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New insights into the dispersion history and adaptive evolution of taxon Aegilops tauschii in China
No full textAegilops tauschii, the wild progenitor of wheat D-genome and a valuable germplasm for wheat improvement, has a wide natural distribution from eastern Turkey to China. However, the phylogenetic relationship and dispersion history of Ae. tauschii in China has not been scientifically clarified. In this study, we genotyped 208 accessions (with 104 in China) using ddRAD sequencing and 55K SNP array, and classified the population into six sublineages. Three possible spreading routes or events were identified, resulting in specific distribution patterns, with four sublineages found in Xinjiang, one in Qinghai, two in Shaanxi and one in Henan. We also established the correlation of SNP-based, karyotype-based and spike-morphology-based techniques to demonstrate the internal classification of Ae. tauschii, and developed consensus dataset with 1245 putative accessions by merging data previously published. Our analysis suggested that eight inter-lineage accessions could be assigned to the putative Lineage 3 and these accessions would help to conserve the genetic diversity of the species. By developing the consensus phylogenetic relationships of Ae. tauschii, our work validated the hypothesis on the dispersal history of Ae. tauschii in China, and contributed to the efficient and comprehensive germplasm-mining of the species. Copyright (C) 2021, The Authors. Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Limited and Science Press
Two chloroplast-localized MORF proteins act as chaperones to maintain tetrapyrrole biosynthesis
No full textTetrapyrroles have essential functions as pigments and cofactors during plant growth and development, and the tetrapyrrole biosynthesis pathway is tightly controlled. Multiple organellar RNA editing factors (MORFs) are required for editing of a wide variety of RNA sites in chloroplasts and mitochondria, but their biochemical properties remain elusive. Here, we uncovered the roles of chloroplast-localized MORF2 and MORF9 in modulating tetrapyrrole biosynthesis and embryogenesis in Arabidopsis thaliana. The lack or reduced transcripts of MORF2 or MORF9 significantly affected biosynthesis of the tetrapyrrole precursor 5-aminolevulinic acid and accumulation of Chl and other tetrapyrrole intermediates. MORF2 directly interacts with multiple tetrapyrrole biosynthesis enzymes and regulators, including NADPH:PROTOCHLOROPHYLLIDE OXIDOREDUCTASE B (PORB) and GENOMES UNCOUPLED4 (GUN4). Strikingly, MORF2 and MORF9 display holdase chaperone activity, alleviate the aggregation of PORB in vitro, and are essential for POR accumulation in vivo. Moreover, both MORF2 and MORF9 significantly stimulate magnesium chelatase activity. Our findings reveal a previously unknown biochemical property of MORF proteins as chaperones and point to a new layer of post-translational control of the tightly regulated tetrapyrrole biosynthesis in plants
Anoplocaryum: A newly recorded genus of Boraginaceae from China
No full textAnoplocaryum (Boraginaceae), a small genus previously known from Russia and Mongolia, is newly recorded from China. The specimen was discovered in the rock crevices of Zhangjiakou City, Hebei province, China, and was identified as A. helenae Volot. based on both morphological and molecular data. This study updates our knowledge on the geographic distribution of the genus Anoplocaryum. Two taxonomic keys were provided to distinguish Anoplocaryum and Chinese related genera, also to index taxa in Anoplocaryum
Ectopic expression of Populus MYB10 promotes secondary cell wall thickening and inhibits anthocyanin accumulation
No full textSecondary cell wall (SCW) formation is regulated by a multilevel transcriptional regulatory network, in which MYB transcription factors (TFs) play key roles. In woody plants, hundreds of MYB TFs have been identified, most of which have unknown functions in wood SCW biosynthesis. Here, we characterized the function of a Populus MYB gene, PtoMYB10. PtoMYB10 was found to encode an R2R3-MYB TF and exhibit dominant expression in xylem tissues. PtoMYB10 was determined to be located in the nucleus with the ability to activate transcription. Overexpression of PtoMYB10 in Populus resulted in a drastic increase in SCW thickening in xylem fiber cells as well as ectopic deposition of lignin in cortex cells. The expression of genes associated with lignin biosynthesis was induced in PtoMYB10 overexpressing plants, whereas repressed gene expression was found with the anthocyanin biosynthesis pathway. Lignin and anthocyanin are both produced from metabolites of the phe-nylpropanoid pathway. Accordingly, the anthocyanin content of Populus overexpressing PtoMYB10 decreased by more than 68%. These results indicate that PtoMYB10 can positively regulate xylary fiber SCW thickening, accompanied by the reprogramming of phenylpropanoid metabolism, which redirects metabolic flux from anthocyanin biosynthesis to monolignol biosynthesis
Characterization of a novel arsenite long-distance transporter from arsenic hyperaccumulator fern Pteris vittata
No full textPteris vittata is an arsenic (As) hyperaccumulator that can accumulate several thousand mg As kg(-1) DW in aboveground biomass. A key factor for its hyperaccumulation ability is its highly efficient As long-distance translocation system. However, the underlying molecular mechanisms remain unknown. We isolated PvAsE1 through the full-length cDNA over-expression library of P. vittata and characterized it through a yeast system, RNAi gametophytes and sporophytes, subcellular-location and in situ hybridization. Phylogenomic analysis was conducted to estimate the appearance time of PvAsE1. PvAsE1 was a plasma membrane-oriented arsenite (AsIII) effluxer. The silencing of PvAsE1 reduced AsIII long-distance translocation in P. vittata sporophytes. PvAsE1 was structurally similar to solute carrier (SLC)13 proteins. Its transcripts could be observed in parenchyma cells surrounding the xylem of roots. The appearance time was estimated at c. 52.7 Ma. PvAsE1 was a previously uncharacterized SLC13-like AsIII effluxer, which may contribute to AsIII long-distance translocation via xylem loading. PvAsE1 appeared late in fern evolution and might be an adaptive subject to the selection pressure at the Cretaceaou-Paleogene boundary. The identification of PvAsE1 provides clues for revealing the special As hyperaccumulation characteristics of P. vittata
Conserved responses of nutrient resorption to extreme drought in a grassland: The role of community compositional changes
No full textThe frequency, duration and magnitude of drought are projected to increase in the next few decades, with consequences for community composition and nutrient utilization of plants. Nutrient resorption, a process facilitating plant nutrient conservation, is a crucial driver for ecosystem nutrient cycling. It remains unknown how would extreme drought affect nutrient resorption of plant communities through changing community composition. We examined the contributions of different processes (richness and identity effect of species losses and species gains, as well as the context dependent effect) related with community compositional changes to the alterations of community-level nutrient resorption efficiency after 4-year treatments of chronic drought (66% rainfall reduction from May to August) and intense drought (100% rainfall reduction in June and July) in a temperate steppe in Hulun Buir, Inner Mongolia, China. Both chronic and intense drought significantly reduced nutrient resorption efficiency in most of the common species, but did not affect that at the community level. Drought-induced losses of species made positive contribution to the community-level nutrient resorption, as they generally had lower nutrient resorption efficiency. Such positive contribution balanced the negative effect of drought on the nutrient resorption of the common species. Our results indicate that drought-induced changes in community composition, especially those species being lost, were important in mediating the community-level responses of nutrient resorption to extreme drought in grasslands. Read the free Plain Language Summary for this article on the Journal blog
The complete chloroplast genome of Nymphaea thermarum (Nymphaeaceae) from Rwanda, Africa
No full textNymphaea thermarum is classified in the Nymphaeaceae, and is the smallest water lily in the world. It has been extinct its native environment and needs urgent protection. Here, we report and characterize the complete chloroplast genome of N. thermarum. The total length of the chloroplast genome is 159,849 bp and the GC content is 39.2% (A: 30.1%, C: 20.0%, G: 19.2%, T: 30.8%). The chloroplast genome consists of 8 rRNA, 37 tRNA, and 85 protein-coding genes. Phylogenetic analysis of N. thermarum fully resolved this taxon in a clade with Nymphaea capensis. The chloroplast genome of N. thermarum provides scientific guidance for its conservation genetics and also contributes genome resources for the phylogenetic relationship of Nymphaea
Updated estimation of forest biomass carbon pools in China, 1977-2018
No full textChina is one of the major forest countries in the world, and the accurate estimation of its forest biomass carbon (C) pool is critical for evaluating the country's C budget and ecosystem services of forests. Although several studies have estimated China's forest biomass using national forest inventory data, most of them were limited to the period of 2004-2008. In this study, we extended our estimation to the most recent period of 2014-2018. Using datasets of eight inventory periods from 1977 to 2018 and the continuous biomass expansion factor method, we estimated that the total biomass C pool and average biomass C density in Chinese forests increased from 4717 Tg C (1 Tg = 10(12) g) in the period of 1977-1981 to 7975 Tg C in the period of 2014-2018 and 38.2 Mg C ha(-1) to 45.8 Mg C ha(-1) (1 Mg = 10(6) g), respectively, with a net increase of 3258 Tg C and an annual sink of 88.0 Tg C yr(-1) . Over the most recent 10 years (20092018), the average national forest biomass C density and C sink were 44.6 Mg C ha(-1) and 154.8 Tg C yr(-1) , respectively, much larger than those of 39.6 Mg C ha(-1) and 63.3 Tg C yr(-1) in the period 1977-2008. These pronounced increases were largely attributed to afforestation practices, forest growth, and environmental changes. Our results have documented the importance of ecological restoration practices, provided an essential basis for assessing ecosystem services, and helped to achieve China's C neutrality target
Multiyear CO2 elevation improves PSII efficiency in a japonica rice cultivar
No full textResponses of crop photosystem activity to the short-term elevation of carbon dioxide concentration ([CO2]) have been studied extensively. However, long-term effects of elevated [CO2] (e[CO2]) over multiple cropping generations have received little attention. Using open-top chambers (OTCs), we set up ambient [CO2] (CK) and two multigeneration e[CO2] treatments during rice (Oryza sativa L.) growing seasons in 2016-2019: a stepwise increase (SI) up to +160 mu mol mol(-1) in 2019 and a constant increase (CI) of +200 mu mol mol(-1) above CK over four generations. Beginning in 2017, grains harvested from the previous year in different [CO2] treatments were used as seeds. Seedlings derived from CK OTCs in 2018 were transplanted into both SI and CI OTCs in 2019 to simulate single-generation abrupt elevation of [CO2]. We measured the diurnal changes in photosystem II (PSII) functionality of leaves in 2019. Single-generation elevation of [CO2] had no effects on PSII efficiency. However, a stepwise increase of [CO2] over four generations significantly enhanced predawn maximum photochemical efficiency of PSII (F-v/F-m), the efficiency that trapped exciton moves an electron beyond Q(A)(-) (psi(o)), and the quantum yield of electron transport (phi E-o) in PSII at jointing stage. The constant increase of [CO2] over four generations dramatically improved predawn F-v/F-m, psi(o), phi E-o, perform index, and reaction center at grain-filling stage. Moreover, the multigeneration elevation of [CO2] weakened the depression of F-v/F-m relative to single-generation elevation at midday. All of these results indicated that e[CO2] had transgenerational effects on PSII functionality
Arabidopsis ERdj3B coordinates with ERECTA-family receptor kinases to regulate ovule development and the heat stress response
No full textThe Arabidopsis SDF2-ERdj3B-BiP chaperone complex controls the translocation of ERECTA-family receptor kinases and is required for ovule integument development and the heat stress response. The endoplasmic reticulum-localized DnaJ family 3B (ERdj3B), is a component of the stromal cell-derived factor 2 (SDF2)-ERdj3B-binding immunoglobulin protein (BiP) chaperone complex, which functions in protein folding, translocation, and quality control. We found that ERdj3B mutations affected integument development in the Ler ecotype but not in the Col-0 ecotype of Arabidopsis (Arabidopsis thaliana). Map-based cloning identified the ERECTA (ER) gene as a natural modifier of ERdj3B. The double mutation of ERdj3B and ER caused a major defect in the inner integument under heat stress. Additional mutation of the ER paralog ERECTA-LIKE 1 (ERL1) or ERL2 to the erdj3b er double mutant exacerbated the defective integument phenotype. The double mutation of ER and SDF2, the other component of the SDF2-ERdj3B-BiP complex, resulted in similar defects in the inner integument. Furthermore, both the protein abundance and plasma membrane partitioning of ER, ERL1, and ERL2 were markedly reduced in erdj3b plants, indicating that the SDF2-ERdj3B-BiP chaperone complex might control the translocation of ERECTA-family proteins from the endoplasmic reticulum to the plasma membrane. Our results suggest that the SDF2-ERdj3B-BiP complex functions in ovule development and the heat stress response in coordination with ERECTA-family receptor kinases