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International audience; Acyl lipids are important constituents of the plant cell. Depending on the cell type, requirements in acyl lipids vary greatly, implying a tight regulation of fatty acid and lipid metabolism. The discovery of the WRINKLED1 (WRI1) transcription factors, members of the AP2-EREBP (APETALA2-ethylene-responsive element binding protein) family, has emphasized the importance of transcriptional regulation for adapting the rate of acyl chain production to cell requirements. Here, we describe the identification of another activator of the fatty acid biosynthetic pathway, the Arabidopsis MYB92 transcription factor. This MYB and all the members of the subgroups S10 and S24 of MYB transcription factors can directly activate the promoter of BCCP2 that encodes a component of the fatty acid biosynthetic pathway. Two adjacent MYB cis-regulatory elements are essential for the binding and activation of the BCCP2 promoter by MYB92. Overexpression of MYB92 or WRI1 in Nicotiana benthamiana induces the expression of fatty acid biosynthetic genes but results in the accumulation of different types of acyl lipids. In the presence of WRI1, triacylglycerol biosynthetic enzymes coded by constitutively expressed genes efficiently channel the excess fatty acids toward reserve lipid accumulation. By contrast, MYB92 activates both fatty acid and suberin biosynthetic genes; hence, the remarkable increase in suberin monomers measured in leaves expressing MYB92. These results provide additional insight into the molecular mechanisms that control the biosynthesis of an important cell wall-associated acylglycerol polymer playing critical roles in plants.

The spatiotemporal pattern of deposition, final amount, and relative abundance of oleic acid (cis-ω-9 C18:1) and its derivatives in the different lipid fractions of the seed of Arabidopsis (Arabidopsis thaliana) indicates that omega-9 monoenes are synthesized at high rates in this organ. Accordingly, we observed that four Δ9 stearoyl-ACP desaturase (SAD)-coding genes (FATTY ACID BIOSYNTHESIS2 [FAB2], ACYL-ACYL CARRIER PROTEIN5 [AAD5], AAD1, and AAD6) are transcriptionally induced in seeds. We established that the three most highly expressed ones are directly activated by the WRINKLED1 transcription factor. We characterized a collection of 30 simple, double, triple, and quadruple mutants affected in SAD-coding genes and thereby revealed the functions of these desaturases throughout seed development. Production of oleic acid by FAB2 and AAD5 appears to be critical at the onset of embryo morphogenesis. Double homozygous plants from crossing fab2 and aad5 could never be obtained, and further investigations revealed that the double mutation results in the arrest of embryo development before the globular stage. During later stages of seed development, these two SADs, together with AAD1, participate in the elaboration of the embryonic cuticle, a barrier essential for embryo–endosperm separation during the phase of invasive embryo growth through the endosperm. This study also demonstrates that the four desaturases redundantly contribute to storage lipid production during the maturation phase.

Monounsaturated fatty acids are straight-chain aliphatic monocarboxylic acids comprising a unique carbon‑carbon double bond, also termed unsaturation. More than 50 distinct molecular structures have been described in the plant kingdom, and more remain to be discovered. The evolution of land plants has apparently resulted in the convergent evolution of non-homologous enzymes catalyzing the dehydrogenation of saturated acyl chain substrates in a chemo-, regio- and stereoselective manner. Contrasted enzymatic characteristics and different subcellular localizations of these desaturases account for the diversity of existing fatty acid structures. Interestingly, the location and geometrical configuration of the unsaturation confer specific characteristics to these molecules found in a variety of membrane, storage, and surface lipids. An ongoing research effort aimed at exploring the links existing between fatty acid structures and their biological functions has already unraveled the importance of several monounsaturated fatty acids in various physiological and developmental contexts. What is more, the monounsaturated acyl chains found in the oils of seeds and fruits are widely and increasingly used in the food and chemical industries due to the physicochemical properties inherent in their structures. Breeders and plant biotechnologists therefore develop new crops with high monounsaturated contents for various agro-industrial purposes.

Dans cet article, je présente et analyse le paysage chamanique péruvien internationalisé et façonné par ce que j’appelle des « réappropriations chamaniques ». Ces dernières sont le fruit de rencontres entre nouvelles spiritualités européennes, sud et nord-américaines et néochamanismes locaux, entre celles et ceux qui voyagent à la rencontre de leurs chamanes et ces derniers. Ce paysage en devenir est attesté depuis une époque ancienne – je ne me hasarderai pas ici à donner une date –, comme en témoigne la circulation de plantes rituelles, médicinales et psychotropes et des noms qui les désignent. Autrement dit, ce que d’aucuns appellent le « tourisme chamanique » n’est pas à l’origine, mais participe d’un processus diffus. Pour le montrer, j’appuie mon propos sur une description de l’ayahuasca, cette plante psychotrope emblématique de ce paysage, puis celle du chamanisme awajun (famille linguistique jivaro, Pérou), peu familier, comparativement à d’autres, des « festivals chamaniques » et autres rituels « bricolés » organisés en Amérique ou en Europe. Enfin, j’aborde la rencontre et son intelligence, à travers un essai de compréhension de ce qui se joue dans l’expérience psychotrope des « modernes »., In this paper, I analyze the internationalized Peruvian shamanic landscape, a landscape shaped today by what I call “neo-shamanic appropriations”. These are the result of meetings between new age and local shamanisms, between European, South and North American travelers and shamans. However, the Peruvian shamanic landscape is older–I wouldn’t want to make an estimate–as evidenced by the sharing of ritual, medicinal and psychotropic plants, and the names of those plants. In other words, the so-called “shamanic tourism” does not cause but contribute to a diffuse process. To show this, I support my analysis with the following descriptions: first, a psychotropic plant (ayahuasca) and its usages; second, the Awajun shamanism (Jivaro linguistic family, Peru); third, the shamanic festivals and other unusual rituals organized in America or Europe. Finally, I discuss the encounter and its intelligence, through the understanding of what is playing out in modern psychoactive experiences., En este artículo analizo el paisaje chamánico peruano, internacionalizado y modelado por lo que llamo « reapropiaciones chamánicas ». Estas últimas son hoy día fruto del encuentro entre nuevas espiritualidades europeas, sur y norteamericanas y (neo) chamanismos locales, entre viajeros y chamanes. Sin embargo, hay testimonios de este paisaje en devenir desde una época antigua – no me arriesgaré aquí a dar una fecha –, como lo demuestra la circulación en Suramérica de plantas rituales, medicinales y psicotrópicas y los nombres con las que se las designa. Dicho de otra manera, lo que algunos llaman « el turismo chamánico » no está en el origen, sino que participa de un proceso difuso. Para demostrarlo, apoyo mis afirmaciones en una descripción de la ayahuasca, planta psicotrópica emblemática de este paisaje ; del chamanismo awajun (familia lingüística jíbaro, Perú) ; y de « festivales chamánicos » y otros rituales « montados » que se organizan en América o en Europa. Finalmente, me refiero al encuentro y su inteligencia, a través de un ensayo de comprensión de lo que ocurre en la experiencia psicotrópica de los « modernos ».

International audience; In this paper, I address the processes of constructing person and the acquisition of a new soul in the Awajun society (Jivaro linguistic family, Peru). This is based on psychotropic plants —tobacco, angel trumpet, ayahuasca and chagropanga—, the words and discourses about them as well as the implicit logics. On the other hand, it involves shamanism and vision quest. We will realize that these respective logics have different meanings to different people (common people or shaman): they are both opposite and complementary. Opposite, since the vision quest assumes a purge and a spiritual experience to be “clean, beautiful, adorned” and to have a life of plenty while shamanic practice requires a contamination to be prickly and to be able to gain access to the invisible. These perspectives are complementary, since the shamanic practice protects the individual from magical aggression or witchcraft during the vision quest.; En este artículo analizamos los procesos de construcción de la persona y la adquisición de una nueva vitalidad en la sociedad awajún (familia lingüística jíbaro, Perú). Nos basamos, por un lado, en el análisis del uso de plantas psicoactivas —tabaco, floripondio, ayahuasca y chagropanga—, de términos y palabras sobre ellas y de las lógicas en juego, y, por otro lado, en una categorización antropológica, que distingue búsqueda visionaria y chamanismo, pertinente a tal contexto. Así, nos daremos cuenta de que dichas lógicas, diferentes según las personas (cualquiera o chamán), son simultáneamente opuestas y complementarias. Opuestas porque la búsqueda visionaria supone una limpieza y un encuentro espiritual para ser «limpio, hermoso, adornado» y tener abundancia material, pues la actuación chamánica implica ensuciarse deliberadamente para ser «picante» y acceder, protegido, a lo invisible. Complementarias porque la segunda tiene como función preservar lo que ha sido adquirido con la primera de toda agresión mágica o brujería. Finalmente, este artículo trata de contribuir al esfuerzo de valorización de materiales originales en un momento en el que el chamanismo se presta a interpretaciones sumamente diversas.; Je traite dans cet article des processus de construction de la personne et de l’acquisition d’une vitalité nouvelle dans la société awajun (famille linguistique jivaro, Pérou). Je m’appuie pour ce faire d’une part sur une analyse des usages de quelques plantes psychotropes —tabac, trompette des anges, ayahuasca et chagropanga—, des termes et discours à leur propos et des logiques en jeu; et d’autre part sur une nécessaire catégorisation anthropologique, qui considère séparément quête visionnaire et chamanisme, pertinente à mon sens dans ce contexte culturel. Nous verrons ainsi que les logiques en jeu diffèrent selon les personnes —tout un chacun ou chamane— et qu’elles sont tout à la fois opposées et complémentaires. Opposées, car la quête visionnaire suppose un nettoyage et une rencontre spirituelle pour être « propre, beau, paré » et avoir en abondance matériellement ; car l’agir chamanique implique une souillure délibérée pour être « piquant » et être à même d’accéder à l’invisible sans danger. Complémentaires, car le second a pour fonction de protéger ce qui a été acquis par la première de toute agression magique ou sorcellerie.

A Cuzco (Perou), j’ai participe a des limpieza par le feu, une succession de gestes realisee pour extraire un mal, creer une enveloppe protectrice et renouveler une alliance. Ce rituel bricole temoigne d’une fonction moderatrice et mediatrice, tendant a preserver des equilibres fragiles. Il temoigne de meme d’une fonction reparatrice et restauratrice reiterable, laquelle definit le chamanisme andin contemporain. Lieu de rencontre entre l’experience interieure de la personne et le mode operatoire d’un dispositif symbolique, cette mise en scene d’un abime « contraint la chance a tourner » et permet un devenir au monde heur-eux. Dans cet article, j’aborde le rituel dans sa dynamique operatoire, interrogeant l’espace entre qu’il materialise, la transe qu’il donne a etre et la relation entre actants, ces porteurs d’appartenances specifiques et de marques culturelles qui les faconnent et les transforment.

International audience; The LAFL (i.e. LEC1, ABI3, FUS3, and LEC2) master transcriptional regulators interact to form different complexes that induce embryo development and maturation, and inhibit seed germination and vegetative growth in Arabidopsis. Orthologous genes involved in similar regulatory processes have been described in various angiosperms including important crop species. Consistent with a prominent role of the LAFL regulators in triggering and maintaining embryonic cell fate, their expression appears finely tuned in different tissues during seed development and tightly repressed in vegetative tissues by a surprisingly high number of genetic and epigenetic factors. Partial functional redundancies and intricate feedback regulations of the LAFL have hampered the elucidation of the underpinning molecular mechanisms. Nevertheless, genetic, genomic, cellular, molecular, and biochemical analyses implemented during the last years have greatly improved our knowledge of the LALF network. Here we summarize and discuss recent progress, together with current issues required to gain a comprehensive insight into the network, including the emerging function of LEC1 and possibly LEC2 as pioneer transcription factors.

57 Páginas.-- 2 Tablas.-- 10 Figuras.-- 3 Tablas suplementarias.-- 5 Figuras suplementarias, In the present study, we describe the molecular and biochemical characterization of sunflower (Helianthus annuus L.) enolase (ENO, EC 4.2.1.11) proteins, which catalyze the formation of phosphoenolpyruvate, the penultimate intermediate in the glycolytic pathway. We cloned and characterized three cDNAs encoding different ENO isoforms from developing sunflower seeds. Studies using fluorescently tagged ENOs confirmed the predicted subcellular localization of ENO isoforms: HaENO1 in the plastid while HaENO2 and HaENO3 were found in the cytosol. The cDNAs were used to express the corresponding 6(His)-tagged proteins in Escherichia coli. The proteins were purified to electrophoretic homogeneity, using immobilized metal ion affinity chromatography, and biochemically characterized. Recombinant HaENO1 and HaENO2, but not HaENO3 were shown to have enolase activity, in agreement with data obtained with the Arabidopsis homolog proteins. Site directed mutagenesis of several critical amino acids was used to attempt to recover enolase activity in recombinant HaENO3, resulting in very small increases that were not additive. A kinetic characterization of the two active isoforms showed that pH had similar effect on their velocity, that they had similar affinity for 2-phosphoglycerate, but that the kcat/Km of the plastidial enzyme was higher than that of the cytosolic isoform. Even though HaENO2 was always the most highly expressed transcript, the levels of expression of the three ENO genes were remarkably distinct in all the vegetative and reproductive tissues studied. This indicates that in seeds the conversion of 2-phosphoglycerate to phosphoenolpyruvate takes place through the cytosolic and the plastidial pathways therefore both routes could contribute to the supply of carbon for lipid synthesis. The identity of the main source of carbon during the period of stored products synthesis is discussed., This work was supported by the “Ministerio de Economía y Competitividad” and FEDER (AGL2014-53537-R). JR is supported by a Discovery Grant (RGPIN 227271) from the National Science and Engineering Research Council of Canada. The authors would also like to thank the Hauts-de-France Region and the European Regional Development Fund (ERDF) 2014/2020 for the funding of this work.

La maniere dont un anthropologue apprehende le terrain, goute les choses et les ressent, a un impact tant sur les donnees qu’il collecte que sur les analyses qu’il produit ensuite. Psychotropiques, sous-titre La fievre de l’ayahuasca en foret amazonienne, illustre cette evidence epistemologique. Ce livre de Jean-Loup Amselle est en effet un livre particulier du point de vue anthropologique dans la mesure ou, au nom d’un rationalisme a defendre, il critique une pratique sociale (le « vegetalis...

Acyl-CoA:diacylglycerol acyltransferases 3 (DGAT3) are described as plant cytosolic enzymes synthesizing triacylglycerol. Their protein sequences exhibit a thioredoxin-like ferredoxin domain typical of a class of ferredoxins harboring a [2Fe-2S] cluster. The Arabidopsis thaliana DGAT3 (AtDGAT3; At1g48300) protein is detected in germinating seeds. The recombinant purified protein produced from Escherichia coli, although very unstable, exhibits DGAT activity in vitro. A shorter protein version devoid of its N-terminal putative chloroplast transit peptide, Δ46AtDGAT3, was more stable in vitro, allowing biochemical and spectroscopic characterization. The results obtained demonstrate the presence of a [2Fe-2S] cluster in the protein. To date, AtDGAT3 is the first metalloprotein described as a DGAT.

In the exalbuminous species Arabidopsis thaliana, seed maturation is accompanied by the deposition of oil and storage proteins and the reduction of the endosperm to one cell layer. Here, we consider reserve partitioning between embryo and endosperm compartments. The pattern of deposition, final amount, and composition of these reserves differ between the two compartments, with the embryo representing the principal storage tissue in mature seeds. Complex regulatory mechanisms are known to prevent activation of maturation-related programs during embryo morphogenesis and, later, during vegetative growth. Here, we describe a regulator that represses the expression of maturation-related genes during maturation within the endosperm. MYB118 is transcriptionally induced in the maturing endosperm, and seeds of myb118 mutants exhibit an endosperm-specific derepression of maturation-related genes associated with a partial relocation of storage compounds from the embryo to the endosperm. Moreover, MYB118 activates endosperm-induced genes through the recognition of TAACGG elements. These results demonstrate that the differential partitioning of reserves between the embryo and endosperm in exalbuminous Arabidopsis seeds does not only result from developmental programs that establish the embryo as the preponderant tissue within seeds. This differential partitioning is also regulated by MYB118, which regulates the biosynthesis of reserves at the spatial level during maturation.

Out-of-Body Experiences. A Soul’s Journey to Meet Another Self. In this paper, I would like to write an anthropology of altered states of consciousness, namely to question of the dynamic and content – which makes subjectivity – of such experiences. To do this, I review narratives and perceptions of the body during spiritual experiences (ritual or spontaneous) such as : 1. possession and psychedelic trips, at Peru, Cusco region (in urban areas) and among Awajun, a Jivaro linguistic family ; 2. Out-ofbody experiences from “ modernity” European. These experiences are characterized by the lucid feeling to see in a distance vision their body and its surroundings, which range from what I call another self or a subjectivity which feels itself as such. There is not denial and derealization, but recognition of the body, unlike psychopathological experiences in which the absence creates delusions. As consequence, the experiences are conceived as true by people. Furthermore, they allow a relationship characterized by a verbal exchange -possession or spiritual encounter – and the acquisition of knowledge that can be used for therapeutic purposes or witchcraft, divination and initiation., Dans cet article, je souhaite réaliser une anthropologie des états modifiés de la conscience, à savoir interroger leurs dynamiques et contenus – ce qui fait subjectivité. Pour ce faire, j’analyse récits et perceptions du corps lors d’expériences spirituelles, rituelles ou spontanées : transes de possession et voyages psychotropes au Pérou – précisément dans les Andes cuzquéniennes, et parmi les Awajun, famille linguistique jivaro ; et expériences «hors du corps » issues de la modernité européenne. Ces expériences se caractérisent par l’impression lucide pour les personnes qui les éprouvent de voir leur corps et ce qui l’environne à distance, depuis ce que j’appelle un autre de soi ou une subjectivité qui s’éprouve comme telle. Il n’y a ni déni de la réalité, ni distorsion déréalisante, mais reconnaissance du corps, contrairement aux expériences psychopathologiques dans lesquelles l’absence fonde l’illusion délirante. Conséquence d’une telle aperception, les expériences sont tenues pour vraies par celles et ceux qui les éprouvent. Mieux, elles autorisent une relation caractérisée par sa nature verbale – possession ou rencontre spirituelle – et l’acquisition de connaissances pouvant être utilisées à des fins thérapeutiques ou sorcellaires, divinatoires et initiatiques., Baud Sébastien. Expériences « hors du corps » : un voyage « en esprit » à la rencontre d’un autre de soi. In: Intellectica. Revue de l'Association pour la Recherche Cognitive, n°67, 2017/1. Les états modifiés de conscience en question : anciennes limites et nouvelles approches. pp. 347-366.

International audience; In angiosperms, double fertilization of the embryo sac initiates the development of the embryo and the endosperm. In Arabidopsis thaliana, an exalbuminous species, the endosperm is reduced to one cell layer during seed maturation and reserves such as oil are massively deposited in the enlarging embryo. Here, we consider the strikingly different fatty acid (FA) compositions of the oils stored in the two zygotic tissues. Endosperm oil is enriched in omega-7 monounsaturated FAs, that represent more than 20 mol% of total FAs, whereas these molecular species are 10-fold less abundant in the embryo. Two closely related transcription factors, MYB118 and MYB115, are transcriptionally induced at the onset of the maturation phase in the endosperm and share a set of transcriptional targets. Interestingly, the endosperm oil of myb115 myb118 double mutants lacks omega-7 FAs. The identification of two Delta 9 palmitoyl-ACP desaturases responsible for omega-7 FA biosynthesis, which are activated by MYB115 and MYB118 in the endosperm, allows us to propose a model for the transcriptional control of oil FA composition in this tissue. In addition, an initial characterization of the structure-function relationship for these desaturases reveals that their particular substrate specificity is conferred by amino acid residues lining their substrate pocket that distinguish them from the archetype Delta 9 stearoyl-ACP desaturase.

Plant oils have so far been mostly directed toward food and feed production. Nowadays however, these oils are more and more used as competitive alternatives to mineral hydrocarbon-based products. This increasing demand for vegetable oils has led to a renewed interest in elucidating the metabolism of storage lipids and its regulation in various plant systems. Cereal grains store carbon in the form of starch in a large endosperm and as oil in an embryo of limited size. Complementary studies on kernel development and metabolism have paved the way for breeding or engineering new varieties with higher grain oil content. This could be achieved either by increasing the relative proportion of the oil-rich embryo within the grain, or by enhancing oil synthesis and accumulation in embryonic structures. For instance, diacylglycerol acyltransferase (DGAT) that catalyses the ultimate reaction in the biosynthesis of triacylglycerol appears to be a promising target for increasing oil content in maize embryos. Similarly, over-expression of the maize transcriptional regulators ZmLEAFY COTYLEDON1 and ZmWRINKLED1 efficiently stimulates oil accumulation in the kernels of transgenic lines. Redirecting carbon from starch to oil in the endosperm, though not yet realized, is discussed. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Dans un contexte caractérisé par un nombre limité et clos d’entités singulières, la société awajún témoignait par le passé de deux attitudes inverses envers les morts, selon qu’ils relevaient d’une même communauté dialectale ou non. Toutes deux ont cependant en commun de définir le cadavre comme étant un moyen d’acquérir une âme, censée investir une nouvelle identité (dans le cas de la chasse aux têtes) ; ou décrite en termes de vision-pouvoir intériorisée (dans le cas de la quête d’Ajútap). Aujourd’hui toutefois, ce rapport au corps mort a disparu au profit d’un renforcement de l’usage des plantes psychotropes comme moyen, pour la personne, de favoriser cette rencontre mystique : des plantes qui, selon la mythologie awajún, sont nées de la lente germination du cadavre d’un guerrier dans le giron de la terre., In a context were singular entities are limited, the Awajún expressed in the past two opposite attitudes towards the deads, according to their belonging or not to the same dialectical society. Both attitudes have yet in common to define the corpse as a means to acquire a soul, supposed to incorporate a new individuated existence (in the case of head hunting) ; or described in terms of vision-power, in the sense of “ being able to ” (in the case of the quest of Ajútap). Today, this relationship to the corpse has disappeared and has been replaced by a reinforcement of the usage of psychotropic plants as a means to meet the Ajútap spirit. According to the myth, these plants are born from the slow germination of the corpse inside the earth.

Summary The PII protein is an integrator of central metabolism and energy levels. In Arabidopsis, allosteric sensing of cellular energy and carbon levels alters the ability of PII to interact with target enzymes such as N-acetyl-l-glutamate kinase and heteromeric acetyl-coenzyme A carboxylase, thereby modulating the biological activity of these plastidial ATP- and carbon-consuming enzymes. A quantitative reverse transcriptase-polymerase chain reaction approach revealed a threefold induction of the AtGLB1 gene (At4g01900) encoding PII during early seed maturation. The activity of the AtGLB1 promoter was consistent with this pattern. A complementary set of molecular and genetic analyses showed that WRINKLED1, a transcription factor known to induce glycolytic and fatty acid biosynthetic genes at the onset of seed maturation, directly controls AtGLB1 expression. Immunoblot analyses and immunolocalization experiments using anti-PII antibodies established that PII protein levels faithfully reflected AtGLB1 mRNA accumulation. At the subcellular level, PII was observed in plastids of maturing embryos. To further investigate the function of PII in seeds, comprehensive functional analyses of two pII mutant alleles were carried out. A transient increase in fatty acid production was observed in mutant seeds at a time when PII protein content was found to be maximal in wild-type seeds. Moreover, minor though statistically significant modifications of the fatty acid composition were measured in pII seeds, which exhibited decreased amounts of modified (elongated, desaturated) fatty acid species. The results obtained outline a role for PII in the fine tuning of fatty acid biosynthesis and partitioning in seeds.

Summary The WRINKLED1 (WRI1) protein is an important regulator of oil accumulation in maturing Arabidopsis seeds. WRI1 is a member of a plant-specific family of transcription factors (AP2/EREBP) that share either one or two copies of a DNA-binding domain called the AP2 domain. Here, it is shown that WRI1 acts as a transcriptional enhancer of genes involved in carbon metabolism in transgenic seeds overexpressing this transcription factor. PKp-β1 and BCCP2, two genes encoding enzymes of the glycolysis and fatty acid biosynthetic pathway, respectively, have been chosen to investigate the regulatory action exerted by WRI1 over these pathways. Using the reporter gene uidA, it was possible to demonstrate in planta that WRI1 regulates the activity of both PKp-β1 and BCCP2 promoters. Electrophoretic mobility-shift assays and yeast one-hybrid experiments showed that WRI1 was able to interact with the BCCP2 promoter. To further elucidate the regulatory mechanism controlling the transcription of these genes, functional dissections of PKp-β1 and BCCP2 promoters were performed. Two enhancers, of 54 and 79 bp, respectively, have thus been isolated that are essential to direct the activity of these promoters in oil-accumulating tissues of the embryo. A consensus site is present in these enhancers as well as in other putative target promoters of WRI1. Loss of this consensus sequence in the BCPP2 promoter decreases both the strength of the interaction between WRI1 and this promoter in yeast and the activity of the promoter in planta.

Due to the high reduction level of the carbons in fatty acids, the oxidation of triacylglycerols (TAGs) releases much more energy than the oxidation of other storage compounds like carbohydrates or proteins. TAGs are synthesized in many animal and plant species to act as an energy reserve. Here, we review some of the studies that have contributed to decipher the metabolic and regulatory networks responsible for the biosynthesis of TAGs in two contrasted model systems: the liver of mice and the maturing oilseed of Arabidopsis. A comparison of the two systems illustrates how distinct transcriptional regulatory systems trigger lipogenesis in response to specific signals: a high carbohydrate diet induces TAG synthesis in the liver of mammalians whereas a developmental program initiates TAG accumulation at the onset of embryo maturation in Arabidopsis.

International audience; In Arabidopsis (Arabidopsis thaliana), transcriptional control of seed maturation involves three related regulators with a B3domain, namely LEAFY COTYLEDON2 (LEC2), ABSCISIC ACID INSENSITIVE3 (ABI3), and FUSCA3 (ABI3/FUS3/LEC2[AFLs]). Although genetic analyses have demonstrated partially overlapping functions of these regulators, the underlyingmolecular mechanisms remained elusive. The results presented here confirmed that the three proteins bind RY DNA elements(with a 59-CATG-39 core sequence) but with different specificities for flanking nucleotides. In planta as in the moss Physcomitrellapatens protoplasts, the presence of RY-like (RYL) elements is necessary but not sufficient for the regulation of the OLEOSIN1 (OLE1)promoter by the B3AFLs. G box-like domains, located in the vicinity of the RYL elements, also are required for proper activation ofthe promoter, suggesting that several proteins are involved. Consistentwith this idea, LEC2 andABI3 showed synergistic effects onthe activation of the OLE1 promoter. What is more, LEC1 (a homolog of the NF-YB subunit of the CCAAT-binding complex)further enhanced the activation of this target promoter in the presence of LEC2 and ABI3. Finally, recombinant LEC1 and LEC2proteins produced in Arabidopsis protoplasts could form a ternary complex with NF-YC2 in vitro, providing a molecular explanationfor their functional interactions. Taken together, these results allow us to propose a molecularmodel for the transcriptional regulationof seed genes by the L-AFL proteins, based on the formation of regulatory multiprotein complexes between NF-YBs, which carry aspecific aspartate-55 residue, and B3 transcription factors.

Pyruvate kinase (PK) catalyses the irreversible synthesis of pyruvate and ATP, which are both used in multiple biochemical pathways. These compounds are essential for sustained fatty acid production in the plastids of maturing Arabidopsis embryos. Using a real-time quantitative reverse transcriptase (RT)-PCR approach, the three genes encoding putative plastidial PKs (PKps) in Arabidopsis, namely PKp1 (At3g22960), PKp2 (At5g52920) and PKp3 (At1g32440), were shown to be ubiquitously expressed. However, only PKp1 and PKp2 exhibited significant expression in maturing seeds. The activity of PKp1 and PKp2 promoters was consistent with this pattern, and the study of the PKp1:GFP and PKp2:GFP fusion proteins confirmed the plastidial localization of these enzymes. To further investigate the function of these two PKp isoforms in seeds comprehensive functional analyses were carried out, including the cytological, biochemical and molecular characterization of two pkp1 and two pkp2 alleles, together with a pkp1pkp2 double mutant. The results obtained outlined the importance of these PKps for fatty acid synthesis and embryo development. Mutant seeds were depleted of oil, their fatty acid content was drastically modified, embryo elongation was retarded and, finally, seed germination was also affected. Together, these results provide interesting insights concerning the carbon fluxes leading to oil synthesis in maturing Arabidopsis seeds. The regulation of this metabolic network by the WRINKLED1 transcription factor is discussed, and emphasizes the role of plastidial metabolism and the importance of its tight regulation.

The WRINKLED1 (WRI1) transcription factor has been shown to play a role of the utmost importance during oil accumulation in maturing seeds of Arabidopsis thaliana. However, little is known about the regulatory processes involved. In this paper, comprehensive functional analyses of three new mutants corresponding to null alleles of wri1 confirm that the induction of WRI1 is a prerequisite for fatty acid synthesis and is important for normal embryo development. The strong expression of WRI1 specifically detected at the onset of the maturation phase in oil-accumulating tissues of A. thaliana seeds is fully consistent with this function. Complementation experiments carried out with various seed-specific promoters emphasized the importance of a tight regulation of WRI1 expression for proper oil accumulation, raising the question of the factors controlling WRI1 transcription. Interestingly, molecular and genetic analyses using an inducible system demonstrated that WRI1 is a target of LEAFY COTYLEDON2 and is necessary for the regulatory action of LEC2 towards fatty acid metabolism. In addition to this, quantitative RT-PCR experiments suggested that several genes encoding enzymes of late glycolysis, the fatty acid synthesis pathway, and the biotin and lipoic acid biosynthetic pathways are targets of WRI1. Taken together, these results indicate new relationships in the regulatory model for the control of oil synthesis in maturing A. thaliana seeds. In addition, they exemplify how metabolic and developmental processes affecting the developing embryo can be coordinated at the molecular level.

In the plastids of plant cells, fatty acid (FA) production is a central biosynthetic process. It provides acyl chains for the formation of a variety of acyl lipids fulfilling different biological functions ranging from membrane synthesis to signaling or carbon and energy storage. The biochemical pathway leading to the synthesis of FA has been described for a long time. Over the last 15 years, and after the genome of the model higher plant Arabidopsis thaliana has been sequenced, the scientific community has deployed approaches of functional genomics to identify the actors comprising this pathway. One of the puzzling aspects of the emerging molecular biology of FA synthesis resided in the occurrence of multigene families encoding most enzymes of the pathway. Studies carried out to investigate these families led to the conclusion that most members have acquired non-redundant roles in planta. This is usually the consequence of divergent expression patterns of these isogenes and/or of different substrate specificities of the isoforms they encode. Nevertheless, much remains to be elucidated regarding the molecular bases underpinning these specificities. Protein biochemistry together with emerging quantitative proteomic technologies have then led to a better understanding of the structure of the network, which is composed of multiprotein complexes organized within the stromal compartment of plastids: whereas growing evidence suggests that the early steps of the pathway might be associated to the inner envelope membrane, several late enzymes might be localized next to the thylakoids. The question of the existence of a large integrated protein assembly channeling substrates through the whole pathway that would span the stroma remains uncertain. Finally, recent discoveries regarding the post-translational regulation of the pathway open new research horizons and may guide the development of relevant biotechnological strategies aimed at monitoring FA production in plant systems.

The sucrose transporter gene AtSUC5 was studied as part of a programme aimed at identifying and studying the genes involved in seed maturation in Arabidopsis. Expression profiling of AtSUC5 using the technique of real-time quantitative reverse transcriptase polymerase chain reaction (RT-PCR) showed that the gene was specifically and highly induced during seed development between 4 and 9 days after flowering (DAF). Analysis of the activity of the AtSUC5 promoter in planta was consistent with this timing, and suggested that AtSUC5 expression is endosperm specific, spreading from the micropylar to the chalazal pole of the filial tissue. To demonstrate the function of AtSUC5, the corresponding cDNA was used to complement a sucrose uptake-deficient yeast mutant, thus confirming its sucrose transport capacity. To investigate the function in planta, three allelic mutants disrupted in the AtSUC5 gene were isolated and characterized. A strong but transient reduction in fatty acid concentration was observed in mutant seeds 8 DAF. This biochemical phenotype was associated with a slight delay in embryo development. Taken together, these data demonstrated the role of the AtSUC5 carrier in the nutrition of the filial tissues during early seed development. However, additional sugar uptake systems, which remain to be characterized, must be functional in developing seeds, especially during maturation of the embryo.

The primary objective of this study is to validate a specific finite element code aimed at simulating dynamic tooth loading in geared rotor systems. Experiments have been conducted on a high-precision single stage spur and helical gear reducer with flexible shafts mounted on hydrostatic or hydrodynamic bearings. The numerical model is based on classical elements (shaft, lumped stiffnesses, …) and on a gear element which accounts for non-linear time-varying mesh stiffness, gear errors and tooth shape modifications. External and parametric excitations are derived from the instantaneous contact conditions between the mating flanks by using an iterative contact algorithm inserted in a time-step integration scheme. First, experimental and numerical results at low speeds are compared and confirmed that the proposed tooth mesh interface model is valid. Comparisons were then extended to dynamic fillet stresses on both spur and helical gears between 50–6000 rpm on pinion shaft. Despite a localized problem in the case of spur gears with one particular bearing arrangement, the broad agreement between the experimental and numerical response curves demonstrated that the model is representative of the dynamic behavior of geared systems.

Diacylglycerol acyltransferases (DGATs) catalyze the final and only committed step of triacylglycerol synthesis. DGAT activity is rate limiting for triacylglycerol accumulation in mammals, plants and microbes. DGATs belong to three different evolutionary classes. In Arabidopsis thaliana, DGAT1, encoded by At2g19450, is the major DGAT enzyme involved in triacylglycerol accumulation in seeds. Until recently, the function of DGAT2 (At3g51520) has remained elusive. Previous attempts to characterize its enzymatic function by heterologous expression in yeast were unsuccessful. In the present report we demonstrate that expression of a codon-optimized version of the DGAT2 gene is able to restore neutral lipid accumulation in the Saccharomyces cerevisiae mutant strain (H1246), which is defective in triacylglycerol biosynthesis. Heterologous expression of codon-optimized DGAT2 and DGAT1 induced the biogenesis of subcellular lipid droplets containing triacylglycerols and squalene. Both DGAT proteins were found to be associated with these lipid droplets. The fatty acid composition was affected by the nature of the acyltransferase expressed. DGAT2 preferentially incorporated C16:1 fatty acids whereas DGAT1 displayed preference for C16:0, strongly suggesting that these enzymes have contrasting substrate specificities.

Oil bodies (OBs) are seed-specific lipid storage organelles that allow the accumulation of neutral lipids that sustain plantlet development after the onset of germination. OBs are covered with specific proteins embedded in a single layer of phospholipids. Using fluorescent dyes and confocal microscopy, we monitored the dynamics of OBs in living Arabidopsis (Arabidopsis thaliana) embryos at different stages of development. Analyses were carried out with different genotypes: the wild type and three mutants affected in the accumulation of various oleosins (OLE1, OLE2, and OLE4), three major OB proteins. Image acquisition was followed by a detailed statistical analysis of OB size and distribution during seed development in the four dimensions (x, y, z, and t). Our results indicate that OB size increases sharply during seed maturation, in part by OB fusion, and then decreases until the end of the maturation process. In single, double, and triple mutant backgrounds, the size and spatial distribution of OBs are modified, affecting in turn the total lipid content, which suggests that the oleosins studied have specific functions in the dynamics of lipid accumulation.

We previously showed that trehalose-6-phosphate synthase 1 (TPS1), which catalyses the first step in trehalose synthesis, is essential for embryo maturation in Arabidopsis [Eastmond, van Dijken, Spielman, Kerr, Tissier, Dickinson, Jones, Smeekens and Graham (2002) Plant J. 29, 225–235]. The tps1 mutant embryos develop more slowly than wild type. Patterning in the tps1 embryos appears normal but they do not progress past the torpedo stage to cotyledon stage, which is when storage reserves start to accumulate in the expanding cotyledons. Our initial data led to the hypothesis that trehalose metabolism plays a key role in regulating storage reserve accumulation by allowing the embryo to respond to the dramatic increase in sucrose levels that occurs at the torpedo stage of embryo development. More recent data demonstrate that while the tps1 mutant is blocked in the developmental progression of embryos from torpedo to cotyledon stage the expression of genes involved in the accumulation of storage reserves proceeds in a similar fashion to wild type. Thus it appears that induction of metabolic processes required for accumulation of storage reserves in tps1 occurs independently of the developmental stage and instead follows a temporal programme similar to wild-type seeds in the same silique.

Background Expression traits can vary quantitatively between individuals and have a complex inheritance. Identification of the genetics underlying transcript variation can help in the understanding of phenotypic variation due to genetic factors regulating transcript abundance and shed light into divergence patterns. So far, only a limited number of studies have addressed this subject in Arabidopsis, with contrasting results due to dissimilar statistical power. Here, we present the transcriptome architecture in leaf tissue of two RIL sets obtained from a connected-cross design involving 3 commonly used accessions. We also present the transcriptome architecture observed in developing seeds of a third independent cross. Results The utilisation of the novel R/eqtl package (which goal is to automatize and extend functions from the R/qtl package) allowed us to map 4,290 and 6,534 eQTLs in the Cvi-0 × Col-0 and Bur-0 × Col-0 recombinant populations respectively. In agreement with previous studies, we observed a larger phenotypic variance explained by eQTLs in linkage with the controlled gene (potentially cis-acting), compared to distant loci (acting necessarily indirectly or in trans). Distant eQTLs hotspots were essentially not conserved between crosses, but instead, cross-specific. Accounting for confounding factors using a probabilistic approach (VBQTL) increased the mapping resolution and the number of significant associations. Moreover, using local eQTLs obtained from this approach, we detected evidence for a directional allelic effect in genes with related function, where significantly more eQTLs than expected by chance were up-regulated from one of the accessions. Primary experimental data, analysis parameters, eQTL results and visualisation of LOD score curves presented here are stored and accessible through the QTLstore service database http://qtlstore.versailles.inra.fr/. Conclusions Our results demonstrate the extensive diversity and moderately conserved eQTL landscape between crosses and validate the utilisation of expression traits to explore for candidates behind phenotypic variation among accessions. Furthermore, this stresses the need for a wider spectrum of diversity to fully understand expression trait variation within a species.

Acyl lipids are essential constituents of all cells, but acyl chain requirements vary greatly and depend on the cell type considered. This implies a tight regulation of fatty acid production so that supply fits demand. Isolation of the Arabidopsis thaliana WRINKLED1 (WRI1) transcription factor established the importance of transcriptional regulation for modulating the rate of acyl chain production. Here, we report the isolation of two additional regulators of the fatty acid biosynthetic pathway, WRI3 and WRI4, which are closely related to WRI1 and belong to the APETALA2–ethylene-responsive element binding protein family of transcription factors. These three WRIs define a family of regulators capable of triggering sustained rates of acyl chain synthesis. However, expression patterns of the three WRIs differ markedly. Whereas only WRI1 activates fatty acid biosynthesis in seeds for triacylglycerol production, the three WRIs are required in floral tissues to provide acyl chains for cutin biosynthesis and prevent adherence of these developing organs and subsequent semisterility. The targets of these WRIs encode enzymes providing precursors (acyl chain and glycerol backbones) for various lipid biosynthetic pathways, but not the subsequent lipid-assembling enzymes. These results provide insights into the developmental regulation of fatty acid production in plants.

L'article original est publié par The American Society of Plant Biologists; WRINKLED1 (WRI1), a key regulator of seed oil biosynthesis in Arabidopsis (Arabidopsis thaliana), was duplicated during the genome amplification of the cereal ancestor genome 90 million years ago. Both maize (Zea mays) coorthologs ZmWri1a and ZmWri1b show a strong transcriptional induction during the early filling stage of the embryo and complement the reduced fatty acid content of Arabidopsis wri1-4 seeds, suggesting conservation of molecular function. Overexpression of ZmWri1a not only increases the fatty acid content of the mature maize grain but also the content of certain amino acids, of several compounds involved in amino acid biosynthesis, and of two intermediates of the tricarboxylic acid cycle. Transcriptomic experiments identified 18 putative target genes of this transcription factor, 12 of which contain in their upstream regions an AW box, the cis-element bound by AtWRI1. In addition to functions related to late glycolysis and fatty acid biosynthesis in plastids, the target genes also have functions related to coenzyme A biosynthesis in mitochondria and the production of glycerol backbones for triacylglycerol biosynthesis in the cytoplasm. Interestingly, the higher seed oil content in ZmWri1a overexpression lines is not accompanied by a reduction in starch, thus opening possibilities for the use of the transgenic maize lines in breeding programs.

The PII protein is an integrator of central metabolism and energy levels. In Arabidopsis, allosteric sensing of cellular energy and carbon levels alters the ability of PII to interact with target enzymes such as N-acetyl-l-glutamate kinase and heteromeric acetyl-coenzyme A carboxylase, thereby modulating the biological activity of these plastidial ATP- and carbon-consuming enzymes. A quantitative reverse transcriptase-polymerase chain reaction approach revealed a threefold induction of the AtGLB1 gene (At4g01900) encoding PII during early seed maturation. The activity of the AtGLB1 promoter was consistent with this pattern. A complementary set of molecular and genetic analyses showed that WRINKLED1, a transcription factor known to induce glycolytic and fatty acid biosynthetic genes at the onset of seed maturation, directly controls AtGLB1 expression. Immunoblot analyses and immunolocalization experiments using anti-PII antibodies established that PII protein levels faithfully reflected AtGLB1 mRNA accumulation. At the subcellular level, PII was observed in plastids of maturing embryos. To further investigate the function of PII in seeds, comprehensive functional analyses of two pII mutant alleles were carried out. A transient increase in fatty acid production was observed in mutant seeds at a time when PII protein content was found to be maximal in wild-type seeds. Moreover, minor though statistically significant modifications of the fatty acid composition were measured in pII seeds, which exhibited decreased amounts of modified (elongated, desaturated) fatty acid species. The results obtained outline a role for PII in the fine tuning of fatty acid biosynthesis and partitioning in seeds.

Lipides acyle dans Arabidopsis et toutes les autres plantes ont une myriade de fonctions diverses. Il s'agit notamment de fournir la barriere de diffusion de base des membranes qui separe les cellules et les organites subcellulaires. Cette fonction implique seuls plus de 10 classes de lipides membranaires, y compris les phospholipides, galactolipides, et sphingolipides, et au sein de chaque classe, les variations dans la composition de la chaine acyle augmenter le nombre de structures a plusieurs centaines de possibles especes moleculaires. Lipides acyle dans le sous forme de compte triacylglycerol de 35% du poids de graines d'Arabidopsis et representent leur forme majeure de carbone et de stockage d'energie. Une couche de cutine et les cires cuticulaires qui limite la perte d'eau et offre une protection contre les invasions par des agents pathogenes et autres stress recouvre toute la surface aerienne d'Arabidopsis. Des fonctions similaires sont fournis par la suberine et des cires associes qui sont localisees dans les racines, les teguments et les zones d'abscission et sont produites en reponse a une blessure. Ce chapitre se concentre sur les voies metaboliques qui sont associes a la biosynthese et la degradation des lipides acyle mentionnes ci-dessus. Ces voies, les enzymes et les genes sont egalement presentes en detail dans un site Web associe (ARALIP: http://aralip.plantbiology.msu.edu/ ). Protocoles et methodes utilises pour l'analyse des lipides Arabidopsis sont fournis. Enfin, un resume detaille de la composition des lipides Arabidopsis est fourni en trois chiffres et 15 tables.

Triacylglycerols (TAGs) constitute a highly efficient form of energy storage. In seeds of angiosperms, they can act as a reserve of carbon and energy allowing to fuel post-germinative seedling growth until photosynthesis becomes effective. They also constitute the economic value of seeds in many crops. In the past years, extensive tools allowing the molecular dissection of plant metabolism have been developed together with analytical and cytological procedures adapted for seed material. These tools have allowed gaining a comprehensive overview of the metabolic pathways leading to TAG synthesis. They have also unravelled factors limiting oil production such as metabolic bottlenecks and light or oxygen availability in seed tissues. Beyond these physiological aspects, accumulation of TAGs is developmentally regulated in seeds. The oil biosynthetic process is initiated at the onset of the maturation phase, once embryo morphogenesis is achieved. A wealth of recent studies has shed new lights on the intricate regulatory network controlling the seed maturation phase, including reserve deposition. This network involves a set of regulated transcription factors that crosstalk with physiological signaling. The knowledge thus acquired paves the way for the genetic engineering of oilseed crops dedicated to food applications or green chemistry.

The WRINKLED1 (WRI1) protein is an important regulator of oil accumulation in maturing Arabidopsis seeds. WRI1 is a member of a plant-specific family of transcription factors (AP2/EREBP) that share either one or two copies of a DNA-binding domain called the AP2 domain. Here, it is shown that WRI1 acts as a transcriptional enhancer of genes involved in carbon metabolism in transgenic seeds overexpressing this transcription factor. PKp-beta1 and BCCP2, two genes encoding enzymes of the glycolysis and fatty acid biosynthetic pathway, respectively, have been chosen to investigate the regulatory action exerted by WRI1 over these pathways. Using the reporter gene uidA, it was possible to demonstrate in planta that WRI1 regulates the activity of both PKp-beta1 and BCCP2 promoters. Electrophoretic mobility-shift assays and yeast one-hybrid experiments showed that WRI1 was able to interact with the BCCP2 promoter. To further elucidate the regulatory mechanism controlling the transcription of these genes, functional dissections of PKp-beta1 and BCCP2 promoters were performed. Two enhancers, of 54 and 79 bp, respectively, have thus been isolated that are essential to direct the activity of these promoters in oil-accumulating tissues of the embryo. A consensus site is present in these enhancers as well as in other putative target promoters of WRI1. Loss of this consensus sequence in the BCPP2 promoter decreases both the strength of the interaction between WRI1 and this promoter in yeast and the activity of the promoter in planta.

International audience; The hydroxysteroid dehydrogenase HSD1, identified in the proteome of oil bodies from mature Arabidopsis seeds, is encoded by At5g50600 and At5g50700, two gene copies anchored on a duplicated region of chromosome 5. Using a real-time quantitative reverse transcriptasepolymerase chain reaction (RTPCR) approach, the accumulation of HSD1 mRNA was shown to be specifically and highly induced in oil-accumulating tissues of maturing seeds. HSD1 mRNA disappeared during germination. The activity of HSD1 promoter and the localization of HSD1 transcripts by in situ hybridization were consistent with this pattern. A complementary set of molecular and genetic analyses showed that HSD1 is a target of LEAFY COTYLEDON2, a transcriptional regulator able to bind the promoter of HSD1. Immunoblot analyses and immunolocalization experiments using anti-AtHSD1 antibodies established that the pattern of HSD1 deposition faithfully reflected mRNA accumulation. At the subcellular level, the study of HSD1:GFP fusion proteins showed the targeting of HSD1 to the surface of oil bodies. Transgenic lines overexpressing HSD1 were then obtained to test the importance of proper transcriptional regulation of HSD1 in seeds. Whereas no impact on oil accumulation could be detected, transgenic seeds exhibited lower cold and light requirements to break dormancy, germinate and mobilize storage lipids. Interestingly, overexpressors of HSD1 over-accumulated HSD1 protein in seeds but not in vegetative organs, suggesting that post-transcriptional regulations exist that prevent HSD1 accumulation in tissues deprived of oil bodies.

As a Brassicaceae, Arabidopsis thaliana constitutes an excellent model system to investigate oil biosynthesis in seeds. Extensive tools for the genetic and molecular dissection of this model species are now available. Together with analytical procedures adapted to its tiny seeds, these tools have allowed major advances in isolating and characterising the factors that participate in the metabolic and developmental control of seed filling. Once the biochemical pathways producing storage lipids, namely triacylglycerols, were elucidated, the question of the regulation of this metabolic network has arisen. The coordinated up regulation of genes encoding enzymes of the fatty acid biosynthetic pathway observed at the onset of seed maturation suggests that the pathway may be subjected to a system of global transcriptional regulation. This has been further established by the study of master regulators of the maturation program like LEAFY COTYLEDON2 and the characterisation of the WRINKLED1 transcription factor. These factors have been shown to participate in a regulatory cascade controlling the induction of the genes involved in fatty acid biosynthesis at the onset of the maturation phase. Although much remains to be elucidated, the framework of the regulatory system controlling fatty acid biosynthesis in Arabidopsis seeds is coming into focus.

In the life cycle of higher plants, seed development is a key process connecting two distinct sporophytic generations. Seed development can be divided into embryo morphogenesis and seed maturation. An essential metabolic function of maturing seeds is the deposition of storage compounds that are mobilised to fuel post-germinative seedling growth. Given the importance of seeds for food and animal feed and considering the tremendous interest in using seed storage products as sustainable industrial feedstocks to replace diminishing fossil reserves, understanding the metabolic and developmental control of seed filling constitutes a major focus of plant research. Arabidopsis thaliana is an oilseed species closely related to the agronomically important Brassica oilseed crops. The main storage compounds accumulated in seeds of A. thaliana consist of oil stored as triacylglycerols (TAGs) and seed storage proteins (SSPs). Extensive tools developed for the molecular dissection of A. thaliana development and metabolism together with analytical and cytological procedures adapted for very small seeds have led to a good description of the biochemical pathways producing storage compounds. In recent years, studies using these tools have shed new light on the intricate regulatory network controlling the seed maturation process. This network involves sugar and hormone signalling together with a set of developmentally regulated transcription factors. Although much remains to be elucidated, the framework of the regulatory system controlling seed filling is coming into focus.