EuHDZ25 positively affects rubber biosynthesis by targeting EuFPS1 in Eucommia leaves.

Eucommia ulmoides is a temperate gum source plant that produces trans-polyisoprene (TPI), also known as Eucommia rubber. The structural configuration and function of TPI offer a new material with important potential for industrial development. In this study, we detected the TPI content in the leaves of diploid and triploid E. ulmoides plants. The average TPI content in the leaves of triploid E. ulmoides was significantly higher than that of diploid. Transcriptome data and weighted gene co-expression network analyses identified a significant positive correlation between the EuFPS1 gene and TPI content. Overexpression of EuFPS1 increased the density of rubber particles and TPI content, indicating its crucial role in TPI biosynthesis. In addition, the expression of EuHDZ25 in E. ulmoides was significantly positively correlated with EuFPS1 expression. Yeast one-hybrid and dual-luciferase assays demonstrated that EuHDZ25 mainly promotes TPI biosynthesis through positive regulation of EuFPS1 expression. The significantly up-regulated expression of EuHDZ25 and its consequent upregulation of EuFPS1 during the biosynthesis of TPI may partially explain the increased TPI content of triploids. This study provides an important theoretical foundation for further exploring the molecular mechanism of secondary metabolites content variation in polyploids and can help to promote the development and utilization of rubber resources.

The NAC transcription factor family in Eucommia ulmoides: Genome-wide identification, characterization, and network analysis in relation to the rubber biosynthetic genes.

The NAC transcription factor family is a large plant gene family, participating in plant growth and development, secondary metabolite synthesis, biotic and abiotic stresses responses, and hormone signaling. Eucommia ulmoides is a widely planted economic tree species in China that can produce trans-polyisoprene: Eucommia rubber (Eu-rubber). However, genome-wide identification of the NAC gene family has not been reported in E. ulmoides. In this study, 71 NAC proteins were identified based on genomic database of E. ulmoides. Phylogenetic analysis showed that the EuNAC proteins were distributed in 17 subgroups based on homology with NAC proteins in Arabidopsis, including the E. ulmoides-specific subgroup Eu_NAC. Gene structure analysis suggested that the number of exons varied from 1 to 7, and multitudinous EuNAC genes contained two or three exons. Chromosomal location analysis revealed that the EuNAC genes were unevenly distributed on 16 chromosomes. Three pairs of genes of tandem duplicates genes and 12 segmental duplications were detected, which indicated that segmental duplications may provide the primary driving force of expansion of EuNAC. Prediction of cis-regulatory elements indicated that the EuNAC genes were involved in development, light response, stress response and hormone response. For the gene expression analysis, the expression levels of EuNAC genes in various tissues were quite different. To explore the effect of EuNAC genes on Eu-rubber biosynthesis, a co-expression regulatory network between Eu-rubber biosynthesis genes and EuNAC genes was constructed, which indicated that six EuNAC genes may play an important role in the regulation of Eu-rubber biosynthesis. In addition, this six EuNAC genes expression profiles in E. ulmoides different tissues were consistent with the trend in Eu-rubber content. Quantitative real-time PCR analysis showed that EuNAC genes were responsive to different hormone treatment. These results will provide a useful reference for further studies addressing the functional characteristics of the NAC genes and its potential role in Eu-rubber biosynthesis.

Effect of a suitable treatment period on the genetic transformation efficiency of the plant leaf disc method.

BACKGROUND: Agrobacterium tumefaciens-mediated leaf disc genetic transformation is an important way to achieve transgenics or gene editing. Ensuring stable and efficient genetic transformation is still an important problem in modern biology. It is assumed that the difference in the development status of genetic transformation cells of receptor materials is the main reason for the difference and instability of genetic transformation efficiency; the stable and efficient genetic transformation rate can be obtained by defining the appropriate treatment period of the receptor material and applying genetic transformation in a timely manner. RESULTS: Based on these assumptions, we studied and established an efficient and stable Agrobacterium-mediated plant transformation system with hybrid poplar (Populus alba × Populus glandulosa, 84 K) leaves, stem segments and tobacco leaves as the research objects. There were differences in the development process of leaf bud primordial cells from different explants, and the genetic transformation efficiency was significantly related to the cell development stage of the in vitro cultured materials. Among them, the genetic transformation rate of poplar and tobacco leaves was the highest on the 3rd and 2nd day of culture, reaching 86.6% and 57.3%, respectively. The genetic transformation rate of poplar stem segments was the highest on the 4th day of culture, reaching 77.8%. The best treatment period was from the development of leaf bud primordial cells to the S phase of the cell cycle. The number of cells detected using flow cytometry and 5-ethynyl-2'-deoxyuridine (EdU) staining, the expression of cell cycle-related protein CDKB1; 2, CDKD1; 1, CYCA3; 4, CYCD1; 1, CYCD3; 2, CYCD6; 1, and CYCH; 1 of explants, and morphological changes of explants can be used as indicators to determine the appropriate treatment period for genetic transformation. CONCLUSIONS: Our study provides a new and universal set of methods and characteristics to identify the S phase of the cell cycle and apply genetic transformation treatments at the appropriate time. Our results are of great significance for improving the efficiency and stability of plant leaf disc genetic transformation.

Morphological, Transcriptome, and Hormone Analysis of Dwarfism in Tetraploids of Populus alba × P. glandulosa.

Breeding for dwarfism is an important approach to improve lodging resistance. Here, we performed comparative analysis of the phenotype, transcriptome, and hormone contents between diploids and tetraploids of poplar 84K (Populus alba × P. glandulosa). Compared with diploids, the indole-3-acetic acid (IAA) and gibberellin (GA3) contents were increased, whereas the jasmonic acid (JA) and abscisic acid (ABA) contents were decreased in tetraploids. RNA-sequencing revealed that differentially expressed genes (DEGs) in leaves of tetraploids were mainly involved in plant hormone pathways. Most DEGs associated with IAA and GA promotion of plant growth and development were downregulated, whereas most DEGs associated with ABA and JA promotion of plant senescence were upregulated. Weighted gene co-expression network analysis indicated that certain transcription factors may be involved in the regulation of genes involved in plant hormone pathways. Thus, the altered expression of some genes in the plant hormone pathways may lead to a reduction in IAA and GA contents, as well as an elevation in ABA and JA contents, resulting in the dwarfing of tetraploids. The results show that polyploidization is a complex biological process affected by multiple plant hormone signals, and it provides a foundation for further exploration of the mechanism of tetraploids dwarfing in forest trees.

Effect of Electrolytic Manganese Residue in Fly Ash-Based Cementitious Material: Hydration Behavior and Microstructure.

Electrolytic manganese residue (EMR) is a solid waste with a main mineralogical composition of gypsum. It is generated in the production of metal manganese by the electrolysis process. In this research, EMR, fly ash, and clinker were blended to make fly ash-based cementitious material (FAC) to investigate the effect of EMR on strength properties, hydration behavior, microstructure, and environmental performance of FAC. XRD, TG, and SEM studied the hydration behavior of FAC. The pore structure and [SiO4] polymerization degree were characterized by MIP and 29Si NMR, respectively. The experimental results indicate that FAC shows excellent mechanical properties when the EMR dosage is 10%. Moderate content of sulfate provided by EMR can promote hydration reaction of FAC, and it shows a denser pore structure and higher [SiO4] polymerization degree in this case. Heavy metal ions derived from EMR can be adsorbed in the hydration products of FAC to obtain better environmental properties. This paper presents an AFt covering model for the case of excessive EMR in FAC, and it importantly provides theoretical support for the recycling of EMR in cementitious materials.

Integrated transcriptome and miRNA sequencing approaches provide insights into salt tolerance in allotriploid Populus cathayana.

MAIN CONCLUSION: Some salt-stress responsive DEGs, mainly involved in ion transmembrane transport, hormone regulation, antioxidant system, osmotic regulation, and some miRNA jointly regulated the salt response process in allotriploid Populus cathayana. The molecular mechanism of plant polyploid stress resistance has been a hot topic in biological research. In this study, Populus diploids and first division restitution (FDR) and second division restitution (SDR) triploids were selected as research materials. All materials were treated with 70 mM NaCl solutions for 30 days in the same pot environment. We observed the growth state of triploids and diploids and determined the ratio of potassium and sodium ions, peroxidase (POD) activity, proline content, and ABA and jasmonic acid (JA) hormone content in leaves in the same culture environment with the same concentration of NaCl solution treatment. In addition, RNA-seq technology was used to study the differential expression of mRNA and miRNA. The results showed that triploid Populus grew well and the K+ content and the K+/Na+ ratio in the salt treatment were significantly lower than those in the control. The contents of ABA, JA, POD, and proline were increased compared with contents in diploid under salt stress. The salt-stress responsive DEGs were mainly involved in ion transport, cell homeostasis, the MAPK signaling pathway, peroxisome, citric acid cycle, and other salt response and growth pathways. The transcription factors mainly included NAC, MYB, MYB_related and AP2/ERF. Moreover, the differentially expressed miRNAs involved 32 families, including 743 miRNAs related to predicted target genes, among which 22 miRNAs were significantly correlated with salt-stress response genes and related to the regulation of hormones, ion transport, reactive oxygen species (ROS) and other biological processes. Our results provided insights into the physiological and molecular aspects for further research into the response mechanisms of allotriploid Populus cathayana to salt stress. This study provided valuable information for the salt tolerance mechanism of allopolyploids.

Binary reaction behaviors of red mud based cementitious material：Hydration characteristics and Na+ utilization.

Bayer red mud (RM) occupies a large amount of land, which excessive Na+ seriously damages groundwater resources. In this research, a RM based cementitious material (RMC) composed of RM and ordinary Portland cement (OPC) was developed. It is interesting to find that a binary reaction consisting of cement hydration and geopolymer reaction in RMC. The mechanical and Na+ consolidation rate of RMC were improved by the synergistic effect of binary reaction. The results indicated that the compressive strength of RMC is the highest and reaches 32.5R OPC when the mass ratio of CaO/(SiO2+Al2O3) is 1.37, and the Na+ leaching concentration is environmentally acceptable. The 7 days compressive strength of RM-based cementitious material No.2 (RMC2) can reach 93.80% of that of 28 days. As the predominant hydration products, cement hydration product (Ca5(SiO4)2(OH)2) and geopolymer (CaAl2Si2O8·2H2O and Na3Al3Si3O12·2H2O) were principally responsible for the strength development of RMC2 at 7 days. The optimal densification microstructure and [SiO4] polymerization structure was presented in RMC2. The supreme Na+ consolidation rate was 99.23% in RMC2 due to the cooperation of physical fixation and [Si(Al)O4] charge balance principle. This paper provides a fresh theoretical guidance for the utilization of RM and its Na+ in building materials.

High-quality de novo assembly of the Eucommia ulmoides haploid genome provides new insights into evolution and rubber biosynthesis.

We report the acquisition of a high-quality haploid chromosome-scale genome assembly for the first time in a tree species, Eucommia ulmoides, which is known for its rubber biosynthesis and medicinal applications. The assembly was obtained by applying PacBio and Hi-C technologies to a haploid that we specifically generated. Compared to the initial genome release, this one has significantly improved assembly quality. The scaffold N50 (53.15 MB) increased 28-fold, and the repetitive sequence content (520 Mb) increased by 158.24 Mb, whereas the number of gaps decreased from 104,772 to 128. A total of 92.87% of the 26,001 predicted protein-coding genes identified with multiple strategies were anchored to the 17 chromosomes. A new whole-genome duplication event was superimposed on the earlier γ paleohexaploidization event, and the expansion of long terminal repeats contributed greatly to the evolution of the genome. The more primitive rubber biosynthesis of this species, as opposed to that in Hevea brasiliensis, relies on the methylerythritol-phosphate pathway rather than the mevalonate pathway to synthesize isoprenyl diphosphate, as the MEP pathway operates predominantly in trans-polyisoprene-containing leaves and central peels. Chlorogenic acid biosynthesis pathway enzymes were preferentially expressed in leaves rather than in bark. This assembly with higher sequence contiguity can foster not only studies on genome structure and evolution, gene mapping, epigenetic analysis and functional genomics but also efforts to improve E. ulmoides for industrial and medical uses through genetic engineering.

Molecular Mechanism of Vegetative Growth Advantage in Allotriploid Populus.

Allotriploid poplar has a prominent vegetative growth advantage that impacts dramatically on lumber yield. The growth regulation is complex which involves abundant genes, metabolic and signaling pathways, while the information about the functional control process is very little. We used high-throughput sequencing and physiological index measurement to obtain a global overview of differences between allotriploid and diploid Populus. The genes related to plant growth advantage show a higher expression compared to diploid, and most of them are revolved around hormones, photosynthesis and product accumulation. Thus, allotriploid Populus showed more efficient photosynthesis, carbon fixation, sucrose and starch synthesis, and metabolism as well as augmented biosynthesis of auxin, cytokinin, and gibberellin. These data enable the connection of metabolic processes, signaling pathways, and specific gene activity, which will underpin the development of network models to elucidate the process of triploid Populus advantage growth.