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Boreal tree species are migrating northwards due to rising temperatures, and differences in heat tolerance can impact the range limits of boreal species. Soil warming may benefit tree growth by promoting root development, or harm growth by creating a high-stress environment, increasing root respiration rates. We assessed the impact of soil warming on the growth of 2-year-old trembling aspen seedlings from 10 families. These families originated from Peace River, in central Alberta, and Camrose, near the southern boreal fringe in Alberta, Canada. We correlated growth traits with climatic data from each region and analyzed the effect of soil warming on the gas exchange of seedlings from Camrose. Families from Peace River exhibited greater growth overall, regardless of warming treatment, while families from Camrose showed a positive growth response under soil warming. Camrose families exposed to soil warming showed greater total leaf area and total leaf biomass compared to those without warming. A Principal Component Analysis (PCA) showed that, regardless of region, some families displayed stronger positive responses and appeared better adapted to soil warming than others. The overall positive response of the Camrose families to soil warming suggests that they have the capacity to take advantage of warmer environmental conditions. Our results indicate regional growth differences in aspen families in Alberta and variation in performance between families within a region, indicating there is differential capacity within local populations to acclimate under rapid climate change.

NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized in

The high Andean forests of the genus Polylepis (Rosaceae) are threatened by extinction due to anthropogenic effects such as timber extraction, burning, and overgrazing. Some species are also affected by Tristerix chodatianus (Loranthaceae), a hemiparasitic plant which induces progressive host damage. To understand this hemiparasitic process, we evaluated the impact of T. chodatianus on growth and the wood anatomy of Polylepis flavipila using growth rings and digital image processing. We found that P. flavipila has a xeromorphic wood anatomy and that the ecological indices of mesomorphism and vulnerability decrease at higher elevations to avoid embolisms and vessel cavitation. Tristerix chodatianus causes anatomical changes in the host wood, mainly in the last 13 years measured. Alterations include a reduction in the vessel density, and an increase in the vessel diameter and Vulnerability Index, all of which are more evident in downstream sections of parasitized branches. These changes in the xylem tissues increase the vulnerability of the parasitized branches to embolisms and cavitation, thus leading to progressive death of the tree crown. Our study confirms that the analysis of the wood anatomy of parasitized branches can be used to determine the years of colonization of a tree branch by a hemiparasite and that it can be a useful tool to monitor the phytosanitary state of parasitized Polylepis trees.

Accurate monitoring of genetic diversity levels of seedlots and mating patterns of parents from seed orchards are crucial to ensure that tree breeding programs are long-lasting and will deliver anticipated genetic gains. We used SNP genotyping to characterize founder trees, five bulk seed orchard seedlots, and trees from progeny trials to assess pollen contamination and the impact of severe roguing on genetic diversity and parental contributions in a first-generation open-pollinated white spruce clonal seed orchard. After severe roguing (eliminating 65% of the seed orchard trees), we found a slight reduction in the Shannon Index and a slightly negative inbreeding coefficient, but a sharp decrease in effective population size (eightfold) concomitant with sharp increase in coancestry (eightfold). Pedigree reconstruction showed unequal parental contributions across years with pollen contamination levels between 12 and 51% (average 27%) among seedlots, and 7–68% (average 30%) among individual genotypes within a seedlot. These contamination levels were not correlated with estimates obtained using pollen flight traps. Levels of pollen contamination also showed a Pearson’s correlation of 0.92 with wind direction, likely from a pollen source 1 km away from the orchard under study. The achievement of 5% genetic gain in height at rotation through eliminating two-thirds of the orchard thus generated a loss in genetic diversity as determined by the reduction in effective population size. The use of genomic profiles revealed the considerable impact of roguing on genetic diversity, and pedigree reconstruction of full-sib families showed the unanticipated impact of pollen contamination from a previously unconsidered source.

Teak (Tectona grandis Linn F.) is a fast-growing deciduous tree. It has a wide geographic distribution in the tropical and subtropical regions of Asia, Africa, South America, and Central America. Its wood is highly priced for its quality, profile, and durability. Therefore, foresters seek to improve growth, reduce crop rotation, and obtain trees that are well adapted to their environment. For this reason, it is important to understand the mechanisms of genetic regulation in the biosynthesis of cellulose, hemicellulose and lignin, and biomolecules that represent the majority of plant biomass. To determine which genes are related to the transcriptional regulation of xylogenesis and abiotic stress in Tectona grandis, the primary structure of 17 differentially expressed transcription factors (TFs) was analyzed using the Information Spectrum Method. The data showed that it occurs as a physical interaction between the TgGATA1 and TgHSP1 TFs, in which TgGATA1 could possibly be an enhancer of the transcriptional regulation of TgHSP1 and acts in response to high light intensity and heat adaptation. Likewise, both of them could be related to the secondary xylem protection under stress conditions. Besides, the physical interaction between the TgNAC2 and TgMYB3 TFs could be involved in the transcriptional regulation of gene members belonging to the phenylpropanoid pathway under abiotic stress. Finally, these genes could play a fundamental role in the organization and development of the distinct parts that constitute the secondary xylem, cell wall, and sapwood. Consequently, it is possible that stress responses are integrated into a large gene regulatory network that determines the specification and differentiation of xylem cells in T. grandis.

Teak is known as one of the world’s premier hardwood tree species. However, despite the commercial interest and the large number of scientific investigations, comprehensive understanding on the genetic, molecular, and biochemical processes of this species has only recently begun to be explored. Functional genomics is the field of molecular biology that utilizes widespread combination of genetic information (e.g., enhancer DNA and non-coding RNA) and genome modification technologies to understand interactions between genes and functional regulatory elements. These technologies have emerged as a novel way to understand plant gene functions. Importance of teak has propelled various studies on transcriptomics and molecular genetics. In the last decade, transcriptomics of T. grandis of secondary wood, vegetative to flowering transition stage, and seedlings under water stress were documented. These transcriptomic studies have led to identification of genes involved in xylogenesis, production of secondary metabolites, flower formation, and drought stress. Teak transformation has not been fully achieved, but model plants are currently being used for studying several teak genes. Thus, future of functional genomics of teak is promising, particularly when the existing transcriptome data are used for wide range of analysis.

NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized inTectona grandis(teak), one of the hardwood trees of highest economic importance in the world. In this work, we characterized the novelTgNAC01gene, which is involved in signaling pathways that mediate teak response to stress. Abscisic acid (ABA) increasesTgNAC01expression in teak plants. Therefore, this gene may have a role in signaling events that mediate ABA-dependent osmotic stress responsive in this plant species. Stable expression in tobacco plants showed that the TgNAC01 protein is localized in the cell nucleus. Overexpression ofTgNAC01in two out three independent transgenic tobacco lines resulted in increased growth, leaf senescence and salt tolerance compared to wild type (WT) plants. Moreover, the stress tolerance of transgenic plants was affected by levels ofTgNAC01gene expression. Water potential, gas exchange and chlorophyll fluorescence were used to determine salt stress tolerance. The 35S:TgNAC01-6 line under 300 mM NaCl stress responded with a significant increase in photosynthesis rate, stomatal conductance, transpiration and carboxylation efficiency, but lower water potential compared to WT plants. The data indicate that theTgNAC01transcription factor acts as a transcriptional activator of the ABA-mediated regulation and induces leaf senescence.

Nine open-pollinated families of Picea glauca (Moench) Voss from the Region D1 Controlled Parentage Program (Alberta, Canada) were systematically chosen from fast, medium and slow-growth rankings based on breeding values for height from field progeny tests at age 30 years. Seeds from these families were sown and grown to age 3 years to analyze the performance and correlations of growth, physiological traits and expression of gibberellin-related genes, with and without elevated gibberellic acid 3 (GA3) application, under greenhouse conditions. We observed a significant interaction effect between families and growth groups subjected to 50 μg μl−1 of GA3 treatment, causing a decrease in apical internode length, diameter, volume and absolute transcript level for fast-growing families but an increase for families in the slow-growth group for the same traits. We also observed that in the apical internode, the gene PgGA20ox1 had significantly more relative expression under the elevated GA3 treatment than the control trees. In the stem, PgGA3ox1 showed a significantly higher relative expression under elevated GA3 treatment compared with control trees. Also, the slow-growth group showed more relative expression of PgGA20ox1 (in the apical internode) and PgGA3ox1 (in the stem) than the fast-growth group. The apical internode length and diameter significantly increased by 24% and 16%, respectively, with the hormone treatment in the slow growing group. In general, the PgGID1 and PgDELLA1 genes were upregulated and downregulated respectively, in spruce shoots under the GA3 treatment, meaning a positive feedback regulation by those genes were influencing PgGA20ox1 and PgGA3ox1 expression in that tissue type. Moreover, there was a significant correlation between absolute transcript levels of PgGA20ox1 in the apical internode and apical internode length, and absolute transcript levels of PgGA3ox1 in the stem and the diameter, in the fast-growth group families. This study shows that expression of GA genes is a limiting factor for growth in certain white spruce families with a complex feedback mechanism. Finally, absolute transcript levels of endogenous GA relative to growth parameters in juvenile seedlings could potentially be used to accelerate the early selection of families with inherently rapid apical and radial growth expansion.

O problema central analisado nessa investigação se constitui da seguinte pergunta: Quais são as características constitucionais e jurisprudenciais que sustentam a integração do Sistema Interamericano de Proteção aos Direitos Humanos, SIPDH no ordenamento jurídico interno? A jurisprudência internacional determina que os Estados estão efetivamente em capacidade de concluir que tipo de normas podem gerar direitos e obrigações relativas a suas relações com os particulares. Para isto é necessário realizar uma análise a partir dos postulados constitucionais e da jurisprudência da Corte Constitucional considerada intérprete da Carta Política, com a finalidade de observar o conceito vinculante do bloco de constitucionalidade na implementação do SIPDH consagrados pelo Pacto de São José da Costa Rica, no interior do Estado Colombiano.

Glyphosate quashes the synthesis of 5-enolpyruvylshikimate-3- phosphate synthase (EPSPS) enzyme which intercedes the functioning of shikimate pathway for the production of aromatic amino acids. Herbicide resistant crops are developed using glyphosate insensitive EPSPS gene isolated from Agrobacterium sp. strain CP4, which give farmers a sustainable weed control option. Intentions behind this study were to design and characterize the synthetic herbicide resistant CP4-EPSPS gene in a model plant system and check the effectiveness of transformed tobacco against application of glyphosate. Putative transgenic plants were obtained from independent transformation events, and stable plant transformation, transgene expression and integration were demonstrated respectively by PCR, qRT-PCR and Southern hybridization. Gene transcript level and gene copy number (1–4) varied among the tested transgenic tobacco lines. Herbicide assays showed that transgenic plants were resistant to glyphosate after 12 days of spraying with glyphosate, and EPSPS activity remained at sufficient level to withstand the spray at 1000 ppm of the chemical. T1 plants analyzed through immunoblot strips and PCR showed that the gene was being translated into protein and transmitted to the next generation successfully. This codon optimized synthetic CP4-EPSPS gene is functionally equivalent to the gene for glyphosate resistance available in the commercial crops and hence we recommend this gene for transformation into commercial crops.

Drought stress is an increasingly common and worrying phenomenon because it causes a loss of production in both agriculture and forestry. Teak is a tropical tree which needs alternating rainy and dry seasons to produce high-quality wood. However, a robust understanding about the physiological characteristics and genes related to drought stress in this species is lacking. Consequently, after applying moderate and severe drought stress to teak seedlings, an infrared gas analyzer (IRGA) was used to measure different parameters in the leaves. Additionally, using the root transcriptome allowed finding and analyzing the expression of several drought-related genes. As a result, in both water deficit treatments a reduction in photosynthesis, transpiration, stomatal conductance and leaf relative water content was found. As well, an increase in free proline levels and intrinsic water use efficiency was found when compared to the control treatment. Furthermore, 977 transcripts from the root contigs showed functional annotation related to drought stress, and of these, TgTPS1, TgDREB1, TgAREB1 and TgPIP1 were selected. The expression analysis of those genes along with TgHSP1, TgHSP2, TgHSP3 and TgBI (other stress-related genes) showed that with moderate treatment, TgTPS1, TgDREB1, TgAREB1, TgPIP1, TgHSP3 and TgBI genes had higher expression than the control treatment, but with severe treatment only TgTPS1 and TgDREB1 showed higher expression than the control treatment. At the end, a schematic model for the physiological and molecular strategies under drought stress in teak from this study is provided. In conclusion, these physiological and biochemical adjustments in leaves and genetic changes in roots under severe and prolonged water shortage situations can be a limiting factor for teak plantlets’ growth. Further studies of those genes under different biotic and abiotic stress treatments are needed.

The cinnamyl alcohol dehydrogenase (CAD) enzyme catalyzes the last step of monolignols synthesis in the lignin pathway. Tectona grandis (teak) is a tropical tree with high valuable tim­ber. As there is few genetic information about lignin formation in teak, the purpose of this study is to characterize members of CAD family in this species. As methodology, PCR amplification using cDNA samples, vector cloning, sequencing, bioinforma­tics analyses and gene expression studies using real time RT-qPCR were performed. As results, four members (TgCAD1- TgCAD4) were obtained. Comparative analyses showed that all of them have conserved residues for catalytic zinc action, structural zinc ligation, NADPH binding and substrate specifici­ty, consistent with the mechanism of alcohol dehydrogenases. Phylogenetic analysis showed that TgCADs are present in three main classes and seven groups. Expression analyses revealed that TgCAD1 was highly expressed in leaves and could be rela­ted with pathogen defense. TgCAD2 was more expressed in branches and roots. Differently, TgCAD3 and TgCAD4 were highly expressed in juvenile and mature sapwood, suggesting a crucial role in wood development and lignin biosynthesis, with tissue-specialized expression profiles. Furthermore, TgCAD4 could be related with teak maturation for being more expressed in sapwood of mature teak trees. As conclusion, this work is the first to characterize genes of CAD family in Tectona grandis. These genes could be interesting to develop transge­nic plants for basic research and field applications.

The aim of this study was to develop a shoot regeneration protocol for Tectona grandis by examining the effects of pretreatments, regeneration culture medium, adventitious rooting, and acclimatization. The best organogenic potential was achieved when hypocotyls and cotyledonary segments from seed - lings germinated on a medium containing TDZ, were cultured for four weeks on MS medium supplemented with BAP/GA 3 . With TDZ pretreatment during seed germination, up to 70% of the cotyledonary segments (0.5 TDZ pretreatment and 1.0 BAP + 0.5 GA 3 during regeneration, mg L -1 ) and 60% of the hypocotyl explants (0.1 TDZ pretreatment and 1.0 BAP + 0.5 GA 3 during regeneration, mg L -1 ) resulted in shoot regeneration. Finally, 65% of the regenerated shoots rooted, of which 60% were successfully acclimatized ex vitro. Our protocol increases regeneration efficiency for teak and it can serve as a platform for genetic transformation to improve this important tree species. Key words : Adventitious rooting, plant growth regulator, plant tissue culture, woody plant.

Weed resistance to herbicides is a natural phenomenon that exerts selection on individuals in a population. In Brazil, glyphosate resistance was recently detected in Digitaria insularis. The objective of this study was to elucidate mechanisms of weed resistance in this plant, including genetic variability, allelism, amino acid substitutions, gene expression, and enzymatic activity levels. Most of these have not previously been studied in this species. D. insularis DNA sequences were used to analyze genetic variability. cDNA from resistant and susceptible plants was used to identify mutations, alleles, and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) expression, using real-time quantitative reverse transcription-polymerase chain reaction. In addition, EPSPS activity was measured. We found a decrease in genetic variability between populations related to glyphosate application. Substitutions from proline to threonine and tyrosine to cysteine led to a decrease in EPSPS affinity for the glyphosate. In addition, the EPSPS enzymatic activity was slightly higher in resistant plants, whereas EPSPS gene expression was almost identical in both biotypes, suggesting feedback regulation at different levels. To conclude, our results suggest new molecular mechanisms used by D. insularis to increase glyphosate resistance.

Several Andean forests in the Guatape municipality and in the eastern Antioquia (Colombia) do not have studies related to population structures and environmental effects. The “San Benito” Forest has previously shown presence of several endangered species, including Godoya antioquensis, an endemic tree to the Antioquia region. The aim of the study is to describe population structures and environmental characteristics of this forest and the occurrence of this species. As methods, species type, Diameter at Breast Height (DBH) and Height (H) (in arboreal, bush and herbaceous layers), Temperature (T) and Relative Humidity (RH) were sampled. The Importance Value Index (IVI), Analysis of Variance (ANOVA), Multiple Comparison Tests, multivariate statistics, Relative abundance, Shannon-Wiener Diversity Index (H) and geostatistics were performed and analyzed. As a result, Tibouchina lepidota, Myrcia popayanensis and Scheffleraela chystocephala exhibited the highest IVI and significant relative abundance in several plots, being considered pioneer plants, followed by Cyathea sp., Croton magdalenensis and Godoya antioquensis with lower IVI. The Tukey Honest Significant difference (HSD) test and diameter classes modeling showed significant variation between the fifteen plots. According to the Principal Component Analysis (PCA) and Canonical Correspondence Analysis (CCA), the variables indicated homogeneous distribution patterns and a correlation between abundance, temperature and humidity in almost all plots, with the plots 8, 14 and 15 showing high diversity and relative abundance of species. Particularly, the plot 15 showed the highest “H” diversity value, the highest relative humidity and temperature and significant presence of G. antioquensis plants when comparing to other plots. Concluding: secondary succession studies are essential to understand population dynamics and environmental effects, to propose ecological restoration and to aid endangered species.

Teak tree (Tectona grandis L.f.) has a high value in the timber trade for fabrication of woody products due to its extraordinary qualities of color, density and durability. Despite the importance of this species, genetic and molecular studies available are limited. Also, the lack of molecular information about secondary xylem and tree maturation has hindered genetic exploration of teak. Therefore, gene expression studies and transcriptomic profiling are essential to explore wood formation and lignin biosynthesis through the development and aging of vascular plants. Aiming the gene expression studies, it was essential to identify and clone reference genes for teak. Eight genes were tested, commonly used in qRT-PCR, including TgRP60S, TgCAC, TgACT, TgHIS3, TgSAND, TgTUB, TgUBQ and TgEF1a. Expression profiles of these genes were evaluated by qRT-PCR in six tissue and organ samples (leaf, flower, seedling, root, stem and branch secondary xylem). Stability validation by NormFinder, BestKeeper, geNorm and Delta Ct programs showed that TgUBQ and TgEF1a are the most stable genes to use as qRT-PCR reference genes in teak in the conditions tested. Due to the availability of 12- and 60-year-old teak trees, RNA-seq was performed in diferent organs (seedlings, leaves, flowers, root, stem and branch secondary xylem). A total of 462,260 transcripts were obtained by assembling with \"Trinity\" software. Also, 1,502 and 931 genes differentially expressed were identified for stem and branch secondary xylem, respectively, using DESeq program, and MYB transcription factors, which were characterized. TgMYB1 amino acid sequence displayed a predicted coiled-coil (CC) motif while TgMYB2, TgMYB3 and TgMYB4 showed R2R3-MYB domain. All of them were phylogenetically grouped with several gymnosperms and flowering plants. High expression of TgMYB1 and TgMYB4 in lignified tissues of 60-year-old trees was observed. In this work, the Cinnamyl Alcohol Dehydrogenase (CAD) gene family was also studied. One complete (TgCAD1) and three partial (TgCAD2 to TgCAD4) members were characterized. The four enzymes presented residues for catalytic and structural zinc action, NADPH binding and substrate specificity, consistent with the mechanism of alcohol dehydrogenases. TgCAD3 and TgCAD4 were highly expressed in young and mature sapwood and seem to be duplicated and highly related with lignin biosynthesis. Tree genetic improvement, marker-assisted selection and plant transformation seem to be promising lines of research for the data obtained from this research. This is the first study addressing gene characterization and expression, phylogeny and transcriptomic profiling in teak. A árvore de teca (Tectona grandis L.f.) tem alto valor no comércio de madeira para a fabricação de produtos lenhosos, devido às suas qualidades extraordinárias de cor, densidade e durabilidade. Apesar da importância desta espécie, são poucos os estudos genéticos e moleculares disponíveis. Também, a falta de informação molecular sobre xilema secundário e maturação da árvore tem dificultado a exploração genética de teca. Assim, estudos de expressão gênica e perfis transcricionais são relevantes para explorar a formação da madeira e a biossíntese de lignina durante o desenvolvimento e envelhecimento das plantas vasculares. Visando os estudos de expressão gênica, foi essencial identificar e clonar genes de referencia para a teca. Foram testados oito genes comumente usados em qRT-PCR, TgRP60S, TgCAC, TgACT, TgHIS3, TgSAND, TgTUB, TgUBQ e TgEF1a. Perfis de expressão destes genes foram avaliados por qRT-PCR em seis amostras de tecidos e órgãos (folhas, flores, plântulas, raiz, xilema secundário de caule e ramo). A validação da estabilidade pelos programas NormFinder, BestKeeper, geNorm e Delta CT mostrou que TgUBQ e TgEF1a são os genes mais estáveis para usar como genes de referência em teca nas condições testadas. Em virtude da disponibilidade de árvores de teca de diferentes idades, entre 12 e 60 anos, foi realizado o RNAseq de diferentes órgãos (plântulas, folhas, flores, raiz, ramos e caules de árvores de 12 e 60 anos). Obteve-se um total de 462.260 transcritos pela montagem com o software \"Trinity\". Foram identificados 1.502 e 931 genes diferencialmente expressos para xilema secundário de caule e ramo, respectivamente, utilizando o programa DESeq e fatores de transcrição MYB, que foram posteriormente caracterizados. A sequência de aminoácidos do TgMYB1 exibiu um motivo \"coiled-coil\" (CC), enquanto TgMYB2, TgMYB3 e TgMYB4 mostraram domínio R2R3-MYB. Todos eles foram filogeneticamente agrupados com várias gimnospermas e angiospermas. Observou-se alta expressão do TgMYB1 e TgMYB4 em tecidos lignificados de árvores de 60 anos de idade. Neste trabalho também foi estudada a família gênica Cinamil álcool desidrogenase (CAD). Foi caracterizado um membro completo (TgCAD1) e três parciais (TgCAD2 a TgCAD4). As quatro enzimas apresentaram resíduos de ação catalítica e estrutural de zinco, de ligação ao NADPH e de especificidade de substrato, em conformidade com o mecanismo conservado de álcool desidrogenases. TgCAD3 e TgCAD4 foram altamente expressos no alburno jovem e maduro e parecem estar duplicados e relacionados com a biossíntese de lignina. O melhoramento genético de árvores, a seleção assistida utilizando marcadores moleculares e a transformação de plantas parecem ser linhas promissoras de pesquisa, a partir dos dados obtidos nesta pesquisa. Este é o primeiro estudo sobre caracterização e expressão gênica, filogenia e perfis transcricionais em teca.

Made available in DSpace on 2022-04-28T19:02:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Sourgrass(Digitaria insularis, L. Mez ex Ekman) is a weed that requires high rates of glyphosate ((N-[phosphonomethyl]-glycine) forcontrol, verylittle of the herbicide applied isabsorbed by theleaves. Morphological and histological differences in leaves of glyphosate-resistant and glyphosate-susceptible plantsshould explain the contrast of variance between herbicide susceptibility. Leaves of different growth and phenological stages were collected and submitted to histological and electron microscopy scanning analysis. Those plants were also submitted to a glyphosate dose-response curve analysis. The results suggest thatbiotypes exhibits differences infoliar structures that can influence the uptake and translocation of glyphosate. A thinparenchyma, lesser distance amongvascular bundles, and higher phloem sizewere found in resistant biotypes (differences close to 10%). Minor stomata number and higher epicuticular waxy deposition in stomata and leaf surface were found in resistant plants when leaves came from regrowth, leading to a possiblelesser herbicide absorption. Resistant plants showed absence of trichomes in late stages of development (64% less trichomes than susceptible plants). The higher concentration of trichomes in susceptible plants can be an absorption pathfor glyphosate getthrough the cuticle. Universidade Estadual Paulista Universidade de São Paulo Universidade Federal do Paraná Universidade Estadual Paulista

Background Currently, Tectona grandis is one of the most valuable trees in the world and no transcript dataset related to secondary xylem is available. Considering how important the secondary xylem and sapwood transition from young to mature trees is, little is known about the expression differences between those successional processes and which transcription factors could regulate lignin biosynthesis in this tropical tree. Although MYB transcription factors are one of the largest superfamilies in plants related to secondary metabolism, it has not yet been characterized in teak. These results will open new perspectives for studies of diversity, ecology, breeding and genomic programs aiming to understand deeply the biology of this species. Results We present a widely expressed gene catalog for T. grandis using Illumina technology and the de novo assembly. A total of 462,260 transcripts were obtained, with 1,502 and 931 genes differentially expressed for stem and branch secondary xylem, respectively, during age transition. Analysis of stem and branch secondary xylem indicates substantial similarity in gene ontologies including carbohydrate enzymes, response to stress, protein binding, and allowed us to find transcription factors and heat-shock proteins differentially expressed. TgMYB1 displays a MYB domain and a predicted coiled-coil (CC) domain, while TgMYB2, TgMYB3 and TgMYB4 showed R2R3-MYB domain and grouped with MYBs from several gymnosperms and flowering plants. TgMYB1, TgMYB4 and TgCES presented higher expression in mature secondary xylem, in contrast with TgMYB2, TgHsp1, TgHsp2, TgHsp3, and TgBi whose expression is higher in young lignified tissues. TgMYB3 is expressed at lower level in secondary xylem. Conclusions Expression patterns of MYB transcription factors and heat-shock proteins in lignified tissues are dissimilar when tree development was evaluated, obtaining more expression of TgMYB1 and TgMYB4 in lignified tissues of 60-year-old trees, and more expression in TgHsp1, TgHsp2, TgHsp3 and TgBi in stem secondary xylem of 12-year-old trees. We are opening a door for further functional characterization by reverse genetics and marker-assisted selection with those genes. Investigation of some of the key regulators of lignin biosynthesis in teak, however, could be a valuable step towards understanding how rigidity of teak wood and extractives content are different from most other woods. The obtained transcriptome data represents new sequences of T. grandis deposited in public databases, representing an unprecedented opportunity to discover several related-genes associated with secondary xylem such as transcription factors and stress-related genes in a tropical tree. Electronic supplementary material The online version of this article (doi:10.1186/s12870-015-0599-x) contains supplementary material, which is available to authorized users.

Background Teak (Tectona grandis L.f.) is currently the preferred choice of the timber trade for fabrication of woody products due to its extraordinary qualities and is widely grown around the world. Gene expression studies are essential to explore wood formation of vascular plants, and quantitative real-time reverse transcription PCR (qRT-PCR) is a sensitive technique employed for quantifying gene expression levels. One or more appropriate reference genes are crucial to accurately compare mRNA transcripts through different tissues/organs and experimental conditions. Despite being the focus of some genetic studies, a lack of molecular information has hindered genetic exploration of teak. To date, qRT-PCR reference genes have not been identified and validated for teak. Results Identification and cloning of nine commonly used qRT-PCR reference genes from teak, including ribosomal protein 60s (rp60s), clathrin adaptor complexes medium subunit family (Cac), actin (Act), histone 3 (His3), sand family (Sand), β-Tubulin (Β-Tub), ubiquitin (Ubq), elongation factor 1-α (Ef-1α), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Expression profiles of these genes were evaluated by qRT-PCR in six tissue and organ samples (leaf, flower, seedling, root, stem and branch secondary xylem) of teak. Appropriate gene cloning and sequencing, primer specificity and amplification efficiency was verified for each gene. Their stability as reference genes was validated by NormFinder, BestKeeper, geNorm and Delta Ct programs. Results obtained from all programs showed that TgUbq and TgEf-1α are the most stable genes to use as qRT-PCR reference genes and TgAct is the most unstable gene in teak. The relative expression of the teak cinnamyl alcohol dehydrogenase (TgCAD) gene in lignified tissues at different ages was assessed by qRT-PCR, using TgUbq and TgEf-1α as internal controls. These analyses exposed a consistent expression pattern with both reference genes. Conclusion This study proposes a first broad collection of teak tissue and organ mRNA expression data for nine selected candidate qRT-PCR reference genes. NormFinder, Bestkeeper, geNorm and Delta Ct analyses suggested that TgUbq and TgEf-1α have the highest expression stability and provided similar results when evaluating TgCAD gene expression, while the commonly used Act should be avoided.