Taxus yunnanensis genome offers insights into gymnosperm phylogeny and taxol production

Taxol, a natural product derived from Taxus, is one of the most effective natural anticancer drugs and the biosynthetic pathway of Taxol is the basis of heterologous bio-production. Here, we report a high-quality genome assembly and annotation of Taxus yunnanensis based on 10.7 Gb sequences assembled into 12 chromosomes with contig N50 and scaffold N50 of 2.89 Mb and 966.80 Mb, respectively. Phylogenomic analyses show that T. yunnanensis is most closely related to Sequoiadendron giganteum among the sampled taxa, with an estimated divergence time of 133.4−213.0 MYA. As with most gymnosperms, and unlike most angiosperms, there is no evidence of a recent whole-genome duplication in T. yunnanensis. Repetitive sequences, especially long terminal repeat retrotransposons, are prevalent in the T. yunnanensis genome, contributing to its large genome size. We further integrated genomic and transcriptomic data to unveil clusters of genes involved in Taxol synthesis, located on the chromosome 12, while gene families encoding hydroxylase in the Taxol pathway exhibited significant expansion. Our study contributes to the further elucidation of gymnosperm relationships and the Taxol biosynthetic pathway.

Botryosphaeria Dothidea and Neofusicoccum Yunnanense Causing Canker and Die-Back of Sequoiadendron Giganteum in Croatia

Sequoiadendron giganteum Lindl. [Buchholz] is a long-lived tree species endemic to the Sierra Nevada Mountains in California. Due to its massive size and beauty, S. giganteum is a popular ornamental tree planted in many parts of the world, including Europe. Since 2017, scattered branch die-back has been observed on S. giganteum trees in Zagreb, Croatia. Other symptoms included resinous branch cankers, reddish-brown discoloration of the sapwood and, in severe cases, crown die-back. Branches showing symptoms of die-back and cankers were collected from six S. giganteum trees in Zagreb and the aim of this study was to identify the causal agent of the disease. The constantly isolated fungi were identified using morphology and phylogenetic analyses based on the internal transcribed spacer (ITS) of the ribosomal DNA (rDNA), and partial sequencing of two housekeeping genes, i.e., translation elongation factor 1-α (TEF 1-α), and β tubulin 2 (TUB2). The fungi were identified as Botryosphaeria dothidea (Moug.) Ces. and De Not. and Neofusicoccum yunnanense G.Q. Li & S.F. Chen. The pathogenicity test was conducted in a plant growth chamber on S. giganteum seedlings and revealed that N. yunnanense was more aggressive compared to B. dothidea. N. yunnanense was able to reproduce symptoms of canker and die-back and kill plants seven weeks after inoculation whereas B. dothidea produced cankers. To the best of our knowledge, this is the first report of B. dothidea and N. yunnanense causing canker and die-back disease of S. giganteum in Croatia. It is also the first record on the identity and pathogenicity of any fungal species associated with S. giganteum in this country. The study expended the known host range of N. yunnanense to include S. giganteum, which is a valuable ornamental tree in Croatian landscapes. Disease management strategies should be developed to mitigate or reduce the impact of the disease.

Neofusicoccum parvum, a New Agent of Sequoia Canker and Dieback Identified in Geneva, Switzerland

Fungi were isolated in pure cultures from decaying giant sequoias in Geneva (Switzerland). Isolates were genetically identified by ITS rDNA sequencing. Young giant sequoia trees were artificially infected with a pure culture of Botryosphaeria parva. Henle-Koch’s Postulates demonstrated that Botryosphaeria parva was pathogenic to Sequoiadendron giganteum. When analysing the microorganisms associated to canker and dieback symptoms in a giant sequoias (Sequoiadendron giganteum) in Geneva, the fungus Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, teleomorph Botryosphaeria parva (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, was isolated, whereas such symptoms are commonly associated to Fusicoccum aesculi (teleomorph Botryosphaeria dothidea). These two fungal species belong to the same genus Botryosphaeria of the Botryosphaeriaceae family. Because Neofusicoccum parvum was causing cankers and diebacks in other woody species around the world, we extended the analysis to other trees displaying sequoia dieback symptoms in order to evaluate the involvement of Neofusicoccum parvum in such increasing symptoms in sequoias in Geneva. Dried twigs, trunk, and branch cankers from diseased trees were sampled on several distinct sites. From all samples, isolated fungi in pure cultures showed a phenotype typical of Botryosphaeriaceae species. Isolates were then genetically identified at the species level. Subsequently Neofusicoccum parvum was inoculated to young giant sequoia trees, re-isolated in pure culture from provoked symptoms, and re-identified to fulfil Henle-Koch’s postulates. The identification confirmed that Neofusicoccum parvum was present on all sites, while Fusicoccum aesculi was retrieved only once alone. The inoculation of Neofusicoccum parvum isolates on young sequoias demonstrated for the first time that this fungus was able to develop cankers in Sequoiadendron gigantean. Neofusicoccum parvum could, therefore, be the major cause for dying of giant sequoias in the Geneva Lake area.

Аутфітосозологічне оцінювання дендроекзотів відділу Pinophyta ботанічного саду Чернівецького національного університету імені Юрія Федьковича

Здійснено інтегральне аутфітосозологічне оцінювання 41 виду деревних інтродуцентів відділу Pinophyta, які ростуть у ботанічному саду Чернівецького національного університету ім. Юрія Федьковича в умовах відкритого ґрунту. Відповідно до значень вирахуваного для кожного виду аутфітосозологічного індексу досліджувані дендроекзоти віднесено до чотирьох аутфітосозологічних класів (II-V); найбільше видів (27) увійшли до ІІІ класу. Для рослин кожного із аутфітосозологічних класів охарактеризовано ознаки, які найістотніше впливають на фітосозологічну цінність видів: категорія раритетності у Червоному списку МСОП, фітогеографічне та історичне значення, регіональна репрезентативність та кількість штучних природоохоронних об'єктів у межах Чернівецької області, де росте той чи інший вид. Зокрема, найчастіше у дендропарках, парках-пам'ятках садово-паркового мистецтва та у складі пам'яток природи Чернівецької області трапляються Thuja occidentalis L. (30 місцезростань), Pinus strobus L. (22), Platycladus orientalis (L.) Franco (19 місцезростань), і в межах 12-14 природоохоронних об'єктів – Pinus nigra J. F. Arnold, Ginkgo biloba L., Chamaecyparis pisifera (Siebold & Zucc.) Endl. Відзначено, що 51,2 % із досліджуваних видів трапляються, окрім ботанічного саду Чернівецького національного університету, також у дендропарках, парках-пам'ятках садово-паркового мистецтва та пам'ятках природи місцевого значення Чернівецької області. Раритетні види деревних інтродуцентів відділу Pinophyta цінні як резерв генетичного матеріалу. Тому особливої охорони потребують ті з них, які перебувають під загрозою зникнення (категорія раритетності у Червоному списку МСОП – CR, EN та VU), а також ті, що увійшли до ІІ аутфітосозологічного класу (Taxodium distichum (L.) Rich., Sequoiadendron giganteum (Lindl.) J. Buchholz, Metasequoia glyptostroboides Hu & W. C. Cheng, Picea koyamae Shiras.), та частина видів, віднесених до ІІІ класу (зокрема, ті з них, які представлені 1-2 особинами лише у ботанічному саду Чернівецького національного університету, і не здатні розмножуватися насіннєвим шляхом). Під час розроблення рекомендацій з ефективної охорони досліджуваних деревних інтродуцентів варто звертати увагу на екологічні вимоги видів, оскільки від цього значною мірою залежить успішність росту і розвитку інтродуцентів.

Patterns of Fine-Scale Spatial Genetic Structure and Pollen Dispersal in Giant Sequoia (Sequoiadendron giganteum)

Research Highlights: Patterns of dispersal shape the distribution and temporal development of genetic diversity both within and among populations. In an era of unprecedented environmental change, the maintenance of extant genetic diversity is crucial to population persistence. Background and Objectives: We investigate patterns of pollen dispersal and spatial genetic structure within populations of giant sequoia (Sequoiadendron giganteum). Materials and Methods: The leaf genotypes of established trees from twelve populations were used to estimate the extent of spatial genetic structure within populations, as measured by the Sp statistic. We utilized progeny arrays from five populations to estimate mating parameters, the diversity of the pollen pool, and characteristics of pollen dispersal. Results: Our research indicates that giant sequoia is predominantly outcrossing, but exhibits moderate levels of bi-parental inbreeding (0.155). The diversity of the pollen pool is low, with an average of 7.5 pollen donors per mother tree. As revealed by the Sp-statistic, we find significant genetic structure in ten of twelve populations examined, which indicates the clustering of related individuals at fine spatial scales. Estimates of pollen and gene dispersal indicate predominantly local dispersal, with the majority of pollen dispersal <253 m, and with some populations showing fat-tailed dispersal curves, suggesting potential for long-distance dispersal. Conclusions: The research presented here represent the first detailed examination of the reproductive ecology of giant sequoia, which will provide necessary background information for the conservation of genetic resources in this species. We suggest that restoration planting can mitigate potential diversity loss from many giant sequoia populations.

The Protective Role of Bark and Bark Fibers of the Giant Sequoia (Sequoiadendron giganteum) during High-Energy Impacts

The influences of (1) a high fiber content, (2) the arrangement of fibers in fiber groups, and (3) a layered hierarchical composition of the bark of the giant sequoia (Sequoiadendron giganteum) on its energy dissipation capability are analyzed and discussed regarding the relevance for an application in bioinspired components in civil engineering. The giant sequoia is native to the Sierra Nevada (USA), a region with regular rockfalls. It is thus regularly exposed to high-energy impacts, with its bark playing a major protective role, as can be seen in the wild and has been proven in laboratory experiments. The authors quantify the fundamental biomechanical properties of the bark at various length scales, taking into account its hierarchical setup ranging from the integral level (whole bark) down to single bark fibers. Microtensile tests on single fibers and fiber pairs give insights into the properties of single fibers as well as the benefits of the strong longitudinal interconnection between single fibers arranged in pairs. Going beyond the level of single fibers or fiber pairs, towards the integral level, quasistatic compression tests and dynamic impact tests are performed on samples comprising the whole bark (inner and outer bark). These tests elucidate the deformation behavior under quasistatic compression and dynamic impact relevant for the high energy dissipation and impact-damping behavior of the bark. The remarkable energy dissipation capability of the bark at the abovementioned hierarchical levels are linked to the layered and fibrous structure of the bark structurally analyzed by thin sections and SEM and µCT scans.