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.

XIV International Symposium on Iron Nutrition and Interactions in Plants

The ＂XIV International Symposium on Iron Nutrition and Interactions in Plants＂ （14th ISINIP） will be held in Beijing, China, on 11-15 October 2008. It will be held together with the Annual Meeting of HarvestPlus-China. The joint symposium will provide opportunities to scientists from soil sciences, plant nutrition, plant breeding, animal and human nutrition around the world to communicate their new results and experiences in studying iron nutrition of plants, animal and human for a better understanding of the mechanisms of iron from soils, over plants to animals and human beings. The scientific topics of the symposium are as follows：

Ethnobotanical inventory and medicinal uses of some important woody plant species of Kotli,Azad Kashmir,Pakistan

Objective:To document ethnobotanical informations of useful woody plant species in the region of Kotli,Azad Kashmir.Methods:An ethnobotanical survey was conducted in Kotli.Data were collected by interview and semi structured questionnaire from selected local informants and traditional practitioners as well as by field assessment.Results:The present study documented the etnobotanical uses of 33 woody plant species.Most of the species have been used for dual purpose.Only 5 species are used for one purpose.Study revealed all species have medicinal value,among which 21 were used as fuel wood species,16 as fodder species,4 as timber wood species,12 as edible fruit species,6 as fence or hedge plant,7 as ornamental species and 12 species had other uses.Conclusions:Medicinal plants are still widely used for health care by locals of Kotli.Some species of woodlands seem to be vulnerable to overcollection and deforestation.As the young generation is diverted toward allelopathic medicines,ethnobotanical knowledges of important medicinal plants are restricted to the old people only.It is suggested to close the forest of district Kotli for next two to three decades for the conservation of plant biodiversity.

Annual-perennial plant relationships and species selection for desert restoration

Exotic plant invasion is a growing concern in the conservation and management of indigenous arid land ecosystems. By creating areas of ameliorated microclimates and fertile soil below their canopies, perennial plants might influence exotic annual plant invasions. We conducted a quantitative literature review of studies that compared exotic annual plant abundance among native perennial plant species and interspace （open areas） microsites in North America＇s Mojave Desert, where exotic plant invasion has corresponded with increasing extent of wildfire and broad-scale ecosystem transformation. Ten studies compared exotic annual plant abundance between inter- spaces and below a total of 36 native perennial species. These studies revealed that： （1） With few exceptions, most native perennial species supported a greater abundance of exotic annuals than interspaces, indicating overall facilitation of exotic species by native perennials. （2） Exotic species abundance varied by orders of magnitude among native perennial species, with some perennial species harboring amounts of exotics similar to interspaces. （3） Distributions of dominant exotic species varied, where Bromus rubens displayed a greater affinity for below-perennial microsites than did Schismus spp. and Erodium cicutarium that often were most abundant in interspaces. Results suggest that the degree of facilitation of exotic plants warrants consideration when selecting native perennial species for revegetation and restoration projects.

Response of nitrogen fractions in the rhizosphere and bulk soil to organic mulching in an urban forest plantation

Nitrogen is an essential component in forest ecosystem nutrient cycling.Nitrogen fractions,such as dissolved nitrogen,ammonium,nitrate,and microbial biomass nitrogen,are sensitive indicators of soil nitrogen pools which affect soil fertility and nutrient cycling.However,the responses of nitrogen fractions in forest soils to organic mulching are less well understood.The rhizosphere is an important micro-region that must be considered to better understand element cycling between plants and the soil.A field investigation was carried out on the effect of mulching soil in a 15-year-old Ligustrum lucidum urban plantation.Changes in total nitrogen and nitrogen fractions in rhizosphere and bulk soil in the topsoil(upper 20 cm)and in the subsoil(20-40 cm)were evaluated following different levels of mulching,in addition to nitrogen contents in fine roots,leaves,and organic mulch.The relationships between nitrogen fractions and other measured variables were analysed.Organic mulching had no significant effect on most nitrogen fractions except for the rhizosphere microbial biomass nitrogen(MBN),and the thinnest(5 cm)mulching layer showed greater effects than other treatments.Rhizosphere MBN was more sensitive to mulching compared to bulk soil,and was more affected by soil environmental changes.Season and soil depth had more pronounced effects on nitrogen fractions than mulching.Total nitrogen and dissolved nitrogen were correlated to soil phosphorus,whereas other nitrogen fractions were strongly affected by soil physical properties(temperature,water content,bulk density).Mulching also decreased leaf nitrogen content,which was more related to soil nitrogen fractions(except for MBN)than nitrogen contents in either fine roots or organic mulch.Frequent applications of small quantities of organic mulch contribute to nitrogen transformation and utilization in urban forests.

Comparative Analysis of Various Strains of Plant Growth Promoting Rhizobacteria on the Physiology of Garlic (Allium sativum)

Garlic is a most important medicinal herb belonging to the family Liliaceae. Both its leaves and bulb are edible. The current study was based on evaluating the growth promoting potential of plant growth promoting rhizobacteria (PGPR) on garlic (Allium sativum L.) growth and biochemical contents. Garlic cloves were inoculated with 3 kinds of PGPRs, Pseudomonas putida (KX574857), Pseudomonas stutzeri (Kx574858) and Bacillus cereus (ATCC14579) at 108 cells/mL prior to sowing. Under natural conditions, plants were grown in the net house. The PGPR significantly enhanced % germination, leaf and root growth and their biomass also increased the diameter of bulb and fresh and dry weight. The flavonoids, phenolics, chlorophyll, protein and sugar content were also significantly increased due to PGPR inoculation. The Pseudomonas stutzeri was found most effective for producing longer leaves with moderate sugar, high flavonoids (129%) and phenolics (263%) in bulb over control (Tap). The Pseudomonas putida exhibited a maximum increase in bulb diameter and bulb biomass with maximum phenolics and flavonoid contents.

Advances on the Molecular Mechanism of the Interaction between Ralstonia solanacearum and Hosts

Ralstonia solanacearum is an important model phytopathogenic bacterium that causes bacterial wilt disease on many plant species and leads to serious economic losses. The interactions between R. solanacearum and host plants have become a model system for the study of plants and pathogens interactions. This paper reviews the advances on the molecular mechanisms between R. solanacearum and hosts interaction including the formation of plant innate immunity, the suppression of plant innate immunity by this pathogen and the activation of effector-triggered immunity. Furthermore, we made a prospect on how to utilize the interaction mechanism between R. solanacearum and hosts to control the disease.

Disruption of non-classically secreted protein(MoMtp)compromised conidiation,stress homeostasis,and pathogenesis of Magnaporthe oryzae

Blast disease,caused by the hemibiotrophic ascomycete fungus,Magnaporthe oryzae,is a significant threat to sustainable rice production worldwide.Studies have shown that the blast fungus secretes vast arrays of functionally diverse proteins into the host cell for a successful disease progression.However,the final destinations of these effector proteins inside the host cell and their role in advancing fungal pathogenesis remain a mystery.Here,we reported that a putative mitochondrial targeting non-classically secreted protein(MoMtp)positively regulates conidiogenesis and appressorium maturation in M.oryzae.Moreover,MoM TP gene deletion mutant strains triggered a hypersensitive response when inoculated on rice leaves displaying that MoMtp is essential for the virulence of M.oryzae.In addition,cell wall and oxidative stress results indicated that MoMtp is likely involved in the maintenance of the structural integrity of the fungus cell.Our study also demonstrates an upregulation in the expression pattern of the MoMTP gene at all stages of infection,indicating its possible regulatory role in host invasion and the infectious development of M.oryzae.Furthermore,Agrobacterium infiltration and sheath inoculation confirmed that MoMtpGFP protein is predominantly localized in the host mitochondria of tobacco leaf and rice cells.Taken together,we conclude that MoMtp protein likely promotes the normal conidiation and pathogenesis of M.oryzae and might have a role in disturbing the proper functioning of the host mitochondria during pathogen invasion.

Mechanistic insights toward identification and interaction of plant parasitic nematodes:A review

Nematode identification serves as an important param-eter to study their behaviour,importance and pathogenic-ity.Application of classical morphometric based identifica-tion methods prove to be lacking due to insufficient knowledge on morphological variations among closely related taxa.Molecular approaches such as DNA and protein-based information,microarray,probing,sequence-based methods and others have been used to supplement morphology-based methods for nematode identification.Ascarosides and certain protein-based nematode-associated molecular patterns(NAMPs),can be perceived by the host plants,and can initiate a signalling cascade.This review primarily emphasizes on an updated account of different classical and modern tools used for the identification of nematodes.Besides we also summa-rize the mechanism of some important signalling pathways which are involved in the different plant nematode interactions.Nematodes constitute most diverse and least studied group of soil inhabiting invertebrates.They are ecologically and physiologically important,however,wide range of nematodes show harmful impact on the individuals that live within their vicinity.Plant parasitic nematodes(PPNs)are transparent,pseudocoelomate,free living or parasitic microorganisms.PPNs lack morphometric identification methods due to insufficient knowl-edge on morphological variations among closely related taxa.As such,molecular approaches such as DNA and protein-based information,microarray,probing,sequence-based methods and others have been used to supplement morphology-based methods for their identification.To invade the defense response of different plant species,parasitic nematodes have evolved different molecular strategies.Ascarosides and certain protein-based nematode-associated molecular patterns(NAMPs),can be perceived by the host plants,and can initiate a signaling cascade.To overcome the host confrontation and develop certain nematode feeding sites,some members can inject effectors into the cells of susceptible hosts to reprogram the basal resistance signaling.This review primarily emphasizes on an updated account of different classical and modem tools used for the identification of PPNs.Besides we also summarize the mechanism of some important signaling pathways which are involved in the different plant nematode interactions.

A size-gradient hypothesis for alpine treeline ecotones

Research on the stress gradient hypothesis recognizes that positive(i.e. facilitative) and negative(i.e. competitive) plant interactions change in intensity and effect relative to abiotic stress experienced on a gradient. Motivated by observations of alpine treeline ecotones, we suggest that this switch in interaction could operate along a gradient of relative size of individual plants. We propose that as neighbors increase in size relative to a focal plant they improve the environment for that plant up to a critical point. After this critical point is surpassed, however, increasing relative size of neighbors will degrade the environment such that the net interaction intensity becomes negative. We developed a conceptual(not site or species specific) individual based model to simulate a single species with recruitment, growth, and mortality dependent on the environment mediated by the relative size of neighbors. Growth and size form a feedback. Simulation results show that the size gradient model produces metrics similar to that of a stress gradient model. Visualizations reveal that the size gradient model produces spatial patterns that are similar to the complex ones observed at alpine treelines. Size-mediated interaction could be a mechanism of the stress gradient hypothesis or it could operate independent of abiotic stress.

Phyllosphere microbiota:Community dynamics and its interaction with plant hosts

Plants are colonized by various microorganisms in natural environments.While many studies have demonstrated key roles of the rhizosphere microbiota in regulating biological processes such as nutrient acquisition and resistance against abiotic and biotic challenges,less is known about the role of the phyllosphere microbiota and how it is established and maintained.This review provides an update on current understanding of phyllosphere community assembly and the mechanisms by which plants and microbes establish the phyllosphere microbiota for plant health.

Performance and transcriptomic response of the English grain aphid, Sitobion avenae, feeding on resistant and susceptible wheat cultivars

Plant resistance against insects mainly depends on nutrient restriction and toxic metabolites, but the relative importance of nutrition and toxins remains elusive. We examined performance, nutrition ingestion, and transcriptome response of the English grain aphid, Sitobion avenae, feeding on resistant Xiaoyan 22(XY22) and susceptible Xinong 979(XN979) wheat cultivars. Aphids had lower body weight and fecundity when feeding on XY22 than on XN979, although the phloem sap of XY22 had a higher nutritive quality(in terms of amino acid:sucrose ratio). Aphids feeding on XY22 also had a lower honeydew excretion rate than those on XN979, suggesting that aphids ingested less phloem sap from XY22. The transcriptome data showed 600 differentially expressed genes(DEGs), and 11 of the top 20 KEGG pathways significantly enriched in DEGs were involved in nutrient metabolism. We found 81 DEGs associated with the metabolism of sugars, lipids, and amino acids, 59 of which were significantly downregulated in aphids feeding on XY22. In contrast, there were 18 DEGs related to detoxifying metabolism, namely eight UDP-glucuronosyltransferases, six cytochromes P450 monooxygenases, one glutathione S-transferase, two ATP-binding cassette transporters, and one major facilitator superfamily transporter;12 of these were upregulated in the aphids feeding on XY22. Our results indicated that both the quantity and quality of phloem nutrition available to aphids are critical for the growth and development of aphids, and the higher resistance of XY22 is mainly due to the reduction in phloem sap ingested by aphids, rather than toxic metabolites.

Implications of carbon catabolite repression for plant–microbe interactions

Carbon catabolite repression(CCR)plays a key role in many physiological and adaptive responses in a broad range of microorganisms that are commonly associated with eukaryotic hosts.When a mixture of different carbon sources is available,CCR,a global regulatory mechanism,inhibits the expression and activity of cellular processes associated with utilization of secondary carbon sources in the presence of the preferred carbon source.CCR is known to be executed by completely different mechanisms in different bacteria,yeast,and fungi.In addition to regulating catabolic genes,CCR also appears to play a key role in the expression of genes involved in plant–microbe interactions.Here,we present a detailed overview of CCR mechanisms in various bacteria.We highlight the role of CCR in beneficial as well as deleterious plant–microbe interactions based on the available literature.In addition,we explore the global distribution of known regulatory mechanisms within bacterial genomes retrieved from public repositories and within metatranscriptomes obtained from different plant rhizospheres.By integrating the available literature and performing targeted meta-analyses,we argue that CCR-regulated substrate use preferences of microorganisms should be considered an important trait involved in prevailing plant–microbe interactions.

Systems understanding of plant-pathogen interactions through genome-wide protein-protein interaction networks

Plants are frequently affected by pathogen infections.To effectively defend against such infections,two major modes of innate immunity have evolved in plants;pathogen-associated molecular pattern-triggered immunity and effector-triggered immunity.Although the molecular components as well as the corresponding pathways involved in these two processes have been identified,many aspects of the molecular mechanisms of the plant immune system remain elusive.Recently,the rapid development of omics techniques(e.g.,genomics,proteomics and transcriptomics) has provided a great opportunity to explore plant–pathogen interactions from a systems perspective and studies on protein–protein interactions(PPIs) between plants and pathogens have been carried out and characterized at the network level.In this review,we introduce experimental and computational identification methods of PPIs,popular PPI network analysis approaches,and existing bioinformatics resources/tools related to PPIs.Then,we focus on reviewing the progress in genome-wide PPI networks related to plant–pathogen interactions,including pathogen-centric PPI networks,plant-centric PPI networks and interspecies PPI networks between plants and pathogens.We anticipate genome-wide PPI network analysis will provide a clearer understanding of plant–pathogen interactions and will offer some new opportunities for crop protection and improvement.

Effects of 17β-Estradiol on Growth, Primary Metabolism, Phenylpropanoid-Flavonoid Pathways and Pathogen Resistance in Arabidopsis thaliana

Mammalian sex hormones are spread in the environment from natural and anthropogenic sources. In the present study, the effect of estradiol on Arabidopsis thaliana growth primary metabolism, phenylpropanoid and flavonoid pathways and pathogen resistance were investigated. Treatments of Arabidopsis plants with 10 and 100 nM 17β-estradiol resulted in enhanced root growth and shoot biomass. In addition, treated plants had an increased rate of photosynthesis with a concomitant increase in carbohydrate and protein accumulation. Plants exposed to higher concentrations of 17β-estradiol (10 μM) had significantly lower root growth, biomass, photosynthesis rate, primary metabolite and phenylpropanoid and flavonoid contents indicating a toxic effect of estradiol. Treatments with increasing estradiol concentrations (10 nM, 100 nM and 10 μM) resulted in the downregulation of phenylpropanoid-flavonoid pathway genes (PAL1, PAL4, CHI and ANS) and subsequent decreased accumulation of phenolics, flavonoids and anthocyanins. Estradiol-treated plants were inoculated with Pseudomonas syringae pv. Tomato DC3000 and basal resistance was determined. Estradiol treatments rendered plants susceptible to the pathogen, thus compromising the plant defense mechanisms. These results indicate that at low concentrations, estradiol functions as a biostimulant of growth, yield and primary metabolism of Arabidopsis. However, estradiol functions as a potential transcriptional regulator of the phenylpropanoid pathway genes in Arabidopsis, having a negative effect on the phenylpropanoid and flavonoid biosynthetic pathways.

Proteomic studies of plant and bacteria interactions during benzene remediation

Phytoremediation is a sustainable remedial approach for removing benzene from environment.Plant associated bacteria could ameliorate the phytotoxic effects of benzene on plant,although the specificity of these interactions is unclear.Here,we used proteomics approach to gain a better understanding of the mechanisms involved in plant-bacteria interactions.Plant associated bacteria was isolated and subsequently inoculated into the sterilized Helianthus annuus,and the uptake rates of benzene by these inoculated plants were evaluated.At the end of the experiment,leaves and roots proteins were analyzed.The results showed inoculated H.annuus with strain EnL3 removed more benzene than other treatments after 96 h.EnL3 was identified as Enterobacter sp.according to 16S rDNA analysis.Based on the comparison of proteins,62 proteins were significantly up or down regulated in inoculated leaves,while 35 proteins were significantly up or down regulated in inoculated roots.Furthermore,there were 4 and 3 identified proteins presented only in inoculated H.annuus leaves and roots,respectively.These proteins involved in several functions including transcription and translation,photosynthesis,and stress response.The network among anti-oxidant defense system,protein synthesis,and photosynthetic electron transfer are involved in collaboratively activate the benzene uptake and stress tolerance in plant.

Effects of active molecules of Korean pine seed on rodent health and implications for forest regeneration

After maturation, Korean pine (Pinus koraiensis Siebold & Zucc.) seeds often cannot disperse to reach a suitable germination site. It is therefore difficult to naturally regenerate by itself and relies on animal dispersal. Squirrels hoard pine seeds as winter food and Korean pine seeds stored for overwintering might become the source of regeneration of the species. From field observations, the pine seeds are the food preference for squirrels during autumn in the Lesser Khingan Mountains in Northeast China. Such preference by squirrels has been attributed to high seed energy content and the ease of seed storage. However, it may also be expected from nutritional aspects that a coevolutionary relationship between squirrels and Korean pine species could be partially explained by the effect of active seed components and their physiological regulatory effects on squirrels. To test this hypothesis, control experiments were carried out to examine the modulatory effects of Korean pine nut oil (PNO) on intestinal microbiota, inflammatory profile and oxidative stress in mice. The results showed that, compared with mice fed a high-fat diet, PNO significantly improved the physical and the healthy state of mice. Histological analysis of the liver and epididymal fat tissue showed that PNO alleviated liver and adipocyte lesions, and inflammation caused by high-fat diets. PNO also significantly decreased atherosclerotic index and ameliorate serum lipid accumulation to prevent cardiovascular disease, which effect the positive control SG group. Moreover, PNO elevated superoxide dismutase and glutathione peroxidase enzyme activities and reduced malondialdehyde levels in the serum. 16S rRNA sequencing showed that PNO restored intestinal microbiota composition, significantly increasing the relative abundance of Lactobacillus and Akkermansia bacteria. These results suggest that Korean pine seeds not only provide adequate fat, protein and energy for squirrels, but also promote physical health and improve body immunity.

Seed size affects rodent–seed interaction consistently across plant species but not within species:evidence from a seed tracking experiment of 41 tree species

Scatter-hoarding rodents play a crucial role in seed survival and seed dispersal.As one of the most important seed traits,seed size and its effect on rodent–seed interaction attract lots of attention.Current studies usually target one or a few species and show inconsistent patterns;however,few experiments include a large number of species although many plant species usually coexist in natural forest and overlap in fruiting time.Here,we tracked the dispersal and predation of 26100 seeds belonging to 41 tree species in a subtropical forest for 2 years.Most species showed no relationships between seed size and rodent foraging preference,while the remaining species displayed diverse of patterns:monotonic decrease and increase trends,and hump-shaped and U-shaped patterns,indicating that a one-off study with a few species might give misleading information.However,the seed size effect across species was consistent in both years,indicating that including a large number of species that hold a sufficient range of seed size may avoid the aforementioned bias.Interestingly,seed size effect differed among rodent foraging processes:a negative effect on seed harvest,a hump-shaped effect on seed removal and removal distance,while a positive effect on overwinter survival of cached seeds,indicating that rodents may make trade-offs between large and small seeds both among foraging processes and within a single process,thus lead to a parabolic relationship between seed size and seed dispersal success,that is medium-sized seeds were more likely to be removed and cached,and transported with a further distance.

Chihuahuan Desert Soil Biota

Deserts have traditionally been considered as a low moisture system where biological activity is triggered by unpredictable rainfall in time and space. Studies on desert ecosystems functions, processes, dynamics and diversity of soil biota had been found to contribute to understanding of their role in primary production and management of soil ecosystems. As belowground biota is very diverse they are playing an important role in above as well below ground essential ecosystem processes e.g. primary production, decomposition, nutrient mineralization etc. The challenge is to use the emerging knowledge of soil biota diversity in understanding basic ecosystems function.

How can ecosystem engineer plants boost productivity in east Mediterranean drylands

Background Water availability is the key limiting factor for plant productivity in drylands covering ca.40%of Earth’s land surface.For such ecosystems to retain productivity and biodiversity under climatic change,it would be valu-able to identify/promote keystone plant species that(i)have developed strategies to more efficiently utilize moisture resources not easily accessible and(ii)improve moisture conditions for neighboring plants.The very deep-rooted Ziziphus lotus,considered an ecosystem engineer,is one such example.However,it is not known which biotic traits:(a)canopy interception of moisture/rainfall,(b)hydraulic redistribution of deep ground moisture by roots,or non-biotic factors:(c)soil’s volume,and(d)organic matter content,Z.lotus activates/modulates to play such a role.We,thus,selected dryland ecosystems where the plant dominates and measured for potential effects on the less deep-rooted Thymbra capitata.For assessing impacts on ecosystem productivity,we measured the spatial aggregation of ca.3600 T.capitata plants.As a proxy for soil moisture availability and its spatial variability,we conducted a 7-year-long study using thymes’nighttime rehydration.Sampling extended up to 15 m away from Z.lotus.Results The density of T.capitata plants growing up to 5 m around Z.lotus vs.thymes growing 10-15 m away was found significantly increased(2.5-4.5 times),while their stem/leaf moisture was ca.10%higher at predawn compared to nightfall during the dry season.This suggests that ecosystem productivity is driven by a greater soil moisture avail-ability around Z.lotus permitting more thyme daytime transpiration,in contrast to thymes growing further away.The phenomenon appeared only under dry topsoil(during the dry season;becoming stronger during dry years).Morning dew/rainfall interception from the canopy or soil depth/organic matter did not show significant effects,leaving only the hydraulic lift properties of Z.lotus as the most likely driver for soil moisture availability.Conclusions The deep-rooting properties and hydraulic lift potential of Z.lotus may be the key in permitting it to boost ecosystem productivity.Such hydraulic plant traits require more attention as they may prove valuable in com-bating desertification and restoring ecosystems in arid/semiarid regions threatened by climate change.