A new perspective on structural characterisation and immunomodulatory activity of arabinogalactan in Larix kaempferi from Qinling Mountains

In this study, crude polysaccharide (LAG-C) and homogeneous arabinogalactan (LAG-W) were isolated from Qinling Larix kaempferi of Shaanxi Province. Bioactivity assays showed that LAG-W and LAG-C enhanced the phagocytic ability, NO secretion, acid phosphatase activity, and cytokine production (IL-6, IL-1β, and TNF-α) of RAW264.7 macrophages. Notably, LAG-W exhibited a significantly stronger immunomodulatory effect than LAG-C. The primary structure of LAG-W was characterised by chemical methods (monosaccharide composition, methylation analysis, and alkali treatment) and spectroscopic techniques (gas chromatography-mass spectrometry, high-performance liquid chromatography-mass spectrometry, and 1D/2D nuclear magnetic resonance). LAG-W was identified as a 22.08 kilodaltons (kDa) neutral polysaccharide composed of arabinose and galactose at a 1:7.5 molar ratio. Its backbone consisted of repeated →3)-β-Galp-(1→ residues. Side chains, connected at the O-6 position, were mainly composed of T-β-Galp-(1→ and T-β-Galp-(1→6)-β-Galp-(1→ residues. And it also contained small amounts of T-β-Arap-(1→, T-α-Araf-(1→6)-β-Galp-(1→6)-β-Galp-(1→, and T-α-Araf-(1→3)-α-Araf-(1→6)-β-Galp-(1→ residues. By structurally and functionally characterising L. kaempferi polysaccharides, this study opens the way for the valorisation of this species.

Identification of C2H2 zinc finger genes through genome-wide association study and functional analyses of LkZFPs in response to stresses in Larix kaempferi

BACKGROUND

C2H2 zinc finger proteins (C2H2-ZFPs), one of the largest transcription factors, play a variety of roles in plant development and growth as well as stress response. While, the evolutionary history and expression profile of the C2H2-ZFP genes in Larix kaempferi (LkZFPs) have not been reported so far.

RESULTS

In this study, the whole genome of the LkZFPs was identified and characterized, including physicochemical properties, phylogenetic relationships, conservative motifs, the promoter cis-elements and Gene Ontology (GO) annotation. We identified 47 LkZFPs and divided them into four subfamilies based on phylogenetic analysis and conserved motifs. Subcellular localization prediction showed that most of the LkZFPs were located in the nucleus. Promoter cis-element analysis suggested that the LkZFPs may be involved in the regulation of stress responses. Moreover, Real-time quantitative PCR (RT-qPCR) results showed that Q-type LkZFP genes were involved in the response to abiotic stress, such as salt, drought and hormone stresses. Subcellular localization results showed that LkZFP7 and LkZFP37 were located in the nucleus, LkZFP32 was located in both cytoplasm and nucleus.

CONCLUSION

The identification and functional analysis of LkZFPs suggested that some LkZFP genes might play important roles in coping with both biological and abiotic stresses. These results could further increase understanding of the function of the LkZFPs, and provide some research direction and theoretical support.

Comprehensive Analysis of the NF-YB Gene Family and Expression under Abiotic Stress and Hormone Treatment in Larix kaempferi

NF-YB, a subfamily of Nuclear Factor Y (NF-Y) transcription factor, play crucial role in many biological processes of plant growth and development and abiotic stress responses, and they can therefore be good candidate factors for breeding stress-resistant plants. However, the NF-YB proteins have not yet been explored in Larix kaempferi, a tree species with high economic and ecological values in northeast China and other regions, limiting the breeding of anti-stress L. kaempferi. In order to explore the roles of NF-YB transcription factors in L. kaempferi, we identified 20 LkNF-YB family genes from L. kaempferi full-length transcriptome data and carried out preliminary characterization of them through series of analyses on their phylogenetic relationships, conserved motif structure, subcellular localization prediction, GO annotation, promoter cis-acting elements as well as expression profiles under treatment of phytohormones (ABA, SA, MeJA) and abiotic stresses (salt and drought). The LkNF-YB genes were classified into three clades through phylogenetic analysis and belong to non-LEC1 type NF-YB transcription factors. They have 10 conserved motifs; all genes contain a common motif, and their promoters have various phytohormones and abiotic stress related cis-acting elements. Quantitative real time reverse transcription PCR (RT-qPCR) analysis showed that the sensitivity of the LkNF-YB genes to drought and salt stresses was higher in leaves than roots. The sensitivity of LKNF-YB genes to ABA, MeJA, SA stresses was much lower than that to abiotic stress. Among the LkNF-YBs, LkNF-YB3 showed the strongest responses to drought and ABA treatments. Further protein interaction prediction analysis for LkNF-YB3 revealed that LkNF-YB3 interacts with various factors associated with stress responses and epigenetic regulation as well as NF-YA/NF-YC factors. Taken together, these results unveiled novel L. kaempferi NF-YB family genes and their characteristics, providing the basic knowledge for further in-depth studies on their roles in abiotic stress responses of L. kaempferi.

Comprehensive collection of genes and comparative analysis of full-length transcriptome sequences from Japanese larch (Larix kaempferi) and Kuril larch (Larix gmelinii var. japonica)

BACKGROUND

Japanese larch (Larix kaempferi) is an economically important deciduous conifer species that grows in cool-temperate forests and is endemic to Japan. Kuril larch (L. gmelinii var. japonica) is a variety of Dahurian larch that is naturally distributed in the Kuril Islands and Sakhalin. The hybrid larch (L. gmelinii var. japonica × L. kaempferi) exhibits heterosis, which manifests as rapid juvenile growth and high resistance to vole grazing. Since these superior characteristics have been valued by forestry managers, the hybrid larch is one of the most important plantation species in Hokkaido. To accelerate molecular breeding in these species, we collected and compared full-length cDNA isoforms (Iso-Seq) and RNA-Seq short-read, and merged them to construct candidate gene as reference for both Larix species. To validate the results, candidate protein-coding genes (ORFs) related to some flowering signal-related genes ​were screened from the reference sequences, and the phylogenetic relationship with closely related species was elucidated.

RESULTS

Using the isoform sequencing of PacBio RS ll and the de novo assembly of RNA-Seq short-read sequences, we identified 50,690 and 38,684 ORFs in Japanese larch and Kuril larch, respectively. BUSCO completeness values were 90.5% and 92.1% in the Japanese and Kuril larches, respectively. After comparing the collected ORFs from the two larch species, a total of 19,813 clusters, comprising 22,571 Japanese larch ORFs and 22,667 Kuril larch ORFs, were contained in the intersection of the Venn diagram. In addition, we screened several ORFs related to flowering signals (SUPPRESSER OF OVEREXPRESSION OF CO1: SOC1, LEAFY: LFY, FLOWERING Locus T: FT, CONSTANCE: CO) from both reference sequences, and very similar found in other species.

CONCLUSIONS

The collected ORFs will be useful as reference sequences for molecular breeding of Japanese and Kuril larches, and also for clarifying the evolution of the conifer genome and investigating functional genomics.

The Larix kaempferi genome reveals new insights into wood properties

Here, through single-molecule real-time sequencing, we present a high-quality genome sequence of the Japanese larch (Larix kaempferi), a conifer species with great value for wood production and ecological afforestation. The assembled genome is 10.97 Gb in size, harboring 45,828 protein-coding genes. Of the genome, 66.8% consists of repeat sequences, of which long terminal repeat retrotransposons are dominant and make up 69.86%. We find that tandem duplications have been responsible for the expansion of genes involved in transcriptional regulation and stress responses, unveiling their crucial roles in adaptive evolution. Population transcriptome analysis reveals that lignin content in L. kaempferi is mainly determined by the process of monolignol polymerization. The expression values of six genes (LkCOMT7, LkCOMT8, LkLAC23, LkLAC102, LkPRX148, and LkPRX166) have significantly positive correlations with lignin content. These results indicated that the increased expression of these six genes might be responsible for the high lignin content of the larches' wood. Overall, this study provides new genome resources for investigating the evolution and biological function of conifer trees, and also offers new insights into wood properties of larches.

Pedigree reconstruction and spatial analysis for genetic testing and selection in a Larix kaempferi (Lamb.) Carrière plantation

BACKGROUND

Larix kaempferi is one of the major timber species in Northeast Asia. Demand for the reforestation of the species is rising in South Korea due to an increase in large timber production and utilization. However, progeny trials for the species have not been explored, making it challenging to foster advanced generations of tree improvement. In the present study, genetic testing and selection for diameter growth were conducted using pedigree reconstruction and phenotypic spatial distribution analysis in a plantation of L. kaempferi. The aim of the present study was to select the superior larch individuals using the pedigree reconstruction and phenotypic spatial distribution to substitute progeny trials. The plantation of seed orchard crops was established in 1990 and one-hundred and eighty-eight trees were selected as the study material. Genetic variation was investigated first to validate its adequacy as breeding material. Genetic testing was carried out using a model considering pedigree information and spatial autoregression of the phenotypes.

RESULTS

The expected heterozygosity of the mother trees and offspring were 0.672 and 0.681 presenting the corresponding level of genetic variation between two groups. The pedigree reconstruction using maternity analysis assigned one to six progenies to ninety-two candidate mothers. The accuracy of genetic testing was exceedingly increased with the animal model considering AR1 ⊗ AR1 structure compared to the animal model only. The estimated genetic variance of the former was 9.086 whereas that of the latter was 4.9E-5 for DBH. The predicted breeding values of the offspring for DBH were ranged from -5.937 cm to 5.655 cm and the estimated heritability of diameter growth was 0.344.

CONCLUSIONS

The genetic testing approach based on pedigree reconstruction and phenotypic spatial distribution analysis was considered a useful analytical scheme that could replace or supplement progeny trials.

Over-Expression of the Cell-Cycle Gene LaCDKB1;2 Promotes Cell Proliferation and the Formation of Normal Cotyledonary Embryos during Larix kaempferi Somatic Embryogenesis

Somatic embryogenesis is an effective tool for the production of forest tree seedlings with desirable characteristics; however, the low initiation frequency and productivity of high-quality mature somatic embryos are still limiting factors for Larix kaempferi (Japanese larch). Here, we analyzed the expression pattern of L. kaempferi cyclin-dependent kinase B 1;2 (LaCDKB1;2) during somatic embryogenesis in L. kaempferi and its relationship with the cell proliferation rate. We also analyzed the effect of LaCDKB1;2 over-expression on somatic embryo quality. The results revealed a positive correlation between LaCDKB1;2 expression and the cell proliferation rate during the proliferation stage. After LaCDKB1;2 over-expression, the proliferation rate of cultures increased, and the number of somatic embryos in transgenic cultures was 2.69 times that in non-transformed cultures. Notably, the number of normal cotyledonary embryos in transgenic cultures was 3 times that in non-transformed cultures, indicating that LaCDKB1;2 not only increases the proliferation of cultures and the number of somatic embryos but also improves the quality of somatic embryos. These results provide insight into the regulatory mechanisms of somatic embryogenesis as well as new Larix breeding material.

Physiological and anatomical responses to drought stress differ between two larch species and their hybrid

KEY MESSAGE

Hybrid saplings were more reactive to soil water deficit than Japanese and European larch. European larch had hydraulically safer wood and anisohydric behavior, Japanese and hybrid larch showed isohydric strategy.

ABSTRACT

Deciduous larch species could be an alternative to evergreen conifers in reforestation, but little is known about drought sensitivity of their saplings. The effect of an experimental drought on hydraulics and quantitative wood anatomy was tested on saplings of European larch (EL, Larix decidua), Japanese larch (JL, Larix kaempferi) and their hybrid (HL). Across species, biomass, transpiration rate and relative water content were higher in controls than in drought stressed trees, but transpiration efficiency was lower. JL had the highest transpiration efficiency under drought, and EL the lowest, coinciding with slower growth of EL. Wood of EL formed before drought was hydraulically safer as shown by higher wall/lumen ratio and lower pit cavity area. EL neither had a significant increase in transpiration efficiency nor a reduction in transpiration rate under drought, suggesting that the stomata remained open under soil water deficit. HL saplings were the most reactive to water shortage, indicated by intra-annual density fluctuations and a decrease in relative water content of the sapwood. Significant reduction in transpiration by HL suggested a higher stomatal sensitivity, while the same leaf surface area was maintained and radial growth was still similar to its best parent, the JL. The latter showed a significantly lower leaf surface area under drought than controls. EL, with its hydraulically safer wood, followed an anisohydric behavior, while JL and HL revealed an isohydric strategy. Altogether, our results suggest species dependent acclimations to drought stress, whereby HL followed the strategy of JL rather than that of EL.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00468-021-02129-4.

Gluing Techniques on Bond Performance and Mechanical Properties of Cross-Laminated Timber (CLT) Made from Larix kaempferi

Previous studies have proved that Larix kaempferi is a good material for preparing cross-laminated timber (CLT), but under bending shear stress, CLT made by Larix kaempferi is prone to the phenomenon of bonding face cracking, which seriously affects the shear performance of CLT. To solve this problem, this paper took Larix kaempferi as raw material, conducted experiments on the surface sanding conditions, gluing pressure and adhesive types of sawing timber, and explored the influence of these three factors on the bonding quality of CLT. The microscopic characteristics of the bonding layer were further studied. The results showed that for Larix kaempferi with a density of 0.68 g/cm³ used in this experiment, a high bonding pressure is required. Among the three cold curing adhesives selected in the experiment, emulsion polymer isocyanate (EPI) adhesive needs 1.5 MPa bonding pressure to ensure the bonding quality, while for polyurethane (PUR) and phenol resorcinol formaldehyde (PRF), 1.2 MPa can meet the need of adhesive pressure. This is concerned with the permeability of different adhesives under different pressures. The microscopic results of the bonding layer show that EPI adhesives have poor permeability, so it requires high bonding pressure. The influence of sanding surface of different sand-belt on block shear strength (BSS) and wood failure percentage (WFP) is not obvious, while the durability of bonding layer is better when sanding mesh number is 100. Hence, a high pressure should be used for CLT industrial production when the laminate density is higher, especially when the adhesive has poor permeability. Reasonable sanding surface treatment can be used in laminate surface treatment to improve the durability of CLT.

Functional Characteristics Analysis of Dehydrins in Larix kaempferi under Osmotic Stress

Dehydrins (DHN) belong to the late embryogenesis abundant II family and have been found to enhance plant tolerance to abiotic stress. In the present study, we reported four DHNs in Larix kaempferi (LkDHN) which were identified from the published transcriptome. Alignment analysis showed that these four LkDHNs shared close relationships and belonged to SK3-type DHNs. The electrophoretic mobility shift assay indicated that these four LkDHNs all possess sequence-independent binding capacity for double-strands DNAs. The subcellular localizations of the four LkDHNs were in both the nucleus and cytoplasm, indicating that these LkDHNs enter the nucleus to exert the ability to bind DNA. The preparation of tobacco protoplasts with different concentrations of mannitol showed that LkDHNs enhanced the tolerance of plant cells under osmotic stress. The overexpression of LkDHNs in yeasts enhanced their tolerance to osmotic stress and helped the yeasts to survive severe stress. In addition, LkDHNs in the nucleus of salt treated tobacco increased. All of these results indicated that the four LkDHNs help plants survive from heavy stress by participating in DNA protection. These four LKDHNs played similar roles in the response to osmotic stress and assisted in the adaptation of L. kaempferi to the arid and cold winter of northern China.

In vitro anti-inflammatory and anti-lipid accumulation properties of taxifolin-rich extract from the Japanese larch, Larix kaempferi

The Japanese larch, (Larix kaempferi) is known to contain abundant taxifolin (dihydroquercetin) in its xylem. In this study, to assess the bioactivities of taxifolin rich methanol extract of L. kaempferi (LK-ME), anti-inflammatory effect, and the anti-lipid accumulation effect of LK-ME were investigated. The results showed that nitric oxide (NO) and reactive oxygen species (ROS) were reduced after treatment with LK-ME, and that lipid accumulation in adipocyte differentiated 3T3-L1 cells was inhibited after the cells were grown in medium containing LK-ME. Taxifolin, the major compound contained in LK-ME, and its related compounds, quercetin and luteolin also exhibited similar effects with LK-ME. The LK-ME exhibits relatively strong anti-inflammatory and anti-lipid accumulation activities compared with that of similar amounts of taxifolin contained in LK-ME, suggesting that other minor compounds contained in LK-ME is involved in the effects. These results indicate the potential of taxifolin-rich L. kaempferi extract for use as a supplement to prevent excess inflammation and obesity.

Advancing Timberline on Mt. Fuji between 1978 and 2018

Climate change is a major cause of changes in alpine and polar vegetation, particularly at the edges of distributions. In temperate regions, these changes are expected to occur at the timberline of alpine zones. On Mt. Fuji, the highest mountain in Japan, the timberline is located 2400-2500 m above sea level. Over a 40-year period (1978-2018), we researched changes in the timberline vegetation of Mt. Fuji. A permanent belt transect extending from the upper timberline to subalpine zones was set up in August 1978. Tree diameters and heights were recorded at the establishment of the transect and every 20 years afterwards. Over the 40 years of the study, the timberline advanced rapidly upwards, and the degree of vegetation cover above the timberline increased remarkably. Notably, the expansion of Salix reinii into the upper part of the timberline facilitated the subsequent spread of Larix kaempferi into this zone. Seedlings of L. kaempferi were particularly abundant at the upper timberline and became established on the uppermost part of the slope. The shape of L. kaempferi at the upper timberline changed from a prostrate form to an upright tree form. We conclude that the upward advance of the alpine timberline observed on Mt. Fuji is due to climate change.

Functional Characteristics of Caffeoyl Shikimate Esterase in Larix Kaempferi and Monolignol Biosynthesis in Gymnosperms

Caffeoyl shikimate esterase (CSE) has been reported to be involved in lignin biosynthesis; however, studies of CSE in gymnosperms are lacking. In this study, CSE was successfully cloned from Larix kaempferi (LkCSE) based on Larix laricina transcriptome screening. LkCSE was likely to have catalytic activity based on homologous sequence alignment and phylogenetic analyses of CSEs from different species. In vitro assays with the recombinant enzyme validated the catalytic activity of LkCSE, indicating its function in converting caffeoyl shikimate into caffeate and shikimate. Additionally, the optimum reaction pH and temperature of LkCSE were determined to be 6.0 and 30 °C, respectively. The values of K_m and V_max of CSE for caffeoyl shikimate were 98.11 μM and 14.44 nM min^-1, respectively. Moreover, LkCSE was observed to have tissue expression specificity and was abundantly expressed in stems and leaves, especially stems, which was 50 times higher than the expression levels of roots. Lastly, translational fusion assays using LkCSE fused with green fluorescent proteins (GFP) in tobacco leaves indicated that LkCSE was localized in the plasma membrane and endoplasmic reticulum (ER). These results revealed that CSE clearly functions in gymnosperms and it is possible for LkCSE to interact with other ER-resident proteins and regulate mass flux in the monolignol biosynthesis pathway.

Cell cytotoxity and anti-glycation activity of taxifolin-rich extract from Japanese larch, Larix kaempferi

The larches, the Larix genus of plants are known as a natural source of taxifolin (dihydroquercetin), and extracts of its taxifolin rich xylem are used in dietary supplements to maintain health. In the present study, to assess biological activities of a methanol extract of the Japanese larch, Larix kaempferi (LK-ME), the effects of LK-ME on cell viability, inflammatory cytokine expression, and glycation were investigated. The effects of taxifolin which is known to be a main compound of LK-ME, and its related flavonoids, quercetin and luteolin were also examined. The results show that taxifolin exhibits lower growth inhibition activity and lesser induction activity of inflammatory cytokines in a human monocyte derived cell line, THP-1 cells, while in vitro anti-glycation activities of taxifolin were inhibiting at comparable levels to those of quercetin and luteolin. The growth inhibition and the cytokine induction activities, and the anti-glycation effects of LK-ME are assumed to have properties similar to taxifolin. The results of high performance liquid chromatography (HPLC) analysis indicated that taxifolin was detected as the main peak of LK-ME at the absorbance of 280 nm, and the concentration of taxifolin was measured as 3.12 mg/ml. The actual concentration of taxifolin in LK-ME is lower than the concentration estimated from the IC₅₀ values calculated by the results of glycation assays, suggesting that other compounds contained in LK-ME are involved in the anti-glycation activity.

Functional characterization of LkERF-B2 for improved salt tolerance ability in Arabidopsis thaliana

The ethylene response factors have been reported to play critical roles in developmental and environmental responses in plants. In the present study, an ERF transcription factor gene was aimed to be identified from Larix kaempferi. Molecular characteristics and function of this gene were further explored. The result showed that a 1344 bp ERF transcription factor gene containing initiation and termination codon was obtained by RT-PCR and named LkERF-B2. LkERF-B2 gene encoded 447 amino acids containing a typical AP2/ERF domain. Alignment of predicted amino acid sequence of LkERF-B2 in various plant species showed that this ERF transcription factor was highly homologous (79.0%) with that of Picea sitchensi. To elucidate the function of LkERF-B2, LkERF-B2 overexpression vector was successfully constructed and transformed to Arabidopsis thaliana via dip flower. Compared with control plant, LkERF-B2 overexpressed transgenic A. thaliana showed a significantly higher survival rate under cold, heat, NaCl and drought stresses. NaCl stress analysis revealed that control and transgenic Arabidopsis were both flowering earlier under 100 and 150 mM/L NaCl treatment. While under 200-300 mM/L NaCl treatment, the growth of control plant was significantly inhibited compared with transgenic A. thaliana. Salt injury rate and salt injury index of transgenic Arabidopsis were lower than those of the control. Further investigation showed that transgenic Arabidopsis exhibited much higher content of chloroplast pigments under different NaCl concentration. Meanwhile, the activity of SOD and POD was also enhanced in transgenic A. thaliana. These results suggested that LkERF-B2 was a key transcription factor and could lead to enhanced salt stress tolerance.

Nitrogen loading increases the ozone sensitivity of larch seedlings with higher sensitivity to nitrogen loading

Larch (Larix sp.) tree is a critical species for the future afforestation in Northeast Asia. The impacts of elevated concentrations of ground-level ozone (O₃) and nitrogen (N) deposition are raising concerns. However, knowledge of the combined effects of elevated O₃ and N loading are still limited. We investigated whether nitrogen loading mitigates the negative impacts of ozone on two larch species: the Japanese larch (L. kaempferi) and its hybrid larch F₁ (L. gmelinii var. japonica × L. kaempferi) or not. We used open-top cambers and compared responses of the larch seedlings. Results showed the N loading mitigated the negative effects of O₃ on Japanese larch. However, in hybrid larch F₁, N loading did not mitigate O₃-induced inhibition of growth and photosynthetic capacity. Mitigation effect of N loading on negative O₃ impacts may vary between the two Larix spp., Hybrid larch F₁ could be more affected by the combined effects of O₃ and N loading due to its higher growth response to N loading. Elevated O₃ also reduced leaf nitrogen/phosphorus (N/P) ratio by elevated O₃, with significant effects in hybrid larch F₁, particularly under N loading. In the present study, leaf N/P ratio was utilized to validate the hypothesis that a positive effect of N loading may be observed if O₃ does not induce P limitation in Larix spp. We demonstrated a potential leaf N/P ratio function, which could reflect responses to O₃ and N loading in hybrid larch F₁.

[Effects of N-fixing tree species (Alnus sibirica)on amino sugars in soil aggregates of Larix kaempferi plantation in eastern Liaoning Province, China.]

Soil microbial residues are important components of soil stable carbon (C) pools. How N-fixing tree species influence microbial residues in soil aggregates in larch plantations is still unclear. To determine the effects of N-fixing tree species on the distribution of microbial residues in different aggregates, we compared the distribution of amino sugars, biomarker of microbial residues, among aggregates in a pure larch (Larix kaempferi) plantation and a mixed plantation of larch (Larix kaempferi) and alder (Alnus sibirica) in eastern Liaoning Province. The results showed that alder did not affect the distribution of amino sugars, but significantly increased amino sugars content in soil aggregates. The total amino sugars in different soil aggregates were enriched by 130%-170% in the mixed larch plantation compared with those in pure larch plantation. The contributions of glucosamine, galactosamine and muramic acid to the increases of total amino sugars caused by alder introduction were 66.5%-66.9%, 30.0%-30.6% and 2.5%-3.2%, respectively. Alder introduction significantly accelerated the glucosamine/muramic acid ratios in >2000 μm and <250 μm aggregates, but not in 250-2000 μm aggregates. Moreover, alder introduction increased the microbial contribution to soil organic C in all aggregates, but did not influence this contribution among aggregates, indicating that the effects of alder introduction on microbial contribution to aggregates were homogeneous.

Mating patterns and pollen dispersal in a Japanese larch (Larix kaempferi) clonal seed orchard: a case study

Pollination dynamics highly determines the genetic quality of seed orchard crops. However, there is less research about the effect of mating patterns on seed productivity of orchard crops. So far, clonal seed orchards have been producing genetically improved seedlings used for most Japanese larch (Larix kaempferi (Lamb.) Carr.) plantations in China. In the present study, a total of 17 highly variable simple sequence repeat (SSR) markers were used for genotyping a progeny trial population consisting of 647 open-pollinated progenies germinated from seeds which were collected from 63 maternal clones with 140 potential paternal clones in a Japanese larch clonal seed orchard in China. Paternity analysis was used in the present case study in order to evaluate the level of paternal gametic contribution, estimate pollen contamination and selfing rates, and investigate pollination patterns, pollen dispersal patterns and the impact of mating patterns on seed productivity of orchard crops. We observed 93.7% of the success rate of the parental assignment, unequal paternal gametic contribution (0-12.4%) with 6.3% of the progenies derived from pollen contamination or unsampled pollen donors, and absence of evidence for selfing. We also found that pollination rate highly depended on the distance between pollen donors and maternal parents, the majority of the identified crossing (65.7%) occurred between clones within a 150-m radius, and large variations in growth performance existed among the paternal half-siblings. Progeny growth performance (diameter at breast (DBH) and height (HGT)) was measured at Age-20 in order to investigate the impact of mating patterns on timber production of orchard crops. As either the paternal or maternal, two clones (i. e., clones Z38 and Z62) were identified to have produced progenies with higher average stem volume breeding values than that of all of the progenies. Specifically, the genetic gains for volume were 3.53% for the two clones as paternal parents, and 8.26% as the maternal parents at Age-20. Thus, both elite clones were ideal candidates for the construction of next-generation clonal seed orchards due to their synchronous reproductive phenology with greater crossing rate and higher genetic gain. These results improved the pedigree information to provide solid evidence of mating patterns for future design and effective management of seed orchards and for the development of viable long-term breeding strategies for other coniferous species.

The complete chloroplast genome sequences of Larix kaempferi and Larix olgensis var. koreana (Pinaceae)

The complete chloroplast (cp) genome sequence of Larix kaempferi and L. olgensis var. koreana were determined by Ion torrent Platform sequencing in this study. The L. kaempferi cp genome was 122,158bp consists of two inverted repeat (IR) regions of 436bp each, a large single-copy (LSC) region of 65,394bp, and a small single-copy (SSC) region of 55,892bp. The chloroplast genome sequence of L. olgensis var. koreana was 122,573bp in length, consisting of two IRs (436bp), one LSC (65,597bp), and one SSC (56,104bp), and is longer than that of L. kaempferi. The genome contained 110 genes, including 71 protein-coding genes, 35 tRNA genes, and 4 ribosomal RNA genes. The 13 genes contain introns, including 12 genes with a single intron each and ycf3 gene with two introns. And, the rps12 gene is a trans-spliced gene. The phylogenetic analysis revealed that all sampled species in Pinaceae formed a monophyletic clade with high bootstrap value. The genus Larix is closely related to Pseudotsuga.

Variation in susceptibility to wind along the trunk of an isolated Larix kaempferi (Pinaceae) tree

• Premise of the study: The force of the wind is a significant hazard to the survival of trees and can affect tree morphology. However, the actual distribution of the stress that wind causes to a tree trunk is not well understood in spite of its expected importance to tree morphology. The uniform stress hypothesis (i.e., tree trunks take a form that equalizes the distribution of stress along the outer surface of the stem) has been tested indirectly as a model, placing high importance on the mechanical safety of a trunk, and rejected theoretically. But stress on a tree's trunk has not yet been measured directly.• Methods: Actual strains at the surface of the trunk of an isolated Larix kaempferi tree due to wind loads were measured at seven heights on the trunk for 1 yr.• Key results: During the measurement period, wind-induced stress was higher in the upper portions of the trunk than in the lower portions, regardless of wind speed, and the difference increased as wind speed increased. The deflection of the trunk recorded at each position was also larger in the upper portions than in the lower portions.• Conclusions: The results indicate that the upper portions of the trunk of an isolated Larix kaempferi tree are more susceptible to wind than are the lower portions. These results do not support the uniform stress hypothesis and suggest that another limitation (either mechanical or nonmechanical) acts on the morphology of the tree.

Biochemical functions of the glutathione transferase supergene family of Larix kaempferi

Glutathione transferases (GSTs), which are ubiquitous in plants, play a major role in the detoxification of xenobiotics and oxidative stress metabolism. Due to their role in herbicide detoxification, previous studies of plant GSTs have mainly focused on agricultural plants. In contrast, functional information regarding gymnosperm GSTs is scarce. In this study, we cloned 27 full-length GST genes from the deciduous conifer Larix kaempferi, which is widely distributed across the cooler regions of the northern hemisphere. As with the angiosperm GST gene family, Larix GSTs are divided into eight classes, and tau class GSTs are the most numerous. Compared to the other seven classes of GSTs, Larix tau GST genes show substantially more variation in their expression patterns. The purified Larix GST proteins showed different substrate specificities, substrate activities, and kinetic characteristics. The pH and temperature profiles of purified Larix GST proteins showed broad optimum pH and temperature ranges for enzymatic activity, suggesting that Larix GSTs have evolutionary adaptations to various adverse environments. Taken together, this study provides comprehensive insight into the gymnosperm GST gene family.

Diversity and seasonal variation of endophytic fungi isolated from three conifers in mt. Taehwa, Korea

The needled leaves of three conifer species were collected in Mt. Taehwa during different seasons of the year. Total 59 isolates and 19 species of endophytic fungi were isolated from the leaves and identified using morphological and molecular characteristics. As a result, Shannon index was different in its host plant; Larix kaempferi had a highest value of species diversity. According to the sampling season, 9 species of 19 species were isolated during fall season. The results suggest that the existing of host plant and sampling season are major factors of distribution of endophytic fungi.

Pathogenicity of the pinewood nematode, Bursaphelenchus xylophilus, to Japanese larch, Larix kaempferi, seedlings

Pathogenicity of the pine wood nematode, Bursaphelenchus xylophilus, to Japanese larch, Larix kaempferi, seedlings was tested with inoculation experiments under nursery conditions. Water suspensions of nematodes (mixed stages cultured on Botrytis cinerea or dispersal fourth-stage juveniles (DJ4) extracted from the adult Japanese pine sawyer, Monochamus alternatus) were injected into the stems of 2- and 3-year-old Japanese larch and Japanese black pine, Pinus thunbergii, seedlings growing in a nursery. In another treatment, Japanese pine sawyer adults holding DJ4 were released under a net that covered the upper half of the seedlings. Regardless of nematode inoculation method, Japanese larch seedlings were as susceptible as Japanese black pine seedlings to B. xylophilus under nursery conditions. The rate of disease development was similar on larch and pine seedlings. Nematode population densities were lower in the stems of dead larch seedlings than in the stems of dead pine seedlings. Histopathological observations revealed that the distribution of nematodes in the stems of dead larch seedlings was mostly limited to the cortex, phloem and cambial zone. Traumatic resin canal formation was one of the most characteristic symptoms in larch seedlings which was dissimilar to that in pine seedlings.

Subterranean community structure of ectomycorrhizal fungi under Suillus grevillei sporocarps in a Larix kaempferi forest

•  Internal transcribed spacer (ITS) polymorphism analysis for identifying ectomycorrhizal (ECM) fungal species was improved by applying sequencer electrophoresis and terminal restriction fragment length polymorphism (RFLP). •  The improved method employed polymorphism of ITS_3-4 region and an ITS terminal-RFLP fragment digested with HinfI. This method enabled each ECM fungal species to be identified with more precision in a mixed-species sample and would accelerate studies on identification of ECM fungal species. •  Up to 30 ECM fungal species were detected in narrow areas under Suillus grevillei sporocarps. Compositions of subterranean ECM fungal species were much more abundant than aboveground ones, and varied from one location to another. Every ECM fungal species was not exclusively dominant over the others, and coexisted with other species. At locations where S. grevillei sporocarps had developed in the previous year, only a few Larix kaempferi root tips developed and were colonized by fewer ECM fungal species. •  Results indicate that the ECM fungal community under S. grevillei sporocarps decayed as a whole within 1 yr after sporocarp formation and was not re-established in the next growing season after sporocarp formation.