Project description:BackgroundPoplar trees provide a large amount of wood material, but many parts of the world are arid or semi-arid areas because of insufficient annual precipitation, which seriously affects the growth of poplar trees. Populus simonii 'Tongliao1' shows strong tolerance to stress environments, and Populus deltoides 'Danhong' shows a stronger growth rate in a suitable environment. To identify drought tolerance-related QTLs and genes, an F1 population derived from the cross between the 'Danhong' and 'Tongliao 1' Populus was assessed under drought stress.ResultsWe measured drought-related traits such as the relative height growth, relative diameter growth, leaf senescence number, specific leaf area, and leaf relative water content in the population under control and drought environments. The results showed that drought stress reduced the plant height relative growth, ground diameter relative growth, specific leaf area and leaf relative water content and increased the number of leaf drops. A total of 208 QTLs were identified by QTL mapping analysis, and they consisted of 92, 63 and 53 QTLs under control, drought stress treatment and drought index conditions, respectively. A molecular identification marker for drought tolerance, np2841, which was associated with a QTL (qDLRWC-LG10-1) for relative leaf water content, was initially developed. We mined 187 candidate genes for QTL regions of five traits under a drought environment. The reference genome annotation for Populus trichocarpa and a homologous gene analysis of Arabidopsis thaliana identified two candidate genes, Potri.003G171300 and Potri.012G123900, with significant functions in response to drought stress. We identified five key regulatory genes (Potri.006G273500, Potri.007G111500, Potri.007G111600, Potri.007G111700, and Potri.007G111800) related to drought tolerance through the poplar coexpression network.ConclusionIn this study, our results indicate that the QTLs can effectively enhance the drought tolerance of poplar. It is a step closer towards unravelling the genetic basis of poplar drought tolerance-related traits, and to providing validated candidate genes and molecular markers for future genetic improvement.
Project description:Ploidy affects plant growth vigor and cell size, but the relative effects of pollen fertility and allergenicity between triploid and diploid have not been systematically examined. Here we performed comparative analyses of fertility, proteome, and abundances of putative allergenic proteins of pollen in triploid poplar 'ZhongHuai1' ('ZH1', triploid) and 'ZhongHuai2' ('ZH2', diploid) generated from the same parents. The mature pollen was sterile in triploid poplar 'ZH1'. By applying two-dimensional gel electrophoresis (2-DE), a total of 72 differentially expressed protein spots (DEPs) were detected in triploid poplar pollen. Among them, 24 upregulated and 43 downregulated proteins were identified in triploid poplar pollen using matrix-assisted laser desorption/ionisation coupled with time of-flight tandem mass spectrometer analysis (MALDI-TOF/TOF MS/MS). The main functions of these DEPs were related with "S-adenosylmethionine metabolism", "actin cytoskeleton organization", or "translational elongation". The infertility of triploid poplar pollen might be related to its abnormal cytoskeletal system. In addition, the abundances of previously identified 28 putative allergenic proteins were compared among three poplar varieties ('ZH1', 'ZH2', and '2KEN8'). Most putative allergenic proteins were downregulated in triploid poplar pollen. This work provides an insight into understanding the protein regulation mechanism of pollen infertility and low allergenicity in triploid poplar, and gives a clue to improving poplar polyploidy breeding and decreasing the pollen allergenicity.
Project description:Populus deltoides Marsh has high ornamental value because its leaves remain yellow during the non-dormant period. However, little is known about the regulatory mechanism of leaf coloration in P. deltoides Marsh. Thus, we analyzed the physiological and transcriptional differences of yellow leaves (mutant) and green leaves (wild-type) of P. deltoides Marsh. Physiological experiments showed that the contents of chlorophyll (Chl) and carotenoid were lower in mutant leaves, and the flavonoid content did not differ significantly between mutant and wild-type leaves. Transcriptomic sequencing was further used to identify 153 differentially expressed genes (DEGs). Functional classifications based on Gene Ontology enrichment and Genome enrichment analysis indicated that the DEGs were involved in Chl biosynthesis and flavonoid biosynthesis pathways. Among these, geranylgeranyl diphosphate (CHLP) genes associated with Chl biosynthesis showed down-regulation, while chlorophyllase (CLH) genes associated with Chl degradation were up-regulated in yellow leaves. The expression levels of these genes were further confirmed using quantitative real-time PCR (RT-qPCR). Furthermore, the estimation of the main precursors of Chl confirmed that CHLP is a vital enzyme for the yellow leaf color phenotype. Consequently, the formation of yellow leaf color is due to the disruption of Chl synthesis or catabolism rather than flavonoid synthesis. These results contribute to our understanding of mechanisms and regulation of leaf color variation in poplar at the transcriptional level.
Project description:Colored-leaf plants are increasingly popular, which has higher ecological, economic and social benefits. Caihong poplar, one of colored-leaf plants from Populus deltoides, has been widely used in courtyard embellishment, road greening, garden set King and so on. In this study, the complete chloroplast genome of Caihong poplar was evaluated, and the total chloroplast genome size of which is 156,957 bp in length with 36.69% GC content, including large single-copy region (LSC) of 85,096 bp, a pair of inverted repeat regions (IRs) of 27,649 bp each, and a small single-copy region (SSC) of 16,563 bp. There were 22 tRNA genes, 83 protein-coding genes, and four rRNA genes. The phylogenetic analysis with 22 species indicated that Caihong poplar was closely clustered with Populus deltoides Zhonglin 2025. In conclusion, the complete chloroplast genomes of Caihong poplar in this study provided valuable genomic resources for further phylogeny and species identification in the Populus family.
Project description:Proteomic analysis was used to generate a map of Populus deltoides CL. "2KEN8" mature pollen proteins. By applying 2-D electrophoresis, we resolved 403 protein spots from mature pollen. Using the matrix-assisted laser desorption/ionization time time-of-flight/time-of-flight tandem mass spectrometry method, we identified 178 distinct proteins from 218 protein spots expressed in mature pollen. Moreover, out of these, 28 proteins were identified as putative allergens. The expression patterns of these putative allergen genes indicate that several of these genes are highly expressed in pollen. In addition, the members of profilin allergen family were analyzed and their expression patterns were compared with their homologous genes in Arabidopsis and rice. Knowledge of these identified allergens has the potential to improve specific diagnosis and allergen immunotherapy treatment for patients with poplar pollen allergy.
Project description:UnlabelledBacterial endophytes that colonize Populus trees contribute to nutrient acquisition, prime immunity responses, and directly or indirectly increase both above- and below-ground biomasses. Endophytes are embedded within plant material, so physical separation and isolation are difficult tasks. Application of culture-independent methods, such as metagenome or bacterial transcriptome sequencing, has been limited due to the predominance of DNA from the plant biomass. Here, we describe a modified differential and density gradient centrifugation-based protocol for the separation of endophytic bacteria from Populus roots. This protocol achieved substantial reduction in contaminating plant DNA, allowed enrichment of endophytic bacteria away from the plant material, and enabled single-cell genomics analysis. Four single-cell genomes were selected for whole-genome amplification based on their rarity in the microbiome (potentially uncultured taxa) as well as their inferred abilities to form associations with plants. Bioinformatics analyses, including assembly, contamination removal, and completeness estimation, were performed to obtain single-amplified genomes (SAGs) of organisms from the phyla Armatimonadetes, Verrucomicrobia, and Planctomycetes, which were unrepresented in our previous cultivation efforts. Comparative genomic analysis revealed unique characteristics of each SAG that could facilitate future cultivation efforts for these bacteria.ImportancePlant roots harbor a diverse collection of microbes that live within host tissues. To gain a comprehensive understanding of microbial adaptations to this endophytic lifestyle from strains that cannot be cultivated, it is necessary to separate bacterial cells from the predominance of plant tissue. This study provides a valuable approach for the separation and isolation of endophytic bacteria from plant root tissue. Isolated live bacteria provide material for microbiome sequencing, single-cell genomics, and analyses of genomes of uncultured bacteria to provide genomics information that will facilitate future cultivation attempts.
Project description:Populus deltoides and Populus trichocarpa were exposed to either ambient air or an acute ozone exposure of 200 ppb for 9 hrs and ozone response was profiled for each genotype by hybridising control against ozone-exposed samples per genotype. Keywords: stress response, genotype comparrison, ozone exposure
Project description:Clonal propagations of shoot or root fragments play pivotal roles in adaptation of clonal trees to environmental heterogeneity, i.e. soil nutrient heterogeneity and burials after disturbance. However, little is known about whether burial orientation and nutrient supply can alter the effects of fragment traits in Populus. Shoot and root fragments of Populus deltoides × P. simonii were subjected to burials in two different fragment diameters (0.5 and 2.0 cm), two fragment lengths (5 and 15 cm) and three burial orientations (horizontal, upward and downward). For the shoot fragments, survival and growth were significantly higher in the larger pieces (either in length or diameter) and the horizontal/upward burial position. On the contrary, the effect of burial position was reversed for the root fragments. Shoot/root fragments of 15 cm in length in horizontal burial position were then subjected to two different fragment diameters (0.5 and 2.0 cm) and four types of nutrient supplies (without nutrient, low frequency, high frequency and patchy). Growth of shoot fragments of 2.0 cm in diameter significantly increased in high frequency and patchy nutrient supplies than that of without nutrient treatment. These results suggest that burial orientation and nutrient supply could be employed in clonal propagations of cuttings, afforestation or regeneration in Populus.
Project description:BackgroundTubulin proteins, the main components of microtubules in all eukaryotes, are involved in numerous aspects of plant morphogenesis and adaptation to the environment. In woody plants, microtubules are closely associated with the orientation of cellulose microfibril deposition in the secondary xylem cells and thereby exert an influence on the strength and flexibility of wood. Three major types of tubulin proteins-α-, β- and γ-tubulin-are ubiquitously present in all flowering plants, with α- and β- tubulin serving as basic subunits of microtubules and γ-tubulin directing microtubule nucleation. Compared with herbaceous plants, information on tubulin gene family has been limited in forest trees. This study aimed to characterize the tubulin gene family in the model forest tree Populus deltoides.ResultBased on the whole genome sequence of P. deltoides, 25 PdTubulin genes were identified, including 6 PdTUAs, 17 PdTUBs, and 2 PdTUBGs were identified, with an uneven distribution across 14 chromosomes. Unlike Arabidopsis, which has only three pairs of tubulin paralogs, nearly all PdTubulin were paralogous duplicates, primarily generated by p-whole genome duplication (WGD), γ-WGD, or segmental duplication, indicating multiple rounds of gene family expansion. After the duplication events, the number of TUA genes in Populus was more strictly constrained compared to TUB genes. All paralogous and orthologous tubulin pairs have been under strong purifying selection. Expression analysis revealed that each PdTubulin gene was preferentially expressed in one of three organs: root, leaf, or stem. 5 PdTUB paralogs exhibited similar expression patterns, suggesting potential redundancy. Additionally, expression analysis in male and female floral buds across developmental stages indicated that different members might be involved in sex-specific processes.
Project description:Despite its economic importance as a bioenergy crop and key role in riparian ecosystems, little is known about genetic diversity and adaptation of the eastern cottonwood (Populus deltoides). Here, we report the first population genomics study for this species, conducted on a sample of 425 unrelated individuals collected in 13 states of the southeastern United States. The trees were genotyped by targeted resequencing of 18,153 genes and 23,835 intergenic regions, followed by the identification of single nucleotide polymorphisms (SNPs). This natural P. deltoides population showed low levels of subpopulation differentiation (FST = 0.022-0.106), high genetic diversity (θW = 0.00100, π = 0.00170), a large effective population size (Ne ≈ 32,900), and low to moderate levels of linkage disequilibrium. Additionally, genomewide scans for selection (Tajima's D), subpopulation differentiation (XTX), and environmental association analyses with eleven climate variables carried out with two different methods (LFMM and BAYENV2) identified genes putatively involved in local adaptation. Interestingly, many of these genes were also identified as adaptation candidates in another poplar species, Populus trichocarpa, indicating possible convergent evolution. This study constitutes the first assessment of genetic diversity and local adaptation in P. deltoides throughout the southern part of its range, information we expect to be of use to guide management and breeding strategies for this species in future, especially in the face of climate change.