Large-scale interplant exchange of macromolecules between soybean and dodder under nutrient stresses

Parasitic plants and their hosts communicate through haustorial connections.Nutrient deficiency is a common stress for plants,yet little is known about whether and how host plants and parasites communicate during adaptation to such nutrient stresses.In this study,we used transcriptomics and proteomics to analyze how soybean(Glycine max)and its parasitizing dodder(Cuscuta australis)respond to nitrate and phosphate deficiency(-N and-P).After-N and-P treatment,the soybean and dodder plants exhibited substantial changes of transcriptome and proteome,although soybean plants showed very few transcriptional responses to-P and dodder did not show any transcriptional changes to either-N or-P.Importantly,large-scale interplant transport of mRNAs and proteins was detected.Although the mobile mRNAs only comprised at most 0.2%of the transcriptomes,the foreign mobile proteins could reach 6.8%of the total proteins,suggesting that proteins may be the major forms of interplant communications.Furthermore,the interplant mobility of macromolecules was specifically affected by the nutrient regimes and the transport of these macromolecules was very likely independently regulated.This study provides new insight into the communication between host plants and parasites under stress conditions.

ABI5 promotes heat stress-induced chlorophyll degradation by modulating the stability of MYB44 in cucumber

The yellowing of leaves caused by the decomposition of chlorophyll(Chl)is a characteristic event during senescence,which can be induced by various environmental stresses.However,the molecular mechanisms of high temperature-induced Chl degradation in horticultural plants remain poorly understood.Here,we found that heat stress induced Chl degradation and the expression of ABI5 and MYB44 in cucumber.Silencing of ABI5 compromised heat stress-induced Chl degradation,and the transcription of pheophytinase(PPH)and pheophorbide a oxygenase(PAO),two key genes in Chl catabolic pathway,but silencing of MYB44 exhibited the opposite results.Furthermore,ABI5 interacted with MYB44 in vitro and in vivo.ABI5 positively regulated heat stress-induced Chl degradation through two pathways.ABI5 directly bound to PPH and PAO promoters to promote their expression,leading to accelerating Chl degradation.On the other hand,the interaction between ABI5 and MYB44 reduced the binding of MYB44 to PPH and PAO promoters and led to the ubiquitination-depended protein degradation of MYB44,thereby alleviating the transcription inhibitory effect of MYB44 on PPH and PAO.Taken together,our findings propose a new regulatory network for ABI5 in regulating heat stress-induced Chl degradation.

Current understanding of maize and rice defense against insect herbivores

Plants have sophisticated defense systems to fend off insect herbivores. How plants defend against herbivores in dicotyledonous plants, such as Arabidopsis and tobacco, have been relatively well studied,yet little is known about the defense responses in monocotyledons. Here, we review the current understanding of rice(Oryza sativa) and maize(Zea mays) defense against insects. In rice and maize,elicitors derived from insect herbivore oral secretions or oviposition fluids activate phytohormone signaling, and transcriptomic changes mediated mainly by transcription factors lead to accumulation of defense-related secondary metabolites. Direct defenses, such as trypsin protein inhibitors in rice and benzoxazinoids in maize, have anti-digestive or toxic effects on insect herbivores. Herbivory-induced plant volatiles, such as terpenes, are indirect defenses, which attract the natural enemies of herbivores. R gene-mediated defenses against herbivores are also discussed.

Silencing JA hydroxylases in Nicotiana attenuata enhances jasmonic acid-isoleucine-mediated defenses against Spodoptera litura

Jasmonic acid(JA)plays important roles in plant resistance to insect herbivores.One important derivative of JA is 12-OH-JA,which is produced by two independent pathways:direct hydroxylation of JA by jasmonate-induced oxygenases(JOXs)or hydrolyzation of 12-OH-JA-Ile.Yet the function of 12-OH-JA in plant-herbivore interactions remains largely unknown.In this study,we silenced four JOX homologs independently in the wild tobacco Nicotiana attenuata by virus-induced gene silencing(VIGS),and found that all four JOX homologs are involved in JA hydroxylation.Simultaneously silencing the four JA hydroxylases in VIGS-NaJOXs plants decreased herbivory-induced 12-OH-JA by 33%,but JA and JA-Ile levels increased by 45%and 30%,respectively,compared to those in control plants.Compared to direct hydroxylation from JA,hydrolyzation from 12-OH-JA-Ile is equally important for herbivory-induced 12-OHJA accumulation:in the 12-OH-JA-Ile deficient irJAR4/6 plants,12-OH-JA decreased 34%.Moreover,VIGSNaJOXs plants exhibited enhanced resistance to the generalist herbivore Spodoptera litura.The poor larval performance was strongly correlated with high levels of several JA-Ile-dependent direct defense metabolites in the VIGS-NaJOXs plants.When we simultaneously silenced all four JA hydroxylases in the JAIle-deficient irJAR4/6 background,the enhanced herbivore resistance diminished,demonstrating that enhanced herbivore resistance resulted from elevated JA-Ile levels.Given that silencing these NaJOX-like genes did not detectably alter plant growth but highly increased plant defense levels,we propose that JOX genes are potential targets for genetic improvement of herbivore-resistant crops.

Inter-species mRNA transfer among green peach aphids,dodder parasites,and cucumber host plants

mRNAs are transported within a plant through phloem.Aphids are phloem feeders and dodders(Cuscuta spp.)are parasites which establish phloem connections with host plants.When aphids feed on dodders,whether there is trafficking of mRNAs among aphids,dodders,and host plants and if aphid feeding a匚fects the mRNA transfer between dodders and hosts are unclear.We constructed a green peach aphid(GPA,Myzus persicae)-dodder(Cuscuta austra/is)-cucumber(Cucumis sativus)tritrophic system by infesting GPAs on C.australis,which parasitized cucumber hosts.We found that GPA feeding activated defense-related phytohormonal and transcriptomic responses in both C.australis and cucumbers and large numbers of mRNAs were found to be transferred between C.australis and cucumbers and between C.australis and GPAs;importantly,GPA feeding on C.australis greatly altered inter-species mobile mRNA profiles.Furthermore,three cucumber mRNAs and three GPA mRNAs could be respectively detected in GPAs and cucumbers.Moreover,our statistical analysis indicated that mRNAs with high abundances and long transcript lengths are likely to be mobile.This study reveals the existence of inter-species and even inter-kingdom mRNA movement among insects,parasitic plants,and parasite hosts,and suggests complex regulation of mRNA trafficking.

The key cyclic electron flow protein PGR5 associates with cytochrome b_(6)f, and its function is partially influenced by the LHCⅡ state transition

In plants and algae,PGR5-dependent cyclic electron flow(CEF)is an important regulator of acclimation to fluctuating environments,but how PGR5 participates in CEF is unclear.In this work,we analyzed two PGR5s in cucumber(Cucumis sativus L.)under different conditions and found that CsPGR5a played the dominant role in PGR5-dependent CEF.The results of yeast two-hybrid,biomolecular fluorescence complementation(BiFC),blue native PAGE,and coimmunoprecipitation(CoIP)assays showed that PGR5a interacted with PetC,Lhcb3,and PsaH.Furthermore,the intensity of the interactions was dynamic during state transitions,and the abundance of PGR5 attached to cyt b_(6)f decreased during the transition from state 1 to state 2,which revealed that the function of PGR5a is related to the state transition.We proposed that PGR5 is a small mobile protein that functions when attached to protein complexes.

QTL Analysis of Cold-tolerance at Seedling Stage in Rice

To provided the experimental materials for identifying and cloning the quantitative trait loci （QTLs） of cold tolerance at the seedling stage, the authors analyzed QTLs and evaluated the genetic effects of two parents and a mapping population of 213 lines （recombination inbred lines, RILs） derived from a cross between IR24 and Asominori for cold tolerance at the seedling stage with dead seedling rate by using software QTL IciMapping 4.0, based on a genetic linkage map constructed with 141 SSR molecular markers. The QTLs qCTS -6, qCTS -1 1 and qCTS -1 2 related to cold tolerance at the seedling stage were detected on chromosome 6, 11 and 12, respectively. Individual QTLs （LOD-3.194 3, LOD： 4.688 2, LOD-3.797 0） explained 5.662 7%, 8.549 6% and 12.787 7% of the observed phenotypic variance, respectively. All of the three detected QTLs alleles came from cold-tolerant parent Asominori.

Mapping of QTLs Controlling Panicle Length and Effective Panicle Number of Rice

Panicle length and effective panicle number of rice are closely related to yield. In this experiment, indica V20B as female parent was crossed with javanica CPSLO17 as male parent, recombinant inbred line （RIL） populations were obtained by single seed descent method, and with the RIL populations as mapping populations, QTL mapping and analysis were performed to the two panicle traits, panicle length and effective panicle. A high-density genetic map was constructed with SLAF labels, interval mapping was performed by software Map QTL5 under the threshold of 3.9, and 7 QTLs were detected on 3 chromosomes in total. Among the 7 QTLs, 5 QTLs controlling panicle length （qPLI-1, qPL1-2, qPL6-1, qPI_6-2 and qPL6-3） were located on chromosomes 1 and 6, respectively, and showed the contribution rates of 6.41%, 22.22%, 6.15%, 12.24% and 13.01%, respectively, their effect-increasing loci were mainly from CPSLO17, and qPL1-1 is a new QTL; and 2 QTLs controlling effective panicle number （qPN1 and qPN4） were located on chromosomes 1 and 4, respectively, and exhibited the contribution rates of 13.15% and 8.18%, respectively, and the effect-increasing loci were from parent V2OB. The marking of these loci lays a foundation for further cloning of genes controlling panicle length and effective panicle number and molecular marker-assisted selection.

Assessment of Soil Quality of Tidal Marshes in Shanghai City

We take three types of tidal marshes in Shanghai City as the study object:tidal marshes in mainland,tidal marshes in the rim of islands,and shoal in Yangtze estuary.On the basis of assessing nutrient quality and environmental quality,respectively,we use soil quality index(SQI)to assess the soil quality of tidal flats,meanwhile formulate the quality grading standards,and analyze the current situation and characteristics of it.The results show that except the north of Hangzhou Bay,Nanhui and Jiuduansha with low soil nutrient quality,there are not obvious differences in soil nutrient quality between other regions;the heavy metal pollution of tidal marshes in mainland is more serious than that of tidal marshes in the rim of islands;in terms of the comprehensive soil quality index,the regions are sequenced as follows:Jiuduansha wetland>Chongming Dongtan wetland>Nanhui tidal flat>tidal flat on the periphery of Chongming Island>tidal flat on the periphery of Hengsha Island>Pudong tidal flat>Baoshan tidal flat>tidal flat on the periphery of Changxing Island>tidal flat in the north of Hangzhou Bay.Among them,Jiuduansha wetland and Chongming Dongtan wetland have the best soil quality,belonging to class III,followed by Nanhui tidal flat,tidal flat on the periphery of Chongming Island and tidal flat on the periphery of Hengsha Island,belonging to class IV;tidal flat on the periphery of Changxing Island,Pudong tidal flat,Baoshan tidal flat and tidal flat in the north of Hangzhou Bay belong to class V.

QTL Mapping of Grain Weight Trait in Rice

To provide new experimental materials for QTL analysis of rice yield trait, we constructed a mapping population of 150 1ines （recombination inbred lines, R1L） derived from a cross between rice varieties V20B and CPSLO17, and localized QTLs and evaluated the genetic effects in the two parents and 150 RILs for thousand-grain weight trait by using internal mapping method of software MapQTL5 combining thousand-grain weight phenotypic data of the RILs. The results showed that a new QTL （qTGW-3） related to thousand-grain weight trait was detected. Individual QTL （LOD=4.14） explained 11.9% of the observed phenotypic variance. And the QTL alleles came from the parent V20B.

An acyltransferase gene that putatively functions in anthocyanin modification was horizontally transferred from Fabaceae into the genus Cuscuta

Horizontal gene transfer(HGT) refers to the flow of genetic materials to non-offspring,and occasionally HGT in plants can improve the adaptation of organisms in new niches due to expanded metabolic capability.Anthocyanins are an important group of water-soluble red,purple,or blue secondary metabolites,whose diversity results from modification after the main skeleton biosynthesis.Cuscuta is a stem holoparasitic genus,whose members form direct connection with hosts to withdraw water,nutrients,and macromolecules.Such intimate association is thought to increase the frequency of HGT.By transcriptome screening for foreign genes in Cuscuta australis,we discovered that one gene encoding a putative anthocyanin acyltransferase gene of the BAHD family,which is likely to be involved in anthocyanin modification,was acquired by C.australis from Fabaceae through HGT.The anthocyanin acyltransferase-like(AT-like) gene was confirmed to be present in the genome assembly of C.australis and the transcriptomes of Cuscuta pentagona.The higher transcriptional level in old stems is consistent with its putative function in secondary metabolism by stabilizing anthocyanin at neutral pH and thus HGT of this AT-like gene may have improved biotic and abiotic resistance of Cuscuta.

ZmMYC2s play important roles in maize responses to simulated herbivory and jasmonate

Both herbivory and jasmonic acid(JA)activate the biosynthesis of defensive metabolites in maize,but the mechanism underlying this remains unclear.We generated maize mutants in which ZmMYC2a and ZmMYC2b,two transcription factor genes important in JA signaling,were individually or both knocked out.Genetic and biochemical analyses were used to elucidate the functions of ZmMYC2 proteins in the maize response to simulated herbivory and JA.Compared with the wild-type(WT)maize,the double mutant myc2ab was highly susceptible to insects,and the levels of benzoxazinoids and volatile terpenes,and the levels of their biosynthesis gene transcripts,were much lower in the mutants than in the WT maize after simulated insect feeding or JA treatment.Moreover,ZmMYC2a and ZmMYC2b played a redundant role in maize resistance to insects and JA signaling.Transcriptome and Cleavage Under Targets and TagmentationSequencing(CUT&Tag-Seq)analysis indicated that ZmMYC2s physically targeted 60%of the JAresponsive genes,even though only 33%of these genes were transcriptionally ZmMYC2-dependent.Importantly,CUT&Tag-Seq and dual luciferase assays revealed that ZmMYC2s transactivate the benzoxazinoid and volatile terpene biosynthesis genes IGPS1/3,BX10/11/12/14,and TPS10/2/3/4/5/8 by directly binding to their promoters.Furthermore,several transcription factors physically targeted by ZmMYC2s were identified,and these are likely to function in the regulation of benzoxazinoid biosynthesis.This work reveals the transcriptional regulatory landscapes of both JA signaling and ZmMYC2s in maize and provides comprehensive mechanistic insight into how JA signaling modulates defenses in maize responses to herbivory through ZmMYC2s.

MAPK signaling： A key element in plant defense response to insects

Insects have long been the most abundant herbivores, and plants have evolved sophisticated mechanisms to defend against their attack, In particular, plants can perceive specific patterns of tissue damage associated with insect herbivory. Some plant species can perceive certain elicitors in insect oral secretions （OS） that enter wounds during feeding, and rapidly activate a series of intertwined signaling pathways to orchestrate the biosynthesis of various defensive metabolites. Mitogen-activated protein kinases （MAPKs）, common to all eukaryotes, are involved in the orchestration of many cellular processes, including development and stress responses. In plants, at least two MAPKs, salicylic acid-induced protein kinase （SIPK） and wound-induced protein kinase （WlPK）, are rapidly activated by wounding or insect 0S; importantly, genetic studies us- ing transgenic or mutant plants impaired in MAPK signaling indicated that MAPKs play critical roles in regulating the herbivory-induced dynamics of phytohormones, such as jasmonic acid, ethylene and salicylic acid, and MAPKs are also required for transcriptional activation of herbivore defense-related genes and accumulation of defensive metabolites. In this review, we summarize recent developments in understanding the functions of MAPKs in plant resistance to insect herbivores.

The Essential Role of Jasmonic Acid in Plant-Herbivore Interactions-Using the Wild Tobacco Nicotiana attenuata as a Model

The plant hormone jasmonic acid （JA） plays a central role in plant defense against herbivores. Herbivore damage elicits a rapid and transient JA burst in the wounded leaves and JA functions as a signal to mediate the accumulation of various secondary metabolites that confer resistance to herbivores. Nicotiana attenuata is a wild tobacco species that inhabits western North America. More than fifteen years of study and its unique interaction with the specialist herbivore insect Manduca sexta have made this plant one of the best models for studying plant-herbivore interactions. Here we review the recent progress in understanding the elicitation of JA accumulation by herbivore-specific elicitors, the regulation of JA biosynthesis, JA signaling, and the herbivore-defense traits in N. attenuata.

MYC2, MYC3, and MYC4 function additively in wounding-induced jasmonic acid biosynthesis and catabolism

Jasmonic acid(JA)plays a critical role in plant defenses against insects and necrotrophic fungi.Wounding or lepidopteran insect feeding rapidly induces a burst of JA in plants,which usually reaches peak values within 1 to 2 h.The induced JA is converted to JA-Ile and perceived by the COI1-JAZ co-receptor,leading to activation of the transcription factors MYC2 and its homologs,which further induce JA-responsive genes.Although much is known about JA biosynthesis and catabolism enzymes and JA signaling,how JA biosynthesis and catabolism are regulated remain unclear.Here,we show that in Arabidopsis thaliana MYC2 functions additively with MYC3 and MYC4 to regulate wounding-induced JA accumulation by directly binding to the promoters of genes function in JA biosynthesis and catabolism to promote their transcription.MYC2 also controls the transcription of JAV1 and JAM1,which are key factors controlling JA biosynthesis and catabolism,respectively.In addition,we also found that MYC2 could bind to the MYC2 promoter and self-inhibit its own expression.This work illustrates the central role of MYC2/3/4 in controlling wounding-induced JA accumulation by regulating the transcription of genes involved in JA biosynthesis and catabolism.

Extensive Inter-plant Protein Transfer between Cuscuta Parasites and Their Host Plants

Cuscuta species(dodders)are holoparasites that totally rely on host plants to survive.Although various mobile proteins have been identified to travel within a plant,whether and to what extent protein transfer between Cuscuta and host plants remain unclear.We found that hundreds to more than 1500 proteins were transferred between Cuscuta and the host plants Arabidopsis and soybean,and hundreds of interplant mobile proteins were even detected in the seeds of Cuscuta and the host soybean.Different hosts bridge-connected by dodder were also found to exchange hundreds of proteins.Quantitatively,the mobile proteins represent a few to more than 10%of the proteomes of foreign plants.Using Arabidopsis plants expressing different reporter proteins,we further showed that these reporter proteins could travel between plants and,importantly,retained their activity in the foreign plants.Comparative analysis between the interplant mobile proteins and mRNAs indicated that the majority of mobile proteins were not de novo synthesized from the translocated mRNAs,but bona fide mobile proteins.We propose that large-scale inter-plant protein translocation may play an important role in the interactions between host plants and dodder and even among the dodder bridge-connected hosts.

Silencing Brassinosteroid Receptor BRI1 Impairs Herbivory-elicited Accumulation of Jasmonic Acid-isoleucine and Diterpene Glycosides, but not Jasmonic Acid and Trypsin Proteinase Inhibitors in Nicotiana attenuata

The brassinosteroid （BR） receptor, BR insensitive 1 （BRI1）, plays a critical role in plant development, but whether BRI1-mediated BR signaling is involved in plant defense responses to herbivores was largely unknown. Here, we examined the function of BRI1 in the resistance of Nicotiana attenuata （Solanaceae） to its specialist insect herbivore Manduca sexta. Jasmonic acid （JA） and JA-isoleucine conjugate （JA-Ile） are important hormones that mediate resistance to herbivores and we found that after wounding or simulated herbivory NaBRI1 had little effect on JA levels, but was important for the induction of JA-Ile. Further experiments revealed that decreased JAR （the enzyme for JA-Ile production） activity and availability of Ile in NaBRI1-silenced plants were likely responsible for the low JA-Ile levels. Consistently, M. sexta larvae gained more weight on NaBRI1-silenced plants than on the control plants. Quantification of insect feeding-induced secondary metabolites revealed that silencing NaBRI1 resulted in decreased levels of carbon-rich defensive secondary metabolites （hydroxygeranyllinalool diterpene glycosides, chlorogenic acid, and rutin）, but had little effect on the nitrogen-rich ones （nicotine and trypsin proteinase inhibitors）. Thus, NaBRI1-mediated BR signaling is likely involved in plant defense responses to M. sexta, including maintaining JA-Ile levels and the accumulation of several carbon-rich defensive secondary metabolites.

Arabidopsis Plants Having Defects in Nonsense-mediated mRNA Decay Factors UPF1, UPF2, and UPF3 Show Photoperiod-dependent Phenotypes in Development and Stress Responses

Nonsense-mediated mRNA decay （NMD） is an important mRNA quality surveillance pathway in all eukaryotes that eliminates aberrant mRNAs derived from various sources. Three NMD factor proteins, UPF1, UPF2, and UPF3 are required for the NMD process and were found to be also involved in certain stress responses in mammalian and yeast cells. Using Arabidopsis thaliana mutants of UPF1 and UPF3 and UPF2-silenced lines （irUPF2）, we examined the involvement of UPF1, UPF2, and UPF3 in development and in response to stresses, wounding and infection by Pseudomonas syringae pv. tomato strain DC3000. Under the long （16 h） photoperiod condition, Arabidopsis having a defect in NMD factors exhibited altered morphologies of various organs, disturbed homeostasis of wounding-induced jasmonic acid and pathogen-elicited salicylic acid, and abnormal wounding- and methyl jasmonate-induced changes in the transcript levels of two defense-related genes, LOX2 and VSP2. Importantly, when plants were cultivated under the short （10 h） photoperiod condition, mutants of UPF1 and UPF3 and irUPF2 showed smaller differences from the wild-type plants in growth and stress-induced responses. These data suggest a complex regulatory network, likely composed of light signaling and NMD factor-mediated pathways, in influencing plant development and adaption to environmental stresses.

Elevated CO2 differentially affects tobacco and rice defense against lepidopteran larvae via the jasmonic acid signaling pathway

Atmospheric CO2 levels are rapidly increasing due to human activities. However, the effects of elevated CO2 （ECO2） on plant defense against insects and the underlying mechanisms remain poorly understood. Here we show that ECO2 increased the photosynthetic rates and the biomass of tobacco and rice plants, and the chewing lepidopteran insects Spodoptera litura and Mythimna separata gained less and more mass on tobacco and rice plants, respectively. Consistently, under ECO2, the levels of jasmonic acid （JA）, the main phytohormone controlling plant defense against these lepidopteran insects, as well as the main defense-related metabolites, were increased and decreased in insectdamaged tobacco and rice plants. Importantly, bioassays and quantification of defense-related metabolites in tobacco and rice silenced in JA biosynthesis and perception indicate that ECO2 changes plant resistance mainly by affecting the JA pathway. We further demonstrate that the defensive metabolites, but not total N or protein, are the main factors contributing to the altered defense levels under ECO2. This study illustrates that ECO2 changes the interplay between plants and insects, and we propose that crops should be studied for their resistance to the major pests under ECO2 to predict the impact of ECO2 on future agroecosystems.

Bacterial community response to petroleum contamination in brackish tidal marsh sediments in the Yangtze River Estuary, China

The brackish tidal marsh in the Baimaosha area of the Yangtze River Estuary was severely contaminated by 400 tons of heavy crude petroleum from a tanker that sank in December 2012.The spill accident led to severe environmental damage owing to its high toxicity,persistence and wide distribution.Microbial communities play vital roles in petroleum degradation in marsh sediments.Therefore,taxonomic analysis,high-throughput sequencing and 16 S rRNA functional prediction were used to analyze the structure and function of microbial communities among uncontaminated(CK),lightly polluted(LP),heavily polluted(HP),and treated(TD)sediments.The bacterial communities responded with increased richness and decreased diversity when exposed to petroleum contamination.The dominant class changed from Deltaproteobacteria to Gammaproteobacteria after petroleum contamination.The phylum Firmicutes increased dramatically in oil-enriched sediment by 75.78%,346.19%and 267.26%in LP,HP and TD,respectively.One of the suspected oil-degrading genera,Dechloromonas,increased the most in oil-contaminated sediment,by 540.54%,711.27%and 656.78%in LP,HP and TD,respectively.Spore protease,quinate dehydrogenase(quinone)and glutathione-independent formaldehyde dehydrogenase,three types of identified enzymes,increased enormously with the increasing petroleum concentration.In conclusion,petroleum contamination altered the community composition and microorganism structure,and promoted some bacteria to produce the corresponding degrading enzymes.Additionally,the suspected petroleum-degrading genera should be considered when restoring oil-contaminated sediment.