of Botany,Chinese Academy Of Sciences
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Seed viability testing for research and conservation of epiphytic and terrestrial orchids (vol 63, 3, 2022)
No full textPotential allopolyploid origin of Ericales revealed with gene-tree reconciliation
No full textFew incidents of ancient allopolyploidization (polyploidization by hybridization or merging diverged genomes) were previously revealed, although there is significant evidence for the accumulation of whole genome duplications (WGD) in plants. Here, we focused on Ericales, one of the largest and most diverse angiosperm orders with significant ornamental and economic value. Through integrating 24 high-quality whole genome data selected from similar to 200 Superasterids genomes/species and an algorithm of topology-based genetree reconciliation, we explored the evolutionary history of in Ericales with ancient complex. We unraveled the allopolyploid origin of Ericales and detected extensive lineage-specific gene loss following the polyploidization. Our study provided a new hypothesis regarding the origin of Ericales and revealed an instructive perspective of gene loss as a pervasive source of genetic variation and adaptive phenotypic diversity in Ericales
Phosphorus addition decreases soil fungal richness and alters fungal guilds in two tropical forests
No full textSoil microbes regulate key functions of terrestrial ecosystems, but the effects and underlying mechanisms of elevated nutrient inputs on soil microbial diversity in tropical forests remain unclear. We evaluated the effects of seven-year nitrogen (N) and phosphorus (P) additions on soil microbial diversity in two tropical montane rainforests (P-limited primary forest and N-limited secondary forest). The results showed that soil bacterial richness was not sensitive to N or P addition, whereas soil fungal richness decreased under P and combined N and P additions. Furthermore, P inputs shifted soil fungal community composition: the relative abundance of mutualistic fungi increased and that of saprotrophic fungi decreased. The underlying mechanisms of these effects differed in the two forests. In the P-limited primary forest, the reduction in soil fungal richness was mainly related to a negative microbial interaction between microbial species and a stimulation in plant productivity. In the N-limited secondary forest, P inputs increased soil N and P imbalance, which caused a decline in the fungal richness. Overall, anthropogenic P enrichment could reduce soil fungal richness and alter fungal functional guilds in tropical forests, which will have divergent consequences on plant productivity and microbial functioning
Nitrogen availability determines ecosystem productivity in response to climate warming
No full textOne of the major uncertainties for carbon-climate feedback predictions is an inadequate understanding of the mechanisms governing variations in ecosystem productivity response to warming. Temperature and water availability are regarded as the primary controls over the direction and magnitude of warming effects, but some unexplained results signal that our understanding is incomplete. Using two complementary meta-analyses, we present evidence that soil nitrogen (N) availability drives the warming effects on ecosystem productivity more strongly than thermal and hydrological factors over a broad geographical scale. First, by synthesizing temperature manipulation experiments, a meta-regression model analysis showed that the warming effect on productivity is mainly driven by its effect on soil N availability. Sites with a higher warming-induced increase in N availability were characterized by stronger productivity enhancement and vice versa, suggesting that N is a limiting factor across sites. Second, a synthesis of full-factorial warming x N addition experiments demonstrated that N addition significantly weakened the positive warming effect, because the additional N induced by warming may not further benefit plant growth when N limitation is relieved, providing experimental evidence that N regulates the warming effect. Furthermore, we demonstrated that warming effects on soil N availability were modulated by changes in dissolved organic N and soil microbes. Overall, our findings enrich a new mechanistic understanding of the varying magnitudes of observed productivity response to warming, and the N scaling of warming effects may help to constrain climate projections
Synthesis of Nuclear and Chloroplast Data Combined With Network Analyses Supports the Polyploid Origin of the Apple Tribe and the Hybrid Origin of the Maleae-Gillenieae Clade
No full textPlant biologists have debated the evolutionary origin of the apple tribe (Maleae; Rosaceae) for over a century. The wide-hybridization hypothesis posits that the pome-bearing members of Maleae (base chromosome number x = 17) resulted from a hybridization and/or allopolyploid event between progenitors of other tribes in the subfamily Amygdaloideae with x = 8 and x = 9, respectively. An alternative spiraeoid hypothesis proposed that the x = 17 of Maleae arose via the genome doubling of x = 9 ancestors to x = 18, and subsequent aneuploidy resulting in x = 17. We use publicly available genomic data-448 nuclear genes and complete plastomes-from 27 species representing all major tribes within the Amygdaloideae to investigate evolutionary relationships within the subfamily containing the apple tribe. Specifically, we use network analyses and multi-labeled trees to test the competing wide-hybridization and spiraeoid hypotheses. Hybridization occurred between an ancestor of the tribe Spiraeeae (x = 9) and an ancestor of the clade Sorbarieae (x = 9) + Exochordeae (x = 8) + Kerrieae (x = 9), giving rise to the clade Gillenieae (x = 9) + Maleae (x = 17). The ancestor of the Maleae + Gillenieae arose via hybridization between distantly related tribes in the Amygdaloideae (i.e., supporting the wide hybridization hypothesis). However, some evidence supports an aspect of the spiraeoid hypothesis-the ancestors involved in the hybridization event were likely both x = 9, so genome doubling was followed by aneuploidy to result in x = 17 observed in Maleae. By synthesizing existing genomic data with novel analyses, we resolve the nearly century-old mystery regarding the origin of the apple tribe. Our results also indicate that nuclear gene tree-species tree conflict and/or cytonuclear conflict are pervasive at several other nodes in subfamily Amygdaloideae of Rosaceae
The complete chloroplast genome of Calyptothecium hookeri (Pterobryaceae, Hypnales)
No full textIn this study, the complete chloroplast chloroplast genome of Calyptothecium hookeri was studied and reported. The size of the entire chloroplast genome was 124,401bp in length, comprising of two inverted repeats (IRa and IRb, 9371 bp respectively) separated by one large single copy (LSC: 87,126 bp) and one small single copy (SSC: 18,533 bp). The GC content of the genome sequence was 41.28%. A total of 126 functional genes were predicted, consisting of 82 protein-coding genes, 36 tRNA genes, and eight rRNA genes. Phylogenetic analysis showed that the two Pterobryaceae species C. hookeri and C. recurvulum clustered in one clade, which is sister to the Theliaceae species Myurella julacea
Diverse triterpene skeletons are derived from the expansion and divergent evolution of 2,3-oxidosqualene cyclases in plants
No full textTriterpenoids are one of the largest groups of secondary metabolites and exhibit diverse structures, which are derived from C30 skeletons that are biosynthesized via the isoprenoid pathway by cyclization of 2,3-oxidosqualene. Triterpenoids have a wide range of biological activities, and are used in functional foods, drugs, and as industrial materials. Due to the low content levels in their native plants and limited feasibility and efficiency of chemical synthesis, heterologous biosynthesis of triterpenoids is the most promising strategy. Herein, we classified 121 triterpene alcohols/ketones according to their conformation and ring numbers, among which 51 skeletons have been experimentally characterized as the products of oxidosqualene cyclases (OSCs). Interestingly, 24 skeletons that have not been reported from nature source were generated by OSCs in heterologous expression. Comprehensive evolutionary analysis of the identified 152 OSCs from 75 species in 25 plant orders show that several pentacyclic triterpene synthases repeatedly originated in multiple plant lineages. Comparative analysis of OSC catalytic reaction revealed that stabilization of intermediate cations, steric hindrance, and conformation of active center amino acid residues are primary factors affecting triterpene formation. Optimization of OSC could be achieved by changing of side-chain orientations of key residues. Recently, methods, such as rationally design of pathways, regulation of metabolic flow, compartmentalization engineering, etc., were introduced in improving chassis for the biosynthesis of triterpenoids. We expect that extensive study of natural variation of large number of OSCs and catalytical mechanism will provide basis for production of high level of triterpenoids by application of synthetic biology strategies
Genomic signatures of domestication and adaptation during geographical expansions of rice cultivation
No full textStochastic processes regulate belowground community assembly in alpine grasslands on the Tibetan Plateau
No full textUnderstanding biogeographical patterns and underlying processes of belowground community assembly is crucial for predicting soil functions and their responses to global environmental change. However, little is known about potential differences of belowground community assembly among bacteria, fungi, protists and soil animals, particularly for alpine ecosystems. Based on the combination of large-scale field sampling, high-throughput marker-gene sequencing and multiple statistical analyses, we explored patterns and drivers of belowground community assembly in alpine grasslands on the Tibetan Plateau. Our results revealed that the distance-decay rates varied among trophic levels, with organisms of higher trophic level having weaker distance-decay pattern. The spatial and environmental variables explained limited variations of belowground communities. By contrast, the stochastic processes, mainly consisting of dispersal limitation and drift, played a primary role in regulating belowground community assembly. Moreover, the relative importance of stochastic processes varied among trophic levels, with the role of dispersal limitation weakening whereas that of drift enhancing in the order of bacteria, fungi, protists and soil animals. These findings advance our understanding of patterns and mechanisms driving belowground community assembly in alpine ecosystems and provide a reference basis for predicting the dynamics of ecosystem functions under changing environment