A new genomic resource dedicated to wood formation in Eucalyptus

<p>Abstract</p> <p>Background</p> <p>Renowned for their fast growth, valuable wood properties and wide adaptability, <it>Eucalyptus </it>species are amongst the most planted hardwoods in the world, yet they are still at the early stages of domestication because conventional breeding is slow and costly. Thus, there is huge potential for marker-assisted breeding programs to improve traits such as wood properties. To this end, the sequencing, analysis and annotation of a large collection of expressed sequences tags (ESTs) from genes involved in wood formation in <it>Eucalyptus </it>would provide a valuable resource.</p> <p>Results</p> <p>We report here the normalization and sequencing of a cDNA library from developing <it>Eucalyptus </it>secondary xylem, as well as the construction and sequencing of two subtractive libraries (juvenile <it>versus </it>mature wood and <it>vice versa</it>). A total of 9,222 high quality sequences were collected from about 10,000 cDNA clones. The EST assembly generated a set of 3,857 wood-related unigenes including 2,461 contigs (Cg) and 1,396 singletons (Sg) that we named 'EUCAWOOD'. About 65% of the EUCAWOOD sequences produced matches with poplar, grapevine, <it>Arabidopsis </it>and rice protein sequence databases. BlastX searches of the Uniref100 protein database allowed us to allocate gene ontology (GO) and protein family terms to the EUCAWOOD unigenes. This annotation of the EUCAWOOD set revealed key functional categories involved in xylogenesis. For instance, 422 sequences matched various gene families involved in biosynthesis and assembly of primary and secondary cell walls. Interestingly, 141 sequences were annotated as transcription factors, some of them being orthologs of regulators known to be involved in xylogenesis. The EUCAWOOD dataset was also mined for genomic simple sequence repeat markers, yielding a total of 639 putative microsatellites. Finally, a publicly accessible database was created, supporting multiple queries on the EUCAWOOD dataset.</p> <p>Conclusion</p> <p>In this work, we have identified a large set of wood-related <it>Eucalyptus </it>unigenes called EUCAWOOD, thus creating a valuable resource for functional genomics studies of wood formation and molecular breeding in this economically important genus. This set of publicly available annotated sequences will be instrumental for candidate gene approaches, custom array development and marker-assisted selection programs aimed at improving and modulating wood properties.</p

Identification of genes preferentially expressed during wood formation in Eucalyptus

cited By 76International audienceWood is the most abundant biological resource on earth and it is also an important raw material for a major global industry with rapidly increasing demand. The genus Eucalyptus includes the most widely used tree species for industrial plantation, mainly for making pulp and paper. With the aim of identifying major genes involved in wood formation in Eucalyptus, we have developed a targeted approach of functional genomics based on the isolation of xylem preferentially expressed genes by subtractive PCR. Transcript profiling using cDNA arrays and analysis of variance (ANOVA) were used to identify differentially expressed ESTs between secondary xylem and leaves. Real-time RT-PCR was performed to confirm the differential expression of representative EST. Of 224 independent EST sequences obtained, 81% were preferentially expressed in xylem. One-third of the ESTs exhibiting homologies with proteins of known function fell into two main classes highlighting the importance of the auxin signalling through ubiquitin-dependent proteolysis on one hand, and of the enzymes involved in cell wall biosynthesis and remodelling, on the other. The functions of the genes represented by the remaining 61% of ESTs should be of great interest for future research. This systematic analysis of genes involved in wood formation in Eucalyptus provides valuable insights into the molecular mechanisms involved in secondary xylem differentiation as well as new candidate-genes for wood quality improvement

Transcript profiling of a xylem vs phloem cDNA subtractive library identifies new genes expressed during xylogenesis in Eucalyptus

cited By 45International audience• Eucalyptus is one of the world's main sources of biomass. The genus includes species representing the principle hardwood trees used for pulp and paper. Here, we aimed to identify genes specifically expressed in differentiating secondary xylem compared with phloem. • We constructed a xylem vs phloem subtractive library (Xp) that generated 263 unique sequences. By transcript profiling of xylem, phloem, vascular cambium and leaves using macroarrays, we classified the 263 unigenes into distinct tissue-specific groups. Reverse transcription-polymerase chain reaction (RT-PCR) confirmed the differential expression of representative expressed sequence tags (ESTs). • A total of 87 unigenes were preferentially expressed in xylem. They were involved in functional categories known to play roles in xylogenesis, such as hormone signaling and metabolism, secondary cell wall thickening and proteolysis. Some of these genes, including unknown genes, may be considered xylem-specific and they are likely to control important functions in xylogenesis. • These data shed light on the cellular functions of xylem cells and, importantly, provide us with a portfolio of Eucalyptus xylem genes that may be major players in the control of wood formation and quality. © New Phytologist (2006)

Wood architecture and composition are deeply remodeled in frost sensitive eucalyptus overexpressing CBF/DREB1 transcription factors

Eucalypts are the most planted trees worldwide, but most of them are frost sensitive. Overexpressing transcription factors for CRT-repeat binding factors (CBFs) in transgenic Eucalyptus confer cold resistance both in leaves and stems. While wood plays crucial roles in trees and is affected by environmental cues, its potential role in adaptation to cold stress has been neglected. Here, we addressed this question by investigating the changes occurring in wood in response to the overexpression of two CBFs, taking advantage of available transgenic Eucalyptus lines. We performed histological, biochemical, and transcriptomic analyses on xylem samples. CBF ectopic expression led to a reduction of both primary and secondary growth, and triggered changes in xylem architecture with smaller and more frequent vessels and fibers exhibiting reduced lumens. In addition, lignin content and syringyl/guaiacyl (S/G) ratio increased. Consistently, many genes of the phenylpropanoid and lignin branch pathway were upregulated. Most of the features of xylem remodeling induced by CBF overexpression are reminiscent of those observed after long exposure of Eucalyptus trees to chilling temperatures. Altogether, these results suggest that CBF plays a central role in the cross-talk between response to cold and wood formation and that the remodeling of wood is part of the adaptive strategies to face cold stress.The Centre National pour la Recherche Scientifique (CNRS), the University Paul Sabatier Toulouse III (UPS), the French MERI (Ministry of Education, Research and Innovation), and the French Laboratory of Excellence project ‘TULIP’(ANR-10-LABX-41; ANR-11-IDEX-0002-02). This research was also financially supported by the Vietnamese government for PhD grants (P.B. Cao and C. Nguyen).http://www.mdpi.com/journal/ijmshj2020BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog

The Woody-Preferential Gene EgMYB88 Regulates the Biosynthesis of Phenylpropanoid-Derived Compounds in Wood

International audienceComparative phylogenetic analyses of the R2R3-MYB transcription factor family revealed that five subgroups were preferentially found in woody species and were totally absent from Brassicaceae and monocots (Soler et al., 2015). Here, we analyzed one of these subgroups (WPS-I) for which no gene had been yet characterized. Most Eucalyptus members of WPS-I are preferentially expressed in the vascular cambium, the secondary meristem responsible for tree radial growth. We focused on EgMYB88, which is the most specifically and highly expressed in vascular tissues, and showed that it behaves as a transcriptional activator in yeast. Then, we functionally characterized EgMYB88 in both transgenic Arabidopsis and poplar plants overexpressing either the native or the dominant repression form (fused to the Ethylene-responsive element binding factor-associated Amphiphilic Repression motif, EAR). The transgenic Arabidopsis lines had no phenotype whereas the poplar lines overexpressing EgMYB88 exhibited a substantial increase in the levels of the flavonoid catechin and of some salicinoid phenolic glycosides (salicortin, salireposide, and tremulacin), in agreement with the increase of the transcript levels of landmark biosynthetic genes. A change in the lignin structure (increase in the syringyl vs. guaiacyl, S/G ratio) was also observed. Poplar lines overexpressing the EgMYB88 dominant repression form did not show a strict opposite phenotype. The level of catechin was reduced, but the levels of the salicinoid phenolic glycosides and the S/G ratio remained unchanged. In addition, they showed a reduction in soluble oligolignols containing sinapyl p-hydroxybenzoate accompanied by a mild reduction of the insoluble lignin content. Altogether, these results suggest that EgMYB88, and more largely members of the WPS-I group, could control in cambium and in the first layers of differentiating xylem the biosynthesis of some phenylpropanoid-derived secondary metabolites including lignin

What MYB genes tell us about the specificities of woody plants?

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Implementing the CRISPR/Cas9 Technology in Eucalyptus Hairy Roots Using Wood-Related Genes

International audienceEucalypts are the most planted hardwoods worldwide. The availability of the Eucalyptus grandis genome highlighted many genes awaiting functional characterization, lagging behind because of the lack of efficient genetic transformation protocols. In order to efficiently generate knockout mutants to study the function of eucalypts genes, we implemented the powerful CRISPR/Cas9 gene editing technology with the hairy roots transformation system. As proofs-of-concept, we targeted two wood-related genes: Cinnamoyl-CoA Reductase1 (CCR1), a key lignin biosynthetic gene and IAA9A an auxin dependent transcription factor of Aux/IAA family. Almost all transgenic hairy roots were edited but the allele-editing rates and spectra varied greatly depending on the gene targeted. Most edition events generated truncated proteins, the prevalent edition types were small deletions but large deletions were also quite frequent. By using a combination of FT-IR spectroscopy and multivariate analysis (partial least square analysis (PLS-DA)), we showed that the CCR1-edited lines, which were clearly separated from the controls. The most discriminant wave-numbers were attributed to lignin. Histochemical analyses further confirmed the decreased lignification and the presence of collapsed vessels in CCR1-edited lines, which are characteristics of CCR1 deficiency. Although the efficiency of editing could be improved, the method described here is already a powerful tool to functionally characterize eucalypts genes for both basic research and industry purposes