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Structure Insights Into Photosystem I Octamer From Cyanobacteria
No full textThe diversity of photosystem oligomers is essential to understanding how photosynthetic organisms adapt to light conditions. Due to its structural and physiological significance, the assembly of the PSI supercomplex has been of great interest recently in terms of both chloroplast and cyanobacteria. In this study, two novel photosystem I supercomplexes were isolated for the first time from the low light incubated culture of filamentous cyanobacterium Anabaena sp. PCC 7120. These complexes were defined as PSI hexamers and octamers through biochemical and biophysical characterization. Their 77K emission spectra indicated that the red forms of chlorophylls seemed not to be affected during oligomerization. By cryo-EM single-particle analysis, a near-atomic (7.0 angstrom) resolution structure of a PSI octamer was resolved, and the molecular assemblies of a stable PSI octamer were revealed
How precipitation legacies affect broad-scale patterns of primary productivity: Evidence from the Inner Mongolia grassland
No full textThe legacy effects of precipitation, defined as the impact of precipitation from previous years on current-year net primary productivity (NPP), have been well recognized in field experiments and site-level observational studies. However, it remains unclear how consecutive dry or wet years influence the directions and magnitude of legacies and broad-scale patterns of NPP. Here, we quantified the spatial and temporal patterns of legacy effect across different numbers of consecutive wet and dry years from 2000 to 2020 in the Inner Mongolia grassland. Spatially, the response of legacies to precipitation transitions was asymmetric along the mean annual precipitation gradient. The positive response of legacies to precipitation decrease was found for desert steppe and typical steppe after preceding wetness. In contrast, the response of legacies to precipitation increase was negative for desert steppe and meadow steppe after preceding drought. Moreover, legacies were more sensitive in desert steppe than that in typical steppe and meadow steppe for both the preceding wetness and preceding drought. However, the meadow steppe showed the highest response to the inter-annual precipitation change among the three grassland types. Furthermore, the legacies responded more strongly to precipitation decrease (preceding consecutive wet years) than the increase (preceding consecutive dry years) for meadow steppe and typical steppe. Yet, the desert steppe showed the opposite response to precipitation change. Temporally, the legacy effects lasted for only one year and could be transmitted year by year. Our findings highlight that consecutive wet and dry years play essential roles in controlling the NPP responses to climate fluctuations in arid and semi-arid grasslands. Understanding ecosystem responses to climatic periods can provide insights into the effects of directional changes in rainfall associated with climate change
Highly active repeat-mediated recombination in the mitogenome of the holoparasitic plant Aeginetia indica
No full textMitogenomes of most flowering plants evolve slowly in sequence, but rapidly in structure. The rearrangements in structure are mainly caused by repeat-mediated recombination. However, patterns of repeat-mediated recombination vary substantially among plants, and to provide a comprehensive picture, characterization of repeat-mediated recombination should extend to more plant species, including parasitic plants with a distinct heterotrophic lifestyle. Here we assembled the mitogenome of the holoparasitic plant Aeginetia indica (Orobanchaceae) using Illumina sequencing reads. The mitogenome was assembled into a circular chromosome of 420,362 bp, 18,734 bp longer than that of another individual of A. indica which was assembled before as a linear molecule. Synteny analysis between the two mitogenomes revealed numerous rearrangements, unique regions of each individual and 0.2% sequence divergence in their syntenic regions. The A. indica mitogenome contains a gene content typical of flowering plants (33 protein-coding, 3 rRNA, and 17 tRNA genes). Repetitive sequences >30 bp in size totals 57,060 bp, representing 13.6% of the mitogenome. We examined recombination mediated by repeats >100 bp in size and found highly active recombination for all the repeats, including a very large repeat of similar to 16 kb. Recombination between these repeats can form much smaller subgenomic circular chromosomes, which may lead to rapid replication of mitochondrial DNA and thus be advantageous for A. indica with a parasitic lifestyle. In addition, unlike some other parasitic plants, A. indica shows no evidence for horizontal gene transfer of protein-coding genes in its mitogenome
Carbon allocation patterns in forbs and grasses differ in responses to mowing and nitrogen fertilization in a temperate grassland
No full textMowing has been a routine grassland management with consequences of removing nutrients from the nitrogen (N)-limited grassland ecosystems. Carbon (C) allocation plays important roles in plant growth and responses to changing environments. Despite studies on interactions between N fertilization and mowing, no studies have specifically focused on responses of C allocation priorities to N fertilization and mowing at plant functional groups and individual species levels. In the present study, 13C isotope labelling was used to trace the effects of 3year of N fertilization and mowing on the fate of newly-assimilated C (accumulation and allocation priorities) at community, functional group and species levels in a temperate grassland of northern China. We applied the allometric allocation theory to explain the differential C allocation patterns among the organs of different species. Mowing and N fertilization for three consecutive years had no impacts on accumulation of newlyassimilated C at community level. However, C allocation in forbs and grasses differed markedly in their responses to mowing and N fertilization, such that mowing enhanced C accumulation in forbs and N fertilization enhanced C accumulation in grasses. In addition, mowing increased 13C allocation to stolon of forb species, thus facilitating their propagation. Moreover, N fertilization increased 13C allocation to rhizomes of grass species, ensuring clonal grasses to occupy a new niche. We demonstrated that grasses and forbs in a temperate grassland evolved different strategies of C allocation in response to mowing and N fertilization. The contrasting responses may account for the observation that N fertilization and mowing had no impacts on C accumulation at the community level. Our results highlight the necessity to monitor C allocation at functional group and dominant plant species levels, rather than at community level of grasslands exclusively for mechanistically understanding how grasslands respond to mowing and N fertilization
Characterization of stilbenes, in vitro antioxidant and cellular anti-photoaging activities of seed coat extracts from 18 Paeonia species
No full textPaeonia is famous as ornamental, medicinal plant, and edible oil crop in China. The seeds of peonies are rich in unsaturated fatty acids, monoterpene glycosides, sterols and stilbenes which have antioxidant and anti-inflammatory effects, etc. In this study, the composition and content of stilbenes in the seed coat extracts (SCE) from 50 populations of 18 species and two subspecies of Paeonia were determined by high performance liquid chromatography - diode array detection (HPLC-DAD). The results showed that the composition and content of stilbenes, especially suffruticosol B and gnetin H, differed significantly between Paeonia species, while there were small differences between populations of the same species. All the samples were clustered into two groups according to the stilbenes in SCE. The difference between the two groups was mainly reflected in the content of suffruticosol B and gnetin H. Furthermore, all samples showed high antioxidant activity, which was significantly positively correlated with the total polyphenol content. The SCE of P. anomala and P. lactiflora at different concentrations could effectively inhibit the production of matrix metalloproteinase 1 (MMP-1) in keratinocytes, and then achieve the effect of inhibiting cell aging. This study provided a valuable reference for the value-added utilization of Paeonia seed coat
Organization, Phylogenetic Marker Exploitation, and Gene Evolution in the Plastome of Thalictrum (Ranunculaceae)
No full textThalictrum is a phylogenetically and economically important genus in the family Ranunculaceae, but is also regarded as one of the most challengingly difficult in plants for resolving the taxonomical and phylogenetical relationships of constituent taxa within this genus. Here, we sequenced the complete plastid genomes of two Thalictrum species using Illumina sequencing technology via de novo assembly. The two Thalictrum plastomes exhibited circular and typical quadripartite structure that was rather conserved in overall structure and the synteny of gene order. By updating the previously reported plastome annotation of other nine Thalictrum species, we found that the expansion or contraction of the inverted repeat region affect the boundary of the single-copy regions in Thalictrum plastome. We identified eight highly variable noncoding regions-infA-rps8, ccsA-ndhD, trnS(UGA)-psbZ, trnH(GUG)-psbA, rpl16-rps3, ndhG-ndhI, ndhD-psaC, and ndhJ-ndhK-that can be further used for molecular identification, phylogenetic, and phylogeographic in different species. Selective pressure and codon usage bias of all the plastid coding genes were also analyzed for the 11 species. Phylogenetic relationships showed Thalictrum is monophyly and divided into two major clades based on 11 Thalictrum plastomes. The availability of these plastomes offers valuable genetic information for accurate identification of species and taxonomy, phylogenetic resolution, and evolutionary studies of Thalictrum, and should assist with exploration and utilization of Thalictrum plants
The Plant Interspecific Association in the Revegetated Alpine Grasslands Determines the Productivity Stability of Plant Community Across Restoration Time on Qinghai-Tibetan Plateau
No full textGrassland cultivation is the key measure for restoring Black Beach, the extremely degraded alpine meadow in the Three River Headwater Area of the Qinghai-Tibetan Plateau. In this study, we examined the inter-specific relationship in the vegetation community of cultivated grasslands with different restoration times through the network analysis method. The results showed that with the extension of restoration time, the development of cultivated grassland would lead to increasing neutral interactions among the plant species. The proportion of species with positive and negative associations in the community decreased, while the number of species-independent pairs increased significantly. The complexity of plant interspecific association (species network density) had more influence on community stability with the extension of recovery time, which can be used to quantify the characteristics of community structure
Editorial: Regulation of Light-Harvesting Systems During Acclimation of Photosynthetic Organisms
No full textPharmacophylogenetic study of Scutellaria baicalensis and its substitute medicinal species based on the chloroplast genomics, metabolomics, and active ingredient
No full textThe genetic relationships among the species in Scutellaria genus remain unclear because of the variation in the number of species and complex trait. The usage of S. baicalensis and its four substitute medicinal species (S. amoena, S. hypericifolia, S. likiangensis, and S. viscidula) in traditional medicines make their specialized metabolism important in China, but interspecific genetic and chemical differences have rarely been reported for these species. In this study, the chloroplast genomes of four substitute species for S. baicalensis were assembled, and comparative and phylogenetic analyses were performed with these species and other Scutellaria relatives. In addition, metabolomics analyses were performed and the contents of the main active compounds were determined to reveal the interspecific chemical diversity of S. baicalensis and its four substitute species. The full lengths of their chloroplast genomes ranged from 151,574 to 151,816 bp with an average GC content of 38.34%, and a total of 113 genes were annotated. In the chloroplast genomes of S. baicalensis and its four substitutes, one hypervariable region (petA-psbL) is proposed as a potential DNA barcode. Phylogenetic analysis showed that the subdivision of the genus Scutellaria should be reconsidered. The metabolomics and content determination analyses showed that the four species exhibit a metabolism similar to that of S. baicalensis in different parts. Except for the roots of S. likiangensis, all parts of the substitute species showed high contents of baicalin. Genetic and chemical analyses of four substitute medicinal species for S. baicalensis were performed here for the first time, and their pharmacophylogenetic relationships were further explored, providing a scientific basis for the subsequent development of the medicinal value and resource utilization of Scutellaria