Betula Luminifera Research Articles

华西雨屏区植被恢复对紫色土酸化的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 华西雨屏区植被恢复对紫色土酸化的影响 DOI: 10.5846/stxb202102220488 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 内江师范学院科研启动费项目（18B10）；四川省教育厅重点项目（17ZA0223） Effect of vegetation restoration on Purple soil acidification in rainy area of Western China Author: Affiliation: Fund Project: Neijiang Normal University Research Start-Up Funds;Key Projects of the Education Department of Sichuan Province 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:退耕还林是控制水土流失、恢复森林植被和改善生态环境的重要举措。植被恢复进程中会发生土壤酸化，进而影响植物生长，厘清不同还林树种对土壤酸化的影响程度及作用机制有助于更好地评估退耕还林工程的整体生态效益。以华西雨屏区紫色土坡耕地（玉米）为对照，分析了退耕20a后柳杉纯林、柳杉-光皮桦混交林、慈竹林和茶园土壤pH的变化及其垂直分异。结果表明：玉米地、慈竹林、茶园、混交林和柳杉纯林0-50 cm土壤pH平均值分别为5.66、5.55、5.12、5.03和5.00，相较于玉米地，柳杉纯林、混交林和茶园土壤pH值显著下降（P<0.01），土壤酸化严重。相较于玉米地土壤pH值的均匀分布，植被恢复不同类型人工林pH值随土壤深度的增加而增加，10-50 cm土壤pH值（4.89-5.90）显著高于0-10 cm土壤pH值（4.72-5.21）（P<0.01），表层土壤酸化最明显。土壤pH值与土壤有机质含量呈极显著负相关，而与风化指数Na/K比值呈显著正相关，有机质含量和Na/K比值共同解释了土壤pH值变化的53.9%，表明植被恢复引起的土壤有机质积累与长石类矿物风化是驱动紫色土酸化的重要过程。通过对紫色土人工林酸化特征及其过程的揭示，可为华西雨屏区森林生态系统恢复及其管理提供科学依据。 Abstract:The Chinese Grain for Green Project is crucial for controlling water and soil erosion, rehabilitation forest vegetation, and improvement of the environment. Soil acidification could be induced during the vegetation restoration, which has a negative impact on plant growth. It is important to clarify the degrees and mechanisms of the influences of reforestation species on soil acidification in order to achieve a better ecological benefit of the Grain for Green Project. In this study, we used the Purple soil of sloping farmland (planted Zea mays) as control group (SF) in rainy area of western China, and analyzed the changes and profile distribution of soil pH value after a 20-year farmland to artificial forestland with plant species of Cryptomeria fortune (CF), Cryptomeria fortune & Betula luminifera (MF), Neosinocalamus affinis (NA) and Camellia sinensis (CS). Results showed that the weighted average value of soil pH in the top 50 cm was 5.66 for SF, 5.55 for NA, 5.12 for CS, 5.03 for MF, and 5.00 for CF. Soil pH value of CF, MF and CS decreased significantly compared with SF (P<0.01), and these soils exhibited severe acidification. In addition, vegetation restoration increased the degree of vertical variations of soil pH for SF that showed a uniform profile distribution. By contrast, soil pH for artificial forests exhibited greater profile differentiations. Soil pH values (4.89-5.90) of the 10-50 cm layer for different artificial forests were significantly higher (P<0.01) than those (4.72-5.21) of the 0-10 cm layer suggesting that soil acidification was most intense for the top 10 cm. There were significantly negative correlations between soil pH value and soil organic matter content, while significantly positive correlation between soil pH value and Na/K ratio of weathering index was observed. 53.9% of the variation for soil pH was explained by soil organic matter content and Na/K ratio, indicating that the acidification of Purple soil in this area were driven by the accumulation of soil organic matter during the process of returning farmland to forests and sorts of feldspar weathering. By revealing the acidification characteristics and its processes for Purple soil, this study provides a scientific basis for future vegetation restoration and ecosystem management in rainy area of western China. 参考文献 相似文献 引证文献

A miR169c-NFYA10 module confers tolerance to low-nitrogen stress to Betula luminifera

Betula species constitute a large portion of species in forest ecosystems, are a key player in biomass resources and are recognized as pioneer species with strong stress tolerance. The miR169-NFYA module plays essential roles in the response to abiotic stress, including nutrient stress. However, the functional roles of the miR169-NFYA module in Betula luminifera, an important subtropical and pioneer forestry tree species, in response to nitrogen (N) starvation are not well documented. In the present study, ten BlNFYA genes were identified in B. luminifera. The expression of most BlNFYAs increased under low-nitrogen (LN) stress, while the expression of BlmiR169 was inhibited; among them, BlmiR169c and its corresponding target gene BlNFYA10 might play important regulatory roles in response to N availability. We then functionally investigated BlmiR169c-BlNFYA10 in response to LN stress and determined its regulatory roles in response to N starvation by analyzing the expression patterns, miRNA-mRNA interactions, phenotypes, and physiological and transcriptomic responses of transgenic Arabidopsis and birch roots under LN stress. Overexpression of BlmiR169c and BlNFYA10 resulted in contrasting tolerance to N starvation, and BlNFYA10 provided transgenic plants with LN tolerance with lower growth costs compared with those of the wild type under LN stress. This tolerance might involve a trade-off between growth and defense by upregulating defense- and downregulating photosynthesis- and translation-related activities under LN stress. On the other hand, BlNFYA10 provided transgenic plants with enhanced uptake and assimilation of N, effectively compensating for the defense-growth trade-offs in BlNFYA10-overexpressing plants. Our data demonstrate that a potential regulatory mechanism of BlmiR169c-BlNFYA10 is involved in the LN stress response, providing a basis for increasing the nitrogen-use efficiency (NUE) of B. luminifera and/or other forestry tree species.

Profiling of MicroRNAs and Their Targets in Roots and Shoots Reveals a Potential MiRNA-Mediated Interaction Network in Response to Phosphate Deficiency in the Forestry Tree Betula luminifera.

Inorganic phosphate (Pi) is often lacking in natural and agro-climatic environments, which impedes the growth of economically important woody species. Plants have developed strategies to cope with low Pi (LP) availability. MicroRNAs (miRNAs) play important roles in responses to abiotic stresses, including nutrition stress, by regulating target gene expression. However, the miRNA-mediated regulation of these adaptive responses and their underlying coordinating signals are still poorly understood in forestry trees such as Betula luminifera. Transcriptomic libraries, small RNA (sRNA) libraries, and a mixed degradome cDNA library of B. luminifera roots and shoots treated under LP and normal conditions (CK) were constructed and sequenced using next-generation deep sequencing. A comprehensive B. luminifera transcriptome derived from its roots and shoots was constructed, and a total of 76,899 unigenes were generated. Analysis of the transcriptome identified 8,095 and 5,584 differentially expressed genes in roots and shoots, respectively, under LP conditions. sRNA sequencing analyses indicated that 66 and 60 miRNAs were differentially expressed in roots and shoots, respectively, under LP conditions. A total of 109 and 112 miRNA–target pairs were further validated in the roots and shoots, respectively, using degradome sequencing. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of differential miRNA targets indicated that the “ascorbate and aldarate metabolism” pathway responded to LP, suggesting miRNA-target pairs might participating in the removing of reactive oxidative species under LP stress. Moreover, a putative network of miRNA–target interactions involved in responses to LP stress in B. luminifera is proposed. Taken together, these findings provide useful information to decipher miRNA functions and establish a framework for exploring P signaling networks regulated by miRNAs in B. luminifera and other woody plants. It may provide new insights into the genetic engineering of high use efficiency of Pi in forestry trees.

Plant identity strongly structures the root-associated fungal community in a diverse subtropical forest

Revealing the relationship between plants and root-associated fungi is very important in understanding diversity maintenance and community assembly in ecosystems. However, the community assembly of root-associated fungi of focal plant species along a subtropical plant species diversity gradient is less documented. Here, we examined root-associated fungal communities associated with five ectomycorrhizal (EM) plant species (Betula luminifera, Castanea henryi, Castanopsis fargesii, C. sclerophylla, and Quercus serrate) in a Chinese subtropical woody plant species diversity (1, 2, 4, 8, 16 and 24 species) experiment, using paired-end Illumina MiSeq sequencing of the ITS2 region. In total, we detected 1933 root-associated fungal operational taxonomic units (OTUs) at a 97% sequence similarity level. Plant identity had a significant effect on total and saprotrophic fungal OTU richness, but plant species diversity level had a significant effect on saprotrophic and pathogenic fungal OTU richness. The community composition of total, saprotrophic and EM fungi was structured by plant identity and plant species diversity level. However, the community composition of pathogenic fungi was only shaped by plant identity. This study highlights that plant identity has a stronger effect on the root-associated fungal community than plant species diversity level in a diverse subtropical forest ecosystem.

Spatial distribution and interspecific associations of regenerating saplings in karst secondary forests.

A 140 m×120 m plot was set in a secondary forest with more than 30 years natural reco-very after abandonment in Ziyun Miao and Buyi Autonomous County, a typical karst area in Guizhou Province. We investigated the spatial distribution and interspecific associations of regenerating sapling population using spatial point pattern analytical method. There were 1291 saplings with 39 tree species. Betula luminifera, Platycarya strobilacea, Liquidambar formosana, Pinus massoniana and Populus davidiana were the dominant populations of regenerating saplings, accounting for 83.7% of the saplings and 77.8% of the total importance value. The spatial distributions of B. luminifera, P. strobilacea and L. formosana were strongly aggregated at a spatial scale of 0-60 m, while the spatial distributions of P. massoniana and P. davidiana were aggregated at small scale and randomly distributed at large scale. The spatial associations among those dominant populations were mostly positively correlated, with positive correlations of P. massoniana with L. formosana and P. davidiana at small scale but no associations at large scale. In conclusion, the spatial distributions and interspecific associations differed among the dominant sapling populations, due to the different biological characteristics of different tree species, habitats and uses of spatial resources. Most of the stands investigated were dominated by pioneering species, with poor stand quality and unstable community structure. A mixed forest dominated by P. massoniana and B. luminifera would be the next stage of succession. We recommended that measures of forest management should be adopted to accelerate vegetation restoration.

Structure and dynamic characteristics of Betula luminifera populations in different regions of Southwest Hubei Province, China

We investigated Betula luminifera populations in three regions (Mulinzi, Qizimei Mountains, and Jinzi Mountains) in the southwest Hubei Province, China. Population structure was divided by age classes and height classes. Population structure figures were drawn. The static life tables of B. luminifera populations in different regions were analyzed using the method of substitution of space for time. The survival curve, mortality rate curve and disappearance rate curve were created. Four functions of survival analysis were used to analyze the dynamics of B. luminifera population in different regions. The results showed that the B. luminifera populations in three regions were the increasing type. The height class structures were relatively complete. Some age classes were absent from the age structures of B. luminifera populations in Qizimei Mountains and Jinzi Mountains. Although the dynamic index of trees number Vpi＞0, but it was sensitive to external disturbance. The survival of B. luminifera of different age classes varied greatly in static life table, which gradually decreased with increasing age class, with Deevey-type 2 survival curve. The trend of mortality rate changed similarly to the disappearance rate, but fluctuated differently. All B. luminifera populations in different regions appeared to decrease in the early stage and keep dynamically stable in the medium-late stage.

Variation of Leaf Carbon Isotope in Plants in Different Lithological Habitats in a Karst Area

Drought is the major factor that limits vegetation recovery in rocky desertification areas. The leaf carbon isotope (δ13C) value is related to plant water-use efficiency (WUE) and is of great significance in revealing the WUE characteristics of species in karst areas. Measurements of the δ13C value in plant leaves and the nutrient and water contents of lithologic soils were obtained for six woody species (cypress, Cupressus funebris Endl.; mansur shrub, Coriaria nepalensis Wall.; camphor, Cinnamomum bodinieri Levl.; birch, Betula luminifera H. Winkl.; alder, Alnus cremastogyne Burk. and dyetree, Platycarya longipes Wu.) planted in three different lithologic soil types (dolomite, dolomite sandstone, limestone) in the karst area of Guizhou Province. The results showed that C. funebris in the dolomite sandstone soil had the highest δ13C value (−27.19‰), whereas C. bodinieri in the limestone soil had the lowest δ13C value (−31.50‰). In terms of lithology, the average leaf δ13C values were −28.66‰ (dolomitic sandstone), −28.83‰ (dolomite), and −29.46‰ (limestone). The δ13C values of C. funebris and A. cremastogyne were significantly lower in the limestone soil than in the dolomite and dolomite sandstone soil, indicating that the WUE of some tree species is affected by soil conditions under different lithological development processes. Moreover, the relationship between the δ13C value in the leaves and the comprehensive soil conditions varied among the species, and the δ13C value was negatively correlated with the soil water content in all three soil types. Our study provides basic data on the composition characteristics of the δ13C value of tree species, which is beneficial for the selection of tree species for vegetation restoration and afforestation in karst areas.

湖北省九华山林场不同树种配置杉阔混交林林分空间结构特征分析

PDF HTML阅读 XML下载 导出引用 引用提醒 湖北省九华山林场不同树种配置杉阔混交林林分空间结构特征分析 DOI: 10.5846/stxb201810122215 作者: 作者单位: 北京林业大学水土保持学院,北京林业大学水土保持学院,北京林业大学水土保持学院,北京林业大学水土保持学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划（2017YFC0505500，2017YFC0505504） Analysis of the stand spatial structure of Cunninghamia lanceolata-broadleaved mixed plantation on a Jiuhua Mountain farm, Hubei Province Author: Affiliation: College of Soil and Water Conservation,Beijing Forestry University,College of Soil and Water Conservation,Beijing Forestry University,College of Soil and Water Conservation,Beijing Forestry University,College of Soil and Water Conservation,Beijing Forestry University Fund Project: The National Basic Research Program of China (2017YFC0505500、2017YFC0505504) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以三种（杉木+少量栎类、杉木+栎类+光皮桦、杉木+栎类+光皮桦+马尾松）不同树种配置的杉阔混交林为研究对象，计算了角尺度、大小比数、混交度三个林分空间结构指标，全面分析了湖北省九华山林场不同树种配置杉阔混交防护林林分空间结构特征，结果表明：优势树种主要有杉木（Cunninghamia lanceolata（Lamb.）Hook.）、栎类（Quercus L.）及光皮桦（Betula luminifera）三种，并有少量马尾松（Pinus massoniana）散生于林内，生长优势也较弱。不同树种配置所呈现的林分空间结构也不相同。树种配置Ⅰ（杉木+少量栎类）的角尺度平均值为0.42，大小比数平均值为0.31，混交度平均值为0.18，林木空间分布格局和生长优势度均较好，但混交程度较弱，近乎杉木纯林，对应的生物多样性也会较小。树种配置Ⅱ（杉木+栎类+光皮桦）的角尺度平均值为0.5，大小比数平均值0.32，混交度平均数0.48，空间分布格局整体呈现随机分布；林木主要处于亚优势生长状态，混交度以中度-强度混交为主；而树种配置Ⅲ（杉木+栎类+光皮桦+马尾松）的角尺度平均值为0.58，大小比数平均值0.51，混交度平均数0.54，林木空间格局呈现聚集分布，生长优势水平中庸，为中度混交。全面分析林分空间结构，可以明确林分空间结构中存在的不合理情况，为合理择伐以及近自然经营提供科学依据，使该地区的杉阔混交林的多种功能得到可持续发挥。 Abstract:In order to analyze the spatial structure of Cunninghamia lanceolata-broadleaved mixed plantation on a Jiuhua Mountain farm, three different composition of Cunninghamia lanceolata-Broadleaved Mixed Plantation was taken as the study object, three spatial structure parameters, the angle index, mingling degree, and neighborhood comparison, were calculated. The results showed that the dominant species were C. lanceolata, Quercus L., and Betula luminifera; additionally, a small amount of Pinus massoniana was scattered throughout the forest. Different tree species compositions presented different spatial structures:composition I had an average angle index of 0.42, average neighborhood comparison value of 0.31, and average mingling degree value of 0.18; composition Ⅱ had an average angle index of 0.5, average neighborhood comparison value of 0.32, and average mingling degree value of 0.48; and composition Ⅲ had an average angle index of 0.58, average neighborhood comparison value of 0.51, and an average mingling degree value of 0.54. This comprehensive analysis of the spatial structure of the forest on Jiuhua Mountain farm reflects the unreasonable circumstances in the spatial structure of the forest, provides a scientific basis for guiding reasonable selective cutting and near-natural management, and enables the multiple functions of the Cunninghamia lanceolata-broadleaved mixed plantation in this region to be sustainable. 参考文献 相似文献 引证文献

RNA-Seq analysis of differential gene expression in Betula luminifera xylem during the early stages of tension wood formation.

Background Betula luminifera H. Winkler, which is widely distributed in southern China, is an economically important broadleaf tree species. However, little genomic information of B. luminifera is available, and little is known about the molecular mechanisms of wood formation in this species. Meanwhile, few efforts have focused on investigating the early transcriptional changes during tension wood formation in woody plants.ResultsA reference transcriptome dataset was first generated containing 45,700 Unigenes, and 35,135 (76.9%) Unigenes were annotated by a BLAST similarity search against four public databases. Then, based on an anatomical investigation, the global gene expression changes during the early stages of tension wood formation were analyzed. Gene expression profiling showed that a total of 13,273 Unigenes were differentially regulated during the early stages of tension wood formation. Most genes involved in cellulose and lignin biosynthesis were highlighted to reveal their biological importance in tension wood formation. In addition, the transcription levels of many genes involved in the auxin response pathway were significantly changed during the early stages of tension wood formation. Furthermore, 18 TFs co-expressed with key enzymes of cellulose synthesis were identified.ConclusionsOur results revealed the transcriptional changes associated with TW formation and identified potential key genes in the regulation of this process. These results will help to dissect the molecular mechanism of wood formation and provide key candidate genes for marker-assisted selection in B. luminifera.

Molecular Characterization of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) Gene Family in Betula luminifera.

As a major family of plant-specific transcription factors, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes play vital regulatory roles in plant growth, development and stress responses. In this study, 18 SPL genes were identified and cloned from Betula luminifera. Two zinc finger-like structures and a nuclear location signal (NLS) segments were existed in the SBP domains of all BlSPLs. Phylogenetic analysis showed that these genes were clustered into nine groups (group I-IX). The intron/exon structure and motif composition were highly conserved within the same group. 12 of the 18 BlSPLs were experimentally verified as the targets of miR156, and two cleavage sites were detected in these miR156-targeted BlSPL genes. Many putative cis-elements, associated with light, stresses and phytohormones response, were identified in the promoter regions of BlSPLs, suggesting that BlSPL genes are probably involved in important physiological processes and developmental events. Tissue-specific expression analysis showed that miR156-targeted BlSPLs exhibited a more differential expression pattern, while most miR156-nontargeted BlSPLs tended to be constitutively expressed, suggesting the distinct roles of miR156-targeted and nontargeted BlSPLs in development and growth of B. luminifera. Further expression analysis revealed that miR156-targeted BlSPLs were dramatically up-regulated with age, whereas mature BlmiR156 level was apparently declined with age, indicating that miR156/SPL module plays important roles in vegetative phase change of B. luminifera. Moreover, yeast two-hybrid assay indicated that several miR156-targeted and nontargeted BlSPLs could interact with two DELLA proteins (BlRGA and BlRGL), which suggests that certain BlSPLs take part in the GA regulated processes through protein interaction with DELLA proteins. All these results provide an important basis for further exploring the biological functions of BlSPLs in B. luminifera.

Identification of heat-responsive miRNAs to reveal the miRNA-mediated regulatory network of heat stress response in Betula luminifera

This paper proposes a miRNA-mediated regulatory network of heat stress response in a tree, Betula luminifera. Plants are sessile organisms that must gauge stressful conditions to ensure survival and reproductive success. In nature, plants often encounter chronic or recurring abiotic stresses, such as heat stress, although the strategies to cope with high temperature are poorly understood in woody plants. In this study, we investigated the potential roles of microRNAs (miRNAs) in heat stress response in Betula luminifera. Using next-generation deep sequencing, we identified a total of 206 miRNAs, comprising 115 known and 84 novel miRNAs, and seven potential miRNA candidates. Of these miRNAs, 98 (57 known and 41 novel miRNAs) were differentially expressed under heat stress. A total of 101 miRNA-target pairs consisting of 44 miRNAs and 71 target genes were verified by degradome sequencing. Target annotation suggested that these miRNAs might be important in the regulation of specific stress-responsive genes, including many transcription factors and a series of genes encoding important enzymes of functional proteins targeted by miRNAs. Further functional analysis suggested that these target genes were related to protein synthesis, transport and turnover, cell wall organization, protein folding, antioxidation, defense response, and modulation of attenuated plant growth and development under heat stress. The expression patterns of 15 randomly selected miRNAs derived from quantitative reverse transcription PCR had similar trends as those derived from high-throughput sequencing, as well as the expression patterns of six target genes under heat stress. These results improve our understanding of the miRNA-mediated regulatory network of heat stress response in B. luminifera, which will contribute to improving heat stress-resistant breeding in woody plants.

Identification and evaluation of reference genes for normalization in quantitative real-time PCR analysis in the premodel tree Betula luminifera

Betula luminifera is a commercial tree species that is emerging as a new model system for tree genomics research. A draft genomic sequence is expected to be publicly available in the near future, which means that an explosion of gene expression studies awaits. Thus, the work of selecting appropriate reference genes for qPCR normalization in different tissues or under various experimental conditions is extremely valuable. In this study, ten candidate genes were analyzed in B. luminifera subjected to different abiotic stresses and at various flowering stages. The expression stability of these genes was evaluated using three distinct algorithms implemented using geNorm, NormFinder and BestKeeper. The best-ranked reference genes varied across different sample sets, though RPL39, MDH and EF1a were determined as the most stable by the three programs among all tested samples. RPL39 and EF1a should be appropriate for normalization in N-starved roots, while the combination of RPL39 and MDH should be appropriate for N-starved stems and EF1a and MDH should be appropriate in N-starved leaves. In PEG-treated (osmotic) roots, MDH was the most suitable, whereas EF1a was suitable for PEG-treated stems and leaves. TUA was also stably expressed levels in PEG-treated plants. The combination of RPL39 and TUB should be appropriate for heat-stressed leaves and flowering stage. For reference gene validation, the expression levels of SOD and NFYA-3 were investigated. This work will be beneficial to future studies on gene expression under different abiotic stress conditions and flowering status in B. luminifera.

Genome-wide mining for microRNAs and their targets in Betula luminifera using high-throughput sequencing and degradome analyses

microRNAs (miRNAs) play vital roles in plants regulating a panoply of biological processes, such as development, hormone signaling, and stress response, by inhibiting target genes at the post-transcriptional level. However, the roles of miRNAs in Betula luminifera remain elusive. To mine for B. luminifera miRNAs and targets, we used a deep sequencing approach to analyze the sRNAs and degradome sequencing of mixed samples, including roots, stems, and leaves. A total of 114 known miRNAs or miRNA*s from 44 families, and 24 novel miRNAs and 17 miRNA*s plus 15 plausible miRNA candidates were identified, of which 36 known miRNAs, 29 miRNA*s, and all novel miRNAs had precursor sequences. Additionally, 49 targets for 19 known miRNA families and seven miRNA*s, and seven targets for novel miRNAs were identified using a high-throughput degradome-sequencing approach. The conserved miRNA targets were mainly transcription factors, whereas the miRNA* targets were mainly protein-coding genes, with preferential propensity to functional enzymes. A Gene Ontology analysis showed that the predicted targets were classified into 62 biological processes, 20 cellular components, and 28 molecular functions, respectively. We found two different targets for miR396a* and miR396c*, and the target changed when the miR156d precursor cleavage site was shifted toward the 5′-end by two nucleotides, indicating the diverse regulatory roles of MIRNA genes. Furthermore, three targets identified by degradome sequencing were validated further through 5′ rapid amplification of cDNA ends. The expression patterns of the randomly selected miRNAs varied among different tissues. miR164 expression was induced under nitrogen starvation, with tissue-specific expression patterns, and was negatively correlated with the NAC1 target gene in roots and leaves, but not in stems. This study is a transcriptome-based analysis of miRNAs and the degradome, providing useful information to explore the functions of miRNAs and their target genes in B. luminifera.

Mining for heat-stress responsive genes by large scale gene expression data from Betula luminifera

Global average temperature has been predicted to rise by 1.8–4.0 °C within this century, accompanied by an increase in the magnitude and frequency of high-temperature events. Developing new cultivars better adapted to high temperature is essential for forestry ecosystems. Analyzing smooth-bark birch (Betula luminifera) gene expression profiles in response to heat stress is critical to understanding how birch manages heat stress, and provides vital information to improve thermoresistance for stable wood production. In this study, the leaf transcriptomics of B. luminifera were evaluated, thus up- and down-regulated genes were identified under heat stress through digital gene expression analysis. Expression patterns of 17 related genes of two genotypes following exposure to heat stress were compared. A total of 867 differentially expressed genes were identified, including 447 upregulated genes and 420 downregulated genes under heat stress, while 10 genes and 58 genes were detected only in control and heat-stress leaves, respectively. Among them, Hsfs, HSPs, DREB2, Cpn60-β2, ATP9 and other genes involved in the response to heat stress displayed quantitative differences in expression between the genotypes. The expression levels of the transcription factors MybC2-L1 and MYC1 were repressed significantly under heat stress. These results showed that a panoply of genes were induced by heat stress, while the expression of many genes were reduced or off in the presence of excessively high temperatures. It can be speculated that the distinct expression levels between genotypes in response to heat stress underlie their different capacities to resist high temperatures.

Expression analysis of miR164 and its target gene NAC1 in response to low nitrate availability in Betula luminifera

Nitrogen, an essential macronutrient for the growth and development of plants, affects above- ground biomass accumulation dramatically. Thus, it is very important to reveal the molecular mechanisms of how plants resist or adapt to low nitrogen availability. The NAC1(NAM, ATAF, CUC 1) gene, located in the upstream regulatory network, has been reported to resist low nitrogen by regulating expression of key downstream genes and thus root growth in (Populus tremula × alba).In this study, we detected the responses of miR164 and its target gene NAC1 under nitrate-starvation condition using the Betula luminifera somaclones G49-3 as material. The NAC1 gene which contains 1497 bp sequence, encodes 358 amino acids and contains a highly conserved NAM domain at N terminal was cloned by the RACE method. The NAC1 was then validated to be the target gene of miR164 via 5'-RACE, and the cleavage site was between the 10(th) and 11(th) base. The expression patterns of miR164 and its target gene NAC1 were further detected under nitrate-starvation condition through qRT-PCR analysis. The results showed that miR164 expression was repressed by nitrate-starvation at the beginning of the treatment (4 d) and then ascended. However, the expression pattern of miR164 in roots was different from that in shoots and leaves. Moreover, the expression levels of target gene NAC1 and miR164 were negatively correlated. The expression level of miR164 in root was increased while that of NAC1 was decreased under Re treatment, which indicated that miR164 and its target gene NAC1 play a regulatory role in response to low nitrate availability. The findings of our study may help elucidate the molecular mechanisms by which miR164 regulates target gene NAC1 at post-transcriptional level, and provide valuable information for further study of the regulatory roles of miR164-NAC1 under nitrate-starvation condition.

Cloning of a caffeoyl-coenzyme A O-methyltransferase from Camellia sinensis and analysis of its catalytic activity.

Epigallocatechin-3-O-(3-O-methyl) gallate (EGCG3"Me) present in leaves of Camellia sinensis has many beneficial biological activities for human health. However, EGCG3"Me occurs naturally in tea leaves in extremely limited quantities. Finding an enzyme from C. sinensis to catalyze the synthesis of EGCG3"Me is an alternative method to make up for the scarcity of EGCG3"Me in natural situations. In the present study, a complementary DNA (cDNA) encoding region and genomic DNA of the caffeoyl-coenzyme A O-methyltransferase (CCoAOMT) gene were isolated from C. sinensis (designated CsCCoAOMT). Nucleotide sequence analysis of CsCCoAOMT revealed an open reading frame of 738 bp that encodes a polypeptide with a predicted molecular weight of 28 kDa, which correlated well with the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The full-length DNA sequence (2678 bp) contained five exons and four introns. The deduced amino acid sequence of CsCCoAOMT shared 92% identity with CCoAOMTs from Codonopsis lanceolata and Betula luminifera. The catalytic activity of CsCCoAOMT was analyzed. Three monomethylated epigallocatechin-3-O-gallate (EGCG) compounds (EGCG4"Me, EGCG3"Me, and EGCG3'Me) were produced by CsCCoAOMT with K(m) in the micromolar range. Real-time polymerase chain reaction (RT-PCR) experiments indicated that the CsCCoAOMT transcript was present at low levels during the early stages of leaf maturity (the first leaf and bud on a shoot) but the relative expression was augmented at advanced stages of leaf maturity (the third or fourth leaf on a shoot), which accorded well with changes in EGCG3"Me content in fresh leaves. Hence, we concluded that CsCCoAOMT catalyzes the syntheses of methylated EGCGs.

Eight distinct cellulose synthase catalytic subunit genes from Betula luminifera are associated with primary and secondary cell wall biosynthesis

Cellulose, a significant proportion of the plant cell wall, is the main determining factor of the wood qualities of a timber tree. Cellulose synthase (CESA), an essential catalyst for cellulose biosynthesis, is encoded by the CesA gene family. We isolated eight full-length CesA cDNAs from Betula luminifera on the basis of transcriptome sequencing. The predicted proteins comprised 985–1,103 amino acids, sharing 85–92 % identity with the corresponding PtiCESAs from Populus trichocarpa. Each protein contained typical motifs of plant CESA proteins. Phylogenetic analysis showed that BlCESA1, BlCESA3 and BlCESA4 belonged to three clades linked to secondary cell wall synthesis, and BlCESA2, BlCESA5, BlCESA6, BlCESA7 and BlCESA8 belonged to three clades associated with primary cell wall synthesis. Quantitative reverse transcription PCR and in situ mRNA hybridization indicated that transcripts of BlCesA1, BlCesA3 and BlCesA4 were most abundant in the xylem of the lignified stem and had similar expression patterns when treated with hormones and sucrose. Thus, the proteins encoded by these three genes might be subunits of the secondary wall CesA complex. However, the expression patterns of BlCesA1, BlCesA3 and BlCesA4 were different in response to mechanical stress. These three genes showed much higher expression levels in the tension wood than in the control, and they showed different expression patterns in the opposite wood, suggesting that these genes play different roles during secondary wall formation. BlCesA2, BlCesA5, BlCesA6 and BlCesA7 were predominantly expressed in the leaf and phloem. BlCesA8, which is most similar to BlCesA6, was strongly expressed in the leaf, phloem and cambium. Interestingly, these two genes showed distinct expression patterns when treated with hormones, sucrose and bending. Thus, in addition to biosynthesis of the primary cell wall, BlCesA8 might have other functions.

Carbon Storage in Young Chinese Fir (&lt;i&gt;Cunninghamia lanceolata&lt;/i&gt;) Monoculture and Mixed Plantations in Subtropical China

Mixed plantations of Chinese fir (Cunninghamia lanceolata, CL) and five broadleaf tree species (Ailanthus altissima (AA), Betula luminifera (BL), Sapindus mukurossi (SM), Tciliata varpubescens (TV) and Zelkova schnideriana (ZS)) were established. After 5 years, spatial distributions of carbon stocks were studied in Chinese fir monoculture and mixed plantations. Overstory tree carbon storages were significantly lower (P&lt;0.05) in mixed plantations than that in Chinese fir monoculture plantations. Understory vegetation carbon storages were significantly lower (P&lt;0.05) in CL+BL and CL+ZS plantations than in the monoculture plantations. No significant difference was observed between other mixed plantations and monoculture plantations. Litter carbon storage was significantly lower in CL+ZS plantations than in the monoculture plantations (P&lt;0.05), there was no significant difference between other mixed plantations and monoculture plantations. Soil carbon storages (0-60 cm) in mixed plantations were higher than that in the monoculture plantations, except for CL+SM plantations. Total ecosystem carbon storage was no significant difference between monoculture and mixed plantations, except for CL+SM plantations. Nevertheless, spatial distribution of carbon storage was different among these mixed plantations.

Effect of two patterns of forest rehabilitation on soil enzyme activity and its relationship with soil fertility

Soil enzyme activity and their seasonal variation-vertical distribution, the relationship between soil enzyme activity and soil fertility were measured on the two different patterns of forest rehabilitation with the methods of fixed sample plots, mechanical sampling and conventional enzyme activity- physicochemical characters determination. The results showed that the ranked order of urease and cellulose activity were Pleioblastus amarus plantation>Betula luminifera plantation>cropland, catalase activity was P. amarus plantation> cropland> B. luminifera plantation. The change of enzyme activity in B. luminifera plantation and P. amarusplantation was more acute than cropland, which showed that different utilization types had a close connection with soil enzyme activity. In the aspect of total amount in different soil layers, invertase, urease, cellulose and catalase activities were P. amarus plantation> B. luminifera plantation>cropland, which showed enzyme activity of slope farmland was improved in two patterns of forest rehabilitation. Rhizosphere effect showed the ratio of rhizospheric soil enzyme activity vs. non-rhizospheric soil enzyme activity (R/S value) of those four soil enzyme activities in B. luminifera plantation and P. amarus plantation were more than 1, which showed the two forests had high rhizosphere effect, and had a certain contribution to increase the soil enzyme activity. The enzyme activity is closely related with the soil fertility for forest rehabilitation and this indicated that enzyme activity could be used to characterize soil fertility, which had positive significance to improve the soil and biological fertility. Key words: Forest rehabilitation, soil enzyme, rhizosphere effect, soil fertility.

Response of &lt;I&gt;Betula luminifera&lt;/I&gt; leaf litter decomposition to simulated nitrogen deposition in the Rainy Area of West China

Response of &lt;I&gt;Betula luminifera&lt;/I&gt; leaf litter decomposition to simulated nitrogen deposition in the Rainy Area of West China