Secondary Wall Deposition Research Articles

Spatiotemporal bifurcation of HY5-mediated blue-light signaling regulates wood development during secondary growth

Plants have evolved photoreceptors to optimize their development during primary growth, including germination, hypocotyl elongation, cotyledon opening, and root growth, allowing them to adapt to challenging light conditions. The light signaling transduction pathway during seedling establishment has been extensively studied, but little molecular evidence is available for light-regulated secondary growth, and how light regulates cambium-derived tissue production remains largely unexplored. Here, we show that CRYPTOCHROME (CRY)-dependent blue light signaling and the subsequent attenuation of ELONGATED HYPOCOTYL 5 (HY5) movement to hypocotyls are key inducers of xylem fiber differentiation in Arabidopsis thaliana. Using grafted chimeric plants and hypocotyl-specific transcriptome sequencing of light signaling mutants under controlled light conditions, we demonstrate that the perception of blue light by CRYs in shoots drives secondary cell wall (SCW) deposition at xylem fiber cells during the secondary growth of hypocotyls. We propose that HY5 is a blue light–responsive mobile protein that inhibits xylem fiber formation via direct transcriptional repression of NAC SECONDARY WALL THICKENING PROMOTING 3 ( NST3 ). CRYs retain HY5 in the nucleus, impede its long-distance transport from leaf to hypocotyl, and they initiate NST3- driven SCW gene expression, thereby triggering xylem fiber production. Our findings shed light on the long-range CRYs-HY5-NST3 signaling cascade that shapes xylem fiber development, highlighting the activity of HY5 as a transcriptional repressor during secondary growth.

Natural variation in GhROPGEF5 contributes to longer and stronger cotton fibers.

Length and strength are key parameters impacting the quality of textiles that can be produced from cotton fibers, and therefore are important considerations in cotton breeding. Through map-based cloning and function analysis, we demonstrated that GhROPGEF5, encoding a ROP guanine nucleotide exchange factor, was the gene controlling fiber length and strength at qFSA10.1. Evolutionary analysis revealed that a base deletion in the third exon of GhROPGEF5 resulting in superior fiber length and strength was a rare mutation occurring in a tiny percentage of Upland cottons, with reduced fiber yield hindering its spread. GhROPGEF5 interacted with and activated GhROP10. Knockout or mutation of GhROPGEF5 resulted a loss of the ability to activate GhROP10. Knockout of GhROPGEF5 or GhROP10 affected the expression of many downstream genes associated with fiber elongation and secondary wall deposition, prolonged fiber elongation and delayed secondary wall deposition, producing denser fiber helices and increasing fiber length and strength. These results revealed new molecular aspects of fiber development and revealed a rare favorable allele for improving fiber quality in cotton breeding.

Modification of xylan in secondary walls alters cell wall biosynthesis and wood formation programs and improves saccharification.

Wood of broad-leaf tree species is a valued source of renewable biomass for biorefinery and a target for genetic improvement efforts to reduce its recalcitrance. Glucuronoxylan (GX) plays a key role in recalcitrance through its interactions with cellulose and lignin. To reduce recalcitrance, we modified wood GX by expressing GH10 and GH11 endoxylanases from Aspergillus nidulans in hybrid aspen (Populus tremula L. × tremuloides Michx.) and targeting the enzymes to cell wall. The xylanases reduced tree height, modified cambial activity by increasing phloem and reducing xylem production, and reduced secondary wall deposition. Xylan molecular weight was decreased, and the spacing between acetyl and MeGlcA side chains was reduced in transgenic lines. The transgenic trees produced hypolignified xylem having thin secondary walls and deformed vessels. Glucose yields of enzymatic saccharification without pretreatment almost doubled indicating decreased recalcitrance. The transcriptomics, hormonomics and metabolomics data provided evidence for activation of cytokinin and ethylene signalling pathways, decrease in ABA levels, transcriptional suppression of lignification and a subset of secondary wall biosynthetic program, including xylan glucuronidation and acetylation machinery. Several candidate genes for perception of impairment in xylan integrity were detected. These candidates could provide a new target for uncoupling negative growth effects from reduced recalcitrance. In conclusion, our study supports the hypothesis that xylan modification generates intrinsic signals and evokes novel pathways regulating tree growth and secondary wall biosynthesis.

Downregulation of the GhROD1 Gene Improves Cotton Fiber Fineness by Decreasing Acyl Pool Saturation, Stimulating Small Heat Shock Proteins (sHSPs), and Reducing H2O2 Production.

Cotton fiber is one of the most important natural fiber sources in the world, and lipid metabolism plays a critical role in its development. However, the specific role of lipid molecules in fiber development and the impact of fatty acid alterations on fiber quality remain largely unknown. In this study, we demonstrate that the downregulation of GhROD1, a gene encoding phosphatidylcholine diacylglycerol cholinephosphotransferase (PDCT), results in an improvement of fiber fineness. We found that GhROD1 downregulation significantly increases the proportion of linoleic acid (18:2) in cotton fibers, which subsequently upregulates genes encoding small heat shock proteins (sHSPs). This, in turn, reduces H2O2 production, thus delaying secondary wall deposition and leading to finer fibers. Our findings reveal how alterations in linoleic acid influence cellulose synthesis and suggest a potential strategy to improve cotton fiber quality by regulating lipid metabolism pathways.

Identification of BpEXP family genes and functional characterization of the BpEXPA1 gene in the stems development of Betula platyphylla

Expansins (EXPs) are unique plant cell wall proteins with the ability to induce cell wall expansion and play potential roles in xylem development. In the present study, a total of 25 BpEXP genes were identified in Betula platyphylla. Results of bioinformatics analysis described that BpEXP gene family was highly conserved in the process of evolution. All these genes were clustered into four groups, EXPA (Expansin A), EXPB (Expansin B), EXLA (Expansin-like A) and EXLB (Expansin-like B), according to phylogenetic analysis and BpEXPA1 was highly homologous to PttEXP1 and PttEXP2. The results of RT-qPCR showed that BpEXPA1 was expressed higher in stems and preferentially expressed in the first internodes, followed by apical buds and the third internodes, promoter expression analysis with GUS assay demonstrated that it was expressed in developing xylem, suggesting that BpEXPA1 might be involved in the development of the primary stems of birch. Overexpression of BpEXPA1 can promote cortex cell expansion and then enlarge the cortex cell area and layer, however inhibit the secondary cell wall deposition and result in the thinner cell wall and larger lumens of xylem fiber in transgenic plants. This study will provide information for investigating the regulation mechanism of BpEXP family genes and gene resources for birch genetics improvement.

The transcription factor PagLBD4 represses cell differentiation and secondary cell wall biosynthesis in Populus

LBD (LATERAL ORGAN BOUNDARIES DOMAIN) transcription factors are key regulators of plant growth and development. In this study, we functionally characterized the PagLBD4 gene in Populus (Populus alba × Populus glandulosa). Overexpression of PagLBD4 (PagLBD4OE) significantly repressed secondary xylem differentiation and secondary cell wall (SCW) deposition, while CRISPR/Cas9-mediated PagLBD4 knockout (PagLBD4KO) significantly increased secondary xylem differentiation and SCW deposition. Consistent with the functional analysis, gene expression analysis revealed that SCW biosynthesis pathways were significantly down-regulated in PagLBD4OE plants but up-regulated in PagLBD4KO plants. We also performed DNA affinity purification followed by sequencing (DAP-seq) to identify genes bound by PagLBD4. Integration of RNA sequencing (RNA-seq) and DAP-seq data identified 263 putative direct target genes (DTGs) of PagLBD4, including important regulatory genes for SCW biosynthesis, such as PagMYB103 and PagIRX12. Together, our results demonstrated that PagLBD4 is a repressor of secondary xylem differentiation and SCW biosynthesis in Populus, which possibly lead to the dramatic growth repression in PagLBD4OE plants.

Upregulation of the glycine-rich protein-encoding gene GhGRPL enhances plant tolerance to abiotic and biotic stressors by promoting secondary cell wall development

Abiotic and biotic stressors adversely affect plant survival, biomass generation, and crop yields. As the global availability of arable land declines and the impacts of global warming intensify, such stressors may have increasingly pronounced effects on agricultural productivity. Currently, researchers face the overarching challenge of comprehensively enhancing plant resilience to abiotic and biotic stressors. The secondary cell wall plays a crucial role in bolstering the stress resistance of plants. To increase plant resistance to stress through genetic manipulation of the secondary cell wall, we cloned a cell wall protein designated glycine-rich protein-like (GhGRPL) from cotton fibers, and found that it is specifically expressed during the period of secondary cell wall biosynthesis. Notably, this protein differs from its Arabidopsis homolog, AtGRP, since its glycine-rich domain is deficient in glycine residues. GhGRPL is involved in secondary cell wall deposition. Upregulation of GhGRPL enhances lignin accumulation and, consequently, the thickness of the secondary cell walls, thereby increasing the plant's resistance to abiotic stressors, such as drought and salinity, and biotic threats, including Verticillium dahliae infection. Conversely, interference with GhGRPL expression in cotton reduces lignin accumulation and compromises that resistance. Taken together, our findings elucidate the role of GhGRPL in regulating secondary cell wall development through its influence on lignin deposition, which, in turn, reinforces cell wall robustness and impermeability. These findings highlight the promising near-future prospect of adopting GhGRPL as a viable, effective approach for enhancing plant resilience to abiotic and biotic stress factors.

Multimodal imaging analysis in silver fir reveals coordination in cellulose and lignin deposition.

Despite lignin being a key component of wood, the dynamics of tracheid lignification are generally overlooked in xylogenesis studies, which hampers our understanding of environmental drivers and blurs the interpretation of isotopic and anatomical signals stored in tree rings. Here, we analyzed cell wall formation in silver fir (Abies alba Mill.) tracheids to determine if cell wall lignification lags behind secondary wall deposition. For this purpose, we applied a multimodal imaging approach combining transmitted light microscopy (TLM), confocal laser scanning microscopy (CLSM), and confocal Raman microspectroscopy (RMS) on anatomical sections of wood microcores collected in northeast France on 11 dates during the 2010 growing season. Wood autofluorescence after laser excitation at 405 nm and 488 nm associated with the RMS scattering of lignin and cellulose, respectively, which allowed identification of lignifying cells (cells showing lignified and non-lignified wall fractions at the same time) in CLSM images. The number of lignifying cells in CLSM images mirrored the number of wall-thickening birefringent cells in polarized TLM images, revealing highly synchronized kinetics for wall thickening and lignification (similar timings and durations at the cell level). CLSM images and RMS chemical maps revealed a substantial incorporation of lignin into the wall at early stages of secondary wall deposition. Our results show that most of the cellulose and lignin contained in the cell wall undergo concurrent periods of deposition. This suggests a strong synchronization between cellulose and lignin-related features in conifer tree-ring records, as they originated over highly overlapped time frames.

Cotton sphingosine kinase GhLCBK1 participates in fiber cell elongation by affecting sphingosine-1-phophate and auxin synthesis

Sphingolipids serve as essential components of biomembrane and possess significant bioactive properties. Sphingosine-1-phophate (S1P) plays a key role in plant resistance to stress, but its specific impact on plant growth and development remains to be fully elucidated. Cotton fiber cells are an ideal material for investigating the growth and maturation of plant cells. In this study, we examined the content and composition of sphingosine (Sph) and S1P throughout the progression of fiber cell development. The content of S1P elevated gradually during fiber elongation but declined during the transition stage. Exogenous application of S1P promoted fiber elongation while using of FTY720 (an antagonist of S1P), and DMS (an inhibitor of LCBK) hindered fiber elongation. Cotton Long Chain Base Kinase 1 (GhLCBK1) was notably expressed during the fiber elongation stage, containing all conserved domains of LCBK protein and localized in the endoplasmic reticulum. Overexpression GhLCBK1 increased the S1P content and promoted fiber elongation while retarded secondary cell wall (SCW) deposition. Conversely, downregulation of GhLCBK1 reduced the S1P levels, and suppressed fiber elongation, and accelerated SCW deposition. Transcriptome analysis revealed that upregulating GhLCBK1 or applying S1P induced the expression of GhEXPANSIN and auxin related genes. Furthermore, the levels of IAA were elevated and reduced in the fibers when up-regulating or down-regulating GhLCBK1, respectively. Our investigation demonstrated that GhLCBK1 and its product S1P facilitated the elongation of fiber cells by affecting auxin biosynthesis. This study contributes novel insights into the intricate regulatory pathways involved in fiber cell elongation, identifying GhLCBK1 as a potential target gene and laying the groundwork for enhancing fiber quality via genetic manipulation.

Cortical microtubule dynamics during reaction wood formation ensures context-appropriate cellulose microfibril angle in woody trees

Key messageCortical microtubule arrays are the primary mechanism for guiding the re-orientation of cellulose microfibrils and determining MFA in secondary cell wall of wood fibre and tracheid cells in reaction wood.Microtubules are directly and indirectly involved in guiding cellulose synthase complexes (CSCs) through the plasma membrane. The angle of cellulose deposition is a critical response to environmental signals and/or stress conditions, and particularly crucial during reaction wood formation, a process in which woody plants deposit additional cell wall material to counteract gravitational forces. Tubulin genes are upregulated in response to gravitational stimulus during reaction wood formation, which can result in changes to microtubule assembly. In this study, microtubules were visualised in three woody tree species (two angiosperms: Eucalyptus globulus Labill., Populus alba L., and one gymnosperm: Pinus radiata D. Don.) using immunofluorescence to quantitatively evaluate microtubule organisation during reaction wood formation. Our results suggest that reorientation of the cortical microtubule array affects secondary cell wall deposition, even across different types of reaction wood, by ensuring context-appropriate orientation of cellulose microfibrils and determining MFA in wood cells. Pharmacological studies conducted on in vitro cultured stem segments or in vivo during reaction wood formation corroborated these important roles for microtubules during wood development. This study starts to unveil the role of tubulins during wood formation by exploring cortical microtubule array organisation in trees subjected to gravitational stimulus and it sheds light on cellular and molecular mechanisms behind cellulose deposition in tree species.

GhHB14_D10 and GhREV_D5, two HD-ZIP III transcription factors, play a regulatory role in cotton fiber secondary cell wall biosynthesis.

GhHB14_D10 and GhREV_D5 regulated secondary cell wall formation and played an important role in fiber development. Cotton serves as an important source of natural fiber, and the biosynthesis of the secondary cell wall plays a pivotal role in determining cotton fiber quality. Nevertheless, the intricacies of this mechanism in cotton fiber remain insufficiently elucidated. This study investigates the functional roles of GhHB14_D10 and GhREV_D5, two HD-ZIP III transcription factors, in secondary cell wall biosynthesis in cotton fibers. Both GhHB14_D10 and GhREV_D5 were found to be localized in the nucleus with transcriptional activation activity. Ectopic overexpression of GhHB14_D10 and GhREV_D5 in Arabidopsis resulted in changed xylem differentiation, secondary cell wall deposition, and expression of genes related to the secondary cell wall. Silencing of GhHB14_D10 and GhREV_D5 in cotton led to enhanced fiber length, reduced cell wall thickness, cellulose contents and expression of secondary cell wall-related genes. Moreover, GhHB14_D10's direct interaction with GhREV_D5, and transcriptional regulation of cellulose biosynthesis genes GhCesA4-4 and GhCesA7-2 revealed their collaborative roles in secondary cell wall during cotton fiber development. Overall, these results shed light on the roles of GhHB14_D10 and GhREV_D5 in secondary cell wall biosynthesis, offering a strategy for the genetic improvement of cotton fiber quality.

Transcription factor PagMYB31 positively regulates cambium activity and negatively regulates xylem development in poplar.

Wood formation involves consecutive developmental steps, including cell division of vascular cambium, xylem cell expansion, secondary cell wall (SCW) deposition, and programmed cell death. In this study, we identified PagMYB31 as a coordinator regulating these processes in Populus alba × Populus glandulosa and built a PagMYB31-mediated transcriptional regulatory network. PagMYB31 mutation caused fewer layers of cambial cells, larger fusiform initials, ray initials, vessels, fiber and ray cells, and enhanced xylem cell SCW thickening, showing that PagMYB31 positively regulates cambial cell proliferation and negatively regulates xylem cell expansion and SCW biosynthesis. PagMYB31 repressed xylem cell expansion and SCW thickening through directly inhibiting wall-modifying enzyme genes and the transcription factor genes that activate the whole SCW biosynthetic program, respectively. In cambium, PagMYB31 could promote cambial activity through TRACHEARY ELEMENT DIFFERENTIATION INHIBITORY FACTOR (TDIF)/PHLOEM INTERCALATED WITH XYLEM (PXY) signaling by directly regulating CLAVATA3/ESR-RELATED (CLE) genes, and it could also directly activate WUSCHEL HOMEOBOX RELATED4 (PagWOX4), forming a feedforward regulation. We also observed that PagMYB31 could either promote cell proliferation through the MYB31-MYB72-WOX4 module or inhibit cambial activity through the MYB31-MYB72-VASCULAR CAMBIUM-RELATED MADS2 (VCM2)/PIN-FORMED5 (PIN5) modules, suggesting its role in maintaining the homeostasis of vascular cambium. PagMYB31 could be a potential target to manipulate different developmental stages of wood formation.

A NAC Transcription Factor RsSND1 Regulating Secondary Cell Wall Deposition Involves in Fleshy Taproot Formation in Radish (Raphanus sativus L.)

A NAC Transcription Factor RsSND1 Regulating Secondary Cell Wall Deposition Involves in Fleshy Taproot Formation in Radish (Raphanus sativus L.)

Multi-omics analysis of pigmentation related to proanthocyanidin biosynthesis in brown cotton (Gossypium hirsutum L.).

Naturally-colored brown cotton (NBC) fiber is an environmentally friendly raw source of fiber for textile applications. The fiber of some NBC cultivars exhibits flame-retardant properties, which can be used in textiles that require flame resistance. Proanthocyanidins or their derivatives are responsible for the brown pigment in NBC; however, how flame retardancy is related to pigmentation in NBC is poorly understood. To gain insight into brown pigment biosynthesis, we conducted comparative transcripts and metabolites profiling analysis of developing cotton fibers between the brown (MC-BL) and white (MC-WL) cotton near-isogenic lines (NILs), genetically different only in the Lc1 locus. In this study, mass spectrometry was used to detect metabolites in BL and WL developing fibers at 8, 12, 16, 20, 24, 36, and 40 days post anthesis (DPA) and mature fibers. Transcripts analysis was performed at two critical fiber developmental points, 8 DPA (fiber elongation) and 20 DPA (secondary cell wall deposition). We found 5836 (ESI MS positive mode) and 4541 (ESI MS negative mode) metabolites significantly different accumulated between BL and WL. Among them, 142 were known non-redundant metabolites, including organic acids, amino acids, and derivatives of the phenylpropanoid pathway. Transcript analysis determined 1691 (8 DPA) and 5073 (20 DPA) differentially expressed genes (DEGs) between BL and WL, with the majority of DEGs down-regulated at 20 DPA. Organic acids of the citric acid cycle were induced, while most of the detected amino acids were reduced in the MC-BL line. Both cis- and trans-stereoisomers of flavan-3-ols were detected in developing MC-WL and MC-BL fibers; however, the gallocatechin and catechin accumulated multiple times higher. Gas chromatography-mass spectrometry (GC-MS) analysis of fatty acids determined that palmitic acid long-chain alcohols were the main constituents of waxes of mature fibers. Energy-dispersive X-ray spectrometry (EDS) analysis of mature fibers revealed that potassium accumulated three times greater in MC-BL than in MC-WL mature fibers. This study provides novel insights into the biosynthesis of pigments and its association with flame retardancy in NBC fibers.

An essential role for mannan degradation in both cell growth and secondary cell wall formation.

Coordination of secondary cell wall deposition and cell expansion during plant growth is required for cell development, particularly in vascular tissues. Yet the fundamental coordination process has received little attention. We observed that the Arabidopsis endo-1,4-mannanase gene, AtMAN6, is involved in the formation of cell walls in vascular tissues. In the inflorescence stem, the man6 mutant had smaller vessel cells with thicker secondary cell walls and shorter fiber cells. Elongation growth was reduced in the root, and secondary cell wall deposition in vessel cells occurred early. Overexpression of AtMAN6 resulted in the inverse phenotypes of the man6 mutant. AtMAN6 was discovered on the plasma membrane and was specifically expressed in vessel cells during its early development. The AtMAN6 protein degraded galactoglucomannan to produce oligosaccharides, which caused secondary cell wall deposition in vessel and fiber cells to be suppressed. Transcriptome analysis revealed that the expression of genes involved in the regulation of secondary cell wall synthesis was changed in both man6 mutant and AtMAN6 overexpression plants. AtMAN6's C-terminal cysteine repeat motif (CCRM) was found to facilitate homodimerization and is required for its activity. According to the findings, the oligosaccharides produced by AtMAN6 hydrolysis may act as a signal to mediate this coordination between cell growth and secondary cell wall deposition.

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.

Cotton GhNAC4 promotes drought tolerance by regulating secondary cell wall biosynthesis and ribosomal protein homeostasis.

Drought has a severe impact on the quality and yield of cotton. Deciphering the key genes related to drought tolerance is important for understanding the regulation mechanism of drought stress and breeding drought-tolerant cotton cultivars. Several studies have demonstrated that NAC transcription factors are crucial in the regulation of drought stress, however, the related functional mechanisms are still largely unexplored. Here, we identified that NAC transcription factor GhNAC4 positively regulated drought stress tolerance in cotton. The expression of GhNAC4 was significantly induced by abiotic stress and plant hormones. Silencing of GhNAC4 distinctly impaired the resistance to drought stress and overexpressing GhNAC4 in cotton significantly enhanced the stress tolerance. RNA-seq analysis revealed that overexpression of GhNAC4 enriched the expression of genes associated with the biosynthesis of secondary cell walls and ribosomal proteins. We confirmed that GhNAC4 positively activated the expressions of GhNST1, a master regulator reported previously in secondary cell wall formation, and two ribosomal protein-encoding genes GhRPL12 and GhRPL18p, by directly binding to their promoter regions. Overexpression of GhNAC4 promoted the expression of downstream genes associated with the secondary wall biosynthesis, resulting in enhancing secondary wall deposition in the roots, and silencing of GhRPL12 and GhRPL18p significantly impaired the resistance to drought stress. Taken together, our study reveals a novel pathway mediated by GhNAC4 that promotes secondary cell wall biosynthesis to strengthen secondary wall development and regulates the expression of ribosomal protein-encoding genes to maintain translation stability, which ultimately enhances drought tolerance in cotton.

Tissue-Specific Transcriptomes in the Secondary Cell Wall Provide an Understanding of Stem Growth Enhancement in Solidago canadensis during Invasion.

Invasive plants generally present a significant enhancement in aboveground vegetative growth, which is mainly caused by variation in secondary cell wall (SCW) deposition and vascular tissue development. However, the coordination of the transcriptional regulators of SCW biosynthesis is complex, and a comprehensive regulation map has not yet been clarified at a transcriptional level to explain the invasive mechanism of S. canadensis. Here, RNA sequencing was performed in the phloem and xylem of two typical native (US01) and invasive (CN25) S. canadensis populations with different stem morphologies. A total of 296.14 million high-quality clean reads were generated; 438,605 transcripts and 156,968 unigenes were assembled; and 66,648 and 19,510 differential expression genes (DEGs) were identified in the phloem and xylem, respectively. Bioinformatics analysis indicated that the SCW transcriptional network was dramatically altered during the successful invasion of S.canadensis. Based on a comprehensive analysis of SCW deposition gene expression profiles, we revealed that the invasive population is dedicated to synthesizing cellulose and reducing lignification, leading to an SCW with high cellulose content and low lignin content. A hypothesis thus has been proposed to explain the enhanced stem growth of S. canadensis through the modification of the SCW composition.

The activation of the NAC transcription factor by Poplar PtrGATA9 facilitates the secondary cell wall deposition of interfascicular fiber cell in Arabidopsis

The activation of the NAC transcription factor by Poplar PtrGATA9 facilitates the secondary cell wall deposition of interfascicular fiber cell in Arabidopsis

Ectopic expression of Camellia oleifera Abel. gibberellin 20-oxidase gene increased plant height and promoted secondary cell walls deposition in Arabidopsis.

Ectopic expression of Camellia oleifera Abel. gibberellin 20-oxidase 1 caused a taller phenotype, promoted secondary cell wall deposition, leaf enlargement, and early flowering, and reduced chlorophyll and anthocyanin accumulation and seed enlargement phenotype in Arabidopsis. Plant height and secondary cell wall (SCW) deposition are important plant traits. Gibberellins (GAs) play important roles in regulating plant height and SCWs deposition. Gibberellin 20-oxidase (GA20ox) is an important enzyme involved in GA biosynthesis. In the present study, we identified a GA synthesis gene in Camellia oleifera. The total length of the CoGA20ox1 gene sequence was 1146bp, encoding 381 amino acids. Transgenic plants with CoGA20ox1 had a taller phenotype; a seed enlargement phenotype; promoted SCWs deposition, leaf enlargement, and early flowering; and reduced chlorophyll and anthocyanin accumulation. Genetic analysis showed that the mutant ga20ox1-3 Arabidopsis partially rescued the phenotype of CoGA20ox1 overexpression plants. The results showed that CoGA20ox1 participates in the growth and development of C. oleifera. The morphological changes in CoGA20ox1 overexpressed plants provide a theoretical basis for further exploration of GA biosynthesis and analysis of the molecular mechanism in C. oleifera.