Eucalypts are the world's most widely planted hardwood trees. Their outstanding diversity, adaptability and growth have made them a global renewable resource of fibre and energy. We sequenced and assembled .94% of the 640-megabase genome of Eucalyptus grandis. Of 36,376 predicted protein-coding genes, 34% occur in tandem duplications, the largest proportion thus far in plant genomes. Eucalyptus also shows the highest diversity of genes for specialized metabolites such as terpenes that act as chemical defence and provide unique pharmaceutical oils. Genome sequencing of the E. grandis sister species E. globulus and a set of inbred E. grandis tree genomes reveals dynamic genome evolution and hotspots of inbreeding depression. The E. grandis genome is the first reference for the eudicot order Myrtales and is placed here sister to the eurosids. This resource expands our understanding of the unique biology of large woody perennials and provides a powerful tool to accelerate comparative biology, breeding and biotechnology.A major opportunity for a sustainable energy and biomaterials economy in many parts of the world lies in a better understanding of the molecular basis of superior growth and adaptation in woody plants. Part of this opportunity involves species of Eucalyptus L'Hér, a genus of woody perennials native to Australia 1 . The remarkable adaptability of eucalypts coupled with their fast growth and superior wood properties has driven their rapid adoption for plantation forestry in more than 100 countries across six continents (.20 million ha) 2 , making eucalypts the most widely planted hardwood forest trees in the world. The subtropical E. grandis and the temperate E. globulus stand out as targets of breeding programmes worldwide. Planted eucalypts provide key renewable resources for the production of pulp, paper, biomaterials and bioenergy, while mitigating human pressures on native forests 3 . Eucalypts also have a large diversity and high concentration of essential oils (mixtures of mono-and sesquiterpenes), many of which have ecological functions as well as medicinal and industrial uses. Predominantly outcrossers 1 with hermaphroditic animal-pollinated flowers, eucalypts are highly heterozygous and display pre-and postzygotic barriers to selfing to reduce inbreeding depression for fitness and survival 4 .To mitigate the challenge of assembling a highly heterozygous genome, we sequenced the genome of 'BRASUZ1', a 17-year-old E. grandis genotype derived from one generation of selfing. The availability of annotated forest tree genomes from two separately evolving rosid lineages, Eucalyptus (order Myrtales) and Populus (order Malpighiales 5 ), in combination with genomes from domesticated woody plants (for example, Vitis, Prunus, Citrus), provides a comparative foundation for addressing

Plant peroxidases (class III peroxidases) are present in all land plants. They are members of a large multigenic family. Probably due to this high number of isoforms, and to a very heterogeneous regulation of their expression, plant peroxidases are involved in a broad range of physiological processes all along the plant life cycle. Due to two possible catalytic cycles, peroxidative and hydroxylic, peroxidases can generate reactive oxygen species (ROS) ( • OH, HOO• ), polymerise cell wall compounds, and regulate H 2 O 2 levels. By modulating their activity and expression following internal and external stimuli, peroxidases are prevalent at every stage of plant growth, including the demands that the plant meets in stressful conditions. These multifunctional enzymes can build a rigid wall or produce ROS to make it more flexible; they can prevent biological and chemical attacks by raising physical barriers or by counterattacking with a large production of ROS; they can be involved in a more peaceful symbiosis. They are finally present from the first hours of a plant's life until its last moments. Although some functions look paradoxical, the whole process is probably regulated by a fine-tuning that has yet to be elucidated. This review will discuss the factors that can influence this delicate balance.Keywords Evolution . ROS . (abiotic and biotic) stress . Cell wall loosening and cross-linking . Senescence . Fruit ripening . Symbiosis Multigenic family, evolution and homologyHeme peroxidases specific to plants belong to a superfamily that contains three different classes of peroxidases Communicated by P. Kumar

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Land plants evolved from charophytic algae, among which Charophyceae possess the most complex body plans. We present the genome of Chara braunii; comparison of the genome to those of land plants identified evolutionary novelties for plant terrestrialization and land plant heritage genes. C. braunii employs unique xylan synthases for cell wall biosynthesis, a phragmoplast (cell separation) mechanism similar to that of land plants, and many phytohormones. C. braunii plastids are controlled via landplant-like retrograde signaling, and transcriptional regulation is more elaborate than in other algae. The morphological complexity of this organism may result from expanded gene families, with three cases of particular note: genes effecting tolerance to reactive oxygen species (ROS), LysM receptor-like kinases, and transcription factors (TFs). Transcriptomic analysis of sexual reproductive structures reveals intricate control by TFs, activity of the ROS gene network, and the ancestral use of plant-like storage and stress protection proteins in the zygote.

Summary• The respective distribution of superoxide (O 2• -) and hydrogen peroxide (H 2 O 2 ), two reactive oxygen species (ROS) involved in root growth and differentiation, was determined within the Arabidopsis root tip. We investigated the effect of changing the levels of these ROS on root development and the possible interactions with peroxidases.• H 2 O 2 was detected by confocal laser-scanning microscopy using hydroxyphenyl fluorescein (HPF). Both O 2• -accumulation and peroxidase distribution were assessed by light microscopy, using nitroblue tetrazolium (NBT) and o -dianisidine, respectively. Root length and root hair length and density were also quantified following ROS scavenging.• O 2• -was predominantly located in the apoplast of cell elongation zone, whereas H 2 O 2 accumulated in the differentiation zone and the cell wall of root hairs in formation. Treatments that decrease O 2• -concentration reduced root elongation and root hair formation, while scavenging H 2 O 2 promoted root elongation and suppressed root hair formation.• The results allow to precise the respective role of O 2• -and H 2 O 2 in root growth and development. The consequences of their distinct accumulation sites within the root tip are discussed, especially in relation to peroxidases.

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Xyloglucans are the principal glycans that interlace cellulose microfibrils in most flowering plants. The mur3 mutant of Arabidopsis contains a severely altered structure of this polysaccharide because of the absence of a conserved ␣ -L -fucosyl-(1 → 2)-␤ -D -galactosyl side chain and excessive galactosylation at an alternative xylose residue. Despite this severe structural alteration, mur3 plants were phenotypically normal and exhibited tensile strength in their inflorescence stems comparable to that of wild-type plants. The MUR3 gene was cloned positionally and shown to encode a xyloglucan galactosyltransferase that acts specifically on the third xylose residue within the XXXG core structure of xyloglucan. MUR3 belongs to a large family of type-II membrane proteins that is evolutionarily conserved among higher plants. The enzyme shows sequence similarities to the glucuronosyltransferase domain of exostosins, a class of animal glycosyltransferases that catalyze the synthesis of heparan sulfate, a glycosaminoglycan with numerous roles in cell differentiation and development. This finding suggests that components of the plant cell wall and of the animal extracellular matrix are synthesized by evolutionarily related enzymes even though the structures of the corresponding polysaccharides are entirely different from each other.