Analysis of Wood Development with a Genomic Approach: Eucalyptus ESTs and TAC Genomic Library (original) (raw)
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A new genomic resource dedicated to wood formation in Eucalyptus
BMC Plant Biology, 2009
Background: Renowned for their fast growth, valuable wood properties and wide adaptability, Eucalyptus 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 Eucalyptus would provide a valuable resource.
Identification of genes preferentially expressed during wood formation in Eucalyptus
Plant Molecular Biology, 2004
Wood 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 Eucalyptus xylem genes during tension wood formation
New Phytologist, 2005
• Tension wood formed in response to gravitational force is a striking example of the plasticity of angiosperm wood. In this study our goal was to characterize the early changes in gene expression during tension wood formation in Eucalyptus.• Using cDNA array technology, transcript profiling of 231 genes preferentially expressed in differentiating Eucalyptus xylem was followed from 6 h to 1 wk of a tension time course of artificially bent Eucalyptus trees.• 196 genes were differentially regulated between control and bent trees, some exhibiting distinctive expression patterns related to changes in secondary cell wall structure and composition. For instance, expression of a cellulose synthase gene was well correlated with the appearance of the G-layers. Cluster correlation analysis revealed differential regulation of lignin biosynthetic genes and may also be used to help infer the function of unknown gene products.• Eucalyptus wood transcriptome analysis during tension wood formation not only provided new clues into the transcriptional regulatory network of genes preferentially expressed in xylem, but also highlighted candidate genes responsible for the genetic and environmentally induced variation of wood quality traits.Tension wood formed in response to gravitational force is a striking example of the plasticity of angiosperm wood. In this study our goal was to characterize the early changes in gene expression during tension wood formation in Eucalyptus.Using cDNA array technology, transcript profiling of 231 genes preferentially expressed in differentiating Eucalyptus xylem was followed from 6 h to 1 wk of a tension time course of artificially bent Eucalyptus trees.196 genes were differentially regulated between control and bent trees, some exhibiting distinctive expression patterns related to changes in secondary cell wall structure and composition. For instance, expression of a cellulose synthase gene was well correlated with the appearance of the G-layers. Cluster correlation analysis revealed differential regulation of lignin biosynthetic genes and may also be used to help infer the function of unknown gene products.Eucalyptus wood transcriptome analysis during tension wood formation not only provided new clues into the transcriptional regulatory network of genes preferentially expressed in xylem, but also highlighted candidate genes responsible for the genetic and environmentally induced variation of wood quality traits.
BMC Genomics, 2010
Background: De novo assembly of transcript sequences produced by short-read DNA sequencing technologies offers a rapid approach to obtain expressed gene catalogs for non-model organisms. A draft genome sequence will be produced in 2010 for a Eucalyptus tree species (E. grandis) representing the most important hardwood fibre crop in the world. Genome annotation of this valuable woody plant and genetic dissection of its superior growth and productivity will be greatly facilitated by the availability of a comprehensive collection of expressed gene sequences from multiple tissues and organs. Results: We present an extensive expressed gene catalog for a commercially grown E. grandis × E. urophylla hybrid clone constructed using only Illumina mRNA-Seq technology and de novo assembly. A total of 18,894 transcriptderived contigs, a large proportion of which represent full-length protein coding genes were assembled and annotated. Analysis of assembly quality, length and diversity show that this dataset represent the most comprehensive expressed gene catalog for any Eucalyptus tree. mRNA-Seq analysis furthermore allowed digital expression profiling of all of the assembled transcripts across diverse xylogenic and non-xylogenic tissues, which is invaluable for ascribing putative gene functions.
New Phytologist, 2006
• 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.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.
SAGE transcript profiling of the juvenile cambial region of Eucalyptus grandis
Tree physiology, 2008
Despite the importance of Eucalyptus spp. in the pulp and paper industry, functional genomic approaches have only recently been applied to understand wood formation in this genus. We attempted to establish a global view of gene expression in the juvenile cambial region of Eucalyptus grandis Hill ex Maiden. The expression profile was obtained from serial analysis of gene expression (SAGE) library data produced from 3- and 6-year-old trees. Fourteen-base expressed sequence tags (ESTs) were searched against public Eucalyptus ESTs and annotated with GenBank. Altogether 43,304 tags were generated producing 3066 unigenes with three or more copies each, 445 with a putative identity, 215 with unknown function and 2406 without an EST match. The expression profile of the juvenile cambial region revealed the presence of highly frequent transcripts related to general metabolism and energy metabolism, cellular processes, transport, structural components and information pathways. We made a quanti...
PloS one, 2014
Eucalyptus nitens is a perennial forest tree species grown mainly for kraft pulp production in many parts of the world. Kraft pulp yield (KPY) is a key determinant of plantation profitability and increasing the KPY of trees grown in plantations is a major breeding objective. To speed up the breeding process, molecular markers that can predict KPY are desirable. To achieve this goal, we carried out RNA-Seq studies on trees at extremes of KPY in two different trials to identify genes and alleles whose expression correlated with KPY. KPY is positively correlated with growth measured as diameter at breast height (DBH) in both trials. In total, six RNA bulks from two treatments were sequenced on an Illumina HiSeq platform. At 5% false discovery rate level, 3953 transcripts showed differential expression in the same direction in both trials; 2551 (65%) were down-regulated and 1402 (35%) were up-regulated in low KPY samples. The genes up-regulated in low KPY trees were largely involved in ...
Comprehensive genetic dissection of wood properties in a widely-grown tropical tree: Eucalyptus
BMC Genomics, 2011
Background: Eucalyptus is an important genus in industrial plantations throughout the world and is grown for use as timber, pulp, paper and charcoal. Several breeding programmes have been launched worldwide to concomitantly improve growth performance and wood properties (WPs). In this study, an interspecific cross between Eucalyptus urophylla and E. grandis was used to identify major genomic regions (Quantitative Trait Loci, QTL) controlling the variability of WPs. Results: Linkage maps were generated for both parent species. A total of 117 QTLs were detected for a series of wood and end-use related traits, including chemical, technological, physical, mechanical and anatomical properties. The QTLs were mainly clustered into five linkage groups. In terms of distribution of QTL effects, our result agrees with the typical L-shape reported in most QTL studies, i.e. most WP QTLs had limited effects and only a few (13) had major effects (phenotypic variance explained > 15%). The co-locations of QTLs for different WPs as well as QTLs and candidate genes are discussed in terms of phenotypic correlations between traits, and of the function of the candidate genes. The major wood property QTL harbours a gene encoding a Cinnamoyl CoA reductase (CCR), a structural enzyme of the monolignol-specific biosynthesis pathway.
BMC Genomics, 2013
Eucalyptus is one of the most important sources of industrial cellulose. Three species of this botanical group are intensively used in breeding programs: E. globulus, E. grandis and E. urophylla. E. globulus is adapted to subtropical/temperate areas and is considered a source of high-quality cellulose; E. grandis grows rapidly and is adapted to tropical/subtropical climates; and E. urophylla, though less productive, is considered a source of genes related to robustness. Wood, or secondary xylem, results from cambium vascular differentiation and is mostly composed of cellulose, lignin and hemicelluloses. In this study, the xylem transcriptomes of the three Eucalyptus species were investigated in order to provide insights on the particularities presented by each of these species.