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In this note we prove a stability estimate for an inverse heat source problem. Based on the obtained stability estimate, we present a generalized Tikhonov regularization method and obtain the error estimate. Numerical experiment shows that the generalized Tikhonov regularization works well. [ABSTRACT FROM AUTHOR]

Southwest China is a biodiversity hotspot characterized by complex topography, heterogeneous regional climates and rich flora. The processes and driving factors underlying this hotspot remain to be explicitly tested across taxa to gain a general understanding of the evolution of biodiversity and speciation in the region. In this study, we examined the role played by historically neutral processes, geography and environment in producing the current genetic diversity of the subtropical pine Pinus yunnanensis. We used genetic and ecological methods to investigate the patterns of genetic differentiation and ecological niche divergence across the distribution range of this species. We found both continuous genetic differentiation over the majority of its range, and discrete isolated local clusters. The discrete differentiation between two genetic groups in the west and east peripheries is consistent with niche divergence and geographical isolation of these groups. In the central area of the species’ range, population structure was shaped mainly by neutral processes and geography rather than by ecological selection. These results show that geographical and environmental factors together created stronger and more discrete genetic differentiation than isolation by distance alone, and illustrate the importance of ecological factors in forming or maintaining genetic divergence across a complex landscape. Our findings differ from other phylogenetic studies that identified the historical drainage system in the region as the primary factor shaping population structure, and highlight the heterogeneous contributions that geography and environment have made to genetic diversity among taxa in southwest China. [ABSTRACT FROM AUTHOR]

Southwest China is a biodiversity hotspot characterized by complex topography, heterogeneous regional climates and rich flora. The processes and driving factors underlying this hotspot remain to be explicitly tested across taxa to gain a general understanding of the evolution of biodiversity and speciation in the region. In this study, we examined the role played by historically neutral processes, geography and environment in producing the current genetic diversity of the subtropical pine Pinus yunnanensis. We used genetic and ecological methods to investigate the patterns of genetic differentiation and ecological niche divergence across the distribution range of this species. We found both continuous genetic differentiation over the majority of its range, and discrete isolated local clusters. The discrete differentiation between two genetic groups in the west and east peripheries is consistent with niche divergence and geographical isolation of these groups. In the central area of the species’ range, population structure was shaped mainly by neutral processes and geography rather than by ecological selection. These results show that geographical and environmental factors together created stronger and more discrete genetic differentiation than isolation by distance alone, and illustrate the importance of ecological factors in forming or maintaining genetic divergence across a complex landscape. Our findings differ from other phylogenetic studies that identified the historical drainage system in the region as the primary factor shaping population structure, and highlight the heterogeneous contributions that geography and environment have made to genetic diversity among taxa in southwest China. [ABSTRACT FROM AUTHOR]

Pinus densata is an ecologically successful homoploid hybrid that inhabits vast areas of heterogeneous terrain on the south-eastern Tibetan Plateau as a result of multiple waves of colonization. Its region of origin, route of colonization onto the plateau and the directions of introgression with its parental species have previously been defined, but little is known about the isolation and divergence history of its populations. In this study, we surveyed nucleotide polymorphism over eight nuclear loci in 19 representative populations of P. densata and its parental species. Using this information and coalescence simulations, we assessed the historical changes in its population size, gene flow and divergence in time and space. The results indicate a late Miocene origin for P. densata associated with the recent uplift of south-eastern Tibet. The subsequent differentiation between geographical regions of this species began in the late Pliocene and was induced by regional topographical changes and Pleistocene glaciations. The ancestral P. densata population had a large effective population size but the central and western populations were established by limited founders, suggesting that there were severe bottlenecks during the westward migration out of the ancestral hybrid zone. After separating from their ancestral populations, population expansion occurred in all geographical regions especially in the western range. Gene flow in P. densata was restricted to geographically neighbouring populations, resulting in significant differentiation between regional groups. The new information on the divergence and demographic history of P. densata reported herein enhances our understanding of its speciation process on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

In this paper, a new method is put forward for simultaneous reliability and reliability-sensitivity analyses based on the information-reuse of sparse grid numerical integration (SGNI). First, the reliability analysis is conducted on the basis of fractional exponential moments-based maximum entropy method (FEM-MEM), where the SGNI is employed for FEM assessments. The reliability index can be evaluated by integrating over the distribution derived by FEM-MEM. Then, the reliability-sensitivity analysis is carried out by reusing the output samples in previous reliability analysis and updating the corresponding weights, where no additional model evaluations are required. Then, the FEM-MEM is applied again to derive the conditional distribution and reliability index. By comparing the conditional and original reliability indexes, one can define the reliability-sensitivity index to identify the importance of each random variable to reliability. Since only one-round of model evaluations are necessary in the proposed method, the computational efficiency is highly desirable. Four numerical examples are investigated to check the effectiveness of the proposed method, where pertinent results obtained from Monte Carlo simulations (MCS) and Sobol’s index are compared. The results demonstrate the proposed method is accurate and efficient for simultaneous reliability and reliability-sensitivity analyses. [ABSTRACT FROM AUTHOR]

ABSTRACT The high biosynthetic and energetic demands of floral thermogenesis render thermogenic plants the ideal systems to characterize energy metabolism in plants, but real‐time tracking of energy metabolism in plant cells remains challenging. In this study, a new method was developed for tracking the mitochondrial energy metabolism at the single mitochondria level by real‐time imaging of mitochondrial superoxide production (i.e., mitoflash). Using this method, we observed the increased mitoflash frequencies in the receptacles of Nelumbo nucifera Gaertn. at the thermogenic stages. This increase, combined with the higher expression of antioxidant response‐related genes identified through time‐series transcriptomics at the same stages, shows us a new regulatory mechanism for plant redox balance. Furthermore, we found that the upregulation of respiratory metabolism‐related genes during the thermogenic stages not only correlates with changes in mitoflash frequency but also underscores the critical roles of these pathways in ensuring adequate substrate supply for thermogenesis. Metabolite analysis revealed that sugars are likely one of the substrates for thermogenesis and may be transported over long distances by sugar transporters. Taken together, our findings demonstrate that mitoflash is a reliable tool for tracking energy metabolism in thermogenic plants and contributes to our understanding of the regulatory mechanisms underlying floral thermogenesis. [ABSTRACT FROM AUTHOR]

Populus tomentosa, an indigenous tree species, is widely distributed and cultivated over 1,000,000 km2 in China, contributing significantly to forest production, ecological conservation and urban–rural greening. Although a reference genome is available for P. tomentosa, the intricate interspecific hybrid origins, chromosome structural variations (SVs) and sex determination mechanisms remain confusion and unclear due to its broad and even overlapping geographical distribution, extensive morphological variations and cross infiltration among white poplar species. We conducted a haplotype‐resolved de novo assembly of P. tomentosa elite individual GM107, which comprises subgenomes a and b with a total genome size of 714.9 Mb. We then analysed the formation of hybrid species and the phylogenetic evolution and sex differentiation across the entire genus. Phylogenomic analyses suggested that GM107 likely originated from a hybridisation event between P. alba (♀) and P. davidiana (♂) which diverged at approximately 3.8 Mya. A total of 1551 chromosome SVs were identified between the two subgenomes. More noteworthily, a distinctive inversion structure spanning 2.15–2.95 Mb was unveiled among Populus, Tacamahaca, Turaga, Aigeiros poplar species and Salix, highlighting a unique evolutionary feature. Intriguingly, a novel sex genotype of the ZY type, which represents a crossover between XY and ZW systems, was identified and confirmed through both natural and artificial hybrids populations. These novel insights offer significant theoretical value for the study of the species' evolutionary origins and serve as a valuable resource for ecological genetics and forest biotechnology. [ABSTRACT FROM AUTHOR]

In this paper, stochastic dynamic response and reliability assessment of non-linear structures driven by non-stationary non-Gaussian ground motions are investigated. First, the non-stationary non-Gaussian ground motions are simulated by using the translation process theory. To circumvent the problem of a large number of iterations, an improved upgrading model is developed to obtain a power spectral density which is compatible with the target non-Gaussian probability distribution and is as close as possible to the target non-Gaussian power spectral density. To conduct stochastic dynamic response and reliability analyses of non-linear structures driven by non-stationary non-Gaussian ground motions, the probability density evolution method is employed, whereby a new high-dimensional points selection strategy based on the clustering algorithm is put forward. The new strategy of points selection is quite flexible and simple while taking into account both efficiency and accuracy. The efficacy and applicability of the proposed method are verified through a numerical example and a practical engineering example, in which the influence of non-Gaussianity on the probabilistic seismic response and reliability of the structure is discussed. • Nonstationary non-Gaussian ground motions are simulated with accuracy. • High-dimensional points selection is performed based on the clustering method. • Probabilistic dynamic analysis of nonlinear structures are carried out based on PDEM. • Numerical examples verify the efficacy and applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Color change during flower opening is common; however, little is understood on the biochemical and molecular basis related. Lilac (Syringa oblata), a well-known woody ornamental plant with obvious petal color changes, is an ideal model. Here, we presented chromosome-scale genome assembly for lilac, resolved the flavonoids metabolism, and identified key genes and potential regulatory networks related to petal color change. The genome assembly is 1.05 Gb anchored onto 23 chromosomes, with a BUSCO score of 96.6%. Whole-genome duplication (WGD) event shared within Oleaceae was revealed. Metabolome quantification identified delphinidin-3-O-rutinoside (Dp3Ru) and cyanidin-3-O-rutinoside (Cy3Ru) as the major pigments; gene co-expression networks indicated WRKY an essential regulation factor at the early flowering stage, ERF more important in the color transition period (from violet to light nearly white), while the MBW complex participated in the entire process. Our results provide a foundation for functional study and molecular breeding in lilac. A high-quality genome assembly for the lilac (Syringa oblata) provides insight into the evolution of this shrub and potential mechanisms underlying petal color change. [ABSTRACT FROM AUTHOR]

Summary: Understanding the origin and distribution of genetic diversity across landscapes is critical for predicting the future of organisms in changing climates. This study investigated how adaptive and demographic forces have shaped diversity and population structure in Pinus densata, a keystone species on Qinghai‐Tibetan Plateau (QTP).We examined the distribution of genomic diversity across the range of P. densata using exome capture sequencing. We applied spatially explicit tests to dissect the impacts of allele surfing, geographic isolation and environmental gradients on population differentiation and forecasted how this genetic legacy may limit the persistence of P. densata in future climates.We found that allele surfing from range expansion could explain the distribution of 39% of the c. 48 000 genotyped single nucleotide polymorphisms (SNPs). Uncorrected, these allele frequency clines severely confounded inferences of selection. After controlling for demographic processes, isolation‐by‐environment explained 9.2–19.5% of the genetic structure, with c. 4.0% of loci being affected by selection. Allele surfing and genotype–environment associations resulted in genomic mismatch under projected climate scenarios.We illustrate that significant local adaptation, when coupled with reduced diversity as a result of demographic history, constrains potential evolutionary response to climate change. The strong signal of genomic vulnerability in P. densata may be representative for other QTP endemics. [ABSTRACT FROM AUTHOR]

Poplar (Populus) is a well-established model system for tree genomics and molecular breeding, and hybrid poplar is widely used in forest plantations. However, distinguishing its diploid homologous chromosomes is difficult, complicating advanced functional studies on specific alleles. In this study, we applied a trio-binning design and PacBio high-fidelity long-read sequencing to obtain haplotype-phased telomere-to-telomere genome assemblies for the 2 parents of the well-studied F1 hybrid "84K" (Populus alba × Populus tremula var. glandulosa). Almost all chromosomes, including the telomeres and centromeres, were completely assembled for each haplotype subgenome apart from 2 small gaps on one chromosome. By incorporating information from these haplotype assemblies and extensive RNA-seq data, we analyzed gene expression patterns between the 2 subgenomes and alleles. Transcription bias at the subgenome level was not uncovered, but extensive-expression differences were detected between alleles. We developed machine-learning (ML) models to predict allele-specific expression (ASE) with high accuracy and identified underlying genome features most highly influencing ASE. One of our models with 15 predictor variables achieved 77% accuracy on the training set and 74% accuracy on the testing set. ML models identified gene body CHG methylation, sequence divergence, and transposon occupancy both upstream and downstream of alleles as important factors for ASE. Our haplotype-phased genome assemblies and ML strategy highlight an avenue for functional studies in Populus and provide additional tools for studying ASE and heterosis in hybrids., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)

Long non-coding RNAs (lncRNAs) play essential roles in various biological processes, such as chromatin remodeling, post-transcriptional regulation, and epigenetic modifications. Despite their critical functions in regulating plant growth, root development, and seed dormancy, the identification of plant lncRNAs remains a challenge due to the scarcity of specific and extensively tested identification methods. Most mainstream machine learning-based methods used for plant lncRNA identification were initially developed using human or other animal datasets, and their accuracy and effectiveness in predicting plant lncRNAs have not been fully evaluated or exploited. To overcome this limitation, we retrained several models, including CPAT, PLEK, and LncFinder, using plant datasets and compared their performance with mainstream lncRNA prediction tools such as CPC2, CNCI, RNAplonc, and LncADeep. Retraining these models significantly improved their performance, and two of the retrained models, LncFinder-plant and CPAT-plant, alongside their ensemble, emerged as the most suitable tools for plant lncRNA identification. This underscores the importance of model retraining in tackling the challenges associated with plant lncRNA identification. Finally, we developed a pipeline (Plant-LncPipe) that incorporates an ensemble of the two best-performing models and covers the entire data analysis process, including reads mapping, transcript assembly, lncRNA identification, classification, and origin, for the efficient identification of lncRNAs in plants. The pipeline, Plant-LncPipe, is available at: https://github.com/xuechantian/Plant-LncRNA-pipline., Competing Interests: The authors declare no competing interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of Nanjing Agricultural University.)

Xanthoceras sorbifolium (yellowhorn) is a woody oil plant with super stress resistance and excellent oil characteristics. The yellowhorn oil can be used as biofuel and edible oil with high nutritional and medicinal value. However, genetic studies on yellowhorn are just in the beginning, and fundamental biological questions regarding its very long-chain fatty acid (VLCFA) biosynthesis pathway remain largely unknown. In this study, we reconstructed the VLCFA biosynthesis pathway and annotated 137 genes encoding relevant enzymes. We identified four oleosin genes that package triacylglycerols (TAGs) and are specifically expressed in fruits, likely playing key roles in yellowhorn oil production. Especially, by examining time-ordered gene co-expression network (TO-GCN) constructed from fruit and leaf developments, we identified key enzymatic genes and potential regulatory transcription factors involved in VLCFA synthesis. In fruits, we further inferred a hierarchical regulatory network with MYB-related ( XS03G0296800 ) and B3 ( XS02G0057600 ) transcription factors as top-tier regulators, providing clues into factors controlling carbon flux into fatty acids. Our results offer new insights into key genes and transcriptional regulators governing fatty acid production in yellowhorn, laying the foundation for efforts to optimize oil content and fatty acid composition. Moreover, the gene expression patterns and putative regulatory relationships identified here will inform metabolic engineering and molecular breeding approaches tailored to meet biofuel and bioproduct demands., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Shi, Ma, Wang, Liu, Yan, Tian, Li, Bao, Chen, Zhao, Xiang, Jia, Nie, Guan and Mao.)

Coriaria nepalensis Wall. (Coriariaceae) is a nitrogen-fixing shrub which forms root nodules with the actinomycete Frankia. Oils and extracts of C. nepalensis have been reported to be bacteriostatic and insecticidal, and C. nepalensis bark provides a valuable tannin resource. Here, by combining PacBio HiFi sequencing and Hi-C scaffolding techniques, we generated a haplotype-resolved chromosome-scale genome assembly for C. nepalensis. This genome assembly is approximately 620 Mb in size with a contig N50 of 11 Mb, with 99.9% of the total assembled sequences anchored to 40 pseudochromosomes. We predicted 60,862 protein-coding genes of which 99.5% were annotated from databases. We further identified 939 tRNAs, 7,297 rRNAs, and 982 ncRNAs. The chromosome-scale genome of C. nepalensis is expected to be a significant resource for understanding the genetic basis of root nodulation with Frankia, toxicity, and tannin biosynthesis., (© 2023. The Author(s).)

Populus has a wide ecogeographical range spanning the Northern Hemisphere, and interspecific hybrids are common. Populus tomentosa Carr. is widely distributed and cultivated in the eastern region of Asia, where it plays multiple important roles in forestry, agriculture, conservation, and urban horticulture. Reference genomes are available for several Populus species, however, our goals were to produce a very high quality de novo chromosome-level genome assembly in P. tomentosa genome that could serve as a reference for evolutionary and ecological studies of hybrid speciation throughout the genus. Here, combining long-read sequencing and Hi-C scaffolding, we present a high-quality, haplotype-resolved genome assembly. The genome size was 740.2 Mb, with a contig N50 size of 5.47 Mb and a scaffold N50 size of 46.68 Mb, consisting of 38 chromosomes, as expected with the known diploid chromosome number (2n = 2x = 38). A total of 59,124 protein-coding genes were identified. Phylogenomic analyses revealed that P. tomentosa is comprised of two distinct subgenomes, which we deomonstrate is likely to have resulted from hybridization between Populus adenopoda as the female parent and Populus alba var. pyramidalis as the male parent, with an origin of approximately 3.93 Ma. Although highly colinear, significant structural variation was found between the two subgenomes. Our study provides a valuable resource for ecological genetics and forest biotechnology., (© 2021 John Wiley & Sons Ltd.)

Polyploidization plays a key role in plant evolution, but the forces driving the fate of homoeologs in polyploid genomes, i.e., paralogs resulting from a whole-genome duplication (WGD) event, remain to be elucidated. Here, we present a chromosome-scale genome assembly of tetraploid scarlet sage (Salvia splendens), one of the most diverse ornamental plants. We found evidence for three WGD events following an older WGD event shared by most eudicots (the γ event). A comprehensive, spatiotemporal, genome-wide analysis of homoeologs from the most recent WGD unveiled expression asymmetries, which could be associated with genomic rearrangements, transposable element proximity discrepancies, coding sequence variation, selection pressure, and transcription factor binding site differences. The observed differences between homoeologs may reflect the first step toward sub- and/or neofunctionalization. This assembly provides a powerful tool for understanding WGD and gene and genome evolution and is useful in developing functional genomics and genetic engineering strategies for scarlet sage and other Lamiaceae species., (© 2021. The Author(s).)

LTR retrotransposons (LTR-RTs) are ubiquitous and represent the dominant repeat element in plant genomes, playing important roles in functional variation, genome plasticity and evolution. With the advent of new sequencing technologies, a growing number of whole-genome sequences have been made publicly available, making it possible to carry out systematic analyses of LTR-RTs. However, a comprehensive and unified annotation of LTR-RTs in plant groups is still lacking. Here, we constructed a plant intact LTR-RTs dataset, which is designed to classify and annotate intact LTR-RTs with a standardized procedure. The dataset currently comprises a total of 2,593,685 intact LTR-RTs from genomes of 300 plant species representing 93 families of 46 orders. The dataset is accompanied by sequence, diverse structural and functional annotation, age determination and classification information associated with the LTR-RTs. This dataset will contribute valuable resources for investigating the evolutionary dynamics and functional implications of LTR-RTs in plant genomes., (© 2021. The Author(s).)

Platycladus orientalis is an ecologically important native conifer in Northern China and exotic species in many parts of the world; however, knowledge about the species' genetics and genome are very limited. The availability of well-developed battery of genetic markers, with large genome coverage, is a prerequisite for the species genetic dissection of adaptive attributes and efficient selective breeding. Here, we present a genome-wide genotyping method with double-digestion restriction site associated DNA sequencing (ddRAD-seq) that is effective in generating large number of Mendelian markers for genome mapping and other genetic applications. Using 139 megagametophytes collected from a single mother tree, we assembled 397,226 loci, of which 108,683 (27.4%) were polymorphic. After stringent filtering for 1:1 segregation ratio and missing rate of <20%, the remaining 23,926 loci (22% of the polymorphic loci) were ordered into 11 linkage groups (LGs) and distributed across 7,559 unique positions, with a total map length of 1,443 cM and an average spacing of 0.2 cM between adjacent unique positions. The 11 LGs correspond to the species' 11 haploid genome chromosome number. This genetic map is among few high-density maps available for conifers to date, and represents the first genetic map for P. orientalis The information generated serves as a solid foundation not only for marker-assisted breeding efforts, but also for comparative conifer genomic studies., (Copyright © 2019 Jin et al.)

Background: Malania oleifera, a member of the Olacaceae family, is an IUCN red listed tree, endemic and restricted to the Karst region of southwest China. This tree's seed is valued for its high content of precious fatty acids (especially nervonic acid). However, studies on its genetic makeup and fatty acid biogenesis are severely hampered by a lack of molecular and genetic tools., Findings: We generated 51 Gb and 135 Gb of raw DNA sequences, using Pacific Biosciences (PacBio) single-molecule real-time and 10× Genomics sequencing, respectively. A final genome assembly, with a scaffold N50 size of 4.65 Mb and a total length of 1.51 Gb, was obtained by primary assembly based on PacBio long reads plus scaffolding with 10× Genomics reads. Identified repeats constituted ∼82% of the genome, and 24,064 protein-coding genes were predicted with high support. The genome has low heterozygosity and shows no evidence for recent whole genome duplication. Metabolic pathway genes relating to the accumulation of long-chain fatty acid were identified and studied in detail., Conclusions: Here, we provide the first genome assembly and gene annotation for M. oleifera. The availability of these resources will be of great importance for conservation biology and for the functional genomics of nervonic acid biosynthesis., (© The Author(s) 2019. Published by Oxford University Press.)

Flexibility and low cost make genotyping-by-sequencing (GBS) an ideal tool for population genomic studies of nonmodel species. However, to utilize the potential of the method fully, many parameters affecting library quality and single nucleotide polymorphism (SNP) discovery require optimization, especially for conifer genomes with a high repetitive DNA content. In this study, we explored strategies for effective GBS analysis in pine species. We constructed GBS libraries using HpaII, PstI and EcoRI-MseI digestions with different multiplexing levels and examined the effect of restriction enzymes on library complexity and the impact of sequencing depth and size selection of restriction fragments on sequence coverage bias. We tested and compared UNEAK, Stacks and GATK pipelines for the GBS data, and then developed a reference-free SNP calling strategy for haploid pine genomes. Our GBS procedure proved to be effective in SNP discovery, producing 7000-11 000 and 14 751 SNPs within and among three pine species, respectively, from a PstI library. This investigation provides guidance for the design and analysis of GBS experiments, particularly for organisms for which genomic information is lacking., (© 2014 John Wiley & Sons Ltd.)

Background: Long non-coding RNAs (lncRNAs) play widespread roles in gene regulation and cellular processes. However, the functional roles of lncRNAs in hepatocellular carcinoma (HCC) are not yet well elucidated. The aim of the present study was to measure the levels of lncRNA PCAT-1 expression in HCC and evaluate its clinical significance in the development and progression of HCC., Methods: We examined the expression of PCAT-1 in 117 HCC tissues and adjacent non-tumor tissues using quantitative real-time-PCR and analyzed its correlation with the clinical parameters., Results: Our data showed that PCAT-1 expression in HCC tissues was significantly increased compared with adjacent non-tumor tissues (P<0.05). Up-regulated expression of PCAT-1 was significantly associated with TNM stage and metastasis (P<0.05), but not other clinical parameters. Moreover, Kaplan-Meier survival analysis showed that a high expression level of PCAT-1 resulted in a significantly poor overall survival of HCC patients. The multivariate Cox regression analysis demonstrated that PCAT-1 expression level was an independent prognostic factor for the overall survival rate of HCC patients., Conclusions: Our data suggested that the increased expression of PCAT-1 was associated with advanced clinical parameters and poor overall survival of HCC patients, indicating that PCAT-1 up-regulation may serve as a novel biomarker of poor prognosis in HCC patients.

Genetic analyses indicate that Pinus densata is a natural homoploid hybrid originating from Pinus tabuliformis and Pinus yunnanensis. Needle morphological and anatomical features show relative species stability and can be used to identify coniferous species. Comparative analyses of these needle characteristics and phenotypic differences between the artificial hybrids, P. densata, and parental species can be used to determine the genetic and phenotypic evolutionary consequences of natural hybridization. Twelve artificial hybrid families, the two parental species, and P. densata were seeded in a high-altitude habitat in Linzhi, Tibet. The needles of artificial hybrids and the three pine species were collected, and 24 needle morphological and anatomical traits were analyzed. Based on these results, variations in 10 needle traits among artificial hybrid families and 22 traits among species and artificial hybrids were predicted and found to be under moderate genetic control. Nineteen needle traits in artificial hybrids were similar to those in P. densata and between the two parental species, P. tabuliformis and P. yunnanensis. The ratio of plants with three needle clusters in artificial hybrids was 22.92%, which was very similar to P. densata. The eight needle traits (needle length, the mean number of stomata in sections 2 mm in length of the convex and flat sides of the needle, mean stomatal density, mesophyll/vascular bundle area ratio, mesophyll/resin canal area ratio, mesophyll/(resin canals and vascular bundles) area ratio, vascular bundle/resin canal area ratio) relative to physiological adaptability were similar to the artificial hybrids and P. densata. The similar needle features between the artificial hybrids and P. densata could be used to verify the homoploid hybrid origin of P. densata and helps to better understand of the hybridization roles in adaptation and speciation in plants.

Objective: To investigate the prevalence and antibiotic resistance of Shigella isolated from children with diarrhea for the guidance of clinical treatment and prevention and control of bacillary dysentery., Method: A total of 156 strains of Shigella were isolated from feces of children with diarrhea in Zhejiang Xiaoshan Hospital from January 2008 to December 2010. The antimicrobial resistance of the strains was detected by disk diffusion method and the extended-spectrum beta-lactamases (ESBLs) in these isolates were determined using phenotypic confirmatory test; the isolates of ESBLs producing Shigella sonnei were analyzed by REP-PCR., Result: Among 156 strains of Shigella isolated, the most common groups were Shigella sonnei (130 strains, accounting for 83.3%) and Shigella fleaneri (26 strains, accounting for 16.7%), and 81 (51.9%) strains were identified as ESBLs producers, and the positive rates in 2008, 2009 and 2010 were 32.0%, 41.4% and 59.8%, respectively. The results of antibiotic susceptibility test displayed that the resistance rates of ESBLs producing Shigella to ampicillin, cotrimoxazole, cefotaxime, piperacillin were higher than 90%. However, the resistance rates to cefepime, ceftazidime, levofloxacin and ciprofloxacin were low; The resistance of ESBLs producing strains to piperacillin (100% vs. 77.3%), cefotaxime (100% vs. 0), ceftazidime (14.8% vs. 0), cefepime (28.4% vs. 0), cotrimoxazole (95.1% vs. 86.7%) was significantly higher than that of non-ESBLs producing strains (χ(2) = 20.605, 156.000, 12.037, 24.979, 45.040, respectively; P < 0.05). No isolate was resistant to piperacillin/tazobactam and imipenem. There were 7 genotypes among 74 ESBLs producing Shigella sonnei, respectively type A (50), type B (12), type C (8), type D (1), type E (1), type F (1), and type G (1)., Conclusion: The isolation rate of ESBLs-producing isolate was high in Shigella from pediatric patients with diarrhea, and the number is going up year by year, and these ESBLs producing Shigella sonnei strains in genotype A are dominant in recent years, Piperacillin/tazobactam is the drug of choice for children with ESBLs producing Shigella infection.