Ag2CO3 is the key: The transition‐metal‐catalyzed cycloaddition of isocyanides and unactivated terminal alkynes has been realized with Ag2CO3 as a unique and robust catalyst (see scheme). The ...protocol is highly efficient, allowing a broad range of terminal and internal alkynes to react under base‐ and ligand‐free conditions, generating synthetically useful oligosubstituted pyrroles in high yields.
Most extant genus-level radiations in gymnosperms are of Oligocene age or younger, reflecting widespread extinction during climate cooling at the Oligocene/Miocene boundary ∼23 million years ago ...(Ma). Recent biogeographic studies have revealed many instances of long-distance dispersal in gymnosperms as well as in angiosperms. Acting together, extinction and long-distance dispersal are likely to erase historical biogeographic signals. Notwithstanding this problem, we show that phylogenetic relationships in the gymnosperm family Cupressaceae (162 species, 32 genera) exhibit patterns expected from the Jurassic/Cretaceous breakup of Pangea. A phylogeny was generated for 122 representatives covering all genera, using up to 10,000 nucleotides of plastid, mitochondrial, and nuclear sequence per species. Relying on 16 fossil calibration points and three molecular dating methods, we show that Cupressaceae originated during the Triassic, when Pangea was intact. Vicariance between the two subfamilies, the Laurasian Cupressoideae and the Gondwanan Callitroideae, occurred around 153 Ma (124–183 Ma), when Gondwana and Laurasia were separating. Three further intercontinental disjunctions involving the Northern and Southern Hemisphere are coincidental with or immediately followed the breakup of Pangea.
Despite the high economic and ecological importance of forests, our knowledge of the genomic evolution of trees under salt stress remains very limited. Here we report the genome sequence of the ...desert poplar, Populus euphratica, which exhibits high tolerance to salt stress. Its genome is very similar and collinear to that of the closely related mesophytic congener, P. trichocarpa. However, we find that several gene families likely to be involved in tolerance to salt stress contain significantly more gene copies within the P. euphratica lineage. Furthermore, genes showing evidence of positive selection are significantly enriched in functional categories related to salt stress. Some of these genes, and others within the same categories, are significantly upregulated under salt stress relative to their expression in another salt-sensitive poplar. Our results provide an important background for understanding tree adaptation to salt stress and facilitating the genetic improvement of cultivated poplars for saline soils.
Abstract
Under global warming, advances in spring phenology due to rising temperatures have been widely reported. However, the physiological mechanisms underlying the advancement in spring phenology ...still remain poorly understood. Here, we investigated the effect of temperature during the previous growing season on spring phenology of current year based on the start of season extracted from multiple long-term and large-scale phenological datasets between 1951 and 2018. Our findings indicate that warmer temperatures during previous growing season are linked to earlier spring phenology of current year in temperate and boreal forests. Correspondingly, we observed an earlier spring phenology with the increase in photosynthesis of the previous growing season. These findings suggest that the observed warming-induced earlier spring phenology is driven by increased photosynthetic carbon assimilation in the previous growing season. Therefore, the vital role of warming-induced changes in carbon assimilation should be considered to accurately project spring phenology and carbon cycling in forest ecosystems under future climate warming.
Relationships between biodiversity and multiple ecosystem functions (that is, ecosystem multifunctionality) are context-dependent. Both plant and soil microbial diversity have been reported to ...regulate ecosystem multifunctionality, but how their relative importance varies along environmental gradients remains poorly understood. Here, we relate plant and microbial diversity to soil multifunctionality across 130 dryland sites along a 4,000 km aridity gradient in northern China. Our results show a strong positive association between plant species richness and soil multifunctionality in less arid regions, whereas microbial diversity, in particular of fungi, is positively associated with multifunctionality in more arid regions. This shift in the relationships between plant or microbial diversity and soil multifunctionality occur at an aridity level of ∼0.8, the boundary between semiarid and arid climates, which is predicted to advance geographically ∼28% by the end of the current century. Our study highlights that biodiversity loss of plants and soil microorganisms may have especially strong consequences under low and high aridity conditions, respectively, which calls for climate-specific biodiversity conservation strategies to mitigate the effects of aridification.
Camptothecin and its derivatives are widely used for treating malignant tumors. Previous studies revealed only a limited number of candidate genes for camptothecin biosynthesis in Camptotheca ...acuminata, and it is still poorly understood how its biosynthesis of camptothecin has evolved. Here, we report a high-quality, chromosome-level C. acuminata genome assembly. We find that C. acuminata experiences an independent whole-genome duplication and numerous genes derive from it are related to camptothecin biosynthesis. Comparing with Catharanthus roseus, the loganic acid O-methyltransferase (LAMT) in C. acuminata fails to convert loganic acid into loganin. Instead, two secologanic acid synthases (SLASs) convert loganic acid to secologanic acid. The functional divergence of the LAMT gene and positive evolution of two SLAS genes, therefore, both contribute greatly to the camptothecin biosynthesis in C. acuminata. Our results emphasize the importance of high-quality genome assembly in identifying genetic changes in the evolutionary origin of a secondary metabolite.
Almost all plants in the genus Populus are dioecious (i.e. trees are either male or female), but it is unknown whether dioecy evolved in a common ancestor or independently in different subgenera. ...Here, we sequence the small peritelomeric X- and Y-linked regions of P. deltoides chromosome XIX. Two genes are present only in the Y-linked region. One is a duplication of a non-Y-linked, female-specifically expressed response regulator, which produces siRNAs that block this gene's expression, repressing femaleness. The other is an LTR/Gypsy transposable element family member, which generates long non-coding RNAs. Overexpression of this gene in A. thaliana promotes androecium development. We also find both genes in the sex-determining region of P. simonii, a different poplar subgenus, which suggests that they are both stable components of poplar sex-determining systems. By contrast, only the duplicated response regulator gene is present in the sex-linked regions of P. davidiana and P. tremula. Therefore, findings in our study suggest dioecy may have evolved independently in different poplar subgenera.
The age at which a human environment was made is strongly debated in Quaternary science. The perception of the human footprint requires an understanding of the contrast between the present cultural ...environment and the natural vegetation. This is especially true for high altitude ecosystems, such as the world's largest alpine ecosystem, the 450,000 km2 of golf-course-like pastures dominating the southeastern Tibetan Plateau. This ecosystem is widely considered to be natural, but only because of the unawareness of the effects of grazing management and the incorrect assessment of human signals in palaeo proxies. Here we posit the hypothesis that this ecosystem is a human-induced replacement. To test our hypothesis against defined a priori criteria, we 1) monitored vegetation in grazing exclosures; 2) produced floristically complete vegetation records; 3) compared the vegetation records with data of the nearest climate stations; 4) surveyed forest and experimental reforestation trials with endemic tree species; 5) analyzed pollen and re-evaluated published pollen diagrams; and 6) integrated these results with palaeopedological and anthracological results of previous studies. The results of long-term grazing exclosure experiments, the prevalence of grazing-adapted plant functional types, the occurrence of isolated vigorous forests in “alpine” pastures, and the successful reforestation trials in presently treeless pastures together suggest that dominant pastures replaced forests in the montane belt and tall grassland in the alpine belt. The spatial and temporal coincidence of palaeosols and archaeological sites with tree species charcoal, the decline in forest pollen during the mid-Holocene climatic optimum, and the first appearance of human indicator pollen are most parsimoniously explained by the early presence of foragers and pastoralists. The onset of pastoralism in the Tibetan Highlands is presumed to date from the 8th millennium BP.
•The southeastern Tibetan Plateau is a human-induced replacement of natural habitats.•Pastures replaced forests in the montane, and tall grassland in the alpine belt.•Foragers and pastoralists were present dating back to the 8th millennium BP.
Nickel is an essential nutrient for plants. However, the amount of Ni required for normal growth of plants is very low. Hence, with the level of Ni pollution in the environment increasing, it is ...essential to understand the functional roles and toxic effects of Ni in plants. We briefly review advances in relevant research over the past 20 years. Based on the available data, two new indirect pathways of Ni toxicity in plants are proposed. These are (i) interference with other essential metal ions and (ii) induction of oxidative stress. Research should focus on these mechanisms at the protein and molecular levels. Further research should also be directed at plant species that are capable of accumulating Ni at high concentration, so‐called hyperaccumulators. Such species can provide model systems to study the mechanisms of Ni tolerance and can also be used for phytoremediation by removing nickel from polluted environment.
Review: With the level of nickel pollution in the environment increasing, it is essential to understand the functional roles and toxic effects of the metal in plants. Advances in relevant research over the past 20 years are reviewed. Based on the available data, two new indirect pathways of Ni toxicity in plants are proposed.
Plant secondary growth depends on the activity of the vascular cambium, which produces xylem and phloem. Wood derived from xylem is the most abundant form of biomass globally and has played key ...socio-economic and subsistence roles throughout human history. However, despite intensive study of vascular development, the full diversity of cell types and the gene networks engaged are still poorly understood.
Here, we have applied an optimized protoplast isolation protocol and RNA sequencing to characterize the high-resolution single-cell transcriptional landscape of highly lignified poplar stems. We identify 20 putative cell clusters with a series of novel cluster-specific marker genes and find that these cells are highly heterogeneous based on the transcriptome. Analysis of these marker genes' expression dynamics enables reconstruction of the cell differentiation trajectories involved in phloem and xylem development. We find that different cell clusters exhibit distinct patterns of phytohormone responses and emphasize the use of our data to predict potential gene redundancy and identify candidate genes related to vascular development in trees.
These findings establish the transcriptional landscape of major cell types of poplar stems at single-cell resolution and provide a valuable resource for investigating basic principles of vascular cell specification and differentiation in trees.
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