between the expression of one of them, LjNIP1, and LjPT4, the phosphate transporter which is considered a marker gene for mycorrhizal functionality. By using laser microdissection, we have demonstrated that one of the two genes, LjNIP1, is expressed exclusively in arbuscule-containing cells. LjNIP1, in agreement with its putative role as an aquaporin, is capable of transferring water when expressed in yeast protoplasts. Confocal analysis have demonstrated that eGFP-LjNIP1, under its endogenous promoter, accumulates in the inner membrane system of arbusculated cells. Conclusions Overall, the results have shown different functionality and expression specificity of two mycorrhiza-inducible aquaporins in L. japonicus. One of them, LjNIP1 can be considered a novel molecular marker of mycorrhizal status at different developmental stages of the arbuscule. At the same time, LjXIP1 results to be the first XIP family aquaporin to be transcriptionally regulated during symbiosis.

SUMMARY Plants adjust their architecture by modulating organ growth. This ability is largely dependent on phytohormones. While responses to phytohormones have been studied extensively, it remains unclear to which extent and how these responses are modulated in non‐reference strains. Here, we assess variation of root traits upon treatment with auxin, cytokinin and abscisic acid (ABA) in 192 Arabidopsis accessions. We identify common response patterns, uncover the extent of their modulation by specific genotypes, and find that the Col‐0 reference accession is not a good representative of the species in this regard. We conduct genome‐wide association studies and identify 114 significant associations, most of them relating to ABA treatment. The numerous ABA candidate genes are not enriched for known ABA‐associated genes, indicating that we largely uncovered unknown players. Overall, our study provides a comprehensive view of the diversity of hormone responses in the Arabidopsis thaliana species, and shows that variation of genes that are yet mostly not associated with such a role to determine natural variation of the response to phytohormones., Significance Statement Plant hormones are crucial for regulating root growth, but most studies were based on a single reference strain of Arabidopsis. Here, we study natural variation of root growth upon treatment with auxin, cytokinin and abscisic acid, and find that most strains respond very differently to hormones than the reference strain, and that this extensive natural variation is largely associated with genes that have not yet been implicated in playing a role in hormonal pathways.