Ethylene accelerates maize leaf senescence in response to nitrogen deficiency by regulating chlorophyll metabolism and autophagy

Leaf senescence is an orderly and highly coordinated process,and finely regulated by ethylene and nitrogen(N),ultimately affecting grain yield and nitrogen-use efficiency(NUE).However,the underlying regulatory mechanisms on the crosstalk between ethylene-and N-regulated leaf senescence remain a mystery in maize.In this study,ethylene biosynthesis gene ZmACS7 overexpressing(OE-ZmACS7)plants were used to study the role of ethylene regulating leaf senescence in response to N deficiency,and they exhibited the premature leaf senescence accompanied by increased ethylene release,decreased chlorophyll content and F_v/F_m ratio,and accelerated chloroplast degradation.Then,we investigated the dynamics changes of transcriptome reprogramming underlying ethylene-accelerated leaf senescence in response to N deficiency.The differentially expressed genes(DEGs)involved in chlorophyll biosynthesis were significantly down-regulated,while DEGs involved in chlorophyll degradation and autophagy processes were significantly up-regulated,especially in OE-ZmACS7 plants in response to N deficiency.A gene regulatory network(GRN)was predicted during ethylene-accelerated leaf senescence in response to N deficiency.Three transcription factors(TFs)ZmHSF4,Zmb HLH106,and ZmEREB147 were identified as the key regulatory genes,which targeted chlorophyll biosynthesis gene ZmLES22,chlorophyll degradation gene ZmNYC1,and autophagy-related gene ZmATG5,respectively.Furthermore,ethylene signaling key genes might be located upstream of these TFs,generating the signaling cascade networks during ethylene-accelerated leaf senescence in response to N deficiency.Collectively,these findings improve our molecular knowledge of ethylene-accelerated maize leaf senescence in response to N deficiency,which is promising to improve NUE by manipulating the progress of leaf senescence in maize.

化学实验室废弃物安全管理和处理研究

随着高等教育事业的不断发展和国家对人才培养、科技强国的大力投入,高校实验室废弃物安全管理和规范处置已成为关乎绿色平安校园建设和人类社会可持续发展的重要保障。本文归纳了化学实验室废弃物的类别与特点,从涉及范围广、人员流动大、废弃物杂繁多、安全环保意识不足和管理不够健全五个方面分析了目前废弃物管理和处置中的问题所在,结合学校、学院与当地企业的实际情况探索出一套集结安全环保教育、教学科研实验规划、制度细则完善落实、信息化高效支撑于一体的闭环式管理与处置实践模式,以期为实验室废弃物处理提供参考。

Recent omics progress in nanobiotechnology for plant abiotic stress tolerance improvement

Use of nanomaterials(NMs)to improve plant abiotic stress tolerance(AST)is a hot topic in NM-enabled agriculture.Previous studies mainly focused on the physiological and biochemical responses of plants treated with NMs under abiotic stress.To use NMs for improving plant AST,it is necessary to understand how they act on this tolerance at the omics and epigenetics levels.In this review,we summarized the knowledge of NM-improved abiotic stress tolerance in relation to omics(such as metabolic,transcriptomic,proteomic,and microRNA),DNA methylation,and histone modifications.Overall,NMs can improve plant abiotic stress tolerance through the modulation at omics and epigenetics levels.

Exogenous application of glycine betaine improved water use efficiency in winter wheat(Triticum aestivum L.) via modulating photosynthetic efficiency and antioxidative capacity under conventional and limited irrigation conditions

Improving water use efficiency(WUE)is an important subject in agricultural irrigation for alleviating the scarcity of water resources in semiarid regions of the North China Plain.Moreover,glycine betaine(GB)is one of the most effective compatible solutes synthesized naturally in plants for enhancing stress tolerance under abiotic stress,but little information is available on the involvement of GB in regulating crop WUE under field conditions.This study was conducted to explore the role of exogenously applied GB in improving WUE and plant physiological and biochemical responses inwinterwheat subjected to conventional or limited irrigation during the 2015–2016 and 2016–2017 growing seasons.Exogenous application of GB significantly enhanced antioxidant enzyme activities and reduced the accumulation ofmalondialdehyde and hydrogen peroxide under limited irrigation conditions.Furthermore,GB-treated plantsmaintained higher leaf relative water content andmembrane stability,which led to higher chlorophyll content and gas exchange attributes for better intrinsic and instantaneouswater use efficiencies compared to control plants under limited irrigation conditions.GB-treated plants had higher indole-acetic acid and zeatin riboside levels but lower ABA levels compared to control plants under conventional and limited irrigation conditions.Additionally,GB enhanced the grain filling rate and duration,grain number per spike,and final grainweight,which resulted in higher grain yield compared to the control.Interestingly,GB significantly improved the integrative and photosynthetic WUE under conventional and limited irrigation conditions,although GB treatment did not markedly affect total water consumption.These results suggest the involvement of GB in improving WUEs in winter wheat by modulating hormonal balance,membrane stability,photosynthetic performance and antioxidant systems to maintain higher grain yield under conventional and limited irrigation conditions.

Increase in root density induced by coronatine improves maize drought resistance in North China

Drought stress caused by insufficient irrigation or precipitation impairs agricultural production worldwide.In this study,a two-year field experiment was conducted to investigate the effect of coronatine(COR),a functional analog of jasmonic acid(JA),on maize drought resistance.The experiment included two water treatments(rainfed and irrigation),four COR concentrations(mock,0μmol L^(-1);A1,0.1μmol L^(-1);A2,1μmol L^(-1);A3,10μmol L^(-1))and two maize genotypes(Fumin 985(FM985),a drought-resistant cultivar and Xianyu 335(XY335),a drought-sensitive cultivar).Spraying 1μmol L^(-1)COR at seedling stage increased surface root density and size,including root dry matter by 12.6%,projected root area by 19.0%,average root density by 51.9%,and thus root bleeding sap by 28.2%under drought conditions.COR application also increased leaf area and SPAD values,a result attributed to improvement of the root system and increases in abscisic acid(ABA),JA,and salicylic acid(SA)contents.The improvement of leaves and roots laid the foundation for increasing plant height and dry matter accumulation.COR application reduced anthesis and silking interval,increasing kernel number per ear.COR treatment at 1μmol L^(-1)increased the yield of XY335 and FM985 by 7.9%and 11.0%,respectively.Correlation and path analysis showed that grain yields were correlated with root dry weight and projected root area,increasing maize drought resistance mainly via leaf area index and dry matter accumulation.Overall,COR increased maize drought resistance mainly by increasing root dry weight and root area,with 1μmol L-^(-1)COR as an optimal concentration.

Recent advances in nano-enabled agriculture for improving plant performance

Nano-enabled agriculture is an emerging hot topic.To facilitate the development of nano-enabled agriculture,reviews addressing or discussing the applications,knowledge gap,future research needs,and possible new research field of plant nanobiotechnology in agricultural production are encouraged.Here we review the following topics in plant nanobiotechnology for agriculture:1)improving stress tolerance,2)stress sensing and early detection,3)targeted delivery and controlled release of agrochemicals,4)transgenic events in non-model crop species,and 5)seed nanopriming.We discuss the knowledge gaps in these topics.Besides the use of nanomaterials for harvesting more electrons to improve photosynthetic performance,they could be used to convert n IR and UV to visible light to expand the light spectrum for photosynthesis.We discuss this approach to maintaining plant photosynthesis under light-insufficient conditions.Our aim in this review is to aid researchers to learn quickly how to use plant nanobiotechnology for improving agricultural production.

Brassinosteroids modulate nitrogen physiological response and promote nitrogen uptake in maize(Zea mays L.)

Brassinosteroids(BRs)are steroid hormones that function in plant growth and development and response to environmental stresses and nutrient supplies.However,few studies have investigated the effect of BRs in modulating the physiological response to nitrogen(N)supply in maize.In the present study,BR signalingdeficient mutant zmbri1-RNAi lines and exogenous application of 2,4-epibrassinolide(e BL)were used to study the role of BRs in the regulation of physiological response in maize seedlings supplied with N.Exogenous application of e BL increased primary root length and plant biomass,but zmbri1 plants showed shorter primary roots and less plant biomass than wild-type plants under low N(LN)and normal N(NN)conditions.LN induced the expression of the BR signaling-associated genes Zm DWF4,Zm CPD,Zm DET2,and Zm BZR1 and the production of longer primary roots than NN.Knockdown of Zm BRI1 weakened the biological effects of LN-induced primary root elongation.e BL treatment increased N accumulation in shoots and roots of maize seedlings exposed to LN or NN treatment.Correspondingly,zmbri1 plants showed lower N accumulation in shoots and roots than wild-type plants.Along with reduced N accumulation,zmbri1 plants showed lower NO3-fluxes and^(15)NO_(3)^(-)uptake.The expression of nitrate transporter(NRT)genes(Zm NPF6.4,Zm NPF6.6,Zm NRT2.1,Zm NRT2.2)was lower in zmbri1 than in wild-type roots,but e BL treatments up-regulated the transcript expression of NRT genes.Thus,BRs modulated N physiological response and regulated the transcript expression of NRT genes to promote N uptake in maize.

Monoclonal Antibody-Based Enzyme Linked Immunosorbent Assay for the Analysis of Jasmonates in Plants

Methyl jasmonate （MeJA） and its free-acid form, jasmonic acid （JA） are naturally occurring plant growth regulators widely distributed in higher plants. In order to improve the sensitivity for the analysis of MeJA at low levels in small amounts of plant samples, a monoclonal antibody （MAb） （designated as MAb 3E5D7C4B6） against MeJA was derived from a JA- bovine serum albumin （BSA） conjugate as an immunogen. The antibody belongs to the IgG1 subclass with a κ type light chain and has a dissociation constant of approximately 6.07 ×10^-9 M. MAb3E5D7C4B6 is very specific to MeJA. It was used to develop a direct competitive enzyme-linked immunosorbent assay （dcELISA）, conventional and simplified indirect competitive ELISAs （icELISA）. JA was derivatized into MeJA for the ELISA analysis. The IC50 value and detection range for MeJA were, respectively, 34 and 4-257 nglmL by the conventional icELISA, 21 and 3-226 nglmL by the simplified icELISA and 5.0 and 0.7-97.0 nglmL by the dcELISA. The dcELISA was more sensitive than either the conventional or simplified icELISA. The assays were used to measure the content of jasmonates as MeJA in tobacco leaves under drought stress or inoculated with tobacco mosaic virus and tomato leaves inoculated with tomato mosaic virus or Lirioinyza sativae Blanchard as compared with the corresponding healthy leaves. The increased jasmonates content indicated its role in response to the drought stress and pathogens.

Cotton GhBAK1 Mediates Verticillium Wilt Resistance and Cell Death

Virus-induced gene silencing （VIGS） offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticfllium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line （CA4002） with partial resistance to Verticillium wilt, and GhMKK2 and Gh Ve I are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases （SERKs） with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.

Histone Lysine Methyltransferase SDG8 Is Involved in Brassinosteroid-Regulated Gene Expression in Arabidopsis thaliana

The plant steroid hormones, brassinosteroids （BRs）, play important roles in plant growth, development, and responses to environmental stresses. BRs signal through receptors localized to the plasma membrane and other signaling components to regulate the BES1/BZR1 family of transcription factors, which modulates the expression of thousands of genes. How BESl/BZR1 and their interacting proteins function to regulate the large number of genes are not com- pletely understood. Here we report that histone lysine methyltransferase SDG8, implicated in histone 3 lysine 36 diand trimethylation （H3K36me2 and me3）, is involved in BR-regulated gene expression. BES1 interacts with SDG8, directly or indirectly through IWSl, a transcription elongation factor involved in BR-regulated gene expression. The knockout mutant sdg8 displays a reduced growth phenotype with compromised BR responses. Global gene expression studies demonstrated that, while BR regulates about 5000 genes in wild-type plants, the hormone regulates fewer than 700 genes in sdg8 mutant. In addition, more than half of BR-regulated genes are differentially affected in sdg8 mutant. A Chromatin Immunoprecipitation （CHIP） experiment showed that H3K36me3 is reduced in BR-regulated genes in the sdg8 mutant. Based on these results, we propose that SDG8 plays an essential role in mediating BR-regulated gene expression. Our results thus reveal a major mechanism by which histone modifications dictate hormonal regulation of gene expression.

Coronatine promotes maize water uptake by directly binding to the aquaporin ZmPIP2;5 and enhancing its activity

Water uptake is crucial for crop growth and development and drought stress tolerance. The water channel aquaporins(AQP) play important roles in plant water uptake. Here, we discovered that a jasmonic acid analog, coronatine(COR), enhanced maize(Zea mays) root water uptake capacity under artificial water deficiency conditions. COR treatment induced the expression of the AQP gene Plasma membrane intrinsic protein 2;5(ZmPIP2;5).In vivo and in vitro experiments indicated that COR also directly acts on ZmPIP2;5 to improve water uptake in maize and Xenopus oocytes. The leaf water potential and hydraulic conductivity of roots growing under hyperosmotic conditions were higher in ZmPIP2;5-overexpression lines and lower in the zmpip2;5 knockout mutant, compared to wild-type plants. Based on a comparison between ZmPIP2;5 and other PIP2s, we predicted that COR may bind to the functional site in loop E of ZmPIP2;5. We confirmed this prediction by surface plasmon resonance technology and a microscale thermophoresis assay, and showed that deleting the binding motif greatly reduced COR binding. We identified the N241 residue as the COR-specific binding site, which may activate the channel of the AQP tetramer and increase water transport activity,which may facilitate water uptake under hyperosmotic stress.

GhKT2: a novel K^+ transporter gene in cotton(Gossypium hirsutum)

Potassium is an essential nutrient for plant growth and productivity of crops. K+transporters are important for K+uptake and transport in plants. However,information on the function of K+transporters and K+channels in cotton is limited. The KT/KUP/HAK protein family is essential for a variety of physiological processes in plants, including nutrient acquisition and regulation of development. This study, identified a K+transporter gene,Gh KT2, expressed in the roots of cotton(Gossypium hirsutum) cv. Liaomian17. The deduced transcript of Gh KT2 is highly homologous to Cluster II of KUP/HAK/KT K+transporters and is predicted to contain 11 transmembrane domains. Gh KT2 has been localized to the plasma membrane, and its transcripts were detected in roots, stems, leaves and shoot apices of cotton seedlings.Consistently, b-glucuronidase(GUS) expression driven by the Gh KT2 promoter could be detected in roots, mesophyll cells, and leaf veins in transgenic Arabidopsis. In addition,the expression of Gh KT2 was induced by low K+stress in cotton roots and p Gh KT2::GUS-transgenic Arabidopsis seedlings. The Gh KT2-overexpression Arabidopsis lines plants were larger and showed greater K+accumulation than the wild type(WT) regardless of K+concentration supplied. The net K+influx rate, measured by the noninvasive micro-test technique, in root meristem zone of Gh KT2-transgenic Arabidopsis lines was significantly greater than that of WT. Taken together, this evidence indicates that Gh KT2 may participate in K+acquisition from low or high external K+, as well as K+transport and distribution in plants.

Nano-enabled agriculture: How do nanoparticles cross barriers in plants?

Nano-enabled agriculture is a topic of intense research interest.However,our knowledge of how nanoparticles enter plants,plant cells,and organelles is still insufficient.Here,we discuss the barriers that limit the efficient delivery of nanoparticles at the whole-plant and single-cell levels.Some commonly overlooked factors,such as light conditions and surface tension of applied nano-formulations,are discussed.Knowledge gaps regarding plant cell uptake of nanoparticles,such as the effect of electrochemical gradients across organelle membranes on nanoparticle delivery,are analyzed and discussed.The importance of controlling factors such as size,charge,stability,and dispersibility when properly designing nanomaterials for plants is outlined.We mainly focus on understanding how nanoparticles travel across barriers in plants and plant cells and the major factors that limit the efficient delivery of nanoparticles,promoting a better understanding of nanoparticle–plant interactions.We also provide suggestions on the design of nanomaterials for nano-enabled agriculture.

Improvement of leaf K^(+) retention is a shared mechanism behind CeO_(2) and Mn_(3)O_(4) nanoparticles improved rapeseed salt tolerance

Salinity is a global issue limiting efficient agricultural production.Nanobiotechnology has been emerged as an effective approach to improve plant salt tolerance.However,little known is about the shared mechanisms between different nanomaterials-enabled plant salt tolerance.In this study,we found that both PNC[polyacrylic acid coated nanoceria(CeO_(2) nanoparticles)]and PMO(polyacrylic acid coated Mn_(3)O_(4) nanoparticles)nanozymes improved rapeseed salt tolerance.PNC and PMO treated rapeseed plants showed significantly fresh weight,dry weight,higher chlorophyll content,Fv/Fm,and carbon assimilation rate than control plants under salt stress.Results from confocal imaging with reactive oxygen species(ROS)fluorescent dye and histochemical staining experiments showed that the ROS over-accumulation level in PNC and PMO treated rapeseed was significantly lower than control plants under salt stress.Confocal imaging results with K+fluorescent dye showed that significantly higher cytosolic and vacu-olar K^(+) signals were observed in PNC and PMO treated rapeseed than control plants under salt stress.This is further confirmed by leaf K^(+) content data.Furthermore,we found that PNC and PMO treated rapeseed showed significantly lower cytosolic Na^(+) signals than control plants under salt stress.While,compared with significantly higher vacuolar Na^(+) signals in PNC treated plants,PMO treated rapeseed showed significantly lower vacuolar Na^(+) signals than control plants under salt stress.These results are further supported by qPCR results of genes of Na^(+) and K^(+) transport.Overall,our results suggest that besides maintaining ROS homeostasis,improvement of leaf K^(+) retention could be a shared mechanism in nano-improved plant salt tolerance.

Parasitic plant dodder(Cuscuta spp.):a new natural Agrobacterium-to-plant horizontal gene transfer species

Dear Editor,Horizontal gene transfer(HGT)has long been recognized as asexual means of DNA transfer between different species.Although HGT is common to prokaryotes,it remains uncommon in higher eukaryotic species(Beiko et al.,2005).

Analysis of differential expression of genes induced by ethephon in elongating internodes of maize plants

Plant growth regulators(PGRs) are commonly used in cereal cropping systems to restrict plant height and control lodging. Ethephon has been reported to shorten internodes and increase grain yield of maize. To analyze the transcriptomic profiles of maize internode elongation following ethephon treatment, differentially expressed genes were compared between the treatment and contro samples of inbred line Zong 31 using the Affymetrix Maize Genome Array. According to the microarray data 326 probe sets showed significant change in expression Further research revealed that the most remarkable effects of ethephon on maize internodes elongation occurred during a 48 h period, when 89 differentially expressed genes were detected. There were dramatic change in transcript levels at 24 h and six Auxin transport genes and four gibberellin biosynthesis pathway genes were differentially expressed in Zong 31 in response to ethephon treatment. In summary, we showed that gaseous ethylene release is involved in internode meristem cell elongation through the regulation of plant hormone signaling in maize. This work provides a platform for studies in which candidate genes will be functionally tested for involvement in internode elongation.

Invitation to Contribute to Frontiers of Agricultural Science and Engineering

Colleagues,It is our great pleasure to introduce you to the Frontiers of Agricultural Science and Engineering(FASE),a new international journal launched in 2014.FASE was founded jointly by the Chinese Academy of Engineering,China Agricultural University and

Invitation to Contribute to Frontiers of Agricultural Science and Engineering

Colleagues,It is our great pleasure to introduce you to the Frontiers of Agricultural Science and Engineering(FASE), a new international journal launched in 2014. FASE was founded jointly by the Chinese Academy of Engineering, China Agricultural University and Higher Education Press of China.

Invitation to Contribute to Frontiers of Agricultural Science and Engineering

Colleagues,It is our great pleasure to introduce you to the Frontiers of Agricultural Science and Engineering(FASE),a new international journal launched in 2014.FASE was founded jointly by the Chinese Academy of Engineering,China Agricultural University and

Invitation to Contribute to Frontiers of Agricultural Science and Engineering

Colleagues,It is our great pleasure to introduce you to the Frontiers of Agricultural Science and Engineering(FASE),a new international journal launched in 2014.FASE was founded jointly by the Chinese Academy of Engineering,China Agricultural University and Higher Education Press of China.