Wood Formation
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2021 ◽  
Vol 22 (18) ◽  
pp. 9899
Dade Yu ◽  
Dennis Janz ◽  
Krzysztof Zienkiewicz ◽  
Cornelia Herrfurth ◽  
Ivo Feussner ◽  

Drought is a severe environmental stress that exerts negative effects on plant growth. In trees, drought leads to reduced secondary growth and altered wood anatomy. The mechanisms underlying wood stress adaptation are not well understood. Here, we investigated the physiological, anatomical, hormonal, and transcriptional responses of poplar to strong drought. Drought-stressed xylem was characterized by higher vessel frequencies, smaller vessel lumina, and thicker secondary fiber cell walls. These changes were accompanied by strong increases in abscisic acid (ABA) and antagonistic changes in salicylic acid in wood. Transcriptional evidence supported ABA biosynthesis and signaling in wood. Since ABA signaling activates the fiber-thickening factor NST1, we expected upregulation of the secondary cell wall (SCW) cascade under stress. By contrast, transcription factors and biosynthesis genes for SCW formation were down-regulated, whereas a small set of cellulose synthase-like genes and a huge array of genes involved in cell wall modification were up-regulated in drought-stressed wood. Therefore, we suggest that ABA signaling monitors normal SCW biosynthesis and that drought causes a switch from normal to “stress wood” formation recruiting a dedicated set of genes for cell wall biosynthesis and remodeling. This proposition implies that drought-induced changes in cell wall properties underlie regulatory mechanisms distinct from those of normal wood.

2021 ◽  
Ahmad Sofiman Othman ◽  
Mohd Fahmi Abu Bakar

Hevea brasiliensis (the rubber tree) is a well-known species with high economic value, and it is the primary source of natural rubber globally. Increasing demand for furniture and related industries has made rubberwood production as important as latex production. Molecular markers such as Single Nucleotide Polymorphisms (SNPs) and Simple Sequence Repeats (SSRs) are widely used for Marker Assisted Selection (MAS) which can be detected in large quantity by transcriptome sequencing. MAS is thought to be a useful method for the development of new rubberwood clones for its shorter breeding cycle compared to a conventional breeding procedure. In this study we performed RNA sequencing (RNA-seq) on four H. brasiliensis clones (RRIM 712, RRIM 2025, RRIM 3001 and PB 314) from three tissues including bark, latex and leaf samples to identify SSRs and SNPs associated with wood-formation related genes. The RNA sequencing using the Illumina NextSeq 500 v2 platform, generated 1,697,491,922 raw reads. A total of 101,269 transcripts over 400 bp in size were obtained and similarity search of the non-redundant (nr) protein database returned 83,748 (83%) positive BLASTx hits. The transcriptome analysis was annotated using the NCBI NR (National Center for Biotechnology Information Non-Redundant), UniProtKB/Swiss-Prot, gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Differential expression analysis between later-timber rubber clone and non-later-timber rubber clone on wood-formation related genes, showed genes encoding phenylalanine ammonia-lyase (PAL), caffeic acid O-methyltransferase (COMT) and cinnamoyl-CoA reductase (CCR) were highly up-regulated in a latex-timber rubber clone. In total, about 3,210,629 SNPs and 14,956 SSRs were detected with 1,786 SNPs and 31 SSRs were found for wood-formation biosynthesis of H. brasilensis from 11 lignin and cellulose gene toolboxes. After filtering and primer selection, 103 SNPs and 18 SSR markers were successfully amplified and could be useful as molecular tool for marker assisted breeding to produce new timber rubber clones.

Diversity ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 423
Zachary D. Perry ◽  
Thangasamy Saminathan ◽  
Alok Arun ◽  
Brajesh N. Vaidya ◽  
Chhandak Basu ◽  

Paulownia (Paulownia elongata) is a fast-growing, multipurpose deciduous hardwood species that grows in a wide range of temperatures from –30 °C to 45 °C. Seasonal cues influence the secondary growth of tree stems, including cambial activity, wood chemistry, and transition to latewood formation. In this study, a de novo transcriptome approach was conducted to identify the transcripts expressed in vascular cambial tissue from senescent winter and actively growing spring seasons. An Illumina paired-end sequenced cambial transcriptome generated 297,049,842 clean reads, which finally yielded 61,639 annotated unigenes. Based on non-redundant protein database analyses, Paulownia cambial unigenes shared the highest homology (64.8%) with Erythranthe guttata. KEGG annotation of 35,471 unigenes identified pathways enriched in metabolic activities. Transcriptome-wide DEG analysis showed that 2688 and 7411 genes were upregulated and downregulated, respectively, in spring tissues compared to winter. Interestingly, several transcripts encoding heat shock proteins were upregulated in the spring season. RT-qPCR expression results of fifteen wood-forming candidate genes involved in hemicellulose, cellulose, lignin, auxin, and cytokinin pathways showed that the hemicellulose genes (CSLC4, FUT1, AXY4, GATL1, and IRX19) were significantly upregulated in spring season tissues when compared to winter tissues. In contrast, lignin pathway genes CCR1 and CAD1 were upregulated in winter cambium. Finally, a transcriptome-wide marker analysis identified 11,338 Simple Sequence Repeat (SSRs). The AG/CT dinucleotide repeat predominately represented all SSRs. Altogether, the cambial transcriptomic analysis reported here highlights the molecular events of wood formation during winter and spring. The identification of candidate genes involved in the cambial growth provides a roadmap of wood formation in Paulownia and other trees for the seasonal growth variation.

2021 ◽  
Vol 12 ◽  
Liang Xiao ◽  
Liting Man ◽  
Lina Yang ◽  
Jinmei Zhang ◽  
Baoyao Liu ◽  

MicroRNAs (miRNAs), important posttranscriptional regulators of gene expression, play a crucial role in plant growth and development. A single miRNA can regulate numerous target genes, making the determination of its function and interaction with targets challenging. We identified PtomiR403b target to PtoGT31B-1, which encodes a galactosyltransferase responsible for the biosynthesis of cell wall polysaccharides. We performed an association study and epistasis and Mendelian randomization (MR) analyses to explore how the genetic interaction between PtoMIR403b and its target PtoGT31B-1 underlies wood formation. Single nucleotide polymorphism (SNP)-based association studies identified 25 significant associations (P < 0.01, Q < 0.05), and PtoMIR403b and PtoGT31B-1 were associated with five traits, suggesting a role for PtomiR403b and PtoGT31B-1 in wood formation. Epistasis analysis identified 93 significant pairwise epistatic associations with 10 wood formation traits, and 37.89% of the SNP-SNP pairs indicated interactions between PtoMIR403b and PtoGT31B-1. We performed an MR analysis to demonstrate the causality of the relationships between SNPs in PtoMIR403b and wood property traits and that PtoMIR403b modulates wood formation by regulating expression of PtoGT31B-1. Therefore, our findings will facilitate dissection of the functions and interactions with miRNA-targets.

2021 ◽  
Vol 12 ◽  
Dian Wang ◽  
Yan Chen ◽  
Wei Li ◽  
Quanzi Li ◽  
Mengzhu Lu ◽  

Wood is the most abundant biomass produced by land plants and is mainly used for timber, pulping, and paper making. Wood (secondary xylem) is derived from vascular cambium, and its formation encompasses a series of developmental processes. Extensive studies in Arabidopsis and trees demonstrate that the initiation of vascular stem cells and the proliferation and differentiation of the cambial derivative cells require a coordination of multiple signals, including hormones and peptides. In this mini review, we described the recent discoveries on the regulation of the three developmental processes by several signals, such as auxin, cytokinins, brassinosteroids, gibberellins, ethylene, TDIF peptide, and their cross talk in Arabidopsis and Populus. There exists a similar but more complex regulatory network orchestrating vascular cambium development in Populus than that in Arabidopsis. We end up with a look at the future research prospects of vascular cambium in perennial woody plants, including interfascicular cambium development and vascular stem cell regulation.

Forests ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1002
Shenquan Cao ◽  
Cong Wang ◽  
Huanhuan Ji ◽  
Mengjie Guo ◽  
Jiyao Cheng ◽  

Secondary cell wall (SCW) deposition is an important process during wood formation. Although aspartic proteases (APs) have been reported to have regulatory roles in herbaceous plants, the involvement of atypical APs in SCW deposition in trees has not been reported. In this study, we characterised the Populus trichocarpa atypical AP gene PtAP66, which is involved in wood SCW deposition. Transcriptome data from the AspWood resource showed that in the secondary xylem of P. trichocarpa, PtAP66 transcripts increased from the vascular cambium to the xylem cell expansion region and maintained high levels in the SCW formation region. Fluorescent signals from transgenic Arabidopsis plant roots and transiently transformed P. trichocarpa leaf protoplasts strongly suggested that the PtAP66-fused fluorescent protein (PtAP66-GFP or PtAP66-YFP) localised in the plasma membrane. Compared with the wild-type plants, the Cas9/gRNA-induced PtAP66 mutants exhibited reduced SCW thickness of secondary xylem fibres, as suggested by the scanning electron microscopy (SEM) data. In addition, wood composition assays revealed that the cellulose content in the mutants decreased by 4.90–5.57%. Transcription analysis further showed that a loss of PtAP66 downregulated the expression of several SCW synthesis-related genes, including cellulose and hemicellulose synthesis enzyme-encoding genes. Altogether, these findings indicate that atypical PtAP66 plays an important role in SCW deposition during wood formation.

2021 ◽  
Antonova Galina Feodosievna ◽  
Stasova Victoria Victorovna ◽  
Suvorova Galina Georgievna ◽  
Oskolkov Vladimir Alekcandrovich

Abstract Key message The relationships between cambium activity, cell wall biomass accumulation and photosynthesis/ respiration in Scots pine trees, growing in Eastern Siberia (Russia), change during the season in dependence on combination of summer-weather conditions. The wood formation in tree trunks depends on photosynthesis and respiration and the each of the processes are under the effect of external factors. Each factor effects the growth in combination with other factors and the change in any of these factors leads to strengthen or to weaken of the growth processes in tree. We investigated the formation of xylem and phloem cells by cambium, cell wall biomass accumulation in Scots pine trees, growing in Eastern Siberia (Russia), in dependence on the productivity of photosynthesis and energy cost in separate seasonal periods in the years with opposite summer-weather conditions. The cores extracted throughout 10-day from the stems of 10 trees during the seasons were used to determine the number of cells with different development degree and their morphological parameters. Cambium activity and cell wall biomass accumulated on the separate stages of annual ring wood formation and their connections with the photosynthetic productivity of crown and the level of stem respiration photosynthesis were assessed. The activity of cambial cell division into xylem or phloem sides in separate periods depended on the combination of temperature/precipitation and on the connection with photosynthesis and respiration. The dynamics of biomass accumulation was bimodal with the maximums in June (earlywood development) and mainly in August (development of thick-wall late tracheids), what was due to the combination of optimal temperature and the moisture in the stem tissues. The variation in the external factors changed the balance between the incoming of photoassimilates and the energy cost causing a competition for photosynthesis products and, as a consequence, photoassimilates were used not only for cell-wall biomass synthesis and but also for their reservation of spare substances in the form of starch. The data is useful to understanding of internal processes of wood annual ring formation in pine trees.

2021 ◽  
Vol 22 (14) ◽  
pp. 7615
Fuhua Fan ◽  
Zijing Zhou ◽  
Huijuan Qin ◽  
Jianhui Tan ◽  
Guijie Ding

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.

2021 ◽  
Vol 12 ◽  
Yi An ◽  
Ya Geng ◽  
Junguang Yao ◽  
Chun Wang ◽  
Juan Du

Gene editing technology in woody plants has great potential for understanding gene function, and altering traits affecting economically and ecologically important traits. Gene editing applications in woody species require a high genome editing efficiency due to the difficulty during transformation and complexities resulting from gene redundancy. In this study, we used poplar 84K (Populus alba × P. glandulosa), which is a model hybrid for studying wood formation and growth. We developed a new CRISPR/Cas9 system to edit multiple genes simultaneously. Using this system, we successfully knocked out multiple targets of the PHYTOENE DESATURASE 8 in poplar. We found the mutation rate of our CRISPR/Cas9 system is higher (67.5%) than existing reports in woody trees. We further improved the mutation rate up to 75% at editing sites through the usage of the mannopine synthase (MAS) promoter to drive Cas9. The MAS-CRISPR/Cas9 is an improved genome-editing tool for woody plants with a higher efficiency and a higher mutation rate than currently available technologies.

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