Developing and sustainably utilize the coastal mudflat areas in China.

Coastal mudflat areas are regarded as the important reserve land resource in China. Rational exploitation and development of the mudflat areas can relieve the stress of inadequate land resources. Probing into the developing models of resource exploitation of coastal tidal mudflats is one of the important components of achieving the sustainable development in the coastal areas. Therefore, the development history of coastal mudflats after 1950s in China is briefly introduced in this paper. Then, the status in quo of the modes of development and utilization of coastal mudflat in China the paper is reviewed with a special attention payed to the agricultural use of coastal resource, especially halophytes and improved salt-tolerant varieties planting, agricultural dyke pond and coastal saline-alkali soil remediation. Based on related research frontier, sustainable developmental prospects of these coastal areas are presented as well.

Molecular dissection of mercury-responsive transcriptome and sense/antisense genes in Medicago truncatula.

We described a newly developed approach, namely next-generation tag sequencing, to identify global gene transcripts and complexity regulated by heavy metals in Medicago truncatula. Two cDNA libraries were generated from M. truncatula seedlings: treated and non-treated with the toxic heavy metal mercury Hg(II). With the large number of read-mapped genes generated, we observed that most of the genes were differentially expressed between the two libraries. In addition, several classes of new transcripts including transcription factors, antisense transcripts, and stress responsive genes were detected. The forty genes most altered in expression levels were associated with tolerance to environmental stress and secondary metabolism. Validation of genes by quantitative RT-PCR confirmed the results from deep-sequencing. Most of genes coding for metal transporters, sulfate metabolism, and cell wall solidification were significantly altered by Hg exposure. We also examined altered expression ratios of sense and antisense (S-AS) transcripts between the two libraries. By analyzing strand-specific information of read sequences, S-AS transcripts were found to be enriched with metal treatment. The transcriptome sequences were analyzed further with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) and showed diverse biological functions and metabolic pathways under the metal stress.

[Physiological responses of Enteromorpha linza and Enteromorpha prolifera to seawater salinity stress].

To investigate the physiological responses and adaptation mechanisms of Enteromorpha to seawater salinity stress, a laboratory experiment with Enteromorpha linza and E. prolifera was conducted to study their fresh mass (FM), relative growth rate (RGR), relative electrical conductivity (REC), chlorophyll (Chl) and carotenoid (Car) contents, Chl a/Chl b, Chl/Car, chlorophyll fluorescence parameters, and osmotic adjustment ability (OAA) under the stress of different salinity levels of diluted and concentrated seawater for 10 days. Compared with the control, 10%-200% salinity seawater increased the FM and RGR of the two Enteromorpha species obviously, 100% and 50% salinity seawater made the FM and RGR of E. linza and E. prolifera peaked, respectively, while 300% salinity seawater decreased the FM and RGR of E. linza and E. prolifera significantly, with the decrement being larger for E. linza. The biomass of E. linza and E. prolifer only had an increase in 50% and 100% sanity seawater and in 10%, 50%, 100%, and 200% salinity seawater, respectively. The Chl and Car contents and Chl a/Chl b of E. linza and E. prolifera had a significant increase in 10% salinity seawater, but decreased after an initial increase with the increasing salinity level of seawater. The Chl and Car contents and Chl a/Chl b of E. linza and E. prolifera peaked in 100% and 50% salinity seawater, respectively. With increasing salinity of seawater, the light use efficiency (alpha), maximal photochemical efficiency of PS II (F(v)/F(m)), actual photochemical efficiency of PS II in the light (Yield), maximal relative electron transport rate (rETR(max)), and half-saturation light intensity (I(k)) of E. linza and E. prolifera all showed the same variation trend as Chl. 10% -300% salinity seawater enabled E. linza and E. prolifera to express certain osmotic adjustment ability (OAA), and the OAA of E. linza and E. prolifer peaked in 100% and 50% salinity seawater, respectively. The growth of Enteromorpha had no correlation with Chl/Car, but was significantly negatively correlated with REC and positively correlated with Chl, Car, Chl a/ Chl b, F(v)/F(m), Yield, rETR(max), alpha, I(k), and OAA. To sum up, 100% salinity was the optimal salt concentration for the growth of E. linza, and 50% salinity was optimal for E. prolifera. E. prolifera could adapt to a wider range of salinity than E. linza. The parameters REC, Chl, Car, Chl a/Chl b, F(v)/F(m), Yield, rETR(max), alpha, I(k), and OAA could be used to evaluate the salt adaptation of Enteromorpha.

Molecular dissection of atrazine-responsive transcriptome and gene networks in rice by high-throughput sequencing.

The residue of atrazine (a herbicide) has become hazards in environments due to its intensive use. However, its molecular toxicity to on plants and human beings is not fully understood. In this study, we performed high-throughput sequencing of atrazine-exposed rice (Oryza sativa) to analyze global expression and complexity of genes in the crop. Four libraries were constructed from shoots and roots with or without atrazine exposure. We sequenced 5,751,861, 5,790,013, 5,375,999 and 6,039,618 clean tags that corresponded to 220,806, 111,301, 248,802 and 114,338 distinct tags for Root-Atr (root control, atrazine-free), Shoot-Atr (shoot control, atrazine-free), Root+Atr (root treated with atrazine) and Shoot+Atr (shoot treated with atrazine) libraries, respectively. Mapping the clean tags to gene databases generated 18,833-21,007 annotated genes for each library. Most of annotated genes were differentially expressed among the libraries. The most 40 differentially expressed genes were associated with resistance to environmental stress, degradation of xenobiotics and molecular metabolism. Validation of gene expression by quantitative RT-PCR confirmed the deep-sequencing results. The transcriptome sequences were further subjected to Gene Orthology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and showed modified biological functions and metabolic pathways. Our results not only highlight the transcriptional complexity in rice with atrazine but also represent a major improvement for analyzing transcriptional changes on a large scale in xenobiotics-responsive toxicology.

Genome-wide identification of Medicago truncatula microRNAs and their targets reveals their differential regulation by heavy metal.

We adopted a deep sequencing approach developed by Solexa (Illumina Inc., San Diego, CA, USA) to investigate global expression and complexity of microRNAs (miRNAs) and their targets from Medicago truncatula. Two small RNA libraries and two degradome libraries were constructed from mercury (Hg)-treated and Hg-free M. truncatula seedlings. For miRNAs, each library generated 18.5-18.6 million short sequences, resulting in 10.2-10.8 million clean reads. At least 52 new miRNA candidates with ≈ 21 nucleotides are perfectly matched to the M. truncatula genome. Statistical analysis on transcript abundance of the new candidate miRNAs revealed that most of them were differentially regulated by the heavy metal mercury Hg(II), with 12 miRNAs being specifically induced by Hg exposure. Additionally, we identified 201 individual miRNAs representing 63 known M. truncatula miRNA families, including 12 new conserved and one non-conserved miRNAs that have not been described before. Finally, 130 targets for 58 known (37 conserved and 21 non-conserved) miRNA families and 37 targets for 18 new M. truncatula-specific candidate miRNA families were identified by high-throughput degradome sequencing approach.

Regulation of tolerance of Chlamydomonas reinhardtii to heavy metal toxicity by heme oxygenase-1 and carbon monoxide.

Investigation of heavy metal tolerance genes in green algae is of great importance because heavy metals have become one of the major contaminants in the aquatic ecosystem. In plants, accumulation of heavy metals modifies many aspects of cellular functions. However, the mechanism by which heavy metals exert detrimental effects is poorly understood. In this study, we identified a role for HO-1 (encoding heme oxygenase-1) in regulating the response of Chlamydomonas reinhardtii, a unicellular green alga, to mercury (Hg). Transgenic algae overexpressing HO-1 showed high tolerance to Hg exposure, with a 48.2% increase in cell number over the wild type, but accumulated less Hg. Physiological analysis revealed that expression of HO-1 suppressed the Hg-induced generation of reactive oxygen species. We further identified the effect of carbon monoxide (CO), a product of HO-1-mediated heme degradation, on growth and physiological parameters. Interestingly, administration of exogenous CO at non-toxic levels also conferred the tolerance of algae to Hg exposure. The CO-mediated alleviation of Hg toxicity was closely related to the lower accumulation of Hg and free radical species. These results indicate that functional identification of HO-1 is useful for molecular breeding designed to improve plant tolerance to heavy metals and reduce heavy metal accumulation in plant cells.

Carbon monoxide improves adaptation of Arabidopsis to iron deficiency.

Carbon monoxide (CO) is an endogenous gaseous molecule and regulates a variety of biological processes in animals. However, whether CO regulates nutrient stress responses in plants is largely unknown. In this paper, we described an observation that CO can regulate iron-homeostasis in iron-starved Arabidopsis. Exogenous CO at 50 microm was able to prevent the iron deficient-induced chlorosis and improve chlorophyll accumulation. Expression of AtIRT1, AtFRO2, AtFIT1 and AtFER1 was up-regulated by CO exposure in iron-deficient seedlings. CO-regulated iron homeostasis could also be found in monocot maize and green alga Chlamydomonas reinhardtii. Treatment with external CO increased iron accumulation in iron-deficient Arabidopsis and C. reinhardtii, and restored leaf greening in Maize ys1 and ys3 mutants (defective in Fe uptake). Moreover, endogenous CO level was increased in Arabidopsis under iron-deficiency. Finally, CO exposure induced NO accumulation in root tips. However, such an action could be blocked by NO scavenger cPTIO. These results indicate that CO may play an important role in improving plant adaptation to iron deficiency or cross-talking with NO under the iron deficiency.

Trichlorfon-induced apoptosis in hepatocyte primary cultures of Carassius auratus gibelio.

Trichlorfon, an organophosphorus pesticide, can disrupt metabolism, reproduction and immune functions of some aquatic animals. In the present study, the effect of trichlorfon on apoptosis and the underlying apoptotic mechanism were investigated in primary cultures of Carassius auratus gibelio hepatocytes. Analyses of cultures exposed to 0, 0.01, 0.1, and 1.0 mg L(-1) trichlorfon concentrations for 24h indicated that trichlorfon induced apoptosis and caused nuclear shrinkage, cell membrane rupture, cytoskeletal collapse, loss of cytoplasm, mitochondria vacuolization, and apoptotic body formation, as well as lipid droplet accumulation. Trichlorfon increased intracellular reactive oxygen species and malondialdehyde concentrations and caused cytochrome c release from mitochondria into the cytoplasm, leading to caspase-3 activation. These findings contributed to a better understanding of the mechanisms underlying trichlorfon-induced apoptosis via activation of mitochondrial pathways while clearly indicating that trichlorfon-induced cell death was via apoptosis accompanied by mitochondrial cytochrome c release and consequent caspase-3 activation.

[Comparison of seed oil physicochemical characteristics among three cultivars of Jatropha curcas L].

Taking the cultivars Nanyou 1, 2, and 3 of barbadosnut (Jatropha curcas L. ) with different genotypes that can grow and seed normally at the inshore land in Hainan as test materials, the characters of their seeds and the physicochemical characteristics of their seed oils were analyzed and compared. No significant differences were observed in the seed length, width, thickness, and surface area among the cultivars, but Nanyou 2 had greater 1000 seed mass and lower unsound kernel percentage than Nanyou 1 and Nanyou 3, suggesting that the seed satiation of Nanyou 2 was good and the fecundity was excellent. The kernel oil content of Nanyou 3 was significantly higher than that of Nanyou 1 and Nanyou 2, and there was no significant difference between Nanyou 1 and Nanyou 2. The seed oil peroxide value, refractive index, and saponification value of the three cultivars had no significant differences, but the acid value for Nanyou 2 was much lower than that for Nanyou 1 and Nanyou 3. The seed oil iodine value of the three cultivars was all below 100, and was significantly lower for Nanyou 2 than for Nanyou 1 and Nanyou 3. The fatty acids in the three cultivars seed oils were mainly oleic acid, palmitic acid, linoleic acid, stearic acid, and margaric acid, and dominated by unsaturated fatty acids. The contents of saturated fatty acids in Nanyou 2 seed oil were relatively higher than those in Nanyou 1 and Nanyou 3 seed oils, indicating that comparing with Nanyou 1, cultivars Nanyou 2 and Nanyou 3 had relatively good potential for application.

[Determination of trace elements in Aloe barbadensis Miller irrigated with seawater by atomic absorption spectrophotometry].

The dry leaves of Aloe barbadensis Miller irrigated with seawater were dissolved in nitric acid and then oxygenated by perchloric acid. Nine kinds of trace elements in the samples were determined by atomic absorption spectrophotometry, including calcium, potassium, magnesium, sodium, manganese, zinc, iron, copper and lead, with added lanthanum chloride as releaser to eliminate the interference of co-existent ions. The recoveries were 96.58%-104.31%, and the relative standard deviations of sample determination (10 times) were less than 2%. This method is simple, sensitive and rapid with satisfactory results and good reproducibility. The results indicated that there were rich Ca, Mg, K and Na, and moderate Mn, Zn and Fe elements in the Aloe barbadensis Miller irrigated with seawater. However, the concentrations of Cu and Pb were low. Therefore, Aloe barbadensis Miller irrigated with seawater has officinal and economic values. These results provide data for further research on Aloe barbadensis Miller irrigated with seawater.

Copper-induced proline synthesis is associated with nitric oxide generation in Chlamydomonas reinhardtii.

Excess copper affects the growth and metabolism of plants and green algae. However, the physiological processes under Cu stress are largely unknown. In this study, we investigated Cu-induced nitric oxide (NO) generation and its relationship to proline synthesis in Chlamydomonas reinhardtii. The test alga accumulated a large amount of proline after exposure to relatively low Cu concentrations (2.5 and 5.0 microM Cu2+). A concomitant increase in the intracellular NO level was observed with increasing concentrations of Cu applied. Data analysis revealed that the endogenous NO generated was positively associated with the proline level in Cu-stressed algae. The involvement of NO in Cu-induced proline accumulation was confirmed by using an NO-specific donor, sodium nitroprusside (SNP), and an NO scavenger cPTIO [2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylinidazoline-1-oxyl-3-oxide]. Pre-treatment with 10 microM SNP increased the proline accumulation in Cu-treated cells by about 1.5-fold, while this effect could be blocked by addition of 10 microM cPTIO. We further investigated the effect of Cu and NO on the activity and transcript amount of Delta(1)-pyrroline-5-carboxylate synthetase (P5CS, EC 2.7.2.11), the key enzyme of proline biosynthesis, and observed that application of SNP was able to stimulate the P5CS activity and up-regulate the expression of P5CS in the Cu-treated algae. These results indicate that Cu-responsive proline synthesis is closely related to NO generation in C. reinhardtii, suggesting the regulatory function of NO in proline metabolism under heavy metal stress.

[Effects of NaCl on the growth and alkaloid content of Catharanthus roseus seedlings].

Catharanthus roseus seedlings were grown in 1/2 Hoagland solution containing 0-250 mmol x L(-1) of NaCl, and their fresh and dry mass, malondialdehyde (MDA) and chlorophyll contents, tryptophan decarboxylase (TDC) and peroxidase (POD) activities, and vindoline, catharanthine, vincristine and vinblastine contents were measured after 7 days. The results showed that NaCl markedly decreased the fresh and dry mass but increased the MDA content. The chlorophyll content had no difference with the control when the concentration of NaCl was 50 mmol x L(-1), but decreased with increasing NaCl concentration when the NaCl concentration was above 50 mmol x L(-1). There was a significant enhancement of POD activity under NaCl stress. The TDC activity was the highest when the concentration of NaCl was 50 mmol x L(-1), but decreased with increasing NaCl concentration. The vindoline, catharanthine, vincristine, and vinblastine contents were the highest under 50 mmol x L(-1) NaCl stress, with the values being 4.61, 3.56, 1.19, and 2.95 mg x g(-1), respectively, and significant higher than the control and other treatments. Salt stress could restrain the growth of C. roseus seedlings, but promote the metabolism of alkaloid and increase the alkaloid content. 50 mmol x L(-1) of NaCl had the greatest promotion effect on the alkaloid content of C. roseus seedlings.

Silicate improves growth and ion absorption and distribution in aloe vera under salt stress.

Si 2.0 mmol/L in irrigation solution alleviated significantly the inhibition of NaCl stress of 100 or 200 mmol/L to aloe growth. Exogenously applied Si decreased significantly Na(+) and Cl(-) contents, increased K(+) content and K(+)/Na(+) ratio and selectivity ratio of absorption (AS(K, Na)) and of translocation (TS(K, Na)) to K(+) and Na(+) in aloe plant under both NaCl 100 and 200 mmol/L stresses for 30 d. In this way, the ion homeostasis in aloe plant under NaCl stress was maintained, as was proved by X-ray microanalysis of root tip and leaf across sections. One of the mechanisms to achieve this may be the significant enhancement of H(+)-ATPase activities by the addition of silicate in plasma membrane and tonoplast, H(+)-pyrophosphatase (H(+)-PPase) activity in tonoplast isolated from aloe root tips under NaCl stress.

Induced expression of the gene for NADP-malic enzyme in leaves of Aloe vera L. under salt stress.

A cDNA fragment for NADP-malic enzyme, catalyzing the reversible oxidative decarboxylation of L-malate to produce CO(2), pyruvate and NADPH, was isolated from the leaves of a 2-month-old Aloe vera L., The level of expression of NADP-ME mRNA and accumulation of NADP-ME (AvME) protein under salt stress conditions were compared between a tolerant aloe, Aloe vera L. and a sensitive aloe, Aloe saponarea Haw. The results suggested that both the expression of the gene and the accumulation of the protein were induced in the two kinds of aloe, and the strength was related to the degree of salt tolerance. Northern blot analysis revealed that the gene for NADP-malic enzyme in Aloe vera L.( AvME) was induced by high salt, dehydration, and exogenous abscisic acid (ABA), but not by cold treatment. To further confirm whether the synthesis of AvME protein was induced with hours of treatment, Western blot analysis of the samples was conducted. The results indicated that the induction of AvME protein expression was obvious after 48 h at high salt and the level was increased with the hours of treatment.