Transcriptomic and Metabolomic Analyses Reveal That Fullerol Improves Drought Tolerance in Brassica napus L.

Carbon nanoparticles have potential threats to plant growth and stress tolerance. The polyhydroxy fullerene-fullerol (one of the carbon nanoparticles) could increase biomass accumulation in several plants subjected to drought; however, the underlying molecular and metabolic mechanisms governed by fullerol in improving drought tolerance in Brassica napus remain unclear. In the present study, exogenous fullerol was applied to the leaves of B. napus seedlings under drought conditions. The results of transcriptomic and metabolomic analyses revealed changes in the molecular and metabolic profiles of B. napus. The differentially expressed genes and the differentially accumulated metabolites, induced by drought or fullerol treatment, were mainly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to carbohydrate metabolism (e.g., "carbon metabolism" and "galactose metabolism"), amino acid metabolism (e.g., "biosynthesis of amino acids" and "arginine and proline metabolism"), and secondary metabolite metabolism (e.g., "biosynthesis of secondary metabolites"). For carbohydrate metabolism, the accumulation of oligosaccharides (e.g., sucrose) was decreased, whereas that of monosaccharides (e.g., mannose and myo-inositol) was increased by drought. With regard to amino acid metabolism, under drought stress, the accumulation of amino acids such as phenylalanine and tryptophan decreased, whereas that of glutamate and proline increased. Further, for secondary metabolite metabolism, B. napus subjected to soil drying showed a reduction in phenolics and flavonoids, such as hyperoside and trans-3-coumaric acid. However, the accumulation of carbohydrates was almost unchanged in fullerol-treated B. napus subjected to drought. When exposed to water shortage, the accumulation of amino acids, such as proline, was decreased upon fullerol treatment. However, that of phenolics and flavonoids, such as luteolin and trans-3-coumaric acid, was enhanced. Our findings suggest that fullerol can alleviate the inhibitory effects of drought on phenolics and flavonoids to enhance drought tolerance in B. napus.

Partial and full root-zone drought stresses account for differentiate root-sourced signal and yield formation in primitive wheat.

BACKGROUND: Partial and full root-zone drought stresses are two widely used methods to induce soil drying in plant container-culture experiments. Two methods might lead to different observational results in plant water relation, such as non-hydraulic root-sourced signal (nHRS). We compared partial and full stress methods to induce nHRS in two diploids (MO1 and MO4) and two tetraploids (DM 22 and DM 31) wheat varieties under pot-culture conditions. Partial root-zone stress (PS) was performed using split-root alternative water supply method (one half wetting and the other drying) to induce the continuous operation of nHRS, and full root-zone stress (FS) was exposed to whole soil block to induce periodic operation of nHRS since jointing stage. RESULTS: We tested the two drought methods whether it influenced the nHRS mediated signalling and yield formation in primitive wheat species. Results showed that partial root-zone stress caused more increase in abscisic acid (ABA) production and decline in stomatal closure than full root-zone stress method. The incline in ABA was closely related to triggering reactive oxygen species (ROS) generation, and reducing cytokinin synthesis which, thereby, led to crosstalk with other signalling molecules. Furthermore, PS up-regulated the antioxidant defense system and proline content. Water use efficiency and harvest index was significantly increased in PS, suggesting that PS was more likely to simulate the occurrence of nHRS by increasing the adaptive strategies of plants and closer to natural status of soil drying than FS. CONCLUSION: These findings lead us to conclude that partial root-zone stress method is more feasible method to induce nHRS which has great capacity to reduce water consumption and enhance plant adaptation to constantly changing environment. These observations also suggest that different root-zone planting methods can be considered to improve the plant phenotypic plasticity and tolerance in water-limited rainfed environments.

Physiological and biochemical responses of two spring wheat genotypes to non-hydraulic root-to-shoot signalling of partial and full root-zone drought stress.

Non-hydraulic root-sourced signal (nHRS) is so far affirmed to be a unique positive early-warning response to drying soil, however its physiological and agronomic implications are still unclear. We designed two contrast methods to induce nHRS in two wheat (Triticum aestivum L.) genotypes released in different decades under pot-culture conditions. Partial root-zone stress (PS) was performed using the method of split-root alternative water supply (one half wetting and the other drying) to induce the continuous operation of nHRS, and full root-zone stress (FS) was subjected to whole root system to periodic operation of nHRS. nHRS-mediated signalling increased abscisic acid (ABA) production and triggered ROS (reactive oxygen species) generation, which, thereby, led to up-regulation of antioxidant defense system. Cytokinin synthesis reduced during drought stress while proline and malodialdehyde (MDA) content were increased. Regardless of drought treatment methods and wheat genotype, a significant decrease in grain yield, root biomass and above-ground biomass (p < 0.05) was observed, without significant changes in root-to-shoot ratio. Harvest index was increased, proposing that more energy was allocated to reproductive organs during the action of nHRS. Moreover, higher water use efficiency was witnessed in PS. The data suggest that nHRS triggered ABA accumulation, thereby closing stomata, and reducing water use and also decreases the production of ROS and improves the antioxidant defence enzymes, thus enhancing drought tolerance. This survey of different-decade genotypes suggests that advances in grain yield and drought tolerance would be made by targeted selection for a wheat genetic resource.

Fullerol improves seed germination, biomass accumulation, photosynthesis and antioxidant system in Brassica napus L. under water stress.

Carbon nanoparticles are widely studied for affecting crop production in agriculture. Considering their potential threats to the crops, especially under drought stress, is important for carbon nanoparticle application. However, the influence of polyhydroxy fullerene-fullerol on drought tolerance at the physiological and molecular levels in Brassica napus remains unclear. In the present study, different doses of fullerol were applied to seeds or leaves of B. napus subjected to water stress. The results showed that water stress significantly reduced the seed germination, aboveground dry weight, and photosynthesis, whereas it increased the abscisic acid (ABA) concentration, reactive oxygen species (ROS) accumulation, levels of non-enzymatic substances, and activities of antioxidant enzymes in B. napus. Priming with fullerol at 10 and 100 mg L-1 in seeds exhibited a significant promotional effect on seed germination under 15% polyethylene glycol treatment. Moreover, foliar application of fullerol raised the aboveground dry weight and photosynthesis in B. napus seedlings under soil drying. Compared with soil drying alone, the accumulation of ROS was repressed, which was concomitant with higher concentrations of non-antioxidant substances and increased activities of antioxidant enzymes in leaves of seedlings exposed to fullerol at specific concentrations addition with water shortage. Fullerol treatments at 1-100 mg L-1 dramatically increased the leaf ABA level and induced ABA biosynthesis by down-regulating the expression of the ABA catabolic gene CYP707A3 under drought. It is concluded that exogenous fullerol with seed priming or foliar application can stimulate growth in B. napus when water-stressed. The increased antioxidant ability that collectively detoxified ROS improved the drought tolerance in B. napus seedlings under foliar-applied fullerol treatment.

5-aminolevulinic acid improves salt tolerance mediated by regulation of tetrapyrrole and proline metabolism in Brassica napus L. seedlings under NaCl stress.

5-aminolevulinic acid (ALA), a key biosynthetic precursor of tetrapyrroles, is vital for plant growth and adaptation to stress environments. Although exogenous ALA could enhance photosynthesis and biomass accumulation in plants under stress conditions, the underlying physiological and molecular mechanisms governed by ALA in promoting salt tolerance in Brassica napus L. are not yet clearly understood. In the present study, exogenous ALA with the concentration of 30 mg L-1 was applied to the leaves of B. napus seedlings subjected to 200 mM NaCl. The results showed that NaCl stress decreased the photosynthesis, biomass accumulation, and levels of chlorophyll and heme with the reduction of the concentrations of intermediates including ALA, protoporphyrin IX (Proto IX), Mg-Proto IX, and Pchlide in the tetrapyrrole (chlorophyll and heme) biosynthetic pathway. The transcript levels of genes encoding ALA-associated enzymes and genes encoding Mg-chelatase in the chlorophyll biosynthetic branch were down-regulated, while the expression levels of genes encoding Fe-chelatase in the heme branch were not significantly altered by NaCl stress. Foliar application with ALA enhanced the aboveground biomass, net photosynthetic rate, activities of antioxidant enzymes, accumulation of chlorophyll and heme, and concentrations of intermediates related to chlorophyll and heme biosynthesis in B. napus under 200 mM NaCl. The expression of most genes mentioned above remained constant in ALA-treated plants in comparison with non-ALA-treated plants under NaCl stress. Additionally, exogenous ALA synchronously induced the proline concentration and up-regulated the expression of genes P5CS and ProDH encoding proline metabolic enzymes in the NaCl treatment. These findings suggested that ALA improved salt tolerance through promoting the accumulation of chlorophyll and heme resulting from the increase of intermediate levels in the tetrapyrrole biosynthetic pathway, along with enhancing the proline accumulation in B. napus.

Plant toxin ß-ODAP activates integrin ß1 and focal adhesion: A critical pathway to cause neurolathyrism.

Neurolathyrism is a unique neurodegeneration disease caused by ß-N-oxalyl-L-α, ß- diaminopropionic (ß-ODAP) present in grass pea seed (Lathyrus stativus L.) and its pathogenetic mechanism is unclear. This issue has become a critical restriction to take full advantage of drought-tolerant grass pea as an elite germplasm resource under climate change. We found that, in a human glioma cell line, ß-ODAP treatment decreased mitochondrial membrane potential, leading to outside release and overfall of Ca2+ from mitochondria to cellular matrix. Increased Ca2+ in cellular matrix activated the pathway of ECM, and brought about the overexpression of ß1 integrin on cytomembrane surface and the phosphorylation of focal adhesion kinase (FAK). The formation of high concentration of FA units on the cell microfilaments further induced overexpression of paxillin, and then inhibited cytoskeleton polymerization. This phenomenon turned to cause serious cell microfilaments distortion and ultimately cytoskeleton collapse. We also conducted qRT-PCR verification on RNA-sequence data using 8 randomly chosen genes of pathway enrichment, and confirmed that the data was statistically reliable. For the first time, we proposed a relatively complete signal pathway to neurolathyrism. This work would help open a new window to cure neurolathyrism, and fully utilize grass pea germplasm resource under climate change.

Response of chickpea (Cicer arietinum L.) to terminal drought: leaf stomatal conductance, pod abscisic acid concentration, and seed set.

Flower and pod production and seed set of chickpea (Cicer arietinum L.) are sensitive to drought stress. A 2-fold range in seed yield was found among a large number of chickpea genotypes grown at three dryland field sites in south-western Australia. Leaf water potential, photosynthetic characteristics, and reproductive development of two chickpea genotypes with contrasting yields in the field were compared when subjected to terminal drought in 106kg containers of soil in a glasshouse. The terminal drought imposed from early podding reduced biomass, reproductive growth, harvest index, and seed yield of both genotypes. Terminal drought at least doubled the percentage of flower abortion, pod abscission, and number of empty pods. Pollen viability and germination decreased when the fraction of transpirable soil water (FTSW) decreased below 0.18 (82% of the plant-available soil water had been transpired); however, at least one pollen tube in each flower reached the ovary. The young pods which developed from flowers produced when the FTSW was 0.50 had viable embryos, but contained higher abscisic acid (ABA) concentrations than those of the well-watered plants; all pods ultimately aborted in the drought treatment. Cessation of seed set at the same soil water content at which stomata began to close and ABA increased strongly suggested a role for ABA signalling in the failure to set seed either directly through abscission of developing pods or seeds or indirectly through the reduction of photosynthesis and assimilate supply to the seeds.

Genotypic Variation in the Concentration of ß-N-Oxalyl-L-α,ß-diaminopropionic Acid (ß-ODAP) in Grass Pea (Lathyrus sativus L.) Seeds Is Associated with an Accumulation of Leaf and Pod ß-ODAP during Vegetative and Reproductive Stages at Three Levels of Water Stress.

Grass pea (Lathyrus sativus L.) cultivation is limited because of the presence in seeds and tissues of the nonprotein amino acid ß-N-oxalyl-L-α,ß-diaminopropionic acid (ß-ODAP), a neurotoxin that can cause lathyrism in humans. Seven grass pea genotypes differing in seed ß-ODAP concentration were grown in pots at three levels of water availability to follow changes in the concentration and amount of ß-ODAP in leaves and pods and seeds. The concentration and amount of ß-ODAP decreased in leaves in early reproductive development and in pods as they matured, while water stress increased ß-ODAP concentration in leaves and pods at these stages. The net amount of ß-ODAP in leaves and pods at early podding was positively associated with seed ß-ODAP concentration at maturity. We conclude that variation among genotypes in seed ß-ODAP concentration results from variation in net accumulation of ß-ODAP in leaves and pods during vegetative and early reproductive development.

[Ecological function and application of toxin beta-ODAP in grass pea (Lathyrus sativus)].

Grass pea (Lathyrus sativus) is a legume with various adverse adaptability and rich nutrition. However, it can lead to the human and animal neurotoxicity after long-term consumption due to its neurotoxin, beta-N-oxalyl-L-alpha, beta-diaminopropionic acid (beta-ODAP), limiting its utilization. This paper summarized the influences of beta-ODAP on osmotic adjustment and growth regulation in grass pea under drought stress, the research progress in analysis methods, toxicological mechanisms and practical utility of beta-ODAP, and the breeding strategies for low- and zero-beta-ODAP. Beta-ODAP synthesis was found to be abundant in grass pea under drought stress and its content was enhanced gradually with the increasing extent of drought stress. beta-ODAP could supply nitrogen for plant growth and seed development, scavenge reactive oxygen species (ROS), involve in osmotic adjustment as a soluble amino acid, transport zinc-ions as a carrier molecule, and impact nodule development. However, increasing the content of sulfur-containing amino acids (methionine and cysteine) could decrease the level of toxicity of grass pea. There were a lot of investigations on collecting genetic resources, cross breeding, tissue culture, and gene manipulation for low- and zero-toxin in grass pea in recent years. Although beta-ODAP could induce excitotoxicity by damaging intracellular Ca2+ homeostasis and as glutamate analogues, it has medicinal value on hemostasis and anti-tumor.

[The 1st International Youth Ecologist Forum in China, 2009: a review].

To promote the communication and cooperation between Chinese and overseas youth ecologists, a conference entitled "The 1st International Young Ecologist Forum" was held at Lanzhou University in June 29-30, 2009. This conference was organized by outstanding overseas ecologists and hosted by Lanzhou University. The presentations covered broad areas of ecology, including plant-soil interactions, structure and function of regional ecosystems, ecological security and ecological planning, global change ecology, and environmental sustainability, demonstrating that the development of China ecology is gradually from traditional basic research transforming into applied research. The presentations also reflected in some extent the development characteristics, evolution direction, and distribution pattern of China ecological research. China ecological research has gradually formed four centers, the Northeast, North, Northwest, and Southeast China, and each of them has its definite regional characteristics. Some suggestions about the organization form and future planning of the forum were put forward.