Terminal Buds Research Articles

Abstract F1-2: Clonal evolution of DCIS to invasion

Abstract F1-2: Clonal evolution of DCIS to invasion

Oak stands along an elevation gradient have different molecular strategies for regulating bud phenology

BackgroundGlobal warming raises serious concerns about the persistence of species and populations locally adapted to their environment, simply because of the shift it produces in their adaptive landscape. For instance, the phenological cycle of tree species may be strongly affected by higher winter temperatures and late frost in spring. Given the variety of ecosystem services they provide, the question of forest tree adaptation has received increasing attention in the scientific community and catalyzed research efforts in ecology, evolutionary biology and functional genomics to study their adaptive capacity to respond to such perturbations.ResultsIn the present study, we used an elevation gradient in the Pyrenees Mountains to explore the gene expression network underlying dormancy regulation in natural populations of sessile oak stands sampled along an elevation cline and potentially adapted to different climatic conditions mainly driven by temperature. By performing analyses of gene expression in terminal buds we identified genes displaying significant dormancy, elevation or dormancy-by-elevation interaction effects. Our Results highlighted that low- and high-altitude populations have evolved different molecular strategies for minimizing late frost damage and maximizing the growth period, thereby increasing potentially their respective fitness in these contrasting environmental conditions. More particularly, population from high elevation overexpressed genes involved in the inhibition of cell elongation and delaying flowering time while genes involved in cell division and flowering, enabling buds to flush earlier were identified in population from low elevation.ConclusionOur study made it possible to identify key dormancy-by-elevation responsive genes revealing that the stands analyzed in this study have evolved distinct molecular strategies to adapt their bud phenology in response to temperature.

Effect of terminal bud clipping on growth and yield of soybean cultivars in the Pacific Northwest

AbstractSoybean [Glycine max (L.) Merr.] is one of the four major staple crops and the world's most important vegetable protein source. Very little information is available on the performance, yield, and cultivars of soybean when choosing a cultivar to grow in Pacific Northwest (PNW). Of the oilseed crops, soybean appears to have the best potential to be grown at a profit (high yields) in PNW when considering the high input costs for irrigated crops. The present study was conducted to determine if terminal bud clipping would increase yields of soybean cultivars under irrigated conditions in 2‐year field experiments. Five soybean cultivars were planted in four‐row plots with rows 0.13 m apart. Plots were replicated four times with two treatments (early clipping and late clipping) and control in a randomized complete block design. Data regarding yield and growth traits were recorded using standard procedure. Soybean yield was significantly influenced by the year of production and terminal bud clipping, whereas cultivars showed no effect. Early and late clipping resulted in a 15% and 18% increase in yields in 2018, whereas late clipping resulted in a 16% yield increase in 2019 compared to control. Terminal bud clipping resulted in shorter plants and reduced lowest pod height, lodging, and maturity compared with the control. Lodging and maturity decreased with late‐maturing cultivars. Finally, results suggest that terminal bud clipping increases soybean yields. Early maturing cultivars (maturity group 0.4) are unsuitable for PNW due to the lowest pod height.

NEDD9 Overexpression Causes Hyperproliferation of Luminal Cells and Cooperates with HER2 Oncogene in Tumor Initiation: A Novel Prognostic Marker in Breast Cancer.

HER2 overexpression occurs in 10-20% of breast cancer patients. HER2+ tumors are characterized by an increase in Ki67, early relapse, and increased metastasis. Little is known about the factors influencing early stages of HER2- tumorigenesis and diagnostic markers. Previously, it was shown that the deletion of NEDD9 in mouse models of HER2 cancer interferes with tumor growth, but the role of NEDD9 upregulation is currently unexplored. We report that NEDD9 is overexpressed in a significant subset of HER2+ breast cancers and correlates with a limited response to anti-HER2 therapy. To investigate the mechanisms through which NEDD9 influences HER2-dependent tumorigenesis, we generated MMTV-Cre-NEDD9 transgenic mice. The analysis of mammary glands shows extensive ductal epithelium hyperplasia, increased branching, and terminal end bud expansion. The addition of oncogene Erbb2 (neu) leads to the earlier development of early hyperplastic benign lesions (~16 weeks), with a significantly shorter latency than the control mice. Similarly, NEDD9 upregulation in MCF10A-derived acini leads to hyperplasia-like DCIS. This phenotype is associated with activation of ERK1/2 and AURKA kinases, leading to an increased proliferation of luminal cells. These findings indicate that NEDD9 is setting permissive conditions for HER2-induced tumorigenesis, thus identifying this protein as a potential diagnostic marker for early detection.

Twig selection on mountain birch Betula pubescens by winter‐feeding willow grouse Lagopus lagopus in a subarctic forest

In a subarctic forest at Kvaløya, northern Norway, willow grouse Lagopus lagopus fed at snow level by clipping bits of twigs from mountain birch Betula pubescens during winter. Birch has two types of twigs ending in a terminal bud: long twigs with a smooth bark, and short twigs with rings of thicker bark. The grouse selected ringed twigs above smooth twigs despite a surplus of smooth twigs in the forest. Ringed twigs had more bark cm−1 of twig length and a higher relative bark/wood ratio than smooth twigs. Smooth twigs had growth nodes that increased in diameter inwards from the tip. Because of the non‐linear relation between the area and the circumference of a circle, the bark/wood ratio decreased for each node. Although being able to clip much thicker twigs, 90% of smooth twigs clipped by grouse were ≤ 2 mm in diameter. It is concluded that willow grouse fed optimally on birch in winter by selecting twigs to minimize fibrous wood intake.

Gestational Diabetes Mellitus Impedes Fetal Lung Development Through Exosome-Dependent Crosstalk Between Trophoblasts and Lung Epithelial Cells.

Fetal lung underdevelopment (FLUD) is associated with neonatal and childhood severe respiratory diseases, among which gestational diabetes mellitus (GDM) play crucial roles as revealed by recent prevalence studies, yet mechanism underlying GDM-induced FLUD, especially the role of trophoblasts, is not all known. From the perspective of trophoblast-derived exosomes, we established in vitro, ex vivo, in vivo and GDM trophoblast models. Utilizing placenta-derived exosomes (NUB-exos and GDMUB-exos) isolated from normal and GDM umbilical cord blood plasma and trophoblast-derived exosomes (NC-exos and HG-exos) isolated from HTR8/SVneo trophoblasts medium with/without high glucose treatment, we examined their effects on fetal lung development and biological functions. We found that, compared with the NUB-exos group, the exosome concentration increased in GDMUB-exos group, and the content of exosomes also changed evidenced by 61 dysregulated miRNAs. After applying these exosomes to A549 alveolar type II epithelial cells, the proliferation and biological functions were suppressed while the proportion of apoptotic cells was increased as compared to the control. In ex vivo studies, we found that GDMUB-exos showed significant suppression on the growth of the fetal lung explants, where the number of terminal buds and the area of explant surface decreased and shrank. Besides, the expression of Fgf10, Vegfa, Flt-1, Kdr and surfactant proteins A, B, C, and D was downregulated in GDMUB-exos group, whilst Sox9 was upregulated. For in vivo studies, we found significant suppression of fetal lung development in GDMUB-exos group. Importantly, we found consistent alterations when we used NC-exos and HG-exos, suggesting a dominant role of trophoblasts in placenta-derived exosome-induced FLUD. In conclusion, GDM can adversely affect trophoblasts and alter exosome contents, causing crosstalk disorder between trophoblasts and fetal lung epithelial cells and finally leading to FLUD. Findings of this study will shine insight into the theoretical explanation for the pathogenesis of FLUD.

A Guide Toward Multi-scale and Quantitative Branching Analysis in the Mammary Gland.

The mammary gland consists of a bilayered epithelial structure with an extensively branched morphology. The majority of this epithelial tree is laid down during puberty, during which actively proliferating terminal end buds repeatedly elongate and bifurcate to form the basic structure of the ductal tree. Mammary ducts consist of a basal and luminal cell layer with a multitude of identified sub-lineages within both layers. The understanding of how these different cell lineages are cooperatively driving branching morphogenesis is a problem of crossing multiple scales, as this requires information on the macroscopic branched structure of the gland, as well as data on single-cell dynamics driving the morphogenic program. Here we describe a method to combine genetic lineage tracing with whole-gland branching analysis. Quantitative data on the global organ structure can be used to derive a model for mammary gland branching morphogenesis and provide a backbone on which the dynamics of individual cell lineages can be simulated and compared to lineage-tracing approaches. Eventually, these quantitative models and experiments allow to understand the couplings between the macroscopic shape of the mammary gland and the underlying single-cell dynamics driving branching morphogenesis.

Diallel crosses in Picea abies III. Variation and inheritance patterns in nursery trials

Abstract The complete diallel cross is the only mating design that provides estimates of variance components of general combining (GCA), specific combining ability (SCA), maternal and reciprocal effects, in addition to heritabilities and genetic correlations. To obtain such estimates, complete diallels were made among 10 trees in each of three natural Norway spruce populations from altitude 300 and 500 m in Norway. Nursery trials were performed with the families from these crosses and families from seeds collected from open pollination. Traits measured and analysed are seed weight, germination rate, germination percentage, terminal bud set, and seedling heights the first and second years. The seedlings from the population at origin 500 m had lower seed weight, lower heights and earlier bud set than those from the two populations from lower altitude. A considerable variation was present among families within each diallel, and the GCA variance components had the highest values and were significant for most traits. Variance components for SCA and maternal effects were also significant for some traits, but with inconsistent values in the three diallels. A strong relationship was present between the weight of the seed lots from the maternal parent and mean family height after one and two growing seasons. The highest estimate of heritability was observed for bud set, with similar values in all three diallels.

Effect of nitrogen and boron fertilisation on juvenile stone pine growth. A pot experiment

At the establishment stage of a forest plantation, soil nutritional limitations can lead to insufficient plant growth and predispose plants to biotic and abiotic damages. Adequate plant nutrition contributes to proper plant establishment and subsequent growth. Nitrogen (N) and boron (B), among others, are essential nutrients for plant vigour and growth, and their requirements need to be established. However, there is a lack of information concerning post-transplant fertilisation of stone pine (Pinus pinea L.). The main objective of this work was to evaluate the effect of N and B applications on the vegetative growth of stone pine during the first three years in a conditioned environment. Morphological characteristics such as height growth (HGI), root collar diameter (RCDI), total branches length (TBL) and terminal buds length (BL) were evaluated for each plant, as well as the aboveground and root biomass production. The results showed that N fertilisation caused an increase in all growth variables suggesting that the application of N at a juvenile stage (after transplanting) of this specie will improve its development and obtain a reserve of this nutrient to be used by the plant at later stages of development, especially in soils with low fertility. Boron application had no effect on the evaluated parameters.

In Vitro sterilization protocol for callus induction of Baccaurea courtallensis (Wight) Müll.Arg. - An endemic tree of Southern Western Ghats, India

Experiments were carried out to establish in vitro culture using terminal and lateral buds of the endemic tree Baccaurea courtallensis of Phyllanthaceae which presented formidable difficulties. Besides the profuse phenol exudation, cultures were infected with intense fungal contamination. Efforts directed to control the schedule by adjusting the concentration of disinfectants NaOCl and HgCl2 with additional rinsing of explants with 70% ethanol and pre-soaking of shoots in various concentrations of the fungicide Bavistin never fetched any success. The intricately connected fungus seems to have found a niche amidst the leaf primordia in shoot apices and the axillary crevices of the nodal regions completely establishing itself in cultures. Perplexed with no remedy in sight, an interesting attempt of quick surface washing with 70% acetone was introduced in the surface sterilization schedule. Fresh explants were quickly rinsed with 70% acetone, followed by 0.1% mercuric chloride, 1% bavistin along with 4% PVP in succession and later wash with sterile distilled water enabling effective establishment of culture. Callus formation was observed on MS and WPM supplemented with auxin and cytokinin. Callus induction from the nodal region was observed at all concentrations and combinations of PGRs supplemented. Maximum induction of callus was obtained from MS medium augmented with BAP 4μM alone and in combination with IBA 1 μM +TDZ 4 μM.

Estimating heat tolerance of buds in southeastern US trees in fire-prone forests

BackgroundTraits of mature trees, such as bark thickness and texture, have been documented to promote resistance or resilience to heating in fire-prone forests. These traits often assist managers as they plan and promote prescribed fire management to accomplish specific land management objectives. Species are often grouped together as pyrophobes or pyrophytes as a result of these features. Nonetheless, little is known about species-specific traits of other structures, such as bud diameter, length, mass, moisture content, and surface area, that might be related to heat tolerance. Many prescribed fires are utilized in the eastern United States to control regeneration of less desired species, which could apply a more mechanistic understanding of energy doses that result in topkilling mid-story stems. In this study, we investigated potential relationships between terminal bud mortality from lateral branches of midstory stems and species-specific bud features of six eastern US deciduous trees. Characterized at maturity as either pyrophytes or pyrophobes, each was exposed to different heat dosages in a laboratory setting.ResultsBud diameter, length, mass, moisture content, and surface area differed by species. Bud percent mortality at the first heat flux density (0.255–0.891MJm−2) was highest for two pyrophobes, chestnut oak (Quercus montana Willd.) and scarlet oak (Quercus coccinea Münchh). For the second heat flux density (1.275–1.485MJm−2), bud percent mortality was highest for these species and red maple (Acer rubrum L.). Principal component analysis suggested that bud surface area and length differentiated species. Red maple, chestnut oak, and scarlet oak produced clusters of buds, which may explain their more pronounced bud mortality. Yellow-poplar (Liriodendron tulipifera L.) was also present in that cluster, suggesting that its unique bud architecture of pre-emergent leaves may have elicited responses most similar to those of the clustered buds.ConclusionsContrary to expectations, lateral buds of species regarded as pyrophytes at maturity displayed some of the highest values of bud percent mortality when heated at two heat flux densities generated in a laboratory. Their responses may be related to clustering of their lateral buds. Testing of additional species using these methods in a laboratory setting, and perhaps additional methodologies in the field, is warranted.

Adolescent- and adult-initiated alcohol exposure in mice differentially promotes tumorigenesis and metastasis of breast cancer.

Alcohol exposure increases the risk of breast cancer. Alcohol consumption by adolescents is a serious social and public health issue. This study investigated the impact of adolescent alcohol consumption on mammary tumorigenesis and progression and compared it to that of adult alcohol exposure in animal models. Female adolescent (5 weeks) and adult (8 weeks) MMTV-Wnt1 mice were exposed to alcohol either chronically or acutely. For chronic alcohol exposure, animals were fed a liquid diet containing 6.7% ethanol for 23 weeks. For acute exposure, animals were treated with ethanol (2.5g/kg, 25% w/v) via intraperitoneal (IP) injection for 15 days. In control animals, the tumor latency was 18.5 to 22 weeks. Both chronic and acute alcohol exposure in adolescent mice significantly shortened the tumor latency to 9.5 and 8.4 weeks, respectively. However, adult-initiated alcohol exposure had little effect on the tumor latency. Both adolescent- and adult-initiated alcohol exposure significantly increased lung metastasis. Adolescent-initiated alcohol exposure but not adult-initiated alcohol exposure increased the breast cancer stem cell population. Adolescent-initiated alcohol exposure significantly altered the proliferation of mammary epithelial cells, ductal growth, and the formation of terminal end buds in the mammary glands. Adolescent-initiated alcohol exposure but not adult-initiated alcohol exposure increased estradiol levels in the blood. Acute adolescent alcohol exposure also significantly increased blood progesterone levels. Furthermore, adolescent-initiated alcohol exposure activated PAK1 and p38γ MAPK, critical regulators of mammary tumorigenesis and aggressiveness, respectively, while adult-initiated alcohol exposure activated only p38γ MAPK. In addition, both adolescent and adult alcohol exposure significantly decreased the levels of a prognostic marker miR200b. Adolescent-initiated alcohol exposure enhanced both tumorigenesis and aggressiveness of mammary tumors, while adult-initiated alcohol exposure mainly promoted tumor metastasis. Thus, adolescent mice were more sensitive than adult mice in response to alcohol-induced tumor promotion.

Anatomical inferences on aerial bud protection of three Eugenia shrub species from the Cerrado.

Location and degree of protection of aerial buds are important functional traits in disturbance- or stress-prone environments since aerial buds ensure the development of new organs under favourable growing conditions. This study was carried out in a Brazilian Cerrado area under regeneration after long-term Pinus cultivation, where the trees were clear-cut in 2012 and the remaining material was burned in 2014. After the fire treatment, several species resprouted from belowground organs and their aboveground organs were directly exposed to full sunlight. We collected 15 terminal branches with fully expanded leaves from three individuals of each of three Eugenia species to investigate if those with well-developed belowground organs invest in bark for aboveground bud protection. The samples were analysed using light and electron microscopy. In addition to terminal and axillary buds, all species presented accessory buds, and the number varied according to the node analysed. None of the aerial buds were protected by bark, but all were well protected by cataphylls and densely pubescent leaf primordia. There were also inter- and intra-petiolar colleters that released a mucilaginous protein exudate. The distance between the shoot apical meristem and the outer surface was longer in the terminal bud than in axillary buds. The bud leaf primordia covering the shoot apical meristem had a thick cuticle, unicellular non-glandular trichomes that accumulate phenolic and lipophilic compounds, and secretory cavities. Our study shows that all three Eugenia species studied here had highly protected aerial buds allocated from belowground organs. These morphological traits may improve the chances of the species' persistence in areas subjected to frost events, low relative humidity, high irradiance and harmful UV levels.

Recognition of terminal buds of densely-planted Chinese fir seedlings using improved YOLOv5 by integrating attention mechanism.

Accurate and timely information on the number of densely-planted Chinese fir seedlings is essential for their scientific cultivation and intelligent management. However, in the later stage of cultivation, the overlapping of lateral branches among individuals is too severe to identify the entire individual in the UAV image. At the same time, in the high-density planting nursery, the terminal bud of each seedling has a distinctive characteristic of growing upward, which can be used as an identification feature. Still, due to the small size and dense distribution of the terminal buds, the existing recognition algorithm will have a significant error. Therefore, in this study, we proposed a model based on the improved network structure of the latest YOLOv5 algorithm for identifying the terminal bud of Chinese fir seedlings. Firstly, the micro-scale prediction head was added to the original prediction head to enhance the model’s ability to perceive small-sized terminal buds. Secondly, a multi-attention mechanism module composed of Convolutional Block Attention Module (CBAM) and Efficient Channel Attention (ECA) was integrated into the neck of the network to enhance further the model’s ability to focus on key target objects in complex backgrounds. Finally, the methods including data augmentation, Test Time Augmentation (TTA) and Weighted Boxes Fusion (WBF) were used to improve the robustness and generalization of the model for the identification of terminal buds in different growth states. The results showed that, compared with the standard version of YOLOv5, the recognition accuracy of the improved YOLOv5 was significantly increased, with a precision of 95.55%, a recall of 95.84%, an F1-Score of 96.54%, and an mAP of 94.63%. Under the same experimental conditions, compared with other current mainstream algorithms (YOLOv3, Faster R-CNN, and PP-YOLO), the average precision and F1-Score of the improved YOLOv5 also increased by 9.51-28.19 percentage points and 15.92-32.94 percentage points, respectively. Overall, The improved YOLOv5 algorithm integrated with the attention network can accurately identify the terminal buds of densely-planted Chinese fir seedlings in UAV images and provide technical support for large-scale and automated counting and precision cultivation of Chinese fir seedlings.

Phylogeny and taxonomy of Cinnamomum (Lauraceae).

Taxonomy of Cinnamomum Schaeff. of Lauraceae remains problematic because recent phylogenetic studies have suggested that this genus is not monophyletic. In this study, we assembled three sequence matrices including plastomes (datamatrix I), nrITS sequences alone (datamatrix II), and nrITS plus plastid psbA‐trnH sequences (datamatrix III) of the Cinnamomum‐Ocotea complex of Lauraceae and conducted a new phylogenetic study with thusfar the most extensive species sampling of the Cinnamomum‐Ocotea group. We determined that the Old World Cinnamomum is diphyletic: sect. Camphora Meisn. is sister to Sassafras J.Presl and sect. Cinnamomum is sister to the African Kuloa Trofimov & Rohwer. A recent study indicated that characters of leaf micromorphological anatomy can define the two clades: one possessing reticulate periclinal and the other having non‐reticulate periclinal walls. As result, we divided the genus Cinnamomum of Lauraceae into two genera, i.e., Cinnamomum and Camphora Fabr. The generic name Cinnamomum is retained for those species mainly having reticulate periclinal epidermal cell walls, inconspicuous non‐perulate terminal buds and usually tripliveined leaves; the oldest generic name, Camphora, is applied to the second group which contains those species mainly possessing non‐reticulate periclinal epidermal cell walls, prominent perulate terminal buds and pinnately‐veined leaves. A census of the species and their type specimens listed under Cinnamomum in Asia resulted in the transfer of 18 species to Camphora, including 15 new combinations.

A cost‐effective method to passively sample communities at the forest canopy–aerosphere interface

Abstract The ecology of the canopy–aerosphere interface within forested ecosystems remains underexplored largely due to the challenges of physically accessing this zone. Sky bridges, towers and other permanent structures are most commonly used to sample the forest canopy–aerosphere interface, but these methods are costly, challenging to replicate, and often alter and degrade the local environment during construction. Thus, there is a clear need for cost‐effective and replicable methods for accessing and passively sampling above the forest canopy. We designed and deployed an inexpensive and lightweight telescopic hanger composed of common materials to sample aerial invertebrates above the forest canopy. Deployment involved climbing into tree crowns and securing our hanger design to vertical branches. We sampled the invertebrate community above forest fragments on the campus of the University of Massachusetts Amherst, USA by suspending blue vane traps from hangers, which were extended to approximately 1 m above the highest terminal bud of the tree, continuously from April through August 2021. We also recorded the microclimate conditions above the canopy at each hanger, including temperature and light intensity. All hangers and traps remained in place and active throughout the study period. In May, we made minor repairs at two locations where the hangers were attached to the trees and, following an intense weather event in July, observed damage to one hanger that did not affect sampling effort. We include cost breakdowns of design components as well as detailed building instructions. This tool offers a durable and inexpensive solution for researchers to access and sample the forest canopy–aerosphere interface that has minimal impacts on the environment and is more easily replicated compared to previous methods. Assembly pitfalls and design alterations are discussed based on our experience with the installation and implementation of the tested design, as well as included prototypes.

Dose Estimation Model for Terminal Buds in Radioactively Contaminated Fir Trees

Background: After the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, biological alterations in the natural biota, including morphological changes of fir trees in forests surrounding the power plant, have been reported. Focusing on the terminal buds involved in the morphological formation of fir trees, this study developed a method for estimating the absorbed radiation dose rate using radionuclide distribution measurements from tree organs.Materials and Methods: A phantom composed of three-dimensional (3D) tree organs was constructed for the three upper whorls of the fir tree. A terminal bud was evaluated using Monte Carlo simulations for the absorbed dose rate of radionuclides in the tree organs of the whorls. Evaluation of the absorbed dose targeted <sup>131</sup>I, <sup>134</sup>Cs, and <sup>137</sup>Cs, the main radionuclides subsequent to the FDNPP accident. The dose contribution from each tree organ was calculated separately using dose coefficients (DC), which express the ratio between the average activity concentration of a radionuclide in each tree organ and the dose rate at the terminal bud.Results and Discussion: The dose estimation indicated that the radionuclides in the terminal bud and bud scale contributed to the absorbed dose rate mainly by beta rays, whereas those in 1-year-old trunk/branches and leaves were contributed by gamma rays. However, the dose contribution from radionuclides in the lower trunk/branches and leaves was negligible.Conclusion: The fir tree model provides organ-specific DC values, which are satisfactory for the practical calculation of the absorbed dose rate of radiation from inside the tree. These calculations are based on the measurement of radionuclide concentrations in tree organs on the 1-year-old leader shoots of fir trees. With the addition of direct gamma ray measurements of the absorbed dose rate from the tree environment, the total absorbed dose rate was estimated in the terminal bud of fir trees in contaminated forests.

Manipulation of Senescence of Plants to Improve Biotic Stress Resistance

The physiological state, i.e., senescence or juvenility, of plants and plant organs can have strong effect on their reactions to pathogen attacks. This effect is mainly expressed as changes in the severity of disease symptoms. Generally, necrotrophic pathogens cause more severe symptoms on senescent than on juvenile plants, while biotrophs prefer juvenile tissues. Several factors of senescence have opposite effect on the two pathogen groups, such as decreased photosynthesis, decreased antioxidant capacity, remobilization of nutrients, changes in plant hormonal network, and in fluidity of cell membranes. Furthermore, senescent tissues are less tolerant to toxins and to cell-wall-degrading enzymes. On the other hand, pathogen infection itself has significant effect on the physiology of plants depending on the lifestyle of the pathogen and on the compatibility or incompatibility of the interaction with the plant. There are several possibilities to manipulate the physiological state of plants in order to improve their biotic and abiotic stress tolerance, such as removal of the terminal bud or high doses of nitrogen, external application of cytokinins or of inhibitors of ethylene action, as well as by spontaneous or directed mutation, in vitro selection, or manipulation by various transgenic approach. Even application of mycorrhiza can inhibit the senescence process of plants and improve their tolerance to stresses.

Transcriptome sequencing and DEG analysis in different developmental stages of floral buds induced by potassium chlorate in Dimocarpus longan.

Potassium chlorate can promote off-season flowering in longan, but the molecular mechanisms are poorly understood. In this study, four-year-old 'Shixia' longan trees were injected in the trunk with potassium chlorate, and terminal buds were sampled and analyzed using transcriptomics and bioinformatics tools. To generate a reference longan transcriptome, we obtained 207,734 paired-end reads covering a total of 58,514,149 bp, which we assembled into 114,445 unigenes. Using this resource, we identified 3,265 differentially expressed genes (DEGs) that were regulated in longan terminal buds in response to potassium chlorate treatment for 2, 6 or 30 days, including 179 transcription factor genes. By reference to the Arabidopsis literature, we then defined 38 longan genes involved in flowering, from which we constructed the longan flowering pathway. According to RNA-seq data, at least 24 of these genes, which participate in multiple signaling pathways, are involved in potassium chlorate-stimulated floral induction, and the differential regulation in terminal buds of ten floral pathway genes (GI, CO, GID1, GA4, GA5, FLC, AP1, LFY, FT and SOC1) was confirmed by qRT-PCR. These data will contribute to an improved understanding of the functions of key genes involved in longan floral induction by potassium chlorate.

Beilschmiedia weii (Lauraceae), a new species from Dayaoshan Mountain of Guangxi, China

Beilschmiedia weii, a new species of Lauraceae from Dayaoshan Mountain of Guangxi, China, is described and illustrated. It is morphologically most similar to B. wangii and B. rufohirtella in having ferruginous pubescent terminal buds, branchlets, abaxial leaf blades, panicles and fruiting pedicels, but can be easily distinguished from them by the leaf growth pattern, the color of flowers, the length of panicles and fruiting pedicels, the shape and size of fruits, and the phenology. A table to distinguish the new species from other morphologically similar Beilschmiedia species is provided, as well as a color plate.