Paulownia Fortunei Research Articles

Strategy on rapid selection of woody species for phytoremediation in soils contaminated with copper, lead and zinc in Shanghai

The use of woody species for the remediation of heavy metal-contaminated soils is an environmentally friendly and economically viable strategy. This study investigates the phytoextraction abilities of 15 woody species for copper, lead and zinc in contaminated soil. The results indicated that all species showed phytoextraction ability, with metal concentrations varying from 5.59 to 27.45 mg·kg−1 for Cu, 2.79 to 16.75 mg·kg−1 for Pb and 22.13 to 185.72 mg·kg−1 for Zn in the stem tissues depending on the species. Pterocarya stenoptera, Paulownia fortunei and Salix matsudana were identified as the top performers in terms of overall phytoextraction capacity. Notably, their capacity to transport zinc exceeded that of copper and lead. The enrichment of copper, lead and zinc in the soil showed a synergistic effect in the presence of heavy metal. The distribution of heavy metals within plant tissues was affected by water content and the inherent toxicity of metals. The study highlights that the accumulation of tree biomass and water content in the stem play a significant role in determining the amount of heavy metals phytoextracted. This insight offers a quick method for the rapid selection of woody species for phytoremediation in urban soils contaminated with heavy metals.

Novel Insight into the Prevention and Therapeutic Treatment of Paulownia Witches’ Broom: A Study on the Effect of Salicylic Acid on Disease Control and the Changes in the Paulownia Transcriptome and Proteome

Paulownia species not only have significant economic benefits but also show great potential in ecological conservation. However, they are highly susceptible to phytoplasma infections, causing Paulownia witches’ broom (PaWB), which severely restricts the development of the Paulownia industry. Salicylic acid (SA) plays a crucial role in plant disease resistance. However, there have been no reports on the effect of SA on PaWB. Due to the properties of SA, it may have potential in controlling PaWB. Based on the above speculation, the prevention and therapeutic effect of SA on PaWB and its effect on the PaWB-infected Paulownia transcriptome and proteome were studied in this work. The results indicated that 0.1 mmol/L was the optimal SA concentration for inhibiting the germination of Paulownia axillary buds. In terms of resistance physiological indicators, SA treatment significantly affected both Paulownia tomentosa infected (PTI) seedlings and Paulownia fortunei infected (PFI) seedlings, where the activities of peroxidase (POD) and superoxide dismutase (SOD) were enhanced. Malondialdehyde (MDA), O2−, and H2O2, however, were significantly reduced. Specifically, after SA treatment, SOD activity increased by 28% in PFI and 25% in PTI, and POD activity significantly increased by 61% in PFI and 58% in PTI. Moreover, the MDA content decreased by 30% in PFI and 23% in PTI, the H2O2 content decreased by 26% in PFI and 19% in PTI, and the O2− content decreased by 21% in PFI and 19% in PTI. Transcriptomic analysis showed that there were significant upregulations of MYB, NAC, and bHLH and other transcription factors after SA treatment. Moreover, genes involved in PaWB-related defense responses such as RAX2 also showed significant differences. Furthermore, proteomic analysis indicated that after SA treatment, proteins involved in signal transduction, protein synthesis modification, and disease defense were differentially expressed. This work provides a research foundation for the prevention and treatment of PaWB and offers references for exploring anti-PaWB methods.

Overexpression of a 'Paulownia fortunei' MYB Factor Gene, PfMYB44, Increases Salt and Drought Tolerance in Arabidopsis thaliana.

Paulownia fortunei (Seem.) Hemsl is a Paulownia Sieb.et tree of the family Scrophulariaceae. It has become an important short-to-medium-term fast-growing multi-purpose tree species in China due to its rapid growth, strong adaptability, and excellent material properties. MYB transcription factors in plants have numerous and diverse functions, playing important roles in various aspects such as plant stress response. To investigate the function of MYB transcription factors in Paulownia fortunei, this study used PCR technology to clone the PfMYB44 gene from Paulownia fortunei. The homology of PfMYB44 and SiMYB44 (Sesamum indicum) was the highest. Expression analysis results showed that PfMYB44 was expressed in the root, stem, young leaf, and mature leaf of Paulownia fortunei, with the highest content in the root. Cold, drought, hot, salt, and ABA treatments could increase the expression level of PfMYB44. Overexpression-PfMYB44 plants were constructed, and physiological and molecular analysis showed that PfMYB44 could positively regulate salt and drought stresses. Under drought stress, the expression levels of AtP5CS, AtCAT1, AtNCED3 and AtSnRK2.4 in transgenic lines were significantly induced. Salt stress induced the expression of AtNHX1, AtSOS1, AtSOS2 and AtSOS3 genes, and the relative expression levels of these genes in transgenic Arabidopsis were higher. In conclusion, the functional study of PfMYB44 laid a certain foundation for the study of Paulownia stress resistance, and was helpful to the study of its stress resistance mechanism and the cultivation of new stress resistance varieties.

Identification and Analysis of PPO Gene Family Members in Paulownia fortunei.

Polyphenol oxidase (PPO) is a common metalloproteinase in plants with important roles in plant responses to abiotic and biotic stresses. There is evidence that PPOs contribute to stress responses in Paulownia fortunei. In this study, PPO gene family members in P. fortunei were comprehensively identified and characterized using bioinformatics methods as well as analyses of phylogenetic relationships, gene and protein structure, codon usage bias, and gene expression in response to stress. The genome contained 10 PPO gene family members encoding 406-593 amino acids, with a G/C bias. Most were localized in chloroplasts. The motif structure was conserved among family members, and α-helices and random coils were the dominant elements in the secondary structure. The promoters contained many cis-acting elements, such as auxin, gibberellin, salicylic acid, abscisic acid, and photoresponsive elements. The formation of genes in this family was linked to evolutionary events, such as fragment replication. Real-time quantitative PCR results showed that PfPPO7, PfPPO10, PfPPO1, PfPPO2, PfPPO3, PfPPO4, PfPPO5, and PfPPO8 may be key genes in drought stress resistance. PfPPO1, PfPPO3, PfPPO4, and PfPPO10 were resistant stress-sensitive genes. These results provide a reliable basis for fully understanding the potential functions of these genes and the selection of resistance breeding.

Comprehensive evaluation and application of woody plants in the green spaces of parks in saline-Alkaline areas from a low-carbon perspective: A case study of Tianjin Qiaoyuan Park.

The field of landscape architecture has placed significant emphasis on low-carbon landscapes due to the increasing challenges posed by global warming and environmental deterioration in recent years. The soil ecological conditions in saline-alkaline areas are characterized by poor quality, resulting in suboptimal growth conditions for trees. This, in turn, hampers their ability to effectively sequester carbon, thereby diminishing the potential benefits of carbon sinks. Additionally, the maintenance of tree landscapes in such areas generates more carbon emissions than does conventional green land, making it difficult to reap the benefits of tree-based carbon. A comprehensive evaluation of trees in green park spaces in saline-alkaline areas is conducted from a low-carbon perspective; by identifying the dominant tree species that are well suited to greening, we can offer a precise scientific foundation for implementing low-carbon greening initiatives in cities situated in saline-alkaline environments. Therefore, as a case study, this study investigates Tianjin Qiaoyuan Park, a typical saline park in the Bohai Bay region. The hierarchical analysis method (AHP) was used to evaluate 50 species of trees and shrubs in the park from a low-carbon perspective. The results show that the evaluation system consists of four criterion layers and 15 indicator factors. The relative weight of the criterion layer followed the order of habitat adaptability (B2) > carbon sequestration capacity (B1) > low-carbon management and conservation (B3) > landscape aesthetics (B4). The indicator layer assigned greater weight values to net assimilation (C1), saline and alkaline adaptability (C3), drought tolerance (C4), irr igation and fertilization needs (C8), growth rate (C2), and adaptability to barrenness (C5). The trees were classified into five distinct categories, with each exhibiting significant variation in terms of the strengths and weaknesses of the indicators. According to the comprehensive score, the trees were categorized into three levels. The Grade I plants exhibited the best carbon efficiency performance, comprising a total of 12 species (e.g. Sabina chinensis, Fraxinus chinensis 'Aurea' and Hibiscus syriacu), and demonstrated superior performance in all aspects. Grade II trees, consisting of 26 species (e.g Pinus tabuliformis, Paulownia fortunei, Ligustrum × vicaryi), had the second-highest comprehensive score. Moreover, Grade III trees, encompassing 12 species (e.g Acer mono, Cedrus deodara, Magnolia denudata), exhibited lower comprehensive scores. The extensive use of Grade I and II tree species is recommended in the implementation of low-carbon greening projects in the Bohai Bay region, while Grade III tree species should be judiciously utilized. The findings of this research can serve as a valuable resource for the scientific identification of tree species that are suitable for urban park green spaces in the Bohai Bay region, which is characterized by predominantly saline and alkaline soil. Additionally, the development of an evaluation system can guide the selection of low-carbon tree species when evaluating other types of saline and alkaline lands.

Population genomics analysis reveals footprints of selective breeding in a rapid-growth variety of Paulownia fortunei with apical dominance

Paulownia fortunei is an ecologically and economically valuable tree cultivated for its rapid growth and high-quality timber. To enhance Paulownia germplasm, we have developed the elite variety QingT with patented advantages in growth rate and apical dominance. To illuminate the genetic basis of QingT's superior traits, here we harness comparative population genomics to analyze genomic variation patterns between QingT and common Paulownia. We performed whole-genome re-sequencing of 30 QingT and 30 common samples, detecting 15.6 million SNPs and 2.6 million indels. Phylogeny and population structure analyses robustly partitioned common and QingT into distinct groups which indicate robust genome stabilization. QingT exhibited reduced heterozygosity and linkage disequilibrium decay compared to common Paulownia, reflecting high recombination, indicating hybridizing effects with common white-flowered string is the source of its patented advantages. Genome selection scans uncovered 25 regions of 169 genes with elevated nucleotide diversity, indicating selection sweeps among groups. Functional analysis of sweep genes revealed upregulation of ribosomal, biosynthesis, and growth pathways in QingT, implicating enhanced protein production and developmental processes in its rapid growth phenotype. This study's insights comprehensively chart genomic variation during Paulownia breeding, localizing candidate loci governing agronomic traits, and underpinnings of future molecular breeding efforts to boost productivity.

Paulownia trees as a sustainable solution for CO2 mitigation: assessing progress toward 2050 climate goals

Due to the progressive climate change on our planet, scientists are interested in solving this issue since it threatens not only certain regions or countries but also the world’s ecosystems and economies. Therefore, minimizing carbon dioxide (CO2) emissions and reducing atmospheric levels are global priorities. Thus, it is necessary at this moment to develop an appropriate approach to reduce or stabilize CO2 levels in the atmosphere. However, CO2 capture projects are long-term, low-profitable, and high-risk environmental projects. Consequently, it is necessary to find an appropriate and sustainable CO2 capture approach that is efficient in reducing atmospheric CO2 levels while having a safe impact on the environment. Although carbon (C) is the key basic component used to produce biological compounds by photosynthetic organisms in terrestrial plants, the C pathway is a key factor affecting the capture of CO2 by photosynthetic organisms. Among photosynthetic organisms, Paulownia, a multipurpose tree, is popular around the world for its timber and its potential role in CO2 sequestration. Paulownia spp. belongs to the Paulowniaceae family and comprises a group of trees. These trees are primarily found in southeastern Asia, particularly in China, and have been intentionally grown for more than two millennia due to their ornamental, cultural, and medicinal value. The number of Paulownia species varies depending on taxonomic classification, ranging from 6 to 17. Among them, Paulownia tomentosa, Paulownia elongata, Paulownia fortunei, and Paulownia catalpifolia are the most widely recognized and favored species. The present review provides a comprehensive technical-economic scenario for the capture of one million tons of CO2 by Paulownia trees (as a terrestrial plant model, grown on 2,400 ha−1). P. tomentosa can be utilized in agroforestry systems to mitigate greenhouse gas (GHG) emissions within urban cities and emphasize the carbon storage potential of agroforestry. In conclusion, Paulownia trees as an environmental mass project showed great encouragement to investors and governments to expand these types of projects to achieve global climate goals by 2050.

Comprehensive Analysis of the GRAS Gene Family in Paulownia fortunei and the Response of DELLA Proteins to Paulownia Witches' Broom.

The GRAS (GAI\RGA\SCL) gene family encodes plant-specific transcription factors that play crucial roles in plant growth and development, stress tolerance, and hormone network regulation. Plant dwarfing symptom is mainly regulated by DELLA proteins of the GRAS gene subfamily. In this study, the association between the GRAS gene family and Paulownia witches' broom (PaWB) was investigated. A total of 79 PfGRAS genes were identified using bioinformatics methods and categorized into 11 groups based on amino acid sequences. Tandem duplication and fragment duplication were found to be the main modes of amplification of the PfGRAS gene family. Gene structure analysis showed that more than 72.1% of the PfGRASs had no introns. The genes PfGRAS12/18/58 also contained unique DELLA structural domains; only PfGRAS12, which showed significant response to PaWB phytoplasma infection in stems, showed significant tissue specificity and responded to gibberellin (GA3) in PaWB-infected plants. We found that the internodes were significantly elongated under 100 µmol·L-1 GA3 treatment for 30 days. The subcellular localization analysis indicated that PfGRAS12 is located in the nucleus and cell membrane. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays confirmed that PfGRAS12 interacted with PfJAZ3 in the nucleus. Our results will lay a foundation for further research on the functions of the PfGRAS gene family and for genetic improvement and breeding of PaWB-resistant trees.

Genome-Wide Identification of the Paulownia fortunei Aux/IAA Gene Family and Its Response to Witches' Broom Caused by Phytoplasma.

The typical symptom of Paulownia witches' broom (PaWB), caused by phytoplasma infection, is excessive branching, which is mainly triggered by auxin metabolism disorder. Aux/IAA is the early auxin-responsive gene that participates in regulating plant morphogenesis such as apical dominance, stem elongation, lateral branch development, and lateral root formation. However, no studies have investigated the response of the Aux/IAA gene family to phytoplasma infection in Paulownia fortunei. In this study, a total of 62 Aux/IAA genes were found in the genome. Phylogenetic analysis showed that PfAux/IAA genes could be divided into eight subgroups, which were formed by tandem duplication and fragment replication. Most of them had a simple gene structure, and several members lacked one or two conserved domains. By combining the expression of PfAux/IAA genes under phytoplasma stress and SA-treated phytoplasma-infected seedlings, we found that PfAux/IAA13/33/45 may play a vital role in the occurrence of PaWB. Functional analysis based on homologous relationships showed a strong correlation between PfAux/IAA45 and branching. Protein-protein interaction prediction showed that PfARF might be the binding partner of PfAux/IAA, and the yeast two-hybrid assay and bimolecular fluorescent complementary assay confirmed the interaction of PfAux/IAA45 and PfARF13. This study provides a theoretical basis for further understanding the function of the PfAux/IAA gene family and exploring the regulatory mechanism of branching symptoms caused by PaWB.

Energy and autohydrolysis by-products from industrial crops

The world is experiencing a growing shortage of raw materials which is especially severe in the energy sector and being worsened by the unfavorable environmental impact of a consumerist culture revolving around the exploitation of non-renewable resources. In this work, the calorific value and chemical composition of liquors resulting from the autohydrolysis of six different lignocellulosic materials was determined (Eucalyptus globulus, Arundo donax, Leucaena diversifolia, Paulownia fortunei, Sunflower stalks and Chamaecytisus proliferus –tagasaste-) and was assesed for the obtainment of energy, sugars and other chemical products by using of integral fractionation based on autohydrolisys. Autohydrolysis processes have been considered interesting in the case of timber species studied compared with herbaceous species with variations in the extraction of the xylan fraction at 180 º C and 200 ° C.

Bioinformatic Analysis of the BTB Gene Family in Paulownia fortunei and Functional Characterization in Response to Abiotic and Biotic Stresses.

To learn about the gene structure, phylogenetic evolution, and function under biotic and abiotic stresses of BTB (Bric-a-Brac/Tramtrack/Broad Complex) genes in Paulownia fortunei, a whole-genome sequence evaluation was carried out, and a total of 62 PfBTB genes were identified. The phylogenetic analysis showed that PfBTB proteins are divided into eight groups, and these proteins are highly conserved. PfBTB genes were unevenly distributed on 17 chromosomes. The colinearity analysis found that fragment replication and tandem replication are the main modes of gene amplification in the PfBTB family. The analysis of cis-acting elements suggests that PfBTB genes may be involved in a variety of biological processes. The transcriptomic analysis results showed that PfBTB3/12/14/16/19/36/44 responded to Paulownia witches' broom (PaWB), while PfBTB1/4/17/43 responded to drought stress, and the RT-qPCR results further support the reliability of transcriptome data. In addition, the association analysis between miRNA and transcriptome revealed a 91-pair targeting relationship between miRNAs and PfBTBs. In conclusion, the BTB genes in Paulownia are systematically identified in this research. This work provides useful knowledge to more fully appreciate the potential functions of these genes and their possible roles in the occurrence of PaWB and in response to stress.

RESPUESTA DE TRES ESPECIES MADERABLES DE RÁPIDO CRECIMIENTO A DIFERENTES BIOCLIMAS EN ECUADOR

<p><strong>Background:</strong> The timber sector in Ecuador holds promising potential for growth and development. The intensive utilization of native taxa has depleted their genetic species pool, making them increasingly scarce in meeting the rising demand for wood. Consequently, there has been a growing exploration of new fast-growing forest species to serve as alternatives for lumber and biomass production. <strong>Objective: </strong>To assess the suitability of Andean bioclimatic conditions for the introduction of three tree species: <em>Paulownia elongata, P. fortunei</em>, and the hybrid <em>P. elongata x P. fortunei</em>. This work primarily focused in investigating whether plant density impacts the initial growth of individual tree growth and whether there is a co-dependence between site conditions and plant density in each of the three species. <strong>Methodology:</strong> The National Autonomous Institute of Farming Research (INIAP) imported 3000 seedlings, each about 10cm tall, of <em>Paulownia e</em>longata, <em>Paulownia fortunei</em>, and the hybrid <em>Paulownia elongata</em> x <em>Paulownia fortunei</em> from the World Paulownia Institute of Georgia - USA. Four experimental sites were selected in two regions of Ecuador: humid tropics (Quevedo and Santo Domingo de los Tsachilas), dry sub-peak (el Almendral) and Andes (Riobamba), each site is located at different altitudes. At each site, the experiment was set up in a spatial split-plot arrangement with randomized complete blocks. Three blocks were established, two planting frames (3x3 m and 4x4 m) and the three selected <em>Paulownia</em> species. The three blocks were laid off randomly in each experiment. The two planting frames were randomly placed within each block, and the three species were randomly planted within each planting frame. The experimental subjects (plant species) consisted of nine individuals. <strong>Results:</strong> Plants with higher height and diameter are located in areas with lower elevation, with hybrid Paulownia displaying better performance in high densities. All species showed a survival rate above 85% one-year post-establishment. However, the lowest survival is found in areas above 2000 m. <strong>Implications:</strong> High elevations restrict the individual growth of Paulownia in Andean conditions, but low altitudes enhance it. <strong>Conclusion:</strong> The three specimens performed reasonably well during one-year post-establishment. However, it is necessary to continue observing their growth until they reach their asymptotic point, determining their volumetric yield.</p>

Phytosynthesis of silver nanoparticles by Paulownia fortunei fruit exudates and its application against Fusarium sp. causing dry rot postharvest diseases of banana

Over the recent years, banana cultivation has increased in the South-Eastern provinces of Iran. Management of Fusarium diseases in banana poses considerable yield loss as the application of chemical and biological treatments remains challenging. At the present research, about 10 Fusarium isolates causing dry rot on banana fruits were isolated and based on the pathogenicity test, isolate MSN-7 was considered as the most pathogenic isolate. Isolate MSN-7 was identified by using the ITS (ITS1 and ITS4) genomic region. BLAST results showed that it had the highest similarity (99%) with Fusarium chalmydosporum (MN533778.1). The objective of our research was to examine different concentrations of Silver nanoparticles (SNPs) biosynthesized by Paulownia fortunei L.) Fruit Exudates as a novel antifungal agent for reduce of pathogencity of Fusarium dry rot of banana. The synthesis of SNPs was conducted utilizing Paulownia fruit extracts as an environmentally friendly biosource. The exudates derived from Paulownia fruit demonstrated the capability to generate nanoparticles with an average size of 46 nm. Analysis conducted using a transmission electron microscope (TEM) revealed that these nanoparticles possess a polyhedral structure. Furthermore, when applied at concentrations of 10, 20, 40, and 80 μg/ml, these biosynthetic nanoparticles exhibited the ability to inhibit the growth of Fusarium fungus mycelia, as well as induced the destruction of the fungal hyphae.

Construction of a High-Density Paulownia Genetic Map and QTL Mapping of Important Phenotypic Traits Based on Genome Assembly and Whole-Genome Resequencing

Quantitative trait locus (QTL) mapping based on a genetic map is a very effective method of marker-assisted selection in breeding, and whole-genome resequencing is one of the useful methods to obtain high-density genetic maps. In this study, the hybrid assembly of Illumina, PacBio, and chromatin interaction mapping data was used to construct high-quality chromosomal genome sequences of Paulownia fortunei, with a size of 476.82 Mb, a heterozygosity of 0.52%, and a contig and scaffold N50s of 7.81 Mb and 21.81 Mb, respectively. Twenty scaffolds with a total length of 437.72 Mb were assembled into 20 pseudochromosomes. Repeat sequences with a total length of 243.96 Mb accounted for 51.16% of the entire genome. In all, 26,903 protein-coding gene loci were identified, and 26,008 (96.67%) genes had conserved functional motifs. Further comparative genomics analysis preliminarily showed that the split of P. fortunei with Tectona grandis likely occurred 38.8 (33.3–45.1) million years ago. Whole-genome resequencing was used to construct a merged genetic map of 20 linkage groups, with 2993 bin markers (3,312,780 SNPs), a total length of 1675.14 cm, and an average marker interval of 0.56 cm. In total, 73 QTLs for important phenotypic traits were identified (19 major QTLs with phenotypic variation explained ≥ 10%), including 10 for the diameter at breast height, 7 for the main trunk height, and 56 for branch-related traits. These results not only enrich P. fortunei genomic data but also form a solid foundation for fine QTL mapping and key marker/gene mining of Paulownia, which is of great significance for the directed genetic improvement of these species.

Growth of Paulownia ssp. Interspecific Hybrid ‘Oxytree’ Micropropagated Nursery Plants under the Influence of Plant-Growth Regulators

The aim of the study was to examine the effects of application of plant-growth regulators (PGR) on the growth of paulownia plants and evaluate their usefulness in paulownia nurseries. The experiment was carried out on the paulownia interspecific hybrid (Paulownia elongata × Paulownia fortunei) ‘Oxytree’. Micropropagated plants grown in pots were sprayed with PGR solutions. Gibberellins (GA3, GA4+GA7), 6-benzyladenine (BA), triclopyr (TPA), ethephon (ETH), daminozide (DA), prohexadione-Ca (PH), and trinexapac-ethyl (TE) were used. They were included in commercial products (Florgib 245 mg dm−3, Gibb plus 11 SL 5 cm3 dm−3, Globaryll 100 SL 1.5 cm3 dm−3, Topper 10 ST 200 mg dm−3, Agrostym 480 SL 2 cm3 dm−3, B-Nine 85 SG 2 g dm−3, Regalis plus 10 WG 2.5 g dm−3, Moddus 250 EC 1 cm3 dm−3, respectively). None of the studied preparations modified positive correlations between the longitudinal vs. transverse growth of stems and growth of leaves. Not only GA3, GA4+GA7, but also BA (cytokinin) and unexpectedly TE (retardant) stimulated stem elongation and thickening. Furthermore, the effect of TE lasted longer than influence of GAx and BA. Leaves of TE-treated plants were distinguished by a higher chlorophyll a/b ratio, and a lower relative chlorophyll content and efficiency of photosystem II (Fv/Fm, Fv/F0). TPA strongly deformed the stems and leaves of liners. Other regulators (ETH, DA, PH) retarded the diameter growth of stems and leaf expansion. Some results obtained by GAx, BA, and especially by TE treatment, might be beneficial for paulownia grown as ornamental and/or timber tree.

Carbon Stock Assessment in Natural Forests and Plantations Using Geo-Informatics in Manipur, Northeast India

Uncertainties continue to prevail in the potential of natural forests and plantations in carbon stock assessment. The present study was carried out to assess the carbon stock in natural and plantation forests of Manipur using geo-informatics in Imphal East and West districts. The integrated approach of geospatial technology, along with field inventory based data, was used in spatial modeling of biomass carbon of selected natural and plantation forests. The stand density was similar for both LNG and TRS forests (680 individuals ha−1) and lowest for KHP forest (640 individuals ha−1). Paulownia fortunei (770 individuals ha−1) showed highest density among tree species while Tectona grandis (54.07 m2 ha−1) followed by Gmelina arborea (42.18 m2 ha−1) had higher basal area compared to other tree species. The soil moisture content (%) in the natural forest ranged from 19.13 ± 0.47 to 26.9 ± 0.26%. The soil moisture content in the plantation forest ranged from 19.16 ± 0.98 to 25.83 ± 0.06%. The bulk density of natural forests ranged from 1.27 g cm−3 to 1.37 g cm−3 while for plantation forests it ranged from 1.18 g cm−3 to 1.34 g cm−3. Among the studied sites of natural forest, TRS forest had both the highest AGBC value of 132.74 t ha−1 as well as the BGBC value of 38.49 t ha−1. Similarly, among the plantations, T. grandis plantation showed the highest AGBC (193 t ha−1) and BGBC (55.97 t ha−1). On the other hand, Tharosibi forest and T. grandis plantation had the highest total carbon stock for natural and plantation forest with values of 274.824 t ha−1 and 390.88 t ha−1, respectively. The total above-ground carbon stock estimated for the natural forest of KHP, LNG and TRS were 109.60 t ha−1, 79.49 t ha−1 and 132.74 t ha−1, respectively. On the other hand, the estimated total above-ground carbon stock in plantation of GA, PD, PF and TG were 62.93 t ha−1 62.81 t ha−1, 45.85 t ha−1 and 193.82 t ha−1. In the present study, the relationship with the biomass was observed to be better in SAVI compared to NDVI and TVI. The linear regression analysis performed to determine the relationship between the estimated and predicted biomass resulted in a correlation coefficient of R2 = 0.85 for the present study area, which is an indication of a good relationship between the estimated and predicted biomass.

Genome-Wide Characterization of Calmodulin and Calmodulin-like Protein Gene Families in Paulownia fortunei and Identification of Their Potential Involvement in Paulownia Witches' Broom.

As significant Ca2+ sensors, calmodulin (CaM) and calmodulin-like proteins (CML), have been associated with a variety of environmental conditions in plants. However, whether CaMs/CMLs are related to the stress of phytoplasma infection has not been reported in Paulownia fortunei. In the current study, 5 PfCaMs and 58 PfCMLs were detected through a genome-wide investigation. The number of EF-hand motifs in all PfCaMs/CMLs varied. Bioinformatics analyses, including protein characteristics, conserved domain, gene structure, cis-elements, evolutionary relationship, collinearity, chromosomal location, post-translation modification site, subcellular localization and expression pattern analyses, represented the conservation and divergence of PfCaMs/CMLs. Furthermore, some PfCaMs/CMLs might be involved in plants' reaction to phytoplasma infection and exogenous calcium therapy, indicating these genes may play a role in abiotic as well as biotic stress responses. In addition, subcellular localization analysis showed that PfCML10 was located in the cell membrane and nucleus. In summary, these findings establish a stronger platform for their subsequent functional investigation in trees and further characterize their roles in Paulownia witches' broom (PaWB) occurrence.

N6‐methyladenosine modification changes during the recovery processes for Paulownia witches' broom disease under the methyl methanesulfonate treatment

AbstractPhytoplasmas induce diseases in more than 1000 plant species and cause substantial ecological damage and economic losses, but the specific pathogenesis of phytoplasma has not yet been clarified. N6‐methyladenosine (m6A) is the most common internal modification of the eukaryotic Messenger RNA (mRNA). As one of the species susceptible to phytoplasma infection, the pathogenesis and mechanism of Paulownia has been extensively studied by scholars, but the m6A transcriptome map of Paulownia fortunei (P. fortunei) has not been reported. Therefore, this study aimed to explore the effect of phytoplasma infection on m6A modification of P. fortunei and obtained the whole transcriptome m6A map in P. fortunei by m6A‐seq. The m6A‐seq results of Paulownia witches' broom (PaWB) disease and healthy samples indicate that PaWB infection increased the degree of m6A modification of P. fortunei. The correlation analysis between the RNA‐seq and m6A‐seq data detected that a total of 315 differentially methylated genes were predicted to be significantly differentially expressed at the transcriptome level. Moreover, the functions of PaWB‐related genes were predicted by functional enrichment analysis, and two genes related to maintenance of the basic mechanism of stem cells in shoot apical meristem were discovered. One of the genes encodes the receptor protein kinase CLV2 (Paulownia_LG2G000076), and the other gene encodes the homeobox transcription factor STM (Paulownia_LG15G000976). In addition, genes F‐box (Paulownia_LG17G000760) and MSH5 (Paulownia_LG8G001160) had exon skipping and mutually exclusive exon types of alternative splicing in PaWB‐infected seedling treated with methyl methanesulfonate, and m6A modification was found in m6A‐seq results. Moreover, Reverse Transcription–Polymerase Chain Reaction (RT‐PCR) verified that the alternative splicing of these two genes was associated with m6A modification. This comprehensive map provides a solid foundation for revealing the potential function of the mRNA m6A modification in the process of PaWB. In future studies, we plan to verify genes directly related to PaWB and methylation‐related enzymes in Paulownia to elucidate the pathogenic mechanism of PaWB caused by phytoplasma invasion.

The Potential of Paulownia fortunei L. for the Phytoremediation of Pb

Pb endangers forest ecological health; phytoremediation is an effective Pb remediation technology. Woody plants with Pb tolerance provided a mechanism for the phytoremediation of Pb. Paulownia fortunei (L.), a fast-growing woody plant, has a good tolerance to Pb. However, its tolerance mechanism is unclear. The results in this study revealed that P. fortunei seedlings can withstand 400 mg·L−1 Pb stress. The quantification of Pb in different P. fortunei tissues showed an increasing trend of accumulation in root > leaf > stem; the transport coefficient and enrichment coefficient decreased with an increase in Pb concentration. The tolerance of P. fortunei to Pb may be related to cell partition and immobilization by the cell wall. Microstructural analysis performed using scanning electron microscopy showed that the absorbed Pb is mainly distributed in cell wall components, and when the concentration of Pb increases, it can be transferred to soluble parts and organelles. The Fourier transform infrared spectrometry results showed that excess hydroxyl groups occurred under Pb stress in the outer epidermis cell walls of roots and leaves adsorbing heavy metals. When the concentration of Pb was over 400 mg·L−1, the growth of P. fortunei was inhibited, the root cell wall was deformed, the plasmolysis occurred in the cauline cell, and the internal leaf capsule was ruptured. Furthermore, antioxidant enzyme activity was significantly reduced. Therefore, P. fortunei can transfer the underground part of Pb to the aboveground part up to the concentration of 400 mg·L−1. This study provides a theoretical basis and technical reference for fully utilizing woody plant resources to restore the ecological environment of forests.

Biomass Production and Quality of Twelve Fast-Growing Tree Taxa in Short Rotation under Mediterranean Climate

Sustainable production of lignocellulosic biomass for energy use can contribute to climate change mitigation. This work aims to compare the biomass production of twelve fast-growing woody taxa belonging to the Eucalyptus, Casuarina, Populus and Paulownia genera, the quality of their biomass for energy use and its valorizing through transformation into pellets, as well as the effect of the crop on the soil. Over the course of two rotations, plant growth and biomass production were assessed. The yield of aboveground dry biomass ranged from 9 to 61 Mg ha−1 year−1 (equivalent to 137–867 GJ ha−1 year−1). The highest yields were obtained for Eucalyptus clones (51–61 Mg ha−1 year−1). The N-fixing species Casuarina equisetifolia and two Populus × euramericana clones (‘Adige’ and ‘AF2’) also achieved high yields (28–33 Mg ha−1 year−1), though significantly smaller than those of the eucalypts. Due to its low wood density, Paulownia fortunei was not very productive in terms of biomass (18 Mg ha−1 year−1), despite its good growth in diameter and height. However, some management practices, such as not removing nutrient-rich and poor-quality biomass fractions for energy use (leaves and thin branches) from the harvested crop, as well as the use of N-fixing species and by taking into account all nutrient inputs and outputs, can ensure the sustainability of the cultivation systems and improve degraded soils.