Loic Lepiniec

French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · Institut Jean-Pierre Bourgin

Flavonoids are widely known for the colors they confer to plant tissues, their contribution to plant fitness and health benefits, and impact on food quality. As convenient biological markers, flavonoids have been instrumental in major genetic and epigenetic discoveries. We review recent advances in the characterization of the underlying regulatory...

Elucidating the mechanisms that control seed development, metabolism, and physiology is a fundamental issue in biology. Michel Caboche had long been a catalyst for seed biology research in France up until his untimely passing away last year. To honour his memory, we have updated a review written under his coordination in 2010 entitled "Arabidopsis...

The MYB family of proteins is large, functionally diverse and represented in all eukaryotes. Most MYB proteins function as transcription factors with varying numbers of MYB domain repeats conferring their ability to bind DNA. In plants, the MYB family has selectively expanded, particularly through the large family of R2R3-MYB. Members of this famil...

The Arabidopsis sterol 3-beta-glucosyltransferase UGT80B1/TRANSPARENT TESTA15 (TT15) catalyzes sterol glucoside biosynthesis. Its loss of function causes reduced seed size, defective flavanol, polysaccharide and lipid polyester deposition at the seed coat and reduced seed dormancy. How TT15 controls seed development and physiology is unknown. Here...

Camelina [Camelina sativa (L.) Crantz] is an oilseed crop belonging to the Brassicaceae family that has attracted worldwide attention because of its agronomic and qualitative characteristics. This crop can adapt well to different environments and produce oil suitable for multiple bio-based uses. The most commonly measured and reported components of...

Despite the essential role of Specialized Metabolites (SMs) in the interaction of plants with the environment, studying the ability of crop seeds to produce these protective compounds has been neglected. Furthermore, seeds produce a myriad of SMs providing an interesting model to investigate their diversity and plasticity. Camelina sativa gained a...

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...

Somatic embryogenesis is a method of asexual reproduction that can occur naturally in various plant species and is widely used for clonal propagation, transformation and regeneration of different crops. Somatic embryogenesis shares some developmental and physiological similarities with zygotic embryogenesis as it involves common actors of hormonal,...

Intégrant les derniers acquis de la biologie cellulaire et de la génétique moléculaire, cette quatrième édition, entièrement corrigée, offre un panorama de l’ensemble de la biologie végétale enseignée dans les premières années d’études supérieures (Licence, M1, Pharmacie, classes préparatoires, IUT,). Ce volume traite des aspects physiologiques et...

HEAT SHOCK FACTOR A2 (HSFA2) is a regulator of multiple environmental stress responses required for stress acclimation. We analyzed HSFA2 co-regulated genes and identified 43 genes strongly co-regulated with HSFA2 during multiple stresses. Motif enrichment analysis revealed an over-representation of the site II element (SIIE) in the promoters of th...

Seeds produce a myriad of Specialized Metabolites (SMs). Nevertheless, despite the essential role of SMs in the interaction of plants with their environment, studying the ability of crop seeds to produce these protective compounds has been neglected. Camelina is an oilseed crop, whose seeds are characterized by high oil content and a unique composi...

Seed quality is considered as a major agricultural issue with respect to food and non-food uses, biodiversity preservation and environmental protection. Germination efficiency and seed vigor are key factors to ensure correct plant production and yield. Germination can be limited by seed dormancy and/or suboptimal environmental conditions. In additi...

In plants, light-dependent activation of de novo fatty acid synthesis (FAS) is partially mediated by acetyl-CoA carboxylase (ACCase), the first committed step for this pathway. However, it is not fully understood how plants control light-dependent FAS regulation to meet the cellular demand for acyl chains. We report here the identification of a gen...

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...

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 denote an abundant synthesis of omega-9 monoenes in this organ. Accordingly, four Δ9 stearoyl-ACP desaturase (SAD)-coding genes (FAB2, AAD5, AAD1, and AAD6) are transcriptional...

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 WRINKLED transcription factors, members of the AP2/EREBP family, has emphasized the importance of transcriptional regulations for adaptin...

Plants produce a huge diversity of specialized metabolites (SM) throughout their life cycle that play important physiological and ecological functions. SM can protect plants and seeds against diseases, predators, and abiotic stresses, or support their interactions with beneficial or symbiotic organisms. They also have strong impacts on human nutrit...

Seeds have greatly contributed to the successful colonization of land by plants. Compared to spores, seeds carry nutrients, rely less on water for germination, provide a higher degree of protection against biotic and abiotic stresses, and can disperse in different ways. Such advantages are, to a great extent, provided by the seed coat. The evolutio...

Identifying genetic variation that increases crop yields is a primary objective in plant breeding. We used association analyses of oilseed rape/canola (Brassica napus) accessions to identify genetic variation that influences seed size, lipid content, and final crop yield. Variation in the promoter region of the HECT E3 ligase gene BnaUPL3C03 made a...

Background In flowering plants, proper seed development is achieved through the constant interplay of fertilization products, embryo and endosperm, and maternal tissues. Communication between these compartments is supposed to be tightly regulated at their interfaces. Here, we characterize the deposition pattern of an apoplastic lipid barrier betwee...

FUSCA3 (FUS3) is a master regulator of seed development important in establishing and maintaining embryonic identity whose expression is tightly regulated at genetic and epigenetic levels. Despite this prominent role, the control of FUS3 expression remains poorly understood. Promoter and functional complementation analyses provided insight into the...

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...

Key message: Seed coats as commodities. Seed coats play important roles in the protection of the embryo from biological attack and physical damage by the environment as well as dispersion strategies. A significant part of the energy devoted by the mother plant to seed production is channeled into the production of the cell layers and metabolites t...

Angiosperm seeds are perfect biological factories for pro- ducing food, feed and industrially valuable molecules. They have evolved to accumulate a huge variety of nutritional and protective molecules in a stable (dry and largely qui- escent) environment that can be stored, in some cases for many years, allowing embryo growth to be resumed when pla...

Identifying genetic variation that increases crop yields is a primary objective in plant breeding. We have used association analyses of Brassica napus (oilseed rape/canola) accessions to identify genetic variation in the promoter of a HECT E3 ligase gene, BnaUPL3.C03, that influences seed size and final yield. We establish a mechanism in which UPL3...

The sections in this article are Introduction Development and Anatomy of the Seed Coat Role of the Seed Coat in Seed Dormancy and Germination Link between Seed Coat‐Imposed Dormancy and Longevity Concluding Remarks

The LAFL transcription factors LEC2, ABI3, FUS3 and LEC1 are master regulators of seed development. LEC2, ABI3 and FUS3 are closely related proteins that contain a B3-type DNA binding domain. We have previously shown that LEC1 (a NF-YB type protein) can increase LEC2 and ABI3 but not FUS3 activity. Interestingly, FUS3, LEC2 and ABI3 contain a B2 do...

Background Genome-wide characterization of tissue- or cell-specific gene expression is a recurrent bottleneck in biology. We have developed a sensitive approach based on ultra-low RNA sequencing coupled to laser assisted microdissection for analyzing different tissues of the small Arabidopsis embryo. Methods and results We first characterized the...

Omega-7 monoenoic fatty acids (ω-7 FAs) are increasingly exploited both for their positive effects on health and for their industrial potential. Some plant species produce fruits or seeds with high amounts of ω-7 FAs. However, the low yields and poor agronomic properties of these plants preclude their commercial use. As an alternative, the metaboli...

Analysis of AAD2 and AAD3 transcript levels by quantitative RT-PCR in ProAT2S2:MYB115 seeds. The five independent transformants considered are TCR4, TAR3, TXR2, TGR5, and TJR2 (in order from left to right). RT-qPCR analysis of transcript abundance in cDNA prepared from excised embryos aged 14 DAA was carried out to assess efficient overexpression o...

Complementary results for the characterization of AT2S2 promoter activity. Pattern of activity of the ProAT2S2:uidA cassette in rosette (A) and cauline leaves (B), in inflorescences (C), and in flowers (D). For histochemical detection of GUS activity, tissues were incubated overnight in a buffer containing 2 mM each of potassium ferrocyanide and po...

Characterization of early seed development in ProAT2S2:MYB115 lines. Five independent ProAT2S2:MYB115 lines are presented: TAR3, TCR4, TGR5, TJR2, and TXR2. (A) Observation of seed development. Whole mounts of early developing seeds (from 4 to 8 DAA) and of maturing embryos (10 and 12 DAA) were observed with Nomarski optics. Bars = 50 μm. (B) Obser...

Primers used for quantitative RT-PCR. (PDF)

Complementary results for the characterization of A. thaliana lines overexpressing AAD2 or AAD3. The five independent ProAT2S2:AAD2 transformants considered, T2R3, T19R1, T7R3, T17R1, and T13R8 (in order from left to right) and the five independent ProAT2S2:AAD3 transformants considered, T7R1, T19R5, T16R1, T20R5, and T13R2 (in order from left to r...

Total fatty acid composition (in mol%) of endosperm fractions dissected from seeds of engineered lines of A. thaliana. (PDF)

Total fatty acid composition (in Mol%) of embryos dissected from seeds of engineered lines of Arabidopsis. (PDF)

Primers used for construct preparation. (PDF)

At4g27140/AT2S2 promoter sequence (5’→3’). (PDF)

Total fatty acid composition (in mol%) of seeds from engineered lines of A. thaliana. (PDF)

Background: Totipotency is the ability of a cell to regenerate a whole organism. Plant somatic embryogenesis (SE) is a remarkable example of totipotency because somatic cells reverse differentiation, respond to an appropriate stimulus and initiate embryo development. Although SE is an ideal system to investigate de-differentiation and differentiat...

The seed, the reproductive unit of angiosperms, is generally protected by the seed coat. The seed coat is made of one or two integuments, each comprising two epidermal cells layers and, in some cases, extra sub-epidermal cell layers. The thickness of the seed-coat affects several aspects of seed biology such as dormancy, germination and mortality....

GOA expression. GFP fluorescence image of a ProGOA:gGOA-GFP ovule at stage 3-VI. The contour of the ovule is marked by a white line. A red arrowhead points to the chalazal nuclei expressing GFP. Scale bars, 50 μm. (DOCX)

The LAFL genes (LEC2, ABI3, FUS3, LEC1) encode transcription factors that regulate different aspects of seed development, from early to late embryogenesis and accumulation of storage compounds. These transcription factors form a complex network, with members able to interact with various other players to control the switch between embryo developmen...

The seed, the reproductive unit of angiosperms, is physically protected by the seed coat. The seed coat develops from the ovule integuments after fertilization. The Arabidopsis ovule integuments are made of 5–6 cell layers of epidermal and sub-epidermal origin. The growth of the epidermal integument cell layers responds to an endosperm signal media...

Flavonoids are secondary metabolites that fulfil a multitude of functions during the plant life cycle. In Arabidopsis proanthocyanidins (PAs) are flavonoids that specifically accumulate in the innermost integuments of the seed testa (i.e. endothelium), as well as in the chalaza and micropyle areas, and play a vital role in protecting the embryo aga...

Angiosperm seed development is a paradigm of tissue cross-talking. Proper seed formation requires spatial and temporal coordination of the fertilization products, embryo and endosperm, and the surrounding seed coat maternal tissue. In early Arabidopsis seed development, all seed integuments were thought to respond homogenously to endosperm growth....

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 fat...

Small proteins have long been overlooked due to their poor annotation and the experimental challenges they pose. However, in recent years, their role in various processes has started to emerge opening new research avenues. Here, we present the isolation and characterization of two allelic mutants twisted seed1-1 (tws1-1) and tws1-2 which exhibit an...

Yeast one-hybrid (Y1H) assay has been proven to be a powerful technique to characterize in vivo the interaction between a given transcription factor (TF), or its DNA-binding domain (DBD), and target DNA sequences. Comprehensive characterization of TF/DBD and DNA interactions should allow designing synthetic promoters that would undoubtedly be valua...

Transient expression assays are valuable techniques to study in vivo the transcriptional regulation of gene expression. These methods allow to assess the transcriptional properties of a given transcription factor (TF) or a complex of regulatory proteins against specific DNA motifs, called cis-regulatory elements. Here, we describe a fast, efficient...

This paper presents the SeeDev Task of the BioNLP Shared Task 2016. The purpose of the SeeDev Task is the extraction from scientific articles of the descriptions of genetic and molecular mechanisms involved in seed development of the model plant, Arabidopsis thaliana. The SeeDev task consists in the extraction of many different event types that inv...

In angiosperms, seed architecture is shaped by the coordinated development of three genetically different components: embryo, endosperm and maternal tissues. The relative contribution of these tissues to seed mass and nutrient storage varies considerably among species. The development of embryo, endosperm or nucellus maternal tissue as primary stor...

In Arabidopsis, transcriptional control of seed maturation involves three related regulators with a B3 domain (AFLs), namely LEAFY COTYLEDON2 (LEC2), ABSCISSIC ACID INSENSITIVE 3 (ABI3), and FUSCA 3 (FUS3). Although genetic analyses have demonstrated partially overlapping functions of these regulators, the underlying molecular mechanisms remained e...

Information Extraction Challenge Gene Regulation Network in Arabidopsis thaliana (GRNA)

The control of growth and development of all living organisms is a complex and dynamic process that requires the harmonious expression of numerous genes. Gene expression is mainly controlled by the activity of sequence-specific DNA binding proteins called transcription factors (TFs). Amongst the various classes of eukaryotic TFs, the MYB superfamil...

A comprehensive understanding of the molecular network underlying seed development regulations remains a major scientific challenge with important potential impact for fundamental research, agriculture and industry. Seed development requires the coordinated growth of different tissues that involves complex genetics and environmental regulations. Mo...

Welcome to the 26th International Conference on Arabidopsis Research (ICAR) It is a great pleasure to invite you, on behalf of the organizing committees, to join us in Paris, for this exciting meeting, which includes an outstanding scientific program and terrific social event! ICAR is the largest annual international conference focusing on cutti...

For international PhD students and young post-docs « The summer school aims to foster exchanges between a small group of young resear-chers and top scientists from academia and private companies. These exchanges will cover cutting-edge research and key issues in seed science. The timing and location of the summer school have been coordinated to al...

Seed is the main vector for breeding and production of annual field crops, and the accumulation of seed storage compounds (sugars, lipids, proteins) is of primary importance for food, feed and industrial uses. Seed development requires the coordinated growth of different tissues and involves complex genetics and environmental regulations. A compreh...

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 descr...