Differential proteome analysis of mature and germinated seeds of Magnolia sieboldii K. Koch

Key message

This is the first reported proteomic analysis to study the dormancy breaking of Magnolia sieboldii seeds. Our results provide a fundamental reference for further studies on the regulation of protein expression during seed germination.

Abstract

Magnolia sieboldii K. Koch is an ornamental tree. The deep dormancy of its seeds hinders its cultivation for economic purposes. The biochemical basis of the regulation of seed germination remains poorly understood. The present study aimed to identify differentially expressed proteins in germinated seeds of M. sieboldii using polyethylene glycol fractionation. In total, 59 differentially expressed protein spots from two-dimensional gel maps were detected, 33 of which were identified by mass spectrometry. They were assigned to eight functional classes on the basis of their putative biological functions: photosynthesis (3 %), chaperonin/heat shock protein (9 %), protein and amino acid synthesis (9 %), stress/defense (18 %), cytoskeleton structure (3 %), metabolism (18 %), hormone and polyamine (9 %) and storage proteins (31 %). Among the other functions, the effects of plant hormones on seed germination may be one of the most important functions in plant growth. Gibberellins and ethylene positively regulate seed germination. The activities of several hormone-associated proteins possibly influencing seed germination were increased. The characterization of these proteins will be of great help in identifying the molecular mechanism underlying seed germination.     

Biogenic ethylene promotes seedling emergence from the sediment seed bank in an ephemeral tropical rock pool habitat

Background and aims

Ethylene has been increasingly implicated as a regulatory mechanism in plant germination, growth, and development, and is produced from the sediments of freshwater habitats. In this paper, we analyse the production and origin of ethylene from ephemeral freshwater rock pool sediments, and explore the role of ethylene in regulating seedling emergence from the seed bank.

Methods

The production of ethylene from rock pool sediments subjected to variable moisture content and antibiotic treatments was assessed through gas chromatography, and the role of ethylene in regulating seedling emergence was determined by seedling emergence assays and seed germination experiments.

Results

Biogenic ethylene production from rock pool sediments occurred rapidly (3–6 h) following inundation, with the majority of seedling emergence occurring between 36 and 72 h. Inoculation of sediments with streptomycin and amphotericin B resulted in significantly reduced ethylene production (up to 60 % and 84 % respectively), and completely inhibited seedling emergence. Additionally, the exposure of dormant seeds to ethylene resulted in significantly increased seed germination percentage in five out of six rock pool species.

Conclusions

Biogenic ethylene production may play an important role in regulating seed dormancy and the timing of seedling emergence from the sediment seed bank following inundation events in rock pools and other freshwater aquatic communities.     

Overexpression of a novel salt stress-induced glycine-rich protein gene from alfalfa causes salt and ABA sensitivity in Arabidopsis

Key message

We cloned a novel salt stress-induced glycine-rich protein gene ( MsGRP ) from alfalfa. Its overexpression retards seed germination and seedling growth of transgenic Arabidopsis after salt and ABA treatments.

Abstract

Since soil salinity is one of the most significant abiotic stresses, salt tolerance is required to overcome salinity-induced reductions in crop productivity. Many glycine-rich proteins (GRPs) have been implicated in plant responses to environmental stresses, but the function and importance of some GRPs in stress responses remain largely unknown. Here, we report on a novel salt stress-induced GRP gene (MsGRP) that we isolated from alfalfa. Compared with some glycine-rich RNA-binding proteins, MsGRP contains no RNA recognition motifs and localizes in the cell membrane or cell wall according to the subcellular localization result. MsGRP mRNA is induced by salt, abscisic acid (ABA), and drought stresses in alfalfa seedlings, and its overexpression driven by a constitutive cauliflower mosaic virus-35S promoter in Arabidopsis plants confers salinity and ABA sensitivity compared with WT plants. MsGRP retards seed germination and seedling growth of transgenic Arabidopsis plants after salt and ABA treatments, which implies that MsGRP may affect germination and growth through an ABA-dependent regulation pathway. These results provide indirect evidence that MsGRP plays important roles in seed germination and seedling growth of alfalfa under some abiotic stress conditions.     

Toward understanding the ecological role of mucilage in seed germination of a desert shrub Henophyton deserti: interactive effects of temperature, salinity and osmotic stress

Aims

Seeds of Henophyton deserti (Brassicaceae), an endemic saharan shrub in south Tunisia, produce a pectinaceous mucilage layer that can imbibe a large amount of water when wetted. The aim of this study was to explore the role of mucilage in seed germination of this shrub under heterogeneous stressful environments.

Methods

Germination of both intact and demucilaged seeds was tested over wide ranges of temperature, and in iso-osmotic solutions of NaCl and PEG. Recovery of germination after NaCl and Polyethylene Glycol (PEG)-6000 treatment was also tested. The effect of mucilage on water uptake was measured and the structure of the seed investigated.

Results

A considerable proportion of seed mass (30 %) is made up of mucilage, which is extremely hydrophilic and able to increase seed mass by 550 % over dry seeds. Mucilage water uptake appears to be unaffected by salt concentration, while higher concentrations of PEG inhibit mucilage hydration. Mucilage decreases germination specifically at 10 °C and this effect can be interpreted in relation to oxygen uptake. High concentrations of NaCl and PEG decrease both germination percentage and rate, with some greater tolerance at 15 °C and 20 °C versus 25 °C. Recovery was higher from higher concentrations of NaCl and PEG and lower temperatures, with a clear inhibitory effect of mucilage.

Conclusions

The study has shown that the mucilage of H. deserti may act as a physical barrier for regulating diffusion of water and oxygen to the inner tissue of the seed and thereby prevent germination under unsuitable conditions.     

Effects of nano-sized zero-valent iron on DDT degradation and residual toxicity in soil: a column experiment

Background and aims

Nanoscale zero-valent iron (nZVI) application is a promising technology for degradation of chlorinated contaminants in soil. Plants also play an important role in soil remediation and nZVI should not adversely affect plants growing on treated soils. Large amounts of DDT are still found in certain soils and means to remediate these soils are limited. Our aims were to investigate the effect of nZVI on DDT degradation and evaluate possible negative effects of nZVI on plants.

Methods

Columns with spiked (20 mg DDT kg^?1) soil were percolated with nZVI (1 g nZVI L^?1) and leached with five pore volumes of water to assess leaching of nZVI and residual toxicity of leachates and soil to plants using seed germination and plant growth tests (barley, flax).

Results

Addition of nZVI led to degradation of 45 % of the added DDT. Percolation with water significantly oxidized and transported iron through the columns. The first leachates had negative effects on plant development, but after leaching with 4 pore volumes, neither soil nor leachates affected plant negatively.

Conclusions

nZVI is efficient for degradation of DDT and adverse effects of nZVI on plants seem ephemeral and are alleviated after oxidation mediated by percolating water.     

Fertilization,soil and plant community characteristics determine soil microbial activity in managed temperate grasslands

Background and aims

Contaminated soils can impede germination and growth of selected plant species, restricting effective phytoremediation strategies. The purpose of the present study was to enhance the germination and growth of saltgrass [Distichlis spicata (L.) Greene] by evaluating the efficacy of certain seed pretreatments and soil amendments.

Methods

Ten seed pretreatment methods, two amendments, three soil depths and five saline levels were tested under greenhouse conditions.

Results

Saltgrass germination and growth were negatively correlated with increasing salinity levels when NaCl > 85.6 mM. Among ten seed pretreatments (stratification + Proxy 24 h, hot water + Proxy 24 h, stratification, hot water + Proxy 48 h, Proxy 48 h, Proxy 24 h, hot water, scarification, gibberellins, and KMnO₄), the two best methods were stratification + Proxy 24 h and hot water + Proxy 24 h for enhancing saltgrass germination, with the latter pretreatment being especially useful because of its shorter preparation time and high germination rates. Proxy is a commercial ethephon product. Potting soil (5.0 cm depth) was found to be the best amendment for saltgrass germination and growth in hydrocarbon-contaminated soils.

Conclusion

We conclude that direct seeding of saline soils contaminated with petroleum hydrocarbons is a feasible phytoremediation strategy provided that appropriate seed pretreatments and amendments are utilized.

     

Response characteristics of seed germination and seedling growth of Acorus tatarinowii under diesel stress

Aims

Responses of typical wetland plant Acorus tatarinowii to diesel stress were investigated to provide basis of ecological monitoring system and phytoremediation for diesel-contaminated wetland.

Methods

Greenhouse experiments were established to determine the germinability of seedlings, hydrogen peroxide in leaves, and DNA damage in roots exposed to a range of potentially phytotoxic diesel.

Results

The presence of diesel did not benefit the growth of A. tatarinowii. The germination ratio and germination rate decreased with the increase of diesel concentration, both the lowest value appeared when the concentration of diesel was 10,000 mg?kg^?1. The lowest diesel concentration (2,000 mg?kg^?1) in the soil significantly reduced the length, average diameter, and projected area of root, especially on the stress of the higher diesel concentration (4,000, 8,000, and 10,000 mg?kg^?1). Furthermore, H₂O₂ concentration in leaves rose with the increasing concentration of diesel. However, no DNA oxidative damage to root was observed in our experiment.

Conclusions

Diesel exposure significantly inhabited the seed germination, root elongation, and seedlings growth of A. tatarinowii. Diesel stress caused the accumulation of H₂O₂ in the leaves of A. tatarinowii.     

Peanut as a potential crop for bioenergy production via Cd-phytoextraction: A life-cycle pot experiment

Aims

The current study aimed to assess the potential of peanut (Arachis hypogaea L.) for bioenergy production via phytoextraction in cadmium (Cd) -contaminated soils and screen appropriate cultivars for this approach.

Methods

A life-cycle pot experiment was conducted to determine the biomass, seed yield, oil content and Cd accumulation of seven peanut cultivars under Cd concentration gradients of 0, 2, and 4 mg kg^?1.

Results

Peanut exhibits genotypic variations in Cd tolerance, seed production, oil content, and Cd accumulation. Exposure of plants to 2 and 4 mg kg^?1 Cd did not inhibit shoot biomass, seed yield, and oil content for most of the cultivars tested. There are large amounts of Cd accumulated in the shoots. Although the seed Cd concentration of peanut was relatively high, the Cd concentration in seed oils was very low (0.04-0.08 mg kg^?1). Among the cultivars, Qishan 208 showed significant Cd tolerance, high shoot biomass, high pod and seed yield, high seed oil content, considerable shoot Cd concentration, and the largest translocation factor and total Cd in shoots.

Conclusions

The cultivation of peanut in Cd-contaminated farmland was confirmed to be feasible for bioenergy production via phytoextraction, and Qishan 208 is a good candidate for this approach.     

Polyamines and Nitric Oxide Link in Regulation of Dormancy Removal and Germination of Apple (Malus domestica Borkh.) Embryos

Polyamines (PAs) belong to plant growth regulators and in complex with classical phytohormones take part in regulation of seed dormancy and germination. Although the impact of reactive oxygen (ROS) and nitrogen (RNS) species on seed germination is well described, the cross talk of PAs with ROS/RNS has never been analyzed. Due to the close connection of PAs and ethylene biosynthetic pathways to arginine (Arg)-dependent NO biosynthesis we investigated production of nitric oxide (NO), peroxynitrite (ONOO^?) and the level of O ₂ ^?? or H₂O₂ in apple embryos, germination of which was PA regulated. PAs: putrescine (Put) and spermidine (Spd) in contrast to spermine (Spm) stimulated germination of apple embryos. Among amino acids, stimulation of germination was observed in Arg and ornithine (Orn) only. Dormancy removal of embryos by PAs was associated with increased accumulation of H₂O₂ and O ₂ ^?? in embryonic axes. At the same stage of completion of sensu stricto germination the stimulatory effect of PAs (Put and Spd) and amino acids, mainly Arg and Orn, was accompanied by enhanced NO and ONOO^? production in embryonic axis. The beneficial effect of PAs (Put and Spd) and their precursors on germination of apple embryos was removed by NO scavenging, suggesting a crucial role of NO in termination of embryo germination and radicle growth. Moreover, activity of polyamine oxidase in embryo axes was greatly enhanced by embryo fumigation with NO. Our data demonstrate the interplay of RNS/ROS with PAs and point to NO action as an integrator of endogenous signals activating germination.     

Nitrous oxide emissions and nitrate leaching from a rain-fed wheat-maize rotation in the Sichuan Basin, China

Aims

A 3-year field experiment (October 2004–October 2007) was conducted to quantify N₂O fluxes and determine the regulating factors from rain-fed, N fertilized wheat-maize rotation in the Sichuan Basin, China.

Methods

Static chamber-GC techniques were used to measure soil N₂O fluxes in three treatments (three replicates per treatment): CK (no fertilizer); N150 (300 kg N fertilizer ha^?1 yr^?1 or 150 kg N?ha^?1 per crop); N250 (500 kg N fertilizer ha^?1 yr^?1 kg or 250 kg N?ha^?1 per crop). Nitrate (NO ₃ ^? ) leaching losses were measured at nearby sites using free-drained lysimeters.

Results

The annual N₂O fluxes from the N fertilized treatments were in the range of 1.9 to 6.7 kg N?ha^?1 yr^?1 corresponding to an N₂O emission factor ranging from 0.12 % to 1.06 % (mean value: 0.61 %). The relationship between monthly soil N₂O fluxes and NO ₃ ^- leaching losses can be described by a significant exponential decaying function.

Conclusions

The N₂O emission factor obtained in our study was somewhat lower than the current IPCC default emission factor (1 %). Nitrate leaching, through removal of topsoil NO ₃ ^? , is an underrated regulating factor of soil N₂O fluxes from cropland, especially in the regions where high NO ₃ ^- leaching losses occur.     

Interactive effects of selenium and antimony on the uptake of selenium, antimony and essential elements in paddy-rice

Aims

Selenium (Se) can be used to detoxify antimony (Sb); however, the associated mechanisms are not fully understood, in particular, the responses of essential elements to co-exposure to Se and Sb.

Methods

To resolve the above question, two nested hydroponic experiments based on a two-factor, five-level central composite design, were performed using a conventional indica rice (Fengmeizhan).

Results

The results showed that when the Se concentration was fixed at 0.8 mg L^-1, the addition of Sb, even at concentrations as low as 2.171 mg L^-1, could produce damages to this plant and significantly reduce both the aboveground and root biomasses, suggesting a high toxicity of Sb to this plant. However, when the Sb concentration was fixed at 5 mg L^-1, Se eliminated the negative effects of Sb on the aboveground growth of paddy-rice but did not noticeably affect the root biomass, suggesting a beneficial role of Se in conferring resistance to Sb toxicity in paddy-rice. Interestingly, when the Se concentration was fixed at 0.8 mg L^-1, the addition of Sb caused a consistent decrease in the Se concentration in the roots but a slight increase in the Se concentration in the aboveground, suggesting a dual effect of Sb on Se uptake. Furthermore, the addition of Sb could counterbalance the negative effects of 0.8 mg L^-1 Se on the uptake of most of the tested essential elements, significantly increased their concentrations in the different tissues of this plant.

Conclusions

The Se-mediated alleviation of Sb toxicity could be closely connected with (1) the direct inhibition of Sb uptake; and (2) the uptake regulation of some essential elements, such as calcium (Ca), magnesium (Mg) and potassium (K). This study contributes to the understanding of both the the interactions between Se and Sb and their effects on the uptake of essential elements in paddy-rice.     

Comparative proteomic analysis reveals the positive effect of exogenous spermidine on photosynthesis and salinity tolerance in cucumber seedlings

Key message

Our results based on proteomics data and physiological alterations proposed the putative mechanism of exogenous Spd enhanced salinity tolerance in cucumber seedlings.

Abstract

Current studies showed that exogenous spermidine (Spd) could alleviate harmful effects of salinity. It is important to increase our understanding of the beneficial physiological responses of exogenous Spd treatment, and to determine the molecular responses underlying these responses. Here, we combined a physiological analysis with iTRAQ-based comparative proteomics of cucumber (Cucumis sativus L.) leaves, treated with 0.1 mM exogenous Spd, 75 mM NaCl and/or exogenous Spd. A total of 221 differentially expressed proteins were found and involved in 30 metabolic pathways, such as photosynthesis, carbohydrate metabolism, amino acid metabolism, stress response, signal transduction and antioxidant. Based on functional classification of the differentially expressed proteins and the physiological responses, we found cucumber seedlings treated with Spd under salt stress had higher photosynthesis efficiency, upregulated tetrapyrrole synthesis, stronger ROS scavenging ability and more protein biosynthesis activity than NaCl treatment, suggesting that these pathways may promote salt tolerance under high salinity. This study provided insights into how exogenous Spd protects photosynthesis and enhances salt tolerance in cucumber seedlings.

     

Alfalfa plant-derived biostimulant stimulate short-term growth of salt stressed Zea mays L. plants

Background & Aims

The effects of an alfalfa plant (Medicago sativa L.) hydrolysate-based biostimulant (EM) containing triacontanol (TRIA) and indole-3-acetic acid (IAA) were tested in salt-stressed maize plants.

Methods

Plants were grown for 2 weeks in the absence of NaCl or in the presence (25, 75 and 150 mM). On the 12th day, plants were supplied for 48 h with 1.0 mg L^?1 EM or 11.2 μM TRIA.

Results

EM and TRIA stimulated the growth and nitrogen assimilation of control plants to a similar degree, while NaCl reduced plant growth, SPAD index and protein content. EM or TRIA increased plant biomass under salinity conditions. Furthermore, EM induced the activity of enzymes functioning in nitrogen metabolism. The activity of antioxidant enzymes and the synthesis of phenolics were induced by salinity, but decreased after EM treatment. The enhancement of phenylalanine ammonia-lyase (PAL) activity and gene expression by EM was consistent with the increase of flavonoids.

Conclusion

The present study proves that the EM increases plant biomass even when plants are grown under salinity conditions. This was likely because EM stimulated plant nitrogen metabolism and antioxidant systems. Therefore, EM may be proposed as bioactive product in agriculture to help plants overcome stress situations.     

Soil CO2 efflux in response to the addition of water and fertilizer in temperate semiarid grassland in northern China

Background and aims

Knowledge about the effects of water and fertilizer on soil CO₂ efflux (SCE) and Q ₁₀ is essential for understanding carbon (C) cycles and for evaluating future global C balance. A two-year field experiment was conducted to determine the effects of water, fertilizer, and temperature on SCE in semiarid grassland in northern China.

Methods

SCE, as well as environmental factors was measured in two grasslands, one with bunge needlegrass (BNE, Stipa bungeana) and one with purple alfalfa (ALF, Medicago sativa), with four treatments: CK (unwatered and unfertilized); W (50 mm water addition yr^?1); F (50 kg phosphorus (P) fertilizer ha^?1 yr^?1 for ALF, 100 kg nitrogen (N)?+?50 kg P fertilizer ha^?1 yr^?1 for BNE); and W + F.

Results

During the 11-month experimental period from July 2010 to October 2011, the addition of water consistently stimulated mean SCE in BNE and ALF, and the positive effects were relatively stronger during dry seasons. P fertilization consistently enhanced SCE in ALF, and the positive effect was strongly dependent on the availability of soil water. The effects of N plus P fertilization on SCE in BNE varied seasonally from significant increases to small reductions to no response. Water addition increased the Q ₁₀ of SCE in ALF by 11 % but had no effect in BNE. Fertilization, however, reduced the Q ₁₀ of SCE by 21 % and 13 % for BNE and ALF, respectively. Models that rely only on Q ₁₀ underestimated the emissions of soil CO₂ by 8–15 % at the study site, which was mediated by species and treatment.

Conclusions

Responses of SCE and its temperature sensitivity to water and fertilizer may vary with species and depend on the period of measurement. Models of SCE need to incorporate the availability of ecosystemic water and nutrients, as well as species, and incorporate different environmental factors when determining the impact of water, nutrients, and species on SCE.     

Phase 1 trial of the oral AKT inhibitor MK-2206 plus carboplatin/paclitaxel, docetaxel, or erlotinib in patients with advanced solid tumors

Background

Inhibition of AKT with MK-2206 has demonstrated synergism with anticancer agents. This phase 1 study assessed the MTD, DLTs, PK, and efficacy of MK-2206 in combination with cytotoxic and targeted therapies.

Methods

Advanced solid tumor patients received oral MK-2206 45 or 60 mg (QOD) with either carboplatin (AUC 6.0) and paclitaxel 200 mg/m² (arm 1), docetaxel 75 mg/m² (arm 2), or erlotinib 100 or 150 mg daily (arm 3); alternative schedules of MK-2206 135-200 mg QW or 90-250 mg Q3W were also tested.

Results

MTD of MK-2206 (N?=?72) was 45 mg QOD or 200 mg Q3W (arm 1); MAD was 200 mg Q3W (arm 2) and 135 mg QW (arm 3). DLTs included skin rash (arms 1, 3), febrile neutropenia (QOD, arms 1, 2), tinnitus (Q3W, arm 2), and stomatitis (QOD, arm 3). Common drug-related toxicities included fatigue (68%), nausea (49%), and rash (47%). Two patients with squamous cell carcinoma of the head and neck (arm 1; Q3W) demonstrated a complete and partial response (PR); additional PRs were observed in patients (1 each) with melanoma, endometrial, neuroendocrine prostate, NSCLC, and cervical cancers. Six patients had stable disease ≥6 months.

Conclusion

MK-2206 plus carboplatin and paclitaxel, docetaxel, or erlotinib was well-tolerated, with early evidence of antitumor activity.

Trial registration

ClinicalTrials.gov: NCT00848718.     

Nickel-enriched seed and externally supplied nickel improve growth and alleviate foliar urea damage in soybean

Background and aims

The importance of seed Ni reserves for plant growth and N metabolism is poorly understood. This study investigated the effects of both seed Ni and externally supplied Ni on the impact of foliarly-applied urea and N-nutritional status of soybean.

Methods

Soybean seeds were produced by growing plants in nutrient solutions containing different Ni levels, and their urease activities were measured. Plants were then grown from these seeds with or without external Ni. After treating half of the plants with foliar urea, the urea damage symptoms, elongation rates and chlorophyll concentrations were followed over one week. Biomass and mineral concentrations of different plant parts were determined.

Results

Nickel supply at increasing rates improved seed yield by up to 25 %. Seeds with Ni concentrations varying between 0.04–8.32 mg.kg^?1 were obtained. Depending on the Ni concentration, the seed urease activities differed up to 100-fold. Leaf damage due to foliar urea spray was significantly alleviated by higher seed Ni as well as external Ni supply. Higher Ni also promoted shoot elongation and improved chlorophyll concentrations. Nickel was 10-times more concentrated in the youngest part than in older leaves. In the absence of foliar urea, Ni enhanced the N concentration of the growing part of the shoot by up to 30 %.

Conclusion

A better utilization of foliarly-applied urea-N is achieved in soybean when adequate Ni is supplied to plants by seed reserves and/or externally. High seed Ni levels are also required for preventing foliar urea damage and improving N remobilization.