Gradients in embolism resistance within stems driven by secondary growth in herbs.

The stems of some herbaceous species can undergo basal secondary growth, leading to a continuum in the degree of woodiness along the stem. Whether the formation of secondary growth in the stem base results in differences in embolism resistance between the base and the upper portions of stems is unknown. We assessed the embolism resistance of leaves and the basal and upper portions of stems simultaneously within the same individuals of two divergent herbaceous species that undergo secondary growth in the mature stem bases. The species were Solanum lycopersicum (tomato) and Senecio minimus (fireweed). Basal stem in mature plants of both species displayed advanced secondary growth and greater resistance to embolism than the upper stem. This also resulted in significant vulnerability segmentation between the basal stem and the leaves in both species. Greater embolism resistance in the woodier stem base was found alongside decreases in the pith-to-xylem ratio, increases in the proportion of secondary xylem, and increases in lignin content. We show that there can be considerable variation in embolism resistance across the stem in herbs and that this variation is linked to the degree of secondary growth present. A gradient in embolism resistance across the stem in herbaceous plants could be an adaptation to ensure reproduction or basal resprouting during episodes of drought late in the lifecycle.

Blue light photoreceptor cryptochrome 1 promotes wood formation and anthocyanin biosynthesis in Populus.

Blue light photoreceptor cryptochrome 1 (CRY1) in herbaceous plants plays crucial roles in various developmental processes, including cotyledon expansion, hypocotyl elongation and anthocyanin biosynthesis. However, the function of CRY1 in perennial trees is unclear. In this study, we identified two ortholog genes of CRY1 (PagCRY1a and PagCRY1b) from Populus, which displayed high sequence similarity to Arabidopsis CRY1. Overexpression of PagCRY1 substantially inhibited plant growth and promoted secondary xylem development in Populus, while CRISPR/Cas9-mediated knockout of PagCRY1 enhanced plant growth and delayed secondary xylem development. Moreover, overexpression of PagCRY1 dramatically increased anthocyanin accumulation. The further analysis supported that PagCRY1 functions specifically in response to blue light. Taken together, our results demonstrated that modulating the expression of blue light photoreceptor CRY1 ortholog gene in Populus could significantly influence plant biomass production and the process of wood formation, laying a foundation for further investigating the light-regulated tree growth.

Transcriptome and miRNAs Profiles Reveal Regulatory Network and Key Regulators of Secondary Xylem Formation in "84K" Poplar.

Secondary xylem produced by stem secondary growth is the main source of tree biomass and possesses great economic and ecological value in papermaking, construction, biofuels, and the global carbon cycle. The secondary xylem formation is a complex developmental process, and the underlying regulatory networks and potential mechanisms are still under exploration. In this study, using hybrid poplar (Populus alba × Populus glandulosa clone 84K) as a model system, we first ascertained three representative stages of stem secondary growth and then investigated the regulatory network of secondary xylem formation by joint analysis of transcriptome and miRNAs. Notably, 7507 differentially expressed genes (DEGs) and 55 differentially expressed miRNAs (DEMs) were identified from stage 1 without initiating secondary growth to stage 2 with just initiating secondary growth, which was much more than those identified from stage 2 to stage 3 with obvious secondary growth. DEGs encoding transcription factors and lignin biosynthetic enzymes and those associated with plant hormones were found to participate in the secondary xylem formation. MiRNA-target analysis revealed that a total of 85 DEMs were predicted to have 2948 putative targets. Among them, PagmiR396d-PagGRFs, PagmiR395c-PagGA2ox1/PagLHW/PagSULTR2/PagPolyubiquitin 1, PagmiR482d-PagLAC4, PagmiR167e-PagbHLH62, and PagmiR167f/g/h-PagbHLH110 modules were involved in the regulating cambial activity and its differentiation into secondary xylem, cell expansion, secondary cell wall deposition, and programmed cell death. Our results give new insights into the regulatory network and mechanism of secondary xylem formation.

A novel method for age identification of mountain-cultivated ginseng.

Panax ginseng, a slow-growing perennial herb, is the most praised and popular traditional medicinal herb. Mountain-cultivated ginseng (MCG) and cultivated ginseng (CG) both belong to Panax ginseng C. A. Meyer. The market price and medical effects of this popular health product are closely related to its age. It is widely acknowledged that CG is typically harvested after 4-6 years of growth, but MCG is often collected after 10 years. Until now, the age identification of MCG or mountain wild ginseng (MWG) has remained a major challenge. In this study, we established a novel and rapid method for staining xylem vessels with phloroglucinol and identifying the "annual growth rings" of ginseng by utilizing a stereoscope, which serves as a reliable indicator of the age of MCG. Statistical analysis of the ring radius and the ring density of MCG aged from 1 to 20 years shows that the secondary xylem of MCG increases rapidly in the first 3 years but then gradually slows down from 4 to 10 years, and minor fluctuation is observed in the next 10 years. Meanwhile, the space between the growth rings (ring density) becomes increasingly small with age. This straightforward staining approach can reveal the age of MCG with remarkable clarity and can distinguish MCG from CG. RESEARCH HIGHLIGHTS: A novel rapid staining method for Panax ginseng was established. The age of mountain-cultivated ginseng (MCG) can be identified by microscopic techniques. MCG and cultivated ginseng (CG) can be discriminated by microstructure characteristics.

MiR395c Regulates Secondary Xylem Development Through Sulfate Metabolism in Poplar.

Secondary xylem development requires the coordination of multiple regulatory factors, including plant hormones, transcription factors, and microRNAs (miRNAs). MiR395 is an important regulator involved in sulfate metabolism, but its function in plant development is unclear. This study investigated the functions of miR395c in the secondary xylem development in Populus alba × P. glandulosa. MiR395c was highly expressed in the shoot apex and secondary xylem. The overexpression of miR395c resulted in an increase in both secondary xylem width and vessel dimension, as well as a decrease in the thickness of the secondary cell wall of the xylem fiber. Further analysis showed that miR395c inhibited biosynthesis of sulfate metabolic products by targeting ATPS genes, which led to the reduction of Abscisic acid (ABA) synthesis and down-regulation of MYB46 expression. Our results indicate that miR395c regulates the secondary xylem development process via sulfate metabolism in Populus.

Integrated Degradome and Srna Sequencing Revealed miRNA-mRNA Regulatory Networks between the Phloem and Developing Xylem of Poplar.

Lignin and cellulose are the most abundant natural organic polymers in nature. MiRNAs are a class of regulatory RNAs discovered in mammals, plants, viruses, and bacteria. Studies have shown that miRNAs play a role in lignin and cellulose biosynthesis by targeting key enzymes. However, the specific miRNAs functioning in the phloem and developing xylem of Populus deltoides are still unknown. In this study, a total of 134 miRNAs were identified via high-throughput small RNA sequencing, including 132 known and two novel miRNAs, six of which were only expressed in the phloem. A total of 58 differentially expressed miRNAs (DEmiRNAs) were identified between the developing xylem and the phloem. Among these miRNAs, 21 were significantly upregulated in the developing xylem in contrast to the phloem and 37 were significantly downregulated. A total of 2431 target genes of 134 miRNAs were obtained via high-throughput degradome sequencing. Most target genes of these miRNAs were transcription factors, including AP2, ARF, bHLH, bZIP, GRAS, GRF, MYB, NAC, TCP, and WRKY genes. Furthermore, 13 and nine miRNAs were involved in lignin and cellulose biosynthesis, respectively, and we validated the miRNAs via qRT-PCR. Our study explores these miRNAs and their regulatory networks in the phloem and developing xylem of P.deltoides and provides new insight into wood formation.

Overexpression of EgrIAA20 from Eucalyptus grandis, a Non-Canonical Aux/IAA Gene, Specifically Decouples Lignification of the Different Cell-Types in Arabidopsis Secondary Xylem.

Wood (secondary xylem) formation is regulated by auxin, which plays a pivotal role as an integrator of developmental and environmental cues. However, our current knowledge of auxin-signaling during wood formation is incomplete. Our previous genome-wide analysis of Aux/IAAs in Eucalyptus grandis showed the presence of the non-canonical paralog member EgrIAA20 that is preferentially expressed in cambium. We analyzed its cellular localization using a GFP fusion protein and its transcriptional activity using transactivation assays, and demonstrated its nuclear localization and strong auxin response repressor activity. In addition, we functionally tested the role of EgrIAA20 by constitutive overexpression in Arabidopsis to investigate for phenotypic changes in secondary xylem formation. Transgenic Arabidopsis plants overexpressing EgrIAA20 were smaller and displayed impaired development of secondary fibers, but not of other wood cell types. The inhibition in fiber development specifically affected their cell wall lignification. We performed yeast-two-hybrid assays to identify EgrIAA20 protein partners during wood formation in Eucalyptus, and identified EgrIAA9A, whose ortholog PtoIAA9 in poplar is also known to be involved in wood formation. Altogether, we showed that EgrIAA20 is an important auxin signaling component specifically involved in controlling the lignification of wood fibers.

Control of cambium initiation and activity in Arabidopsis by the transcriptional regulator AHL15.

Plant secondary growth, which is the basis of wood formation, includes the production of secondary xylem, which is derived from meristematic cambium cells embedded in vascular tissue. Here, we identified an important role for the Arabidopsis thaliana (Arabidopsis) AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED 15 (AHL15) transcriptional regulator in controlling vascular cambium activity. The limited secondary xylem development in inflorescence stems of herbaceous Arabidopsis plants was significantly reduced in ahl15 loss-of-function mutants, whereas constitutive or vascular meristem-specific AHL15 overexpression produced woody inflorescence stems. AHL15 was required for enhanced secondary xylem formation in the woody suppressor of overexpression of constans 1 (soc1) fruitfull (ful) double loss-of-function mutant. Moreover, we found that AHL15 induces vascular cambium activity downstream of the repressing SOC1 and FUL transcription factors, most likely similar to how it enhances lateral branching by promoting biosynthesis of the hormone cytokinin. Our results uncover a novel pathway driving cambium development, in which AHL15 expression levels act in parallel to and are dependent on the well-established TDIF-PXY-WOX pathway to differentiate between herbaceous and woody stem growth.

Dimerization of PtrMYB074 and PtrWRKY19 mediates transcriptional activation of PtrbHLH186 for secondary xylem development in Populus trichocarpa.

Wood formation is controlled by transcriptional regulatory networks (TRNs) involving regulatory homeostasis determined by combinations of transcription factor (TF)-DNA and TF-TF interactions. Functions of TF-TF interactions in wood formation are still in the early stages of identification. PtrMYB074 is a woody dicot-specific TF in a TRN for wood formation in Populus trichocarpa. Here, using yeast two-hybrid and bimolecular fluorescence complementation, we conducted a genome-wide screening for PtrMYB074 interactors and identified 54 PtrMYB074-TF pairs. Of these pairs, 53 are novel. We focused on the PtrMYB074-PtrWRKY19 pair, the most highly expressed and xylem-specific interactor, and its direct transregulatory target, PtrbHLH186, the xylem-specific one of the pair's only two direct TF target genes. Using transient and CRISPR-mediated transgenesis in P. trichocarpa coupled with chromatin immunoprecipitation and electrophoretic mobility shift assays, we demonstrated that PtrMYB074 is recruited by PtrWRKY19 and that the PtrMYB074-PtrWRKY19 dimers are required to transactive PtrbHLH186. Overexpressing PtrbHLH186 in P. trichocarpa resulted in retarded plant growth, increased guaiacyl lignin, a higher proportion of smaller stem vessels and strong drought-tolerant phenotypes. Knowledge of the PtrMYB074-PtrWRKY19-PtrbHLH186 regulation may help design genetic controls of optimal growth and wood formation to maximize beneficial wood properties while minimizing negative effects on growth.

Seasonal changes in cambium activity from active to dormant stage affect the formation of secondary xylem in Pinus tabulaeformis Carr.

Understanding the changing patterns of vascular cambium during seasonal cycles is crucial to reveal the mechanisms that control cambium activity and wood formation, but this area has been underexplored, especially in conifers. Here, we quantified the changing cellular morphology patterns of cambial zones during the active, transition and dormant stages. With the help of toluidine blue and periodic acid-Schiff staining to visualize cell walls and identify their constituents, we observed decreasing cambial cell layers, thickening of newly formed xylem cell walls and increased polysaccharide granules in phloem from June to the following March over the course of our collecting period. Pectin immunofluorescence showed that dormant-stage cambium can produce highly abundant de-esterified homogalacturonan and (1-4)-ß-d-galactan epitopes, whereas active cambium can strong accumulate high methylesterified homogalacturonan. Calcofluor white staining and confocal Raman spectroscopy analysis revealed regular changes in the chemical composition of cell walls, such as relative lower cellulose deposition in transition stage in vascular cambium, and higher lignin accumulation was found in dormant stage in secondary xylem. Moreover, real-time quantitative polymerase chain reaction analysis suggested that various IAA (Aux/IAA protein), CesA, CslA and HDZ genes, as well as NAC, PME3 and PME4, may be involved in cambium activities and secondary xylem formation. Taken together, these findings provide new information about cambium activity and cell differentiation in the formation, structure and chemistry in conifers during the active-dormant transition.

Exogenous Brassinosteroid Facilitates Xylem Development in Pinus massoniana Seedlings.

Brassinosteroids (BRs) are known to be essential regulators for wood formation in herbaceous plants and poplar, but their roles in secondary growth and xylem development are still not well-defined, especially in pines. Here, we treated Pinus massoniana seedlings with different concentrations of exogenous BRs, and assayed the effects on plant growth, xylem development, endogenous phytohormone contents and gene expression within stems. Application of exogenous BR resulted in improving development of xylem more than phloem, and promoting xylem development in a dosage-dependent manner in a certain concentration rage. Endogenous hormone determination showed that BR may interact with other phytohormones in regulating xylem development. RNA-seq analysis revealed that some conventional phenylpropanoid biosynthesis- or lignin synthesis-related genes were downregulated, but the lignin content was elevated, suggesting that new lignin synthesis pathways or other cell wall components should be activated by BR treatment in P. massoniana. The results presented here reveal the foundational role of BRs in regulating plant secondary growth, and provide the basis for understanding molecular mechanisms of xylem development in P. massoniana.

The transcription factor PagLBD3 contributes to the regulation of secondary growth in Populus.

LATERAL ORGAN BOUNDARIES DOMAIN (LBD) genes encode plant-specific transcription factors that participate in regulating various developmental processes. In this study, we genetically characterized PagLBD3 encoding an important regulator of secondary growth in poplar (Populus alba × Populus glandulosa). Overexpression of PagLBD3 increased stem secondary growth in Populus with a significantly higher rate of cambial cell differentiation into phloem, while dominant repression of PagLBD3 significantly decreased the rate of cambial cell differentiation into phloem. Furthermore, we identified 1756 PagLBD3 genome-wide putative direct target genes (DTGs) through RNA sequencing (RNA-seq)-coupled DNA affinity purification followed by sequencing (DAP-seq) assays. Gene Ontology analysis revealed that genes regulated by PagLBD3 were enriched in biological pathways regulating meristem development, xylem development, and auxin transport. Several central regulator genes for vascular development, including PHLOEM INTERCALATED WITH XYLEM (PXY), WUSCHEL RELATED HOMEOBOX4 (WOX4), Secondary Wall-Associated NAC Domain 1s (SND1-B2), and Vascular-Related NAC-Domain 6s (VND6-B1), were identified as PagLBD3 DTGs. Together, our results indicate that PagLBD3 and its DTGs form a complex transcriptional network to modulate cambium activity and phloem/xylem differentiation.

Identification and characterization of circular RNAs during wood formation of poplars in acclimation to low nitrogen availability.

MAIN CONCLUSION: Circular RNA (circRNA) identification and expression profiles, and construction of circRNAs-miRNAs-mRNAs networks indicates that circRNAs are involved in wood formation of poplars in acclimation to low nitrogen availability. Circular RNAs (circRNAs) are covalently closed non-coding RNAs that play pivotal roles in various biological processes. However, circRNAs' roles in wood formation of poplars in acclimation to low nitrogen (N) availability are currently unknown. Here, we undertook a systematic identification and characterization of circRNAs in the wood of Populus × canescens exposed to either 50 (low N) or 500 (normal N) µM NH4NO3 using rRNA-depleted RNA-sequencing. A total of 2,509 unique circRNAs were identified, and 163 (ca. 6.5%) circRNAs were significantly differentially expressed (DE) under low N condition. We observed a positive correlation between the expression patterns of DE circRNAs and their hosting protein-coding genes. Moreover, circRNAs-miRNAs-mRNAs' networks were identified in the wood of poplars under low N availability. For instance, upregulated several circRNAs, such as circRNA1226, circRNA 1732, and circRNA392 induced increases in nuclear factor Y, subunit A1-A (NFYA1-A), NFYA1-B, and NFYA10 transcript levels via the mediation of miR169b members, which is in line with reduced xylem width and cell layers of the xylem in the wood of low N-supplied poplars. Upregulation of circRNA1006, circRNA1344, circRNA1941, circRNA901, and circRNA146 caused increased transcript level of MYB61 via the mediation of a miR5021 member, corresponding well to the higher lignin concentration in the wood of low N-treated poplars. Overall, these results indicated that DE circRNAs play an essential role in regulating gene expression via circRNAs-miRNAs-mRNAs' networks to modulate wood anatomical and chemical properties of poplars in acclimation to low N availability.

Using the CODIT model to explain secondary metabolites of xylem in defence systems of temperate trees against decay fungi.

BACKGROUND: In trees, secondary metabolites (SMs) are essential for determining the effectiveness of defence systems against fungi and why defences are sometimes breached. Using the CODIT model (Compartmentalization of Damage/Dysfunction in Trees), we explain defence processes at the cellular level. CODIT is a highly compartmented defence system that relies on the signalling, synthesis and transport of defence compounds through a three-dimensional lattice of parenchyma against the spread of decay fungi in xylem. SCOPE: The model conceptualizes 'walls' that are pre-formed, formed during and formed after wounding events. For sapwood, SMs range in molecular size, which directly affects performance and the response times in which they can be produced. When triggered, high-molecular weight SMs such as suberin and lignin are synthesized slowly (phytoalexins), but can also be in place at the time of wounding (phytoanticipins). In contrast, low-molecular weight phenolic compounds such as flavonoids can be manufactured de novo (phytoalexins) rapidly in response to fungal colonization. De novo production of SMs can be regulated in response to fungal pathogenicity levels. The protective nature of heartwood is partly based on the level of accumulated antimicrobial SMs (phytoanticipins) during the transitionary stage into a normally dead substance. Effectiveness against fungal colonization in heartwood is largely determined by the genetics of the host. CONCLUSION: Here we review recent advances in our understanding of the role of SMs in trees in the context of CODIT, with emphasis on the relationship between defence, carbohydrate availability and the hydraulic system.We also raise the limitations of the CODIT model and suggest its modification, encompassing other defence theory concepts. We envisage the development of a new defence system that is modular based and incorporates all components (and organs) of the tree from micro- to macro-scales.

Competing Endogenous RNA Networks Underlying Anatomical and Physiological Characteristics of Poplar Wood in Acclimation to Low Nitrogen Availability.

Although poplar plantations are often established on nitrogen (N)-poor soil, the physiological and molecular mechanisms underlying wood properties of poplars in acclimation to low N availability remain largely unknown. To investigate wood properties of poplars in acclimation to low N, Populus � canescens saplings were exposed to either 50 (low N) or 500 (normal N) �M NH4NO3 for 2 months. Low N resulted in decreased xylem width and cell layers of the xylem (the number of cells counted along the ray parenchyma on the stem cross section), narrower lumina of vessels and fibers, greater thickness of double fiber walls (the walls between two adjacent fiber cells), more hemicellulose and lignin deposition, and reduced cellulose accumulation in poplar wood. Consistently, concentrations of gibberellins involved in cell size determination and the abundance of various metabolites including amino acids, carbohydrates and precursors for cell wall biosynthesis were decreased in low N-supplied wood. In line with these anatomical and physiological changes, a number of mRNAs, long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) were significantly differentially expressed. Competing endogenous RNA regulatory networks were identified in the wood of low N-treated poplars. Overall, these results indicate that miRNAs-lncRNAs-mRNAs networks are involved in regulating wood properties and physiological processes of poplars in acclimation to low N availability.

Wood anatomy of two species of the genus Chrysochlamys (Clusiaceae: Clusioideae: Clusieae) from the northern Andes of Colombia.

Chrysochlamys is a genus of neotropical angiosperms distributed in wet and riparian forests from Bolivia to Mexico in altitudes from near sea-level to close to 3000 m. The wood anatomy of two species of the genus was investigated. Branches of mature stems were collected in a secondary wet forest in Colombian Northern Andes. Slides were obtained and visualized using light microscopy. Gelatinous fiber bands were found and described in C. colombiana and C. dependens. There was a higher amount of septate fibers in the latter. Average ray height and pigment deposit content in ray cells was greater in C. colombiana relative to C. dependens, but rays were commonly wider in the second one. The diversity of vessel-ray pit shapes in C. dependens is greater than in C. colombiana. In both cases rays are considered to be paedomorphic type I. Scanty to absent axial and apotracheal parenchyma was found for both species. We discuss the similarities and differences of the two species in order to establish diagnostic wood features. Also we include brief notes in comparative anatomy with other members of the Clusieaceae family, emphasizing in the incongruences found with previous reports for the genus. This is the first descriptive work in wood anatomy of C. colombiana and C. dependens.

Phosphorylation of LTF1, an MYB Transcription Factor in Populus, Acts as a Sensory Switch Regulating Lignin Biosynthesis in Wood Cells.

Lignin is specifically deposited in plant secondary cell walls, and initiation of lignin biosynthesis is regulated by a variety of developmental and environmental signals. However, the mechanisms governing the regulation of lignin biosynthesis remain to be elucidated. In this study, we identified a lignin biosynthesis-associated transcription factor (LTF) from Populus, LTF1, which binds the promoter of a key lignin biosynthetic gene encoding 4-coumarate-CoA ligase (4CL). We showed that LTF1 in its unphosphorylated state functions as a regulator restraining lignin biosynthesis. When LTF1 becomes phosphorylated by PdMPK6 in response to external stimuli such as wounding, it undergoes degradation through a proteasome pathway, resulting in activation of lignification. Expression of a phosphorylation-null mutant version of LTF1 led to stable protein accumulation and persistent attenuation of lignification in wood cells. Taken together, our study reveals a mechanism whereby LTF1 phosphorylation acts as a sensory switch to regulate lignin biosynthesis in response to environmental stimuli. The discovery of novel modulators and mechanisms modifying lignin biosynthesis has important implications for improving the utilization of cell-wall biomass.

Endocytosis acts as transport pathway in wood.

In trees, dead and living cells of secondary xylem (wood) function collectively, rendering cell-to-cell communication challenging. Water and solutes are transported over long distances from the roots to the above-ground organs via vessels, the main component of wood, and then radially over short distances to the neighboring cells. This enables proper functioning of trees and integrates whole-plant activity. In this study, tracer loading, immunolocalization experiments and inhibitor assays were used to decipher the mechanisms enabling transport in wood of Acer pseudoplatanus (maple), Fraxinus excelsior (ash) and Populus tremula × tremuloides (poplar) trees. We show that tracer uptake from dead water-conducting vessels, elements of the apoplasm, to living vessel-associated cells (VACs) of the xylem parenchyma of the symplasm system proceeds via the endocytic pathway, including clathrin-mediated and clathrin-independent processes. These findings enhance our understanding of the transport pathways in complex wood tissue, providing experimental evidence of the involvement of VACs and endocytosis in radial uptake from vessels.

ANÁLISIS in silico Y EXPRESIÓN GÉNICA DEL FACTOR DE TRANSCRIPCIÓN TgNACO1 IMPLICADO EN XILOGÉNESIS Y ESTRÉS ABIÓTICO EN Tectona grandis / In silico Analysis and Gene Expression of TgNACO1 Transcription Factor Involved in Xylogenesis and Abiotic Stress in Tectona grandis

RESUMEN El xilema secundario es el componente más abundante de la biomasa vegetal. Por tanto, conocer los genes que regulan su formación ayudaría a diseñar estrategias para el mejoramiento genético de la madera. Así, el objetivo de este trabajo fue realizar el análisis computacional de la estructura primaria y secundaria del factor de transcripción (FT) TgNACO1 de Tectona grandis, además de evaluar su historia evolutiva, dominios conservados y expresión génica en tejidos lignificados de árboles de 12 y 60 años. Para ello, se realizó una evaluación del potencial de interacción ion-electrón (PIIE), mediante el método del espectro de la información (MEI) utilizando la librería SFAPS de R-Project, seguido del modelamiento estructural utilizando el software MODELLER y visualizado mediante PyMol. Además, el análisis de alineamiento de secuencia múltiple y filogenia fue mediante el software Bioedit y MrBayes respectivamente. También se evaluó los niveles de síntesis del FT TgNACO1 mediante qRT-PCR. Como resultados, se evidenció que el FT mantiene una estructura (3-hoja antiparalela retorcida, que se compacta contra una a-hélice en la región N-terminal, teniendo así tres dominios a hélice y siete dominios (3 plegada. Asimismo, mediante el MEI se demostró que tiene alrededor de cinco funciones biológicas y mutaciones sobre los aminoácidos con mayor PIIE, lo que conlleva a evoluciones sobre las redes de regulación genética. Finalmente, el FT TgNACO1 podría presentar un papel fundamental en la organización y desarrollo de las partes que componen la albura, como las células radiales de la zona cambial, los vasos, fibras y los anillos de crecimiento.

ABSTRACT Secondary xylem is the most abundant component of plant biomass. Therefore, knowing the genes that regulate its formation would help to design strategies for wood genetic improvement. Thus, the objective of this work was to perform computational analysis of the primary and secondary structure of the TgNACO1 transcription factor (FT) of Tectona grandis, and to evaluate its evolutionary history, conserved domains and gene expression in lignified tissues of trees with 12 and 60 years old. For this, an ion-electron interaction potential (IEP) was evaluated using the information-spectrum method (IEM) using the R-Project and SFAPS library, followed by structural modeling using the MODELLER software and visualized by PyMol program. In addition, the analysis of multiple sequence alignment and phylogeny was performed using Bioedit and MrBayes software, respectively. We also evaluated the qRT-PCR levels of TgNACO1. As results, it was found that TgNACO1 maintains a twisted antiparallel 3-sheet structure, which is compacted against an a-helix in the N-terminal region, having three a-helix domains and seven folded ((-domains. Also, through the IEM, it was demonstrated that it has about five biological functions, and mutations on amino acids with higher IEP, which leads to evolutions on genetic regulation networks. Finally, the FT TgNACO1 could play an esential role in the organization and development of the parts that make up the sapwood, such as the radial cells of the cambial zone, the vessels, fibers and the growth rings.