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Land Degradation Changes the Role of Above- and Belowground Competition in Regulating Plant Biomass Allocation in an Alpine Meadow
No full textThe allocation pattern of plant biomass presents the strategy of the plant community to adopt environmental changes, while the driver of biomass allocation is still unclear in degraded alpine grassland ecosystems. To explore the issue, this study investigated the shoot-to-root (R/S) ratio, plant aboveground traits, and root competition of three functional groups (i.e., grasses, sedges, and forbs) at three degradation levels (i.e., no obvious degradation, ND; moderate degradation, MD; and severe degradation, SD) in an alpine meadow in the eastern Qinghai-Tibetan Plateau. The relationships among plant aboveground traits, root competition, and R/S ratio were tested using the structural equation model (SEM). The results showed that the shoot and root biomass tended to decrease, but the R/S ratio of the plant community did not change along the degradation gradient. Plant height, lateral spread, and leaf length of most plant functional groups reduced, while leaf width and leaf area of most plant functional groups did not change along the degradation gradients. The root competition ability (presented as the fraction of root biomass in total biomass) of sedges in MD was the lowest, while that of grasses was the highest. The effects of aboveground competition on the R/S ratio were non-linear because of the different roles of plant height, lateral spread, and leaf area in regulating the R/S ratio along the degradation gradient. In contrast, the effects of belowground competition on the R/S ratio were linear because belowground competition promoted the R/S ratio, and the strength of this effect reduced along the degradation gradient. These results indicate that plant competition might be a critical factor to maintain the high R/S ratio in degraded alpine meadows
The loss of plant species diversity dominated by temperature promotes local productivity in the steppe of eastern Inner Mongolia
No full textIn the semiarid grassland ecosystems of eastern Inner Mongolia, the interrelations among the species diversity of different plant communities, productivity, soil nutrients and climate were thoroughly studied through integrated approaches combined with the sample method, correlation analysis and structural equation modelling (SEM) model. The results show that the colonization of perennial grasses was promoted in the wetter and colder climate conditions. The productivity was determined by the perennial grasses, while species diversity was dominated by the perennial forbs. We obtained a U-shaped relationship between biomass and species diversity, which indicated two different strategies for the interaction between grassland biomass and diversity. In our study, air temperature and plant biomass were determined to be the main two indicators of plant species diversity variation. Meanwhile, distinct mutual constraints existed between the biomass of grassland dominant species and species diversity. Furthermore, soil nutrient conditions and climatic factors were found to jointly affect grassland productivity. This study will be helpful in providing deep insight into the dynamics of plant species diversity and the main interactive influencing factors in the semiarid steppe ecosystem and will provide a scientific basis for the maintenance of plant diversity and ecosystem functions in this region
Precipitation variations, rather than N deposition, determine plant ecophysiological traits in a desert steppe in Northern China
No full textUnderstanding how plant ecophysiological traits of coexisting species within a community respond to environ-mental changes could help to predict the shift in plant community structure and function, but it remains limited in the scenarios of co-occurring precipitation variations and N deposition. A two-year field experiment was conducted to explore the effects of large precipitation changes (reduced and increased precipitation amount by 25% and 50% relative to ambient control) and high N deposition (10 g N m(-2) yr(-1)) on a series of leaf ecophysiological traits of three dominant species (Stipa tianschanica, a C-3 grass; Cleistogenes squarrosa, a C4 grass; and Artemisia capillaris, a C-3 forb) in a desert steppe in Northern China. Increasing precipitation significantly linearly promoted the leaf light-saturated photosynthesis rate (Asat) and N use efficiency of the two C-3 species, irrespective of N addition. The rises in Asat of both C-3 species were mainly caused by increased soil moisture, which strongly induced increases in leaf stomatal conductance (gs) and declines in quantum yield of photosystem II (phi PSII). However, the Asat of the two C3 species was weakly correlated with their specific leaf area and leaf N concentration, whereas the Asat of the C4 grass was negatively related to its leaf N. Moreover, the Asat, height, and aboveground biomass of the forbs were much more water-sensitive than those of both grass species, with a consequence of the most dominant species turning from grass to forbs as precipitation increased. Our findings highlight that water limitation, rather than N deficit, is the largest factor controlling plant growth in drylands, and plant species-specific ecophysiological responses to precipitation fluctuations will cause a substantial shift in the production and composition of plant community
Sunflower Leaf Structure Affects Chlorophyll a Fluorescence Induction Kinetics In Vivo
No full textChlorophyll a fluorescence induction kinetics (CFI) is an important tool that reflects the photosynthetic function of leaves, but it remains unclear whether it is affected by leaf structure. Therefore, in this study, the leaf structure and CFI curves of sunflower and sorghum seedlings were analyzed. Results revealed that there was a significant difference between the structures of palisade and spongy tissues in sunflower leaves. Their CFI curves, measured on both the adaxial and abaxial sides, also differed significantly. However, the differences in the leaf structures and CFI curves between both sides of sorghum leaves were not significant. Further analysis revealed that the differences in the CFI curves between the adaxial and abaxial sides of sunflower leaves almost disappeared due to reduced incident light scattering and refraction in the leaf tissues; more importantly, changes in the CFI curves of the abaxial side were greater than the adaxial side. Compared to leaves grown under full sunlight, weak light led to decreased differences in the CFI curves between the adaxial and abaxial sides of sunflower leaves; of these, changes in the CFI curves and palisade tissue structure on the adaxial side were more obvious than on the abaxial side. Therefore, it appears that large differences in sunflower leaf structures may affect the shape of CFI curves. These findings lay a foundation for enhancing our understanding of CFI from a new perspective
Phylogenomic relationships and species identification of the olive genus Olea (Oleaceae)
No full textThe olive genus Olea includes c. 30-40 taxa in three subgenera (Olea, Tetrapilus, and Paniculatae) within the family Oleaceae. Historically, the Olea genus was classified into four groups that were overall well supported by reconstructed phylogenies, despite incomplete sampling of subgenus Tetrapilus and poor resolution within clades. These analyses also showed that the genus was not monophyletic. Reliable identification of Olea species is important for both their conservation and utilization of this economically important genus. In this study, we used phylogenomic data from genome skimming to resolve relationships within Olea and to identify molecular markers for species identification. We assembled the complete plastomes, and nrDNA of 26 individuals representing 13 species using next-generation sequencing and added 18 publicly available accessions of Olea. We also developed nuclear SNPs using the genome skimming data to infer the phylogenetic relationships of Olea. Large-scale phylogenomic analyses of 138 samples of tribe Oleeae supported the polyphyly of Olea, with Olea caudatilimba and Olea subgenus Tetrapilus not sharing their most recent common ancestor with the main Olea clade (subgenus Paniculatae and subgenus Olea). The interspecific phylogenetic resolution was poor owing to a possible rapid radiation. By comparing with the plastome data, we identified the markers ycf1b and psbE-petL as the best Olea-specific chloroplast DNA barcodes. Compared with universal barcodes, specific DNA barcodes and super-barcode exhibited higher discriminatory power. Our results demonstrated the power of phylogenomics to improve phylogenetic relationships of intricate groups and provided new insights into barcodes that allow for accurate identification of Olea species
Tip growth defective1 interacts with cellulose synthase A3 to regulate cellulose biosynthesis in Arabidopsis
No full textKey message AtTIP1 physically and genetically interacts with AtCESA3. AtCESA3 undergoes S-acylation, possibly mediated by AtTIP1, suggesting a specific role of AtTIP1 in cellulose biosynthesis and plant development. S-acylation is a reversible post-translational lipid modification of proteins catalyzed by protein S-acyl transferases (PATs). S-acylation is important for various biological molecular mechanisms including cellulose biosynthesis. Cellulose is synthesized by the cellulose synthase A (CESA) complexes (CSCs) at the plasma membrane. However, specific PAT involving in cellulose biosynthesis has not been identified and the precise mechanism by which PAT regulates the CESAs is largely unknown. Here, we report isolation of tip1-5, an allele of Tip Growth Defective1 (AtTIP1/AtPAT24) with a premature stop codon. tip1-5 genetically interacts with ixr1-2, a point mutant of AtCESA3 which encodes a catalytic subunit of CSC synthesizing primary wall cellulose. We show that AtTIP1 physically interacts with AtCESA3. AtCESA3 undergoes S-acylation, which is possibly mediated by AtTIP1, suggesting a functional relationship between AtTIP1 and AtCESA3. Moreover, the interfascicular fiber cells in the primary inflorescence stems of tip1-5 ixr1-2 double mutant contain thinner cell walls and significantly less crystalline cellulose compared to the single mutants. These results highlight the positive regulation of AtTIP1 in cellulose biosynthesis, and a specific role of AtPAT in plant development
Distribution analysis, updated checklist, and DNA barcodes of the endemic vascular flora of the Altai mountains, a Siberian biodiversity hotspot
No full textThe Altai Mountains of central Asia are biologically rich and comprise a wide diversity of ecosystems and lineages, including numerous endemic vascular plant species. Here we provide an updated checklist of the endemic vascular flora of the Altai Mountains with more taxa and higher geographic resolution than previously reported, as well as first molecular data and specimen images for many of these species. This flora is now known to contain 321 endemic species distributed in 34 families, many of which are narrowly restricted to one subregion of the Altai. The Fabaceae has given rise to the most endemic species in the Altai (74 spp.), and most of this diversity is found in the large and ecologically important genera Astragalus and Oxytropis. Approximately 60% of the endemic flora was imaged and successfully barcoded with at least one of three common DNA barcoding loci, and a phylogenetic tree based upon these loci is also presented to display the evolutionary breadth of endemism in the Altai. The distribution of each endemic species is presented in terms of a standard geographic subdivision of the Altai region, with general conservation priorities discussed based on areas currently afforded protected status
MdWOX4-2 modulated MdLBD41 functioning in adventitious shoot of apple
No full textApple (Malus domestica Borkh.) is not only an important fruit crop distributed worldwide, but also a common model plant. However, the lack of efficient genetic transformation procedures for apples limits the in-depth studies of their gene functions. Although leaf-regenerated adventitious shoots (LRAS) are a prerequisite for successful genetic transformation of apple, little is known about the underlying molecular mechanism of LRAS. Here, we identified the WUSCHEL-related homeobox (WOX) transcription factor in apple, MdWOX4-2, which was a transcriptional activator. Gene expression as well as morphological and histological observations revealed that MdWOX4-2 is involved in the development of LRAS. Overexpression of MdWOX4-2 conferred higher regenerative capacity in transgenic tobacco (Nicotiana tabacum) as compared to the wild type (WT). The com-bined results of the yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), dual luciferase assays, and transient transactivation assay, revealed that MdWOX4-2 directly bound to and activated the MdLBD41 promoter. Moreover, transgenic experiments further demonstrated that MdLBD41 could significantly enhance the formation of adventitious shoot in transgenic tobacco. Collectively, our findings demonstrate that MdWOX4-2 is important for regulating the LRAS development by activating MdLBD41
Measuring and evaluating SDG indicators with Big Earth Data
No full textThe United Nations 2030 Agenda for Sustainable Development provides an important framework for eco-nomic, social, and environmental action. A comprehensive indicator system to aid in the systematic implementation and monitoring of progress toward the Sustainable Development Goals (SDGs) is unfortunately limited in many countries due to lack of data. The availability of a growing amount of multi-source data and rapid advancements in big data methods and infrastructure provide unique oppor-tunities to mitigate these data shortages and develop innovative methodologies for comparatively mon-itoring SDGs. Big Earth Data, a special class of big data with spatial attributes, holds tremendous potential to facilitate science, technology, and innovation toward implementing SDGs around the world. Several programs and initiatives in China have invested in Big Earth Data infrastructure and capabilities, and have successfully carried out case studies to demonstrate their utility in sustainability science. This paper pre-sents implementations of Big Earth Data in evaluating SDG indicators, including the development of new algorithms, indicator expansion (for SDG 11.4.1) and indicator extension (for SDG 11.3.1), introduction of a biodiversity risk index as a more effective analysis method for SDG 15.5.1, and several new high-quality data products, such as global net ecosystem productivity, high-resolution global mountain green cover index, and endangered species richness. These innovations are used to present a comprehensive analysis of SDGs 2, 6,11,13, 14, and 15 from 2010 to 2020 in China utilizing Big Earth Data, concluding that all six SDGs are on schedule to be achieved by 2030.(c) 2022 Science China Press. Published by Elsevier B.V. and Science China Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
The unconventional prefoldin RPB5 interactor mediates the gravitropic response by modulating cytoskeleton organization and auxin transport in Arabidopsis
No full textGravity-induced root curvature involves the asymmetric distribution of the phytohormone auxin. This response depends on the concerted activities of the auxin transporters such as PIN-FORMED (PIN) proteins for auxin efflux and AUXIN RESISTANT 1 (AUX1) for auxin influx. However, how the auxin gradient is established remains elusive. Here we identified a new mutant with a short root, strong auxin distribution in the lateral root cap and an impaired gravitropic response. The causal gene encoded an Arabidopsis homolog of the human unconventional prefoldin RPB5 interactor (URI). AtURI interacted with prefoldin 2 (PFD2) and PFD6, two beta-type PFD members that modulate actin and tubulin patterning in roots. The auxin reporter DR5(rev):GFP showed that asymmetric auxin redistribution after gravistimulation is disordered in aturi-1 root tips. Treatment with the endomembrane protein trafficking inhibitor brefeldin A indicated that recycling of the auxin transporter PIN2 is disrupted in aturi-1 roots as well as in pfd mutants. We propose that AtURI cooperates with PFDs to recycle PIN2 and modulate auxin distribution