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Identification and Fine Mapping of the Recessive Gene BK-5, Which Affects Cell Wall Biosynthesis and Plant Brittleness in Maize
No full textThe cellulose of the plant cell wall indirectly affects the cell shape and straw stiffness of the plant. Here, the novel brittleness mutant brittle stalk-5 (bk-5) of the maize inbred line RP125 was characterized. We found that the mutant displayed brittleness of the stalk and even the whole plant, and that the brittleness phenotype existed during the whole growth period from germination to senescence. The compressive strength was reduced, the cell wall was thinner, and the cellulose content was decreased compared to that of the wild type. Genetic analysis and map-based cloning indicated that bk-5 was controlled by a single recessive nuclear gene and that it was located in a 90.2-Kb region on chromosome 3 that covers three open reading frames (ORFs). Sequence analysis revealed a single non-synonymous missense mutation, T-to-A, in the last exon of Zm00001d043477 (B73: version 4, named BK-5) that caused the 951th amino acid to go from leucine to histidine. BK-5 encodes a cellulose synthase catalytic subunit (CesA), which is involved with cellulose synthesis. We found that BK-5 was constitutively expressed in all tissues of the germinating stage and silking stage, and highly expressed in the leaf, auricula, and root of the silking stage and the 2-cm root and bud of the germinating stage. We found that BK-5 mainly localized to the Golgi apparatus, suggesting that the protein might move to the plasma membrane with the aid of Golgi in maize. According to RNA-seq data, bk-5 had more downregulated genes than upregulated genes, and many of the downregulated genes were enzymes and transcription factors related to cellulose, hemicellulose, and lignin biosynthesis of the secondary cell wall. The other differentially expressed genes were related to metabolic and cellular processes, and were significantly enriched in hormone signal transduction, starch and sucrose metabolism, and the plant-pathogen interaction pathway. Taken together, we propose that the mutation of gene BK-5 causes the brittle stalk phenotype and provides important insights into the regulatory mechanism of cellulose biosynthesis and cell wall development in maize
Reconstruction of the evolutionary biogeography reveals the origins of Alpinia Roxb. (Zingiberaceae): A case of out-of-Asia migration to the Southern Hemisphere
No full textAlpinia is considered the largest genus of Zingiberaceae with ca. 250 species occurring in tropical and subtropical Asia, Australia, and Pacific Islands. The historical biogeography of Alpinia was conducted to explain where Alpinia originated and how it migrated to other regions. The phylogeny, divergence times and ancestral area reconstruction of Alpinia were performed by using the molecular data based on the comprehensive taxon sampling. Our results provide an objective approach to understand the historical biogeography of Alpinia. The genus originated in Asia during the Late Cretaceous ca. 69 Ma and started to diverge after the K???Pg boundary during the early Paleocene with the presence and development of the tropical rainforest and a warm, moist climate. Alpinia migrated to Malesia and then dispersed to Australasia. The molecular analyses supported the diversification of Alpinia in Asia and Malesia. Additionally, the Indian Alpinia has likely a common ancestor with Renealmia and Aframomum, and it is possible that after originating in Asia, Alpinia migrated from Asia to India then to Africa during the early period of collision between the Indian subcontinent and Eurasia to form the common ancestor of Indian Alpinia, Renealmia, and Aframomum. Our phylogeny provides a framework for studies in biogeography, comparative ecology, and evolution
Crop Root Responses to Drought Stress: Molecular Mechanisms, Nutrient Regulations, and Interactions with Microorganisms in the Rhizosphere
No full textRoots play important roles in determining crop development under drought. Under such conditions, the molecular mechanisms underlying key responses and interactions with the rhizosphere in crop roots remain limited compared with model species such as Arabidopsis. This article reviews the molecular mechanisms of the morphological, physiological, and metabolic responses to drought stress in typical crop roots, along with the regulation of soil nutrients and microorganisms to these responses. Firstly, we summarize how root growth and architecture are regulated by essential genes and metabolic processes under water-deficit conditions. Secondly, the functions of the fundamental plant hormone, abscisic acid, on regulating crop root growth under drought are highlighted. Moreover, we discuss how the responses of crop roots to altered water status are impacted by nutrients, and vice versa. Finally, this article explores current knowledge of the feedback between plant and soil microbial responses to drought and the manipulation of rhizosphere microbes for improving the resilience of crop production to water stress. Through these insights, we conclude that to gain a more comprehensive understanding of drought adaption mechanisms in crop roots, future studies should have a network view, linking key responses of roots with environmental factors
A Comprehensive Evolutionary Study of Chloroplast RNA Editing in Gymnosperms: A Novel Type of G-to-A RNA Editing Is Common in Gymnosperms
No full textAlthough more than 9100 plant plastomes have been sequenced, RNA editing sites of the whole plastome have been experimentally verified in only approximately 21 species, which seriously hampers the comprehensive evolutionary study of chloroplast RNA editing. We investigated the evolutionary pattern of chloroplast RNA editing sites in 19 species from all 13 families of gymnosperms based on a combination of genomic and transcriptomic data. We found that the chloroplast C-to-U RNA editing sites of gymnosperms shared many common characteristics with those of other land plants, but also exhibited many unique characteristics. In contrast to that noted in angiosperms, the density of RNA editing sites in ndh genes was not the highest in the sampled gymnosperms, and both loss and gain events at editing sites occurred frequently during the evolution of gymnosperms. In addition, GC content and plastomic size were positively correlated with the number of chloroplast RNA editing sites in gymnosperms, suggesting that the increase in GC content could provide more materials for RNA editing and facilitate the evolution of RNA editing in land plants or vice versa. Interestingly, novel G-to-A RNA editing events were commonly found in all sampled gymnosperm species, and G-to-A RNA editing exhibits many different characteristics from C-to-U RNA editing in gymnosperms. This study revealed a comprehensive evolutionary scenario for chloroplast RNA editing sites in gymnosperms, and reported that a novel type of G-to-A RNA editing is prevalent in gymnosperms
Characterization of an Endophytic Antagonistic Bacterial Strain Bacillus halotolerans LBG-1-13 with Multiple Plant Growth-Promoting Traits, Stress Tolerance, and Its Effects on Lily Growth
No full textMicrobial inoculants are an important tool for increasing arable land productivity and decreasing mineral fertilizer application. This study was aimed at isolating and identifying endophytic antagonistic bacteria from lily (Lilium davidii var. unicolor) roots grown in Northwestern China and at evaluating their antifungal activity and plant growth-promoting characteristics. For this purpose, endophytic bacteria were isolated from plant roots, and plant growth-promoting strains were identified. One bacterial strain, isolated from the root part, was identified as Bacillus halotolerans based on 16S rRNA gene sequence analysis and was designated as LBG-1-13. The strain showed antagonistic activities against important plant pathogens of lily including Botrytis cinerea, Botryosphaeria dothidea, and Fusarium oxysporum. The highest percentage of growth inhibition, i.e., 71.65 +/- 2.39%, was observed for LBG-1-13 against Botryosphaeria dothidea followed by 68.33 +/- 4.70% and 48.22 +/- 4.11% against Botrytis cinerea and Fusarium oxysporum, respectively. Meanwhile, the isolated strain also showed plant growth-promoting traits such as the production of indole-3-acetic acid (IAA), siderophore, ACC deaminase, and phosphate solubilization activity. The strain showed ACC deaminase activity and was able to cleave 58.41 & PLUSMN;2.62 nmol alpha-ketobutyrate (mg protein)(-1) min(-1). The strain exhibited tolerance to salt and drought stress in an in vitro experiment. The strain LBG-1-13 was able to grow in the presence of 10% NaCl and 20% polyethylene glycol (PEG) in the growth medium. Inoculation of Lilium varieties, Tresor and Bright Diamond, with LBG-1-13 enhanced plant growth under greenhouse and field conditions, respectively. All these results demonstrated that Bacillus halotolerans LBG-1-13 could be utilized as a good candidate in the biocontrol of lily disease and plant growth promotion in sustainable agriculture
Changes in wheat traits under future climate change and their contributions to yield changes in conventional vs. conservational tillage systems
No full textExploring the changes in wheat traits under future climate change and their contributions to yield changes is essential to improve the understanding of climate impact mechanisms and develop climate-resilient cultivars, which however has been seldom conducted. In this study, using a process-based crop model (APSIM-Wheat), meta-regression analyses, and machine learning approaches, we assessed the impacts of different warming levels on soil environments and wheat traits; investigated the impacts of future climate change on wheat traits, growth and development; and identified the favorable wheat traits for breeding under future climate change conditions. Meta-analyses showed that climate warming could significantly advance anthesis date by 3.50% and shorten the entire growth duration by 1.18%, although the duration from anthesis to maturity could be elongated by 7.72%. It could also increase grain yield slightly by 2.72% in the North China Plain, mainly due to the increase in biomass by 6.66%, grain weight by 3.86% and the elongating grain-filling period. However, high temperatures could significantly reduce aboveground biomass. 'the APSIM-Wheat model was validated based on three years' high-quality environment-controlled experimental data in the long-term warming and conservation tillage fields at Yucheng comprehensive experiment station in the North China Plain. The results showed that the mean yield would decrease under RCP4.5 for both tillage managements (conservational tillage: 0.55%, no-tillage: 6.88%), but increase conservational tillage yield (7.7%) under RCP8.5, relative to 1980-2010, owing to the interactive impacts of climate, CO2 and tillage on wheat traits. Soil moisture would play a more important role in biomass, yield, height, LAI, and grain number for conventional tillage than for no-tillage system, and in the future than in the historical period. Our findings gained insights into the impacts of climate change on wheat traits and yield under different tillage managements, which are essential to understand climate change impact mechanisms and develop climate-resilient cultivars
Lower Devonian Lycophytes from Sichuan and the Paleogeographic Context of Coeval Plant Assemblages from South China
No full textPremise of research. Devonian assemblages from South China have become an important source of data on the rise of land plants and are thus supplementary to a scenario historically based on fossils from the Laurussian region and Siberia. Less attention has been given to assemblages from Sichuan and their paleogeographic significance than to those from Yunnan and adjacent provinces in China.Methodology. Descriptions of plants, including lycopsids, with enations are based on coalified compression fossils lacking anatomy, and they complete our analyses of the Sichuan Lower Devonian assemblages. Compiled species lists for the entire assemblage are compared with those from coeval assemblages from South China using simple statistical methods (including Simpson's coefficient of similarity).Pivotal results. Studies confirm the presence of endemic lycophytes and emphasize the importance of detailed study of Drepanophycus spinaeformis before any conclusions about its global occurrence can be made.Conclusions. Statistical analysis of the whole flora confirms that the assemblage from Sichuan is distinct from that at Yunnan, but distinguishing two further subregions in South China requires descriptions of further taxa
Assessing the accumulation efficiency of various microbial carbon components in soils of different minerals
No full textHeterotrophic soil microbes are increasingly recognized as a key mediator transforming labile organic carbon (OC) into relatively stable soil carbon (C) in the form of microbial necromass (dead cells) and extracellular compounds associated with minerals. However, the accumulation of microbial necromass relative to labile OC consumption and its regulating factors remain poorly understood, although it has vital implications for soil C sequestration and modeling. Here by mimicking microbial C accumulation in constructed model soils using fructose as the sole OC substrate, we present a benchmark comparison of microbial C accrual versus OC mineralization under declining substrate availability and mineralogy. By quantifying various microbial components including biomass (living cells; indicated by phospholipid fatty acids), necromass (indicated by amino sugars) and total microbial C (including biomass, necromass and extracellular compounds; estimated as the difference between added and residual substrate C minus respiration) in a simple soil system, we compare microbial metabolic quotient (qCO2; i.e., microbial respiration rate per unit of biomass), amino sugar accumulation efficiency (AAE; i.e., ratio of amino sugars to respiration) and microbial C accumulation efficiency (mCAE; i.e., ratio of total microbial C to total microbial C and respiration), and assess their regulating factors. We find that while clay (bentonite) promotes microbial respiration, it enhances the rate as well as efficiency of amino sugar accumulation without affecting qCO2 or mCAE. On the contrary, ferrihydrite increases qCO2 and decreases AAE but promotes labile OC preservation via inhibiting microbial growth in the alkaline model soil. Hence, amino sugar accrual is more efficient in clay-rich model soils while labile OC is less consumed in model soils containing iron (hydr)oxide. Furthermore, while mCAE was correlated with qCO2 in all but the model soil with 6% clay, AAE was correlated with qCO2 only in model soils with 12% clay when the mineral treatments were considered separately. Collectively, our findings suggest that mCAE and AAE heavily depend on mechanisms preserving microbial C components but not solely on the metabolic efficiency and is mediated by soil mineral content as well as composition. Parameters considering microbial C preservation such as mCAE or AAE warrant further study for modelling and managing the formation of microbial derived stable soil OC
Identification and Characterization of Regulatory Pathways Controlling Dormancy Under Lower Temperature in Alfalfa (Medicago sativa L.)
No full textAlfalfa (Medicago sativa L.), a kind of high-quality perennial legume forage, is widely distributed in the northern regions of China. In recent years, low temperatures have frequently occurred and limited alfalfa productivity and survival in early spring and late fall. However, the underlying molecular mechanisms of alfalfa response to cold tolerance are not well-documented. In this study, dormancy and non-dormancy alfalfa standard varieties were characterized under low-temperature stress. Our analysis revealed that plant height of the dormancy genotype was strongly inhibited by low temperature; flavonoids content, and higher expression of flavonoids biosynthesis genes (chalcone synthase, leucoanthocyanidin dioxygenase, and flavonoid 3'-monooxygenase) may play essential roles in response to low-temperature stress in dormancy genotype alfalfa. Further analyses revealed that receptor-like kinase family genes (such as cysteine-rich RLK10, lectin protein kinase, and S-locus glycoprotein like kinase), RNA and protein synthesis genes (RNA polymerases, ribosomal protein, and protein phosphatase 2C family protein), and proteasome degradation pathway genes (such as F-box family protein, RING/U-box superfamily protein, and zinc finger family protein) also highly upregulated and contributed to cold tolerance phenotype in dormancy genotype alfalfa. This will provide new insights into future studies for cold tolerance in alfalfa and offer new target genes for further functional characterization and genetic improvement of alfalfa
Comprehensive assessment of integrated rice-crayfish farming system as a new paradigm to air-water-food nexus sustainability
No full textIntegrated rice-crayfish farming (IRCF) is becoming a popular agricultural production mode and has expanded rapidly in China. However, serious concerns over the ecologically and environmentally friendly development of IRCF are still growing. Despite its importance, there is no comprehensive assessment study of IRCF to evaluate if it is a green and sustainable development in agricultural sector. To address such concerns, the life cycle assessment method at the endpoint level and water footprint were employed to elucidate the potential envi-ronmental risk caused by the fast development of IRCF. Furthermore, the economic assessment was also carried out using cost-benefit analysis. The results showed that, IRCF systems have higher impacts in the human health damage category compared to rice monoculture (RM) systems. This was attributed to the higher direct field emissions such as methane emission and high-water consumption in IRCF. However, IRCF had lower environ-mental impacts in the ecosystem damage category than RM, primarily due to decreased fertilizer inputs. Water footprint was the primary concern in IRCF, with 379% higher water consumption than RM. The expansion of IRCF can affect food security for the following two reasons: i) Outer ridge and ditch that are built around rice fields decrease rice planting area and hence total production, ii) Crayfish occupy rice fields in winter and the following spring, so winter-season crops such as winter wheat cannot be grown in IRCF fields. Economic assessment approved that the gross profit is the main motivation for farmers to shift from RM to IRCF, where 297% higher economic benefit can be achieved. Our results indicated that IRCF expansion improved farmers' income but came with potentially environmental and food security risks. Therefore, strict measures and rational land use planning should be implemented for the sustainable development of IRCF