Application of PagSIZ1 gene in regulating growth and development of poplar

Abstract

The present invention discloses the application of the PagSIZ1 gene in regulating the growth and development of poplars, and belongs to the field of genetic engineering technology. The present invention provides the application of the PagSIZ1 gene in regulating the growth and development of poplars, and the nucleotide sequence of the PagSIZ1 gene is shown in SEQ ID NO.1. A vector comprising the PagSIZ1 gene. And the application of the vector in regulating the growth and development of poplars, wherein the vector promotes the growth and development of poplars by overexpressing the PagSIZ1 gene. The present invention proposes the application of the PagSIZ1 gene in regulating the growth and development of poplars, and overexpressing the PagSIZ1 gene can increase the growth and development speed of poplars, enable poplars to better adapt to the growth environment, achieve higher plant height and thicker stems in a shorter period of time, significantly increase wood yield, and optimize wood quality.

Description

Technical Field

[0001] The invention belongs to the technical field of genetic engineering, and in particular relates to the application of the PagSIZ1 gene in regulating the growth and development of poplars. Background Art

[0002] Poplars, a fast-growing broadleaf tree, are widely distributed across temperate and boreal zones in the Northern Hemisphere. Due to their rapid growth, adaptability, and diverse timber uses, they hold significant economic value in forestry, papermaking, and bioenergy. Furthermore, poplars play a vital role in ecological restoration and soil and water conservation. With the growing emphasis on sustainable development, improving the growth efficiency and quality of poplars has become a research hotspot.

[0003] Genes are the fundamental units that control an organism's genetic characteristics. By regulating the expression of specific genes, effective interventions in plant growth and development can be achieved. In recent years, with the advancement of molecular biology techniques, scientists have identified and isolated many key genes involved in regulating poplar growth, including those involved in photosynthesis, cell division, and hormone signaling. However, translating these fundamental research findings into practical productivity remains a significant challenge. On the one hand, it is necessary to overcome the technical difficulties associated with introducing foreign genes; on the other hand, it is also necessary to ensure the safety and stability of transgenic plants and avoid potential environmental risks.

[0004] Currently, the introduction of genes associated with drought and salt tolerance, among other stress responses, can significantly improve the survival rate and growth rate of poplar trees in harsh environments. Using gene-editing tools like CRISPR / Cas9 to selectively knock out or overexpress key regulatory factors can effectively promote xylem cambium activity and accelerate stem thickening, thereby shortening the tree's lifespan. Modifying the rate-limiting steps in the synthesis pathway of secondary biomass, such as phenylpropanoid compounds like tannic acid, not only improves wood quality but also opens the possibility of developing new medicinal resources.

[0005] In summary, gene regulation, as an important means of improving poplar growth performance, presents unprecedented opportunities but also presents certain challenges. This paper aims to combine existing research and propose a new strategy based on gene editing technology to further explore the growth potential of poplars while ensuring safety, thereby contributing to the development of the forestry industry and ecological and environmental protection. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes the application of the PagSIZ1 gene in regulating the growth and development of poplars. Overexpression of the PagSIZ1 gene can increase the growth and development rate of poplars, enable poplars to better adapt to the growth environment, achieve higher plant height and thicker stems in a shorter period of time, significantly increase timber yield, and optimize timber quality.

[0007] To achieve the above object, the present invention provides an application of the PagSIZ1 gene in regulating the growth and development of poplars. The nucleotide sequence of the PagSIZ1 gene is shown in SEQ ID NO.1.

[0008] Preferably, the growth and development of poplar trees is promoted by overexpressing the PagSIZ1 gene.

[0009] The present invention also provides a vector comprising the PagSIZ1 gene.

[0010] The present invention also provides an application of the vector in regulating the growth and development of poplars. The vector promotes the growth and development of poplars by overexpressing the PagSIZ1 gene.

[0011] The present invention also provides an application of the PagSIZ1 gene in regulating the height of poplar trees, and the growth rate of the height of poplar trees is increased by overexpressing the PagSIZ1 gene.

[0012] The present invention also provides an application of the PagSIZ1 gene in regulating the stem diameter of poplars, and the thickening speed of the stem diameter of poplars is increased by overexpressing the PagSIZ1 gene.

[0013] The present invention also provides an application of the PagSIZ1 gene in regulating the xylem differentiation of poplars. By overexpressing the PagSIZ1 gene, the widening of the xylem region of the poplars is promoted, thereby promoting the xylem differentiation of the poplars.

[0014] The present invention also provides the use of the PagSIZ1 gene in regulating the activity of poplar cambium. By overexpressing the PagSIZ1 gene, the number of cell layers in the poplar cambium is promoted to increase, thereby improving the activity of the poplar cambium.

[0015] The present invention also provides an application of the PagSIZ1 gene in regulating the cellulose content of poplars, and the cellulose content in poplars is increased by overexpressing the PagSIZ1 gene.

[0016] The present invention also provides an application of the PagSIZ1 gene in regulating the lignin content of poplars, and the lignin content in poplars is increased by overexpressing the PagSIZ1 gene.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects:

[0018] The present invention discovered that overexpressing the PagSIZ1 gene can promote the growth and development of poplar trees, helping them better adapt to various environments. Overexpressing the PagSIZ1 gene can enable poplar trees to achieve taller plant heights and thicker stems in a shorter period of time, meaning more timber resources can be obtained within the same timeframe, significantly increasing timber yields. Fast-growing poplar trees not only increase the amount of timber produced per tree, but also, because they develop a larger crown width early on, help increase total timber output per hectare. Furthermore, fast-growing poplar trees can form a larger crown in a short period of time, effectively conserving soil and water. Their well-developed root system helps stabilize soil and prevent soil erosion, which is of great significance for the ecological restoration of degraded land.

[0019] The present invention promotes the widening of the xylem region, increases the number of cambium cell layers, and affects the thickness and arrangement of the xylem cell walls by overexpressing the PagSIZ1 gene, thereby optimizing the physical properties of the wood, such as strength and density, reducing defects such as cracks and knots in the wood, and improving the overall quality of the wood. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 The results of positive identification of 3HA tag primer fragments are shown in Figure 1, where A is the identification result part 1, B is the identification result part 2, and C is the identification result part 3. Numbers 1 to 21 in the figure represent 21 positive seedlings.

[0022] Figure 2 The results of fluorescence quantitative PCR analysis are shown in Figure WT, which represents wild-type plants, and OE, which represents transgenic plants.

[0023] Figure 3 The figure shows the phenotypic comparison of wild-type plants and transgenic plants at the same growth period. WT represents wild-type plants, and SIZ1-OE-8 and SIZ1-OE-10 represent transgenic plants.

[0024] Figure 4 This is a statistical analysis of the plant height of wild-type plants and transgenic plants at the same growth period. WT in the figure represents wild-type plants, and SIZ1-OE-8 and SIZ1-OE-10 in the figure represent transgenic plants. ” represents significant difference;

[0025] Figure 5 This is a statistical analysis of the stem diameter of wild-type plants and transgenic plants at the same growth period. WT in the figure represents wild-type plants, and SIZ1-OE-8 and SIZ1-OE-10 in the figure represent transgenic plants. ” represents significant difference;

[0026] Figure 6 The stained sections of wild-type plants and transgenic plants at the same growth period, where A is the xylem width of the wild-type plant, B is the xylem width of the transgenic plant SIZ1-OE-8, C is the xylem width of the transgenic plant SIZ1-OE-10, D is the number of cambium cell layers of the wild-type plant, E is the number of cambium cell layers of the transgenic plant SIZ1-OE-8, and F is the number of cambium cell layers of the transgenic plant SIZ1-OE-10;

[0027] Figure 7 The figure shows the statistical analysis of the xylem width of wild-type plants and transgenic plants at the same growth period. WT represents wild-type plants, and SIZ1-OE-8 and SIZ1-OE-10 represent transgenic plants. ” represents significant difference;

[0028] Figure 8 This is a statistical analysis of the number of cambium cell layers in wild-type plants and transgenic plants at the same growth period. WT in the figure represents wild-type plants, and SIZ1-OE-8 and SIZ1-OE-10 in the figure represent transgenic plants. ” represents significant difference;

[0029] Figure 9 The statistical analysis of cellulose content in wild-type plants and transgenic plants at the same growth period. WT in the figure represents wild-type plants, and SIZ1-OE-8 and SIZ1-OE-10 represent transgenic plants. ” represents significant difference;

[0030] Figure 10 This is a statistical analysis of the lignin content of wild-type plants and transgenic plants at the same growth period. WT in the figure represents wild-type plants, and SIZ1-OE-8 and SIZ1-OE-10 in the figure represent transgenic plants. ” indicates a significant difference. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] Example 1

[0037] 1. Construct a poplar genetic transformation system.

[0038] 1. Construction of expression vector.

[0039] (1) Three-month-old stems of '84k' poplar were used for gene cloning and isolation;

[0040] (2) RNA was extracted from poplar stem segments using an RNA extraction kit (Shandong Sikoje Biotechnology Co., Ltd.);

[0041] (3) The extracted RNA from the poplar stem segments was reverse transcribed into cDNA using a reverse transcription kit (Cuisheng Biotechnology (Shanghai) Co., Ltd.);

[0042] (4) The PagSIZ1 gene (SEQ ID NO. 1) was amplified using the 2xTaq Master Mix (Nanjing Novozyme Biotechnology Co., Ltd.) and PCR. The DNA sequence of the PagSIZ1 gene was found on the phytozome (https: / / phytozome-next.jgi.doe.gov / ) website, Potri.009G015000.

[0043] (5) The pCAMBIA1300 vector was digested with BamHI restriction enzyme (New England Biotechnology (Beijing) Co., Ltd.);

[0044] (6) The PagSIZ1 amplified fragment was religated with the BamHI restriction site of the pCAMBIA1300 vector by homologous recombination using the ClonExpress®Ⅱ one-step cloning kit (Nanjing Novozyme Biotechnology Co., Ltd.);

[0045] (7) Transform Agrobacterium by ice bath, heat shock and other experimental methods ( Agrobacterium rhizogenes After the bacterial solution was correctly identified and sequenced, the Agrobacterium was mixed with 50% glycerol and stored at −80°C for subsequent poplar infection.

[0046]

[0047] The specific primers for the PagSIZ1 gene fragment were as follows: forward primer: 5′-TAACATGTCGACACGTGGATCCATGGATTTAGTAGCTAGTTGCAAGG-3′ (SEQ ID NO. 2);

[0048] Reverse primer: 5′-AGCCTGCGGCCGCGCCGGATCCCTCAGAGTCTGAGTCGTCAATAGA-3′ (SEQ ID NO. 3).

[0049] 2. Genetic transformation of poplar leaves.

[0050] (1) Take out 1 mL of the bacterial suspension from the -80°C refrigerator and incubate it in a liquid LB medium containing "Kanam and Rifampicin" resistance at 28°C and 220 rpm for 24 hours to activate the strain. Then take a certain amount of bacterial suspension and add it to 50 mL of liquid LB medium containing the corresponding resistance and culture it until the OD 600 0.6~0.8;

[0051] (2) The cells were collected by centrifugation at 5000 rpm for 10 min and cultured in a co-culture liquid medium containing 100 μM / L acetosyringone (AS) at 28°C and 220 rpm in an incubator until the OD 600 is 0.3~0.4, as the infection solution;

[0052] (3) Take the 2nd to 5th tender leaves from the top of the sterile seedlings, cut several times on the main vein with a sterile blade, and soak them in the invading dye solution for 7 minutes. Place the leaves on sterilized filter paper to absorb the water, spread them flat on the co-culture solid medium, and keep them in the dark for 2 days;

[0053] (4) Transfer the leaves to the selective medium and culture in the dark;

[0054] (5) When the callus grows to the size of a rice grain, cut it with a sterile blade and transfer it to a screening medium for bud induction for cultivation; (6) When the callus grows buds, cut the buds and insert them into a rooting medium for cultivation.

[0055] Rooting medium (volume 1 L): 1 / 2MS 2.37 g, sucrose 20 g, MES 0.5 g, agar 8 g.

[0056] 2. Identification of positive plants.

[0057] (1) Take genetically transformed seedlings grown in rooting medium for one month and extract DNA from poplar leaves using the CTAB method;

[0058] (2) The positive identification of poplar leaves was performed using 3HA tag primer fragments. The results were as follows: Figure 1 Middle A, Figure 1 Middle B and Figure 1 As shown in middle C, 21 positive seedlings were obtained.

[0059] 3HA tag primer sequences: forward primer: 5'-AACGAATCTCAAGCAATCAAG-3' (SEQ ID NO. 4); reverse primer: 5'-AGACAAGTTGGTAATGGTAGC-3' (SEQ ID NO. 5).

[0060] 3. Gene transcription identification.

[0061] (1) RNA was extracted from the leaves of wild-type and positive seedlings using an RNA extraction kit (Shandong Sikoje Biotechnology Co., Ltd.).

[0062] (2) It was reverse transcribed into cDNA using a reverse transcription kit (Cuisheng Biotechnology (Shanghai) Co., Ltd.).

[0063] (3) Fluorescence quantitative PCR analysis was performed, with each gene repeated three times and PagUBQ gene used as internal reference. The results were as follows: Figure 2 shown.

[0064] (4) Through fluorescence quantitative PCR analysis, the two strains with the highest expression levels, OE-8 and OE-10, were selected.

[0065] The specific primers for PagUBQ fluorescence quantitative PCR analysis are: forward primer: 5'-AGACCTACACCAAGCCCAAGAAGAT-3' (SEQ ID NO. 6); reverse primer: 5'-CCAGCACCGCACTCAGCATTAG-3' (SEQ ID NO. 7).

[0066] The specific primers for PagSIZ1 fluorescence quantitative PCR analysis are: forward primer: 5'-CAGAGTCGATGATTAAGTGTGAGG-3' (SEQ ID NO. 8); reverse primer: 5'-AGTCGACAAGTCTCACAATAGAACAC-3' (SEQ ID NO. 9).

[0067] 4. Identification of poplar phenotype.

[0068] Wild-type '84k' poplar and PagSIZ1-OE transgenic positive seedlings were transferred from the rooting medium to a greenhouse (photoperiod of 16 h / 8 h, light intensity of 80 μmol / m 2 / s, temperature 24-26℃, humidity 70%) for 90 days, and the plant height and ground diameter of the poplars in the greenhouse were measured every two weeks.

[0069] The results are as follows Figure 3 、 Figure 4 and Figure 5 As shown, Figure 4 As shown in Figure 2, the plant heights of transgenic lines OE-8 and OE-10 increased by 10.9% and 30.3% respectively compared with the wild type. Figure 5 As shown, the stem diameters of transgenic lines OE-8 and OE-10 increased by 4.5% and 13.6%, respectively, compared with those of the wild type.

[0070] 5. Identification of cambium and xylem development.

[0071] 1. Paraffin section observation.

[0072] (1) The 15th internode of the poplar stem (excluding the terminal bud and counting the first leaf in order from the root) was cut into sections as experimental materials. The sections were fixed with 4% paraformaldehyde, dehydrated with different concentrations of ethanol, transparentized with mixed solutions of different concentrations of xylene and ethanol, immersed in wax, and embedded in wax to obtain paraffin blocks containing the experimental materials.

[0073] (2) The paraffin blocks were sliced and spread (slice thickness was 8 μm) using a microtome and a slide spreader, fixed on a glass slide, and placed in a 37°C oven to dry overnight.

[0074] (3) The material slices are treated with xylene and different concentrations of ethanol to obtain dewaxed experimental materials, which can then be stained.

[0075] (4) After staining the slice material with 0.03% toluidine blue (TBO) for 5 minutes, rinse with water and observe and photograph it with a ZEISS microscope.

[0076] The results are as follows Figure 6 As shown in Figure 2, the xylem width of the 15th internode of the PagSIZ1-OE transgenic plants (SIZ1-OE-8 and SIZ1-OE-10) was significantly increased. Figure 7 As shown in Figure 2, the xylem width increased by more than 15%.

[0077] 2. Oscillate and slice for observation.

[0078] (1) Cut the 15th internode of the poplar stem (excluding the terminal bud and counting the first leaf toward the root) into sections as experimental materials, fix them on the vibrating sectioning table, and perform vibrating sectioning.

[0079] (2) Carefully remove the slices (30 μm thick) with tweezers and proceed with staining.

[0080] (3) After staining the slice material with 0.03% toluidine blue (TBO) for 10 minutes, rinse with water and then observe and photograph it with a ZEISS microscope.

[0081] The results are as follows Figure 6 As shown in Figure 2, the results showed that the number of cambium cell layers in the 15th internode of PagSIZ1-OE transgenic plants (SIZ1-OE-8 and SIZ1-OE-10) increased significantly. Figure 8 As shown in the figure, the number of cambium cell layers increases by about 2 to 3 layers.

[0082] In summary, the PagSIZ1 gene enhances the cambium activity of poplar and promotes the differentiation of xylem.

[0083] 6. Identification of cell wall components.

[0084] PagSIZ1 was measured - Changes in cell wall composition between OE spider and wild-type plant stems.

[0085] 1.AIR extraction.

[0086] (1) Wild-type '84k' poplar and PagSIZ1-OE transgenic positive seedlings grown in the greenhouse for 90 days were selected, and the base stems were taken as experimental materials.

[0087] (2) The collected materials were quickly frozen in liquid nitrogen, ground into powder using a tissue crusher, and placed in a centrifuge tube for AIR extraction.

[0088] (3) Place 10 mL of powder sample in a 50 mL centrifuge tube, add 80% ethanol to 10 mL, and centrifuge at 12,000 rpm for 10 min. After centrifugation, gently aspirate the upper layer of liquid with a pipette to avoid aspirating the precipitate.

[0089] (4) Add 10 mL of 80% ethanol and 10 mL of anhydrous ethanol to the above precipitate twice, and repeat the above operation.

[0090] (5) Add 10 mL of a 1:1 mixture of chloroform and methanol to the precipitate, heat in a 37°C water bath for 40 min, centrifuge at 12,000 rpm for 10 min, gently shake the liquid, and repeat once.

[0091] (6) Place in a fume hood and dry the precipitate.

[0092] (7) After drying in a ventilated place, a pure AIR sample can be obtained.

[0093] 2. Determination of cellulose content.

[0094] The cellulose content of PagSIZ1-OE and wild-type plants was determined using a cellulose (CLL) content kit (Suzhou Keming Biotechnology Co., Ltd.) as follows:

[0095] (1) Weigh 10 mg of the above AIR sample into an EP tube, add 1 mL of reagent 1, mix thoroughly, and incubate in a 90°C water bath for 30 min;

[0096] (2) After cooling, centrifuge at 8000g at 25°C for 10 min and discard the supernatant;

[0097] (3) The precipitate was washed three times with distilled water (add 1 mL of distilled water, mix well, vortex for 2 min, centrifuge at 8000 g, 25 °C for 10 min, and discard the supernatant);

[0098] (4) Add 1 mL of acetone to the precipitate, mix well, and centrifuge at 8000 g for 10 min at 25°C. Discard the supernatant and dry the precipitate for later use.

[0099] (5) Add 0.5 mL of distilled water to the dried precipitate, place in an ice-water bath, slowly add 0.75 mL of concentrated sulfuric acid, mix well, let stand in an ice-water bath for 30 min, centrifuge at 8000 g, 4°C for 10 min, remove the supernatant, dilute 20 times with distilled water and then wait for determination;

[0100] (6) Working solution preparation: Add 4 mL of reagent 3 to reagent 2 and dissolve thoroughly;

[0101] (7) Add 300 μL of distilled water, 70 μL of working solution, and 630 μL of concentrated sulfuric acid to the blank tube in sequence, and add 300 μL of sample, 70 μL of working solution, and 630 μL of concentrated sulfuric acid to the assay tube in sequence, mix well, place in a 95°C water bath for 10 min, cool to room temperature, and read the absorbance of the blank tube and assay tube at 620 nm, respectively. ΔA = A assay tube - A blank tube;

[0102] (8) Calculation based on sample mass: Cellulose (mg / g dry weight) = [(ΔA + 0.0043) ÷ 7.875 × V1] ÷ (W × V1 ÷ V2) × 20 = 3.17 × (ΔA + 0.0043) ÷ W, where V1 is the volume of sample added, 0.3 mL; V2 is the volume of extract added, 1.25 mL; W is the dry weight of the sample, 0.01 g; and the sample dilution factor is 20.

[0103] The results are as follows Figure 9 As shown in the figure, it was found that the cellulose content of the transgenic lines OE-8 and OE-10 was significantly increased compared with the wild type WT.

[0104] 3. Determination of lignin content.

[0105] The lignin content of PagSIZ1-OE and wild-type plants was measured using a lignin content detection kit (BIXBIO). The steps are as follows:

[0106] (1) Weigh 3 mg of the above AIR sample into a 10 mL quartz tube (one extra tube is used as a control);

[0107] (2) Slowly add 250 μL of reagent 1 and 10 μL of perchloric acid along the wall of the tube;

[0108] (3) After sealing, mix thoroughly and place in a water bath at 80°C for 40 minutes for acetylation. Mix slowly every 10 minutes and cool naturally to room temperature after the reaction is completed.

[0109] (4) Add 250 μL of Reagent 2 to the cooled reaction sample, mix thoroughly, let it stand at room temperature for a while, and then take 10 μL of the supernatant;

[0110] (5) Transfer the supernatant and 490 μL of glacial acetic acid to a 2 ml centrifuge tube and mix thoroughly;

[0111] (6) Pipette 200 μL of the reaction solution into a micro-quartz ELISA plate and measure the absorbance at 280 nm;

[0112] (7) Calculation formula: Lignin content (mg / g) = × (V supernatant + V glacial acetic acid) × V acetylation / ε × d2 × V supernatant × W = 1.092W × ; Lignin content (%) = lignin content × 100% / 1000 = 0.1092 × ,in, Assay tube-A blank tube; Vsupernatant: volume of supernatant, 0.01 mL; Vglacial acetic acid: volume of glacial acetic acid added to the reaction system, 0.49 mL; Vacetylated: volume of acetylated reaction, 0.51 mL; ε: lignin extinction coefficient, 23.35 mL / mg / cm2; d2: 96-well UV plate light path, 1 cm; W: sample mass, g.

[0113] The results are as follows Figure 10 As shown in the figure, it was found that the lignin content of the transgenic lines OE-8 and OE-10 was significantly increased compared with the wild type WT.

[0114] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. The application of PagSIZ1 gene in regulating the cellulose content of poplar is characterized by: The nucleotide sequence of the PagSIZ1 gene is shown in SEQ ID NO.

1. By overexpressing the PagSIZ1 gene, the cellulose content in poplar is increased.

2. The application of PagSIZ1 gene in regulating the content of lignin in poplar is characterized by: The nucleotide sequence of the PagSIZ1 gene is shown in SEQ ID NO.

1. By overexpressing the PagSIZ1 gene, the lignin content in poplar is increased.

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