Problems, challenges and future of plant disease management: from an ecological point of view

Plant disease management faces ever-growing challenges due to： （i） increasing demands for total, safe and diverse foods to support the booming global population and its improving living standards; （ii） reducing production potential in agriculture due to competition for land in fertile areas and exhaustion of marginal arable lands; （iii） deteriorating ecology of agro-ecosystems and depletion of natural resources; and （iv） increased risk of disease epidemics resulting from agricultural intensification and monocultures. Future plant disease management should aim to strengthen food security for a stable society while simultaneously safeguarding the health of associated ecosystems and reducing dependency on natural resources. To achieve these multiple functionalities, sustainable plant disease management should place emphases on rational adaptation of resistance, avoidance, elimination and remediation strategies individually and collectively, guided by traits of specific host-pathogen associations using evolutionary ecology principles to create environmental （biotic and abiotic） conditions favorable for host growth and development while adverse to pathogen reproduction and evolution.

Triple bottom-line consideration of sustainable plant disease management:From economic,sociological and ecological perspectives

Plant disease management plays an important role in achieving the sustainable development goals of the United Nations(UN)such as food security,human health,socio-economic improvement,resource conservation and ecological resilience.However,technologies available are often limited due to different interests between producers and society and lacks of proper understanding of economic thresholds and the complex interactions among ecology,productivity and profitability.A comprehensive synergy and conflict evaluation of economic,sociological and ecological effects with technologies,productions and evolutionary principles as main components should be used to guide sustainable disease management that aims to mitigate crop and economic losses in the short term while maintaining functional farm ecosystem in the long term.Consequently,there should be an increased emphasis on technology development,public education and information exchange among governments,researchers,producers and consumers to broaden the options for disease management in the future.

Pepper mild mottle virus coat protein interacts with pepper chloroplast outer envelope membrane protein OMP24 to inhibit antiviral immunity in plants

Pepper mild mottle virus(PMMoV)is a devastating viral pathogen of pepper(Capsicum annuum)but it is unclear whether and how peppers protect against PMMoV infection.The expression of the chloroplast outer membrane protein 24(OMP24)of C.annuum was upregulated under PMMoV infection and it interacted with PMMoV coat protein(CP).Silencing of OMP24 in either C.annuum or Nicotiana benthamiana facilitated PMMoV infection,whereas overexpression of N.benthamiana OMP24 in transgenic plants inhibited PMMoV infection.Both C.annuum OMP24(CaOMP24)and N.benthamiana OMP24(NbOMP24)localized to the chloroplast and have a moderately hydrophobic transmembrane domain that is necessary for their localization.Overexpression of CaOMP24 induced stromules,perinuclear chloroplast clustering,and accumulation of reactive oxygen species(ROS),the typical defense responses of chloroplasts transferring the retrograde signaling to the nucleus to regulate resistance genes.The expression of PR1 and PR2 was also upregulated significantly in plants overexpressing OMP24.Self-interaction of OMP24 was demonstrated and was required for OMP24-mediated plant defense.Interaction with PMMoV CP interfered with the self-interaction of OMP24 and impaired OMP24-induced stromules,perinuclear chloroplast clustering and ROS accumulation.The results demonstrate the defense function of OMP24 in pepper during viral infection and suggest a possible mechanism by which PMMoV CP modulates the plant defense to facilitate viral infection.

Plant virology in the 21st century in China:Recent advances and future directions

Plant viruses are a group of intracellular pathogens that persistently threaten global food security.Significant advances in plant virology have been achieved by Chinese scientists over the last 20 years,including basic research and technologies for preventing and controlling plant viral diseases.Here,we review these milestones and advances,including the identification of new crop-infecting viruses,dissection of pathogenic mechanisms of multiple viruses,examination of multilayered interactions among viruses,their host plants,and virus-transmitting arthropod vectors,and in-depth interrogation of plantencoded resistance and susceptibility determinants.Notably,various plant virus-based vectors have also been successfully developed for gene function studies and target gene expression in plants.We also recommend future plant virology studies in China.

Molecular Characterization of Banana streak virus Isolate from Musa Acuminata in China

香蕉条纹病毒(BSV ) ，类 Badnavirus 的一个成员，是在全世界的香蕉条纹疾病的一个原因的代理人。从香蕉种植园的不同区域的 BSV 的基因差异以前被调查了，但是有相对 episomal 的基因特征的很少报告(非综合) 从中国孤立的 BSV 染色体。这里，完全的染色体， 7722bp (GenBank 就职数字 DQ092436 ) 的一个总数，一在云南的栽培变种卡文迪什(BSAcYNV ) 上的香蕉条纹病毒(BSV ) 的 isolate，中国被决定。染色体以 badnaviruses 的典型方式组织。genomic DNA 的 intergenic 区域包含一个大茎环，它可以贡献核糖体移动进下列开的读物框架(ORF ) 。BSAcYNV 的编码区域由三重叠 ORF 组成，有编码二小蛋白质的非 8 月开始 codon 和 ORF2 的 ORF1 个别地涉及病毒的运动， ORF3 编码 polyprotein。除完全的染色体以外，缺乏整个 RNA 领导人区域和 ORF1 的一个多数的一个有缺点的染色体并且它包含 6525bp 也在感染的香蕉植物从这座 BSV DNA 水库被孤立并且定序。顺序分析证明 BSAcYNV 与 BSV 以染色体组织和编码任务有最靠近的类似从越南(BSAcVNV ) 孤立。相应编码区域分别地在核苷酸和氨基酸层次分享了 88% 和 95% 的身份。种系发生的分析也显示 BSAcYNV 在定序的香蕉条纹 badnaviruses 之中分享了最近地理的进化关系到 BSAcVNV。

Genome-wide identification and analysis of the regulation wheat DnaJ family genes following wheat yellow mosaic virus infection

The co-chaperone DnaJ plays an important role in protein folding and regulation of various physiological activities, and participates in several pathological processes. DnaJ has been extensively studied in many species including humans,drosophila, mushrooms, tomatoes, and Arabidopsis. However, few studies have examined the role of DnaJ in wheat(Triticum aestivum), and the interaction mechanism between TaDnaJs and plant viruses. Here, we identified 236 TaDnaJs and performed a comprehensive genome-wide analysis of conserved domains, gene structure and protein motifs, chromosomal positions and duplication relationships, and cis-acting elements. We grouped these Ta Dna Js according to their domains, and randomly selected six genes from the groups for tissue-specific analysis, and expression profiles analysis under hormone stress, and 17 genes for plant virus infection stress. In qRT-PCR, we found that among the 17 TaDnaJ genes tested, 16 genes were up-regulated after wheat yellow mosaic virus(WYMV) infection, indicating that the TaDnaJ family is involved in plant defense response. Subsequent yeast two-hybrid assays verified the WYMV NIa, NIb and 7 KD proteins interacted with TaDJC(TraesCS7 A02 G506000), which had the most significant changes in gene expression levels after WYMV infection.Insights into the molecular mechanisms of Ta Dna J-mediated stress tolerance and sensitivity could inform different strategies designed to improve crop resistance to abiotic and biotic stress. This study provides a basis for future investigation of the TaDnaJ family and plant defense mechanisms.

Complete genome sequence and proteomic analysis of a thermophilic bacteriophage BV1

Viruses of thermophiles are of great interest due to their roles in gene transfer, global geochemical cycle and evolution of life on earth. However, the thermophilic bacteriophages have not been studied extensively. In this investigation, a typical bacteriophage BV1 was obtained from a thermophilic bacterium Geobacillus sp. 6k512, which was isolated from an inshore hot spring in Xiamen of China. The BV1 contained a double-stranded linear DNA of 35 055 bp, which encodes 54 open reading frames （ORFs）. Interestingly, eight of the 54 BV1 ORFs shared sequence similarities to genes from human disease-relevant bacteria. Seven proteins of the purified BV1 virions were identified by proteomic analysis. Determination of BV1 functional genomics would facilitate the better understanding of the mechanism for virus-thermophile interaction.

Characterization and Proteomic Analysis of Novel Rice Lesion Mimic Mutant with Enhanced Disease Resistance

Lesion mmic mutants(LMMs)are plants that spontaneously form lesions without pathogeninfection or external stimulus and exhibit resistance to pathogens.Here,a rice LMM was created by ethylmethane sulfonate mutagenesis,named as hpil(hydrogen peroxide induced lesion).Diaminobenzidineand trypan blue staining showed that large amounts of H_(2)O_(2) were produced and cell death was occurredat and around the parts of lesion mimic in the rice leaves.The phenotype of hpil is controlled by a singlerecessive gene,localized at a 2 Mb interval on chromosome 2.The data suggested that hpil is a novelLMM with enhanced bacterial and fungal disease resistance,and multiple pathogenesis-related proteins(PRs)were up-regulated.The proteomes of leaves at three positions(different degrees of lesion mimicseverity)were characterized in hpil compared with its wild type plant.Differentially expressed proteinswere detected by two dimensional difference gel electrophoresis and 274 proteins were identified byMALDITOF/TOFTM.These proteins were related to metabolic process,cellular process and response tostimulus,with mostly down-regulated in hpil leaves.Many of these proteins were related to the Calvincycle,photosynthetic electron transport chain,glycolysis/gluconeogenesis and phosphonates pathways.Some resistance-related proteins including 14-3-3 proteins,OsPR10 and antioxidases such asperoxidase,superoxide dismutase and ascorbate peroxidase were up-regulated in leaves with lesionmimic.These results provide the foundation for cloning of the target gene and shed light on themechanism involved in autaimmunity of rice.

Regulation of OsPRIOa Promoter Activity by Phytohormone and Pathogen Stimulation in Rice

OsPRIOa is one of the well known pathogenesis-related genes in rice,and is induced by multiple plant hormones and pathogens.However,the underlying transcriptional regulation mechanisms in response to differe nt signals and their crosstalks are still largely unknown.In order to find new players participated in the activation of OsPRIOa,we systematically analyzed the basal expression patterns as well as the expression responses of a 2.5 kb OsPRIOa promoter in rice transgenic plants after phytohormone and pathogen stimulations.In agreement with the native gene expression,the OsPRIOa promoter can drive glucuronidase(GUS)gene expressing in spots of leaf cells,leaf trichomes,lemmas and paleae,germinating embryos,calli and root tips.The leaf expression of OsPR10a::GUS was dramatically in creased upon jasm onic acid(JA)and cytoki nin(CK)treatme nts,or challe nges of the pathogen Magnaporthe grisea and Xanthomonas oryzae pv.oryzae.Thus,the OsPRIOa promoter reported here can faithfully reflect its native gene expression.The effects of several JA and CK responsive OsWRKY genes on the regulation of OsPRIOa promoter were then inspected by luciferase transient expression assay,and the JA inducible OsWRKYlO transcription factor was found as a new positive regulator of OsPRIOa.However,the key transcription factors of JA and CK signaling pathways,OsMYC2 and B-type response regulators,were not responsible for the activation of OsPRIOa promote Our findings provided new in sights into the regulation of OsPRIOa expression during plan t-hormone/pathoge n interactions,and the OsPRIOa reporter system can be useful to unravel novel regulators from both pathogen and host.

Expression of Rice Gall Dwarf Virus Outer Coat Protein Gene (S8) in Insect Cells

To obtain the P8 protein of Rice gall dwarf virus (RGDV) with biological activity,its outer coat protein gene S8 was expressed in Spodoptera frugiperda (Sf9) insect cells using the baculovirus expression system.The S8 gene was subcloned into the pFastBacTM1 vector,to produce the recombinant baculovirus transfer vector pFB-S8.After transformation,pFB-S8 was introduced into the competent cells (E.coli DH10Bac) containing a shuttle vector,Bacmid,generating the recombinant bacmid rbpFB-S8.After being infected by recombinant baculovirus rvpFB-S8 at different multiplicities of infection,Sf9 cells were collected at different times and analyzed by SDS-PAGE,Western blotting and immunofluorescence microscopy.The expression level of the P8 protein was highest between 48-72 h after transfection of Sf9 cells.Immunofluorescence microscopy showed that P8 protein of RGDV formed punctate structures in the cytoplasm of Sf9 cells.

Construction of chimeric viruses based on pepper mild mottle virus using a modiffed Cre/loxP system

Cre/loxP,a site-specific recombination system,has been widely used for various purposes,including chromosomal translocations,generation of marker-free transgenic plants,tissue-specific activation of a reporter gene and efficient heterologous gene expression in plants.However,stable or transient expression of Cre recombinase in plants can cause chlorosis or necrosis.Here,we describe a modified Cre/loxP recombination system using a DNA fragment flanked with loxP sites in the same orientation in which necrosis induced by Cre recombinase in Nicotiana benthamiana leaves was alleviated.The modified system was successfully used to create functional GFP-tagged pepper mild mottle virus(PMMoV)and a chimeric virus with coat protein(CP)substitution assembled from separate pro-vector modules.Our results provide a new strategy and flexible technique to construct chimeric virus and infectious clones for plant viruses with large genomes.

Rice ferredoxin OsFd4 contributes to oxidative stress tolerance but compromises defense against blight bacteria

Ferredoxins(Fds)in plastids are the most upstream stromal electron receptors shuttling electrons to downstream metabolic systems and function in various physiological processes of dicots,but their roles in monocots’response to stresses are still unclear.In this study,the functions of OsFd4,the major non-photosynthetic type Fd in rice,were characterized under oxidative stress and Xanthomonas oryzae pv.oryzae(Xoo)infection.OsFd4-knockout mutants displayed no defects in key agronomic traits and blast resistance,but were more sensitive to hydrogen peroxide(H2O2)treatment than the wild type.Transient expression of OsFd4 alleviated H2O2-induced rice cell death,suggesting that OsFd4 contributes to rice tolerance to exogenous oxidative stress.Deletion of OsFd4 enhanced rice immune responses against Xoo.OsFd4 formed a complex in vivo with itself and OsFd1,the major photosynthetic Fd in rice,and OsFd1 transcripts were increased in leaf and root tissues of the OsFd4-knockout mutants.These results indicate that OsFd4 is involved in regulating rice defense against stresses and interplays with OsFd1.

Ideal type 1 is caused by a point mutation in the a-tubulin gene that affects microtubule arrangement in soybean

Plant architecture is a target of crop improvement.The soybean mutant ideal type 1(it1)displays a pleiotropic phenotype characterized by compact plant architecture,reduced plant height,shortened petioles,wrinkled leaves,and indented seeds.Genetic analysis revealed that the pleiotropic phenotype was controlled by an incomplete dominant gene.We characterized the cellular phenotypes of it1 and positionally cloned the it1 locus.Detailed morphogenetic analysis of the it1 mutant revealed an excess of xylem cells and expanded phloem,and polygonal pavement cells.Positional cloning showed that the phenotype was caused by a G-to-A mutation in the second exon of the a-tubulin gene(Glyma.05G157300).The mutation altered microtubule arrangement in pavement cells,changing their morphology.Overexpression of Gmit1 resulted in an it1-like phenotype and polygonal pavement cells and microtubules of overexpressors were parallel or slightly inclined.Five suppressor mutants able to suppress the phenotype of it1 were obtained by EMS mutagenesis in the it1 background.All these mutants carried an additional mutation in the it1 gene.These results suggest that the pleiotropic phenotype of it1 is caused by the mutation in the atubulin gene.

Coat protein of rice stripe virus enhances autophagy activity through interaction with cytosolic glyceraldehyde-3-phosphate dehydrogenases,a negative regulator of plant autophagy

Viral infection commonly induces autophagy,leading to antiviral responses or conversely,promoting viral infection or replication.In this study,using the experimental plant Nicotiana benthamiana,we demonstrated that the rice stripe virus(RSV)coat protein(CP)enhanced autophagic activity through interaction with cytosolic glyceraldehyde-3-phosphate dehydrogenase 2(GAPC2),a negative regulator of plant autophagy that binds to an autophagy key factor,autophagy-related protein 3(ATG3).Competitive pull-down and co-immunoprecipitation(Co-IP)assays showed that RSV CP activated autophagy by disrupting the interaction between GAPC2 and ATG3.An RSV CP mutant that was unable to bind GAPC2 failed to disrupt the interaction between GAPC2 and ATG3 and therefore lost its ability to induce autophagy.RSV CP enhanced the autophagic degradation of a viral movement protein(MP)encoded by a heterologous virus,citrus leaf blotch virus(CLBV).However,the autophagic degradation of RSV-encoded MP and RNA-silencing suppressor(NS3)proteins was inhibited in the presence of CP,suggesting that RSV CP can protect MP and NS3 against autophagic degradation.Moreover,in the presence of MP,RSV CP could induce the autophagic degradation of a remorin protein(NbREM1),which negatively regulates RSV infection through the inhibition of viral cell-to-cell movement.Overall,our results suggest that RSV CP induces a selective autophagy to suppress the antiviral factors while protecting RSV-encoded viral proteins against autophagic degradation through an as-yet-unknown mechanism.This study showed that RSV CP plays dual roles in the autophagy-related interaction between plants and viruses.

甘蔗花叶病毒3’末端基因的克隆及外壳蛋白序列分析比较

选取我国SCMV优势株系A株系的分离物SCMV CA为材料 ,经过病毒和病毒RNA的提纯 ,反转录获得病毒cDNA ,并克隆到载体 pUC19的SmaI位点上 ,筛选得到多个重组质粒。选取其中一个克隆SCMV CA5 4进行测序 ,得到一个全长为 12 96bp的核苷酸序列。这段序列由一个长为 10 44bp的开放阅读框架 (ORF)和一个长 2 79bp的 3’末端非编码区序列 ( 3’ UTR)及 poly(A)尾巴组成。这个ORF包括病毒完整的外壳蛋白 (CP)及部分核内含体蛋白b(NIb)基因序列。将所得序列同已知SCMV亚组中各株系分离物的核苷酸和氨基酸进行同源性比较 ,结果表明该序列与其它株系分离物CP核苷酸序列的同源性介于 6 3.7%～ 77.6 %之间 ,氨基酸的同源性介于 6 4%～ 89%之间。根据马铃薯Y病毒属的序列同源性划分标准 ,SCMV CA与其它株系或分离物的同源性关系均介于种与株系划分标准之间。

Coat protein of Chinese wheat mosaic virus upregulates and interacts with cytosolic glyceraldehyde-3-phosphate dehydrogenase,a negative regulator of plant autophagy,to promote virus infection

Autophagy is an intracellular degradation mechanism involved in antiviral defense,but the strategies employed by plant viruses to counteract autophagy-related defense remain unknown for the majority of the viruses.Herein,we describe how the Chinese wheat mosaic virus(CWMV,genus Furovirus)interferes with autophagy and enhances its infection in Nicotiana benthamiana.Yeast two-hybrid screening and in vivo/in vitro assays revealed that the 19 k Da coat protein(CP19 K)of CWMV interacts with cytosolic glyceraldehyde-3-phosphate dehydrogenases(GAPCs),negative regulators of autophagy,which bind autophagy-related protein 3(ATG3),a key factor in autophagy.CP19 K also directly interacts with ATG3,possibly leading to the formation of a CP19 K–GAPC–ATG3 complex.CP19 K–GAPC interaction appeared to intensify CP19 K–ATG3 binding.Moreover,CP19 K expression upregulated GAPC gene transcripts and reduced autophagic activities.Accordingly,the silencing of GAPC genes in transgenic N.benthamiana reduced CWMV accumulation,whereas CP19 K overexpression enhanced it.Overall,our results suggest that CWMV CP19 K interferes with autophagy through the promotion and utilization of the GAPC role as a negative regulator of autophagy.

Three-dimensional reconstruction of pore canals in the cuticle of the brown planthopper

Dear Editor,The insect cuticle is a multifunctional coat that defines and stabilizes the shape of the body,appendages and internal organs,serves as a barrier against water and chemical compounds,such as insecticides,prevents infection and protects against predators(Moussian,2010).The surface of insects is covered by a lipid layer composed of diverse hydrocarbons,wax esters,fatty acids,fatty alcohols,sterols and triglycerides.Delivery of lipids to the body surface occurs through the cuticle by a nano-canal system consisting of pore canals(PC)and wax canals(WC).

The marksman: Bioactivated nematicides selectively kill plant-parasitic nematodes

Plant-parasitic nematodes(PPNs) are destructive pathogens that cause great damage to crops and severely limit food production, hindering our ability to meet the growing worldwide demand for food(Topalovi? and Vesterg?rd,2021). The global crop losses caused by PPNs are estimated to be about 8.8%–14.6% of total crop production and 100–157 billion USD annually(Singh et al., 2013).

Microplastics affect activity and spatial distribution of C,N, and P hydrolases in rice rhizosphere

Microplastics provide a new ecological niche for microorganisms,and the accumulation levels of microplastics(MPs)in terrestrial ecosystems are higher than those in marine ecosystems.Here,we applied the zymography to investigate how MPs–polyethylene[PE],and polyvinyl chloride[PVC])at two levels(0.01%and 1%soil weight)impacted the spatial distribution of soil hydrolases,nutrient availability,and rice growth in paddy soil.MPs increased the above-ground biomass by 13.0%–15.5%and decreased the below-ground biomass by 8.0%–15.1%.Addition of 0.01%and 1%MPs reduced soil NH4+content by 18.3%–63.2%and 52.2%–80.2%,respectively.The average activities of N-and P-hydrolases increased by 0.8%–4.8%and 1.9%–6.3%with addition of MPs,respectively.The nutrient uptake by rice plants and the enzyme activities in hotspots increased with MP content in soil.The accumulation of MPs in paddy soil could provide an ecological niche that facilitates microbial survival,alters the spatial distribution of soil hydrolases,and decreases nutrient availability.

Distribution of microplastics in soil aggregates after film mulching

Microplastic distribution is non-homogeneous in agricultural soil following plastic film degradation.However,the distribution of microplastics by shape and particle size in different soil aggregates remains unknown.To elucidate the distribution of microplastic shapes and particle sizes in soil aggregates with increasing years of film mulching,four paired fields with film mulching(FM)and no mulching(NM)were examined at 1,5,10,and 20 years after continuous mulching.An increase in soil aggregates of 0.053–0.25 mm diameter was observed;however,soil organic carbon content decreased after long-term FM.Microplastics primarily combined with 0.053–2 mm soil aggregates.Specifically,long-term FM was associated with dominance of film-and fiber-shaped microplastics in soil aggregates of 0.25–2 mm and 0.053–0.25 mm diameter,respectively.Fiber-and granule-shaped microplastics of 0.25–1 mm diameter primarily combined with 0.053–0.25 and 0.25–2 mm soil aggregates,respectively.Film-shaped microplastics of diameter>1 mm and diameter 0.05–0.25 mm primarily combined with 0.25–2 mm soil aggregates.Therefore,distribution of microplastics in soil aggregates can be used to monitor soil health and quality,greatly enhancing our understanding of the risk posed by microplastics to the environment.