Proteins and Carbohydrates from Red Seaweeds: Evidence for Beneficial Effects on Gut Function and Microbiota

Based on their composition, marine algae, and namely red seaweeds, are good potential functional foods. Intestinal mucosal barrier function refers to the capacity of the intestine to provide adequate containment of luminal microorganisms and molecules. Here, we will first outline the component of seaweeds and will summarize the effects of these on the regulation of mucosal barrier function. Special attention will be paid to unique components of red seaweeds: proteins and derived peptides (e.g., phycobiliproteins, glycoproteins that contain “cellulose binding domains”, phycolectins and the related mycosporine-like amino acids) together with polysaccharides (e.g., floridean starch and sulfated galactans, such as carrageenans, agarans and “dl-hybrid”) and minerals. These compounds have been shown to exert prebiotic effects, to regulate intestinal epithelial cell, macrophage and lymphocyte proliferation and differentiation and to modulate the immune response. Molecular mechanisms of action of peptides and polysaccharides are starting to be elucidated, and evidence indicating the involvement of epidermal growth factor receptor (EGFR), insulin-like growth factor receptor (IGFR), Toll-like receptors (TLR) and signal transduction pathways mediated by protein kinase B (PKB or AKT), nuclear factor-κB (NF-κB) and mitogen activated protein kinases (MAPK) will also be summarized. The need for further research is clear, but in vivo experiments point to an overall antiinflammatory effect of these algae, indicating that they can reinforce membrane barrier function.     

Effects of Different Nitrogen Application Rates on Starch Accumulation,Starch Synthase Gene Expression and Enzyme Activity in Two Distinctive Potato Cultivars

Nitrogen (N) is the most important nutrient for potato growth. N fertilizer has an important effect on the tuber yield and starch content in potatoes. In this study, taking the high-starch cultivar Kexin 22 and the low-starch cultivar Kexin 19 as experimental materials, three N fertilizer application rates—0, 150 and 300 kg/ha—were used to investigate the effects of different N application rates on starch accumulation and the expression of starch synthase genes in potato tubers with different starch contents. In the cultivar Kexin 22, the accumulations of amylose, amylopectin and total starch showed a ranking of N150 > N300 > N0 for the entire growth period. The cultivar Kexin 19 showed an accumulation pattern of N0 > N150 > N300 in the early growth period, N150 > N300 > N0 in the middle growth period and N300 > N150 > N0 in the late growth period. Compared with those in Kexin 19, the expressions of the glucose-1-phosphate adenyltransferase (AGPP-L), granule-bound starch synthase (GBSSI), starch-branching enzyme I (SBEI) and soluble starch synthase III (SSIII) genes in Kexin 22 were upregulated, whereas no obvious difference existed in the expression of the alkylglycerone phosphate synthase (AGPP-S) and soluble starch synthase II (SSII) genes between the two cultivars. In Kexin 22, the different N application rates had a significant effect on the peak expression levels of AGPP-L, GBSSI, SBEI and SSIII but had a small effect on the peak expression time for these genes. Among these genes, most showed a ranking of N150 > N300 > N0 in the early and middle growth periods, and all showed a ranking of N300 > N150 > N0 in the late growth period; most showed a peak expression time on the 65th day after emergence (DAE 65). In Kexin 19, the different N application rates had a significant effect on the peak expression levels and peak expression times of the AGPP-L, GBSSI, SBEI and SSIII genes. Among these genes, all showed a ranking of N0 > N150 > N300 in the early growth period, whereas most showed a ranking of N150 > N300 > N0 in the middle growth period, and all showed a ranking of N300 > N150 > N0 in the late growth period. In Kexin 19, the peak gene expression was shifted to an earlier date under the low N levels, and it was delayed under the high N levels. The effects of the N application rate on the activities of starch synthases AGPP, GBSS, SSS and SBE showed largely the same trends as those in the expression levels of the related genes. Therefore, to obtain a high harvest of starch yield, different N application rates should be recommended for different cultivars.     

Amylase Analysis in Potato Starch Degradation During Cold Storage and Sprouting

As the fourth most important food crop, potato plays a key role in food safety and economic development of the world. Harvested potato tubers can be stored for a long time, but sprouting and cold-induced sweetening (CIS) can seriously affect the quality of tubers during storage. One of the key pathways involved in CIS is starch degradation, in which both α-amylase and β-amylase play important roles. However, each amylase belongs to an extensive gene family and it is not clear which genes are the key regulators. In this study, we identified genes most likely regulating starch degradation. We first selected candidate genes from the public potato genome database and then investigated their expression patterns associated with reducing sugars and amylase activities. The results showed that the activity of α-amylase was mainly caused by StAmy23 and the activity of β-amylase was mainly caused by StBAM1 and StBAM7. In addition, α-amylase and β-amylase may play important roles in starch degradation of the tubers stored at low temperature and during sprouting, and the amylase activity may be regulated by the amylase inhibitor in cold-stored tubers.     

Determination of the Extraction,Physicochemical Characterization,and Digestibility of Sulfated Polysaccharides in Seaweed—Porphyra haitanensis

The aim of the study was to extract Porphyra haitanensis polysaccharides (PHPs) using the water extraction and alcohol precipitation methods and explore their antioxidant activity and physicochemical properties. The single-factor and Box-Behnken response surface methodologies were used to optimize the extraction of polysaccharides from Porphyra haitanensis. Our results showed that the polysaccharide yield was as high as 20.48% with a raw material to water ratio of 0.04, and extraction time of 3 h at 80 °C. The extraction rate observed was similar to the actual extraction rate, thus proving the reliability of the optimization model. The extracted polysaccharides primarily consisted of galactose, glucose, and fucose in the molar ratio 76.2:2.1:1, respectively. The high performance gel permeation chromatography (HPGPC) results showed that the molecular weight of the PHPs obtained was 6.3 × 10⁵ Da, and the sulfate content was 2.7 mg/mL. Fourier infrared spectroscopy was used to analyze the functional groups and structures of the polysaccharides. The effect of concentration, temperature, and pH on the apparent viscosity of the PHPs solution were studied using rheology experiments, which revealed that PHPs were a “non-Newtonian fluid” with shear-thinning behavior. The viscosity of the PHPs gradually increased with increasing sugar concentration, and decreased with increasing temperature, acidity, and alkalinity. Detection of the antioxidant activity of OH*, DPPH*, and ABTS* revealed that the scavenging activity of ABTS* was higher than that of OH* and DPPH* in the concentration range of 1–5 mg/mL. In the experiments of simulating gastric juice and alpha amylase in vitro, it was found that PHPs can better resist digestion of alpha amylase, and have better resistance than fructooligosaccharide (FOS), so PHPs have potential prebiotic activity. These findings demonstrate the potential of PHPs for use in the food and cosmetic industries.     

Floridoside Extracted from the Red Alga Mastocarpus stellatus Is a Potent Activator of the Classical Complement Pathway

Many biological properties of algae have been found to have useful applications in human health, particularly in the fields of oncology and immunology. Floridoside, extracted from the red alga Mastocarpus stellatus, has a structure similar to the xenoantigen Gal alpha 1–3 Gal. This xenoantigen has been described to induce a high immune response in human xenografts and is mediated by natural anti-gal antibodies that activate the classical complement pathway. Based on this property, we analyzed the potential activities of floridoside on the immune system. We demonstrated that floridoside activates a complement cascade via the classical complement pathway, through the recruitment and activation of natural IgM. This algal molecule could represent an important step in the development of a potent new anticomplementary agent for use in therapeutic complement depletion.     

Isolation and Characterization of Microsatellite Markers Useful for Exploring Introgression Among Species in the Diverse New Zealand Cicada Genus Kikihia

The New Zealand cicada genus Kikihia Dugdale 1971 exhibits more than 20 contact zones between species pairs that vary widely in their divergence times (between 20,000 and 2 million years) in which some level of hybridization is evident. Mitochondrial phylogenies suggest some movement of genes across species boundaries. Biparentally inherited and quickly evolving molecular markers like microsatellites are useful for assessing gene flow levels. Here, we present six polymorphic microsatellite loci that amplify DNA from seven species across the genus Kikihia; Kikihia “northwestlandica,” Kikihia “southwestlandica,” Kikihia muta, Kikihia angusta, Kikihia “tuta,” Kikihia “nelsonensis,” and Kikihia “murihikua.” The markers were developed using whole-genome shotgun sequencing on the 454 pyrosequencing platform. Moderate to high levels of polymorphisms were observed with 14–47 alleles for 213 individuals from 15 populations. Observed and expected heterozygosity range from 0 to 1 and 0.129 to 0.945, respectively. These new markers will be instrumental for the assessment of gene flow across multiple contact zones in Kikihia.     

Regulation of C/N Interaction in Model Plant Species

Summary

Carbon (C) and nitrogen (N) metabolisms are two major metabolic pathways which have been intensively studied in plants. Both N and C metabolisms are tightly linked in numerous plant biochemical pathways. Therefore the C to N ratio has to be carefully regulated to ensure proper functioning of the huge metabolic network. In order to maintain a viable C/N status under a large range of growth conditions plants have evolved complex mechanisms to regulate the delicate network of these two major assimilatory pathways. C and N metabolisms are both highly regulated. We will present the current knowledge on the regulation of N and C metabolisms by sugars and N metabolites. Players involved in these regulatory processes are just starting to be uncovered and possible signaling molecules involved in these regulations as well as known or potential candidate regulatory genes willbe discussed.     

A 13CO2 Enrichment Experiment to Study the Synthesis Pathways of Polyunsaturated Fatty Acids of the Haptophyte Tisochrysis lutea

The production of polyunsaturated fatty acids (PUFA) in Tisochrysis lutea was studied using the gradual incorporation of a ¹³C-enriched isotopic marker, ¹³CO₂, for 24 h during the exponential growth of the algae. The ¹³C enrichment of eleven fatty acids was followed to understand the synthetic pathways the most likely to form the essential polyunsaturated fatty acids 20:5n-3 (EPA) and 22:6n-3 (DHA) in T. lutea. The fatty acids 16:0, 18:1n-9 + 18:3n-3, 18:2n-6, and 22:5n-6 were the most enriched in ¹³C. On the contrary, 18:4n-3 and 18:5n-3 were the least enriched in ¹³C after long chain polyunsaturated fatty acids such as 20:5n-3 or 22:5n-3. The algae appeared to use different routes in parallel to form its polyunsaturated fatty acids. The use of the PKS pathway was hypothesized for polyunsaturated fatty acids with n-6 configuration (such as 22:5n-6) but might also exist for n-3 PUFA (especially 20:5n-3). With regard to the conventional n-3 PUFA pathway, Δ6 desaturation of 18:3n-3 appeared to be the most limiting step for T. lutea, “stopping” at the synthesis of 18:4n-3 and 18:5n-3. These two fatty acids were hypothesized to not undergo any further reaction of elongation and desaturation after being formed and were therefore considered “end-products”. To circumvent this limiting synthetic route, Tisochrysis lutea seemed to have developed an alternative route via Δ8 desaturation to produce longer chain fatty acids such as 20:5n-3 and 22:5n-3. 22:6n-3 presented a lower enrichment and appeared to be produced by a combination of different pathways: the conventional n-3 PUFA pathway by desaturation of 22:5n-3, the alternative route of ω-3 desaturase using 22:5n-6 as precursor, and possibly the PKS pathway. In this study, PKS synthesis looked particularly effective for producing long chain polyunsaturated fatty acids. The rate of enrichment of these compounds hypothetically synthesized by PKS is remarkably fast, making undetectable the ¹³C incorporation into their precursors. Finally, we identified a protein cluster gathering PKS sequences of proteins that are hypothesized allowing n-3 PUFA synthesis.     

Heterotrophic Production of Omega-3 Long-Chain Polyunsaturated Fatty Acids by Trophically Converted Marine Diatom Phaeodactylum tricornutum

We have created via metabolic engineering a heterotrophic strain of Phaeodactylum tricornutum that accumulates enhanced levels of the high value omega-3 long chain polyunsaturated fatty acid (LC-PUFAs) docosahexaenoic acid (DHA). This was achieved by generation of transgenic strains in which the Δ5-elongase from Ostreococcus tauri was co-expressed with a glucose transporter from the moss Physcomitrella patens. This double transformant has the capacity to grow in the dark in liquid medium supplemented with glucose and accumulate substantial levels of omega-3 LC-PUFAs. The effects of glucose concentrations on growth and LC-PUFA production of wild type and transformed strains cultivated in the light and dark were studied. The highest omega-3 LC-PUFAs accumulation was observed in cultures grown under mixotrophic conditions in the presence of 1% glucose (up to 32.2% of total fatty acids, TFA). Both DHA and EPA are detected at high levels in the neutral lipids of transgenic cells grown under phototrophic conditions, averaging 36.5% and 23.6% of TFA, respectively. This study demonstrates the potential for P. tricornutum to be developed as a viable commercial strain for both EPA and DHA production under mixo- and heterotrophic conditions.     

Comparative Lipid Profile Analysis of Hermetia illucens Larvae Fed Food Waste at Different Days of Age Using an LC-MS-Based Lipidomics Approach

A lipidomics approach based on liquid chromatography–tandem mass spectrometry (LC-MS) was applied to analyze the molecular-level mechanism of lipid deposition in Hermetia illucens (H. illucens) larvae fed food waste (FW) at different days of age. The H. illucens larvae reared on FW substrates generally became larger, heavier, and fatter at 5–15 d of age. A large amount of glycerolipids (GL) were deposited, while glycerophospholipids (GP), sphingolipids, and derivatized lipids became relatively less abundant during the growth stage of the larvae. Forty-three subclasses of 3,205 lipid molecules were identified in larvae, and 139 lipids (79 upregulated and 60 downregulated during larval growth and development) were identified as potential biomarkers (variable importance in projection > 1; P < 0.05). The differential lipids were mainly enriched in 19 metabolic pathways, of which 9 metabolic pathways related to lipids, including GL and GP metabolisms. The results demonstrate that the lipid composition and mechanisms changed during the growth and development stage of H. illucens larvae. To the best of our knowledge, this is the first work exploring the molecular-level mechanism of lipid deposition during the growth and development stage of H. illucens larvae. The findings provide novel information for determining and utilizing the nutritional value of H. illucens larvae.     

Relative Fitness of Helicoverpa armigera (Lepidoptera: Noctuidae) on Seven Host Plants: A Perspective for IPM in Brazil

The cotton bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a widespread pest of many cultivated and wild plants in Europe, Africa, Asia, and Australia. In 2013, this species was reported in Brazil, attacking various host crops in the midwestern and northeastern regions of the country and is now found countrywide. Aiming to understand the effects of different host plants on the life cycle of H. armigera, we selected seven species of host plants that mature in different seasons and are commonly grown in these regions: cotton (Gossypium hirsutum, “FM993”), corn (Zea mays, “2B587”), soybean (Glycine max, “99R01”), rattlepods (Crotalaria spectabilis), millet (Pennisetum glaucum, “ADR300”), sorghum (Sorghum bicolor, “AGROMEN70G35”), and cowpea (Vigna unguiculata, “SEMPRE VERDE”). The development time of immatures, body weight, survivorship, and fecundity of H. armigera were evaluated on each host plant under laboratory conditions. The bollworms did not survive on corn, millet, or sorghum and showed very low survival rates on rattlepods. Survival rates were highest on soybean, followed by cotton and cowpea. The values for relative fitness found on soybean, cotton, cowpea, and rattlepods were 1, 0.5, 0.43, and 0.03, respectively. Survivorship, faster development time, and fecundity on soybean, cotton, and cowpea were positively correlated. Larger pupae and greater fecundity were found on soybean and cotton. The results indicated that soybean, cotton, and cowpea are the most suitable plants to support the reproduction of H. armigera in the field.     

转录组揭示自养和混合培养栅藻油脂代谢途径差异

为探讨混合培养条件下栅藻脂质高产的调控机理,对栅藻(Desmodesmus sp.)分别进行自养和混合培养,使用转录组测序对比了Desmodesmus sp.在两种培养方式下油脂代谢途径差异.结果表明,混合培养组上调基因共1081个,下调基因共575个,非显著差异表达基因总共23331个.差异基因GO富集主要在光合作用...     

小麦生理型雄性不育系花药内源JA与ABA含量动态变化及其代谢通路差异基因表达研究

为了进一步阐明化学杂交剂SQ-1诱导小麦花粉败育的分子机制,以西农1376为材料,采用RNA-seq技术,对PHYMS-1376及其对照可育系CK-1376四分体、单核早期、单核晚期、二核期、三核期花药进行转录组测序,筛选出差异表达基因,进行GO富集、KEGG富集和GSEA富集分析,并利用高效液相法分别检测了PHYMS-1376及CK-1376上述五个时期花药中ABA和JA含量,通过qRT-PCR技术分析了ABA和JA通路关键差异基因的表达模式。结果发现,与CK-1376相比,在PHYMS-1376花药中共筛选出了 36 058个差异表达基因,主要富集到植物激素信号传导、苯丙素生物合成、淀粉和蔗糖代谢、氨基酸的生物合成4个通路;JA含量在PHYMS-1376四分体花药中显著降低（P<0.05）,至单核早期显著升高,单核晚期又显著降低,二核期显著升高,三核期显著降低;ABA含量在PHYMS-1376四分体至三核期花药中含量均高于CK-1376,其中在单核早期、单核晚期和二核期差异显著,可能与不育系各时期花药中PP2C关键基因TraesCS1D02G271000表达量过低相关,致使PP2C蛋白含量减少,进一步激活BIN2/BILs激酶,使SnRK2s磷酸化,促进ABA含量增加。上述结果表明：PHYMS-1376各发育时期花药中JA含量的异常波动与ABA含量的显著增加及上述2个通路关键基因的差异表达可能与SQ-1诱导小麦花粉败育密切相关。本研究为深入揭示SQ-1诱导小麦生理型雄性不育机理提供了一定的理论基础。     

Effect of various drought stresses and subsequent recovery on proline,total soluble sugar and starch metabolisms in Rice (Oryza sativa L.) varieties

ABSTRACT

Rice (Oryza sativa L.) is one of the most important staple foods in the world, however most improved rice varieties are susceptible to drought stress. A two-year study was conducted to explore the effects of various drought stresses and subsequent recovery on the accumulation and degradation of proline, total soluble sugar and starch in different rice varieties at vegetative stage. The results showed that relative water content in the leaves and sheaths of rice varieties significantly decreased under drought stresses, but not at the same rate. Under control and drought conditions, the water content in sheaths was higher than that in leaves. Interestingly, under severe drought stress in 2015, the leaf water content was higher than the sheath water content. The water distribution between leaves and sheaths might be a response of plants to protect leaf system from devastation by drought. Proline was highly accumulated under drought stress but rapidly decreased after re-watering. The drought tolerant variety DA8 expressed higher ability in accumulation of proline than susceptible varieties. In general, total soluble sugar and starch contents in leaves and sheaths of varieties decreased under drought stress conditions. Total soluble sugar and starch content of DA8 were less affected than other varieties under drought conditions. Our study indicated that metabolisms of total soluble sugar and starch in rice were affected by both environmental conditions and characteristics of varieties. Proline accumulation ability of varieties can be used as a useful indicator for drought tolerant potential in rice breeding for water-limited environments.     

Differential Sensitivity of Chloroplasts in Mesophyll and Bundle Sheath Cells in Maize,an NADP-Malic Enzyme-Type C4 Plant,to Salinity Stress

Abstract

The changes in chloroplast ultrastructure and the contents of chlorophyll, Na and K in response to salinity stress were investigated in leaves of maize, an NADP-malic enzyme-type C₄ plant species possessing dimorphic chloroplasts. The seedlings were treated with 0, 1, 2 or 3% NaCl for three or five days under a light or dark condition. In both light and dark conditions, the dry weight of salt-treated plants decreased as NaCl concentration increased. Chlorophyll and K contents of the second leaf blade decreased as NaCl concentration increased under the light condition but not under the dark condition. Na content of the second leaf blade was significantly higher at high NaCl concentrations under both light and dark conditions. However, Na content was much lower under the dark condition than light condition. Higher concentrations (2 and 3%) of NaCl significantly increased the size of plastoglobules, decreased the number and size of starch granules and altered the chloroplast ultrastructure. Under the light condition, mesophyll cell (MC) chloroplasts appeared more sensitive to the damaging effect of salinity than the bundle sheath cell (BSC) chloroplasts. MC chloroplasts became more globular in shape and showed swollen and disorganized thylakoids and reduced thickness of grana by salinity. BSC chloroplasts were less affected by salinity than MC chloroplasts. Although chloroplast size and number and size of starch granules were reduced, there was no structural distortion in the thylakoids of BSC chloroplasts. However, the thickness of grana was increased by salinity. Under the dark condition, the chloroplast structure was less affected by salinity. Though the envelope of BSC chloroplasts was occasionally damaged, the thylakoids in both MC and BSC chloroplasts were preserved under salinity stress. The present study suggests that the chloroplast damage caused by salinity is light-dependent and MC chloroplasts are more sensitive to salinity than BSC chloroplasts.     

Responses of glutamine synthetase activity and gene expression to nitrogen levels in winter wheat cultivars with different grain protein content

Glutamine synthetase (GS) plays a central role in plant nitrogen (N) metabolism, which improves crops grain protein content. A pot experiment in field condition was carried out to evaluate GS expression and activity, and grain protein content in high (Wanmai16) and low grain protein (Loumai24) wheat cultivars under two N levels (0.05 and 0.15 g N kg⁻¹ soil). High nitrogen (HN) resulted in significant increases in GS1 and GS2 expression at 10 days after anthesis (DAA), and higher GS activity during the entire grain filling stage. HN also significantly increased yield, grain protein content and protein fraction (except for glutenin of Luomai24) in two wheat cultivars, which indicated that it increased grain yield and protein content by improving nitrogen metabolism. Wanmai16 showed higher grain protein content, gliadin and glutenin content, and had higher expression level of GS2 both in flag leaves and grains at early grain filling stage. However, Luomai24 had greater yield and higher expression level of GS1. The difference expression of GS2 and GS1 genes indicates they had various contributions to the accumulation of protein and starch in wheat grains, respectively. The results suggest that GS2 would be serving as a potential breeding target for improving wheat quality.     

First Identification of 12β-Deoxygonyautoxin 5 (12α-Gonyautoxinol 5) in the Cyanobacterium Dolichospermum circinale (TA04) and 12β-Deoxysaxitoxin (12α-Saxitoxinol) in D. circinale (TA04) and the Dinoflagellate Alexandrium pacificum (Group IV) (120518KureAC)

Saxitoxin and its analogues, paralytic shellfish toxins (PSTs), are potent and specific voltage-gated sodium channel blockers. These toxins are produced by some species of freshwater cyanobacteria and marine dinoflagellates. We previously identified several biosynthetic intermediates of PSTs, as well as new analogues, from such organisms and proposed the biosynthetic and metabolic pathways of PSTs. In this study, 12β-deoxygonyautoxin 5 (12α-gonyautoxinol 5 = gonyautoxin 5-12(R)-ol) was identified in the freshwater cyanobacterium, Dolichospermum circinale (TA04), and 12β-deoxysaxitoxin (12α-saxitoxinol = saxitoxin-12(R)-ol) was identified in the same cyanobacterium and in the marine dinoflagellate Alexandrium pacificum (Group IV) (120518KureAC) for the first time from natural sources. The authentic standards of these compounds and 12α-deoxygonyautoxin 5 (12β-gonyautoxinol 5 = gonyautoxin 5-12(S)-ol) were prepared by chemical derivatization from the major PSTs, C1/C2, produced in D. circinale (TA04). These standards were used to identify the deoxy analogues by comparing the retention times and MS/MS spectra using high-resolution LC-MS/MS. Biosynthetic or metabolic pathways for these analogues have also been proposed based on their structures. The identification of these compounds supports the α-oriented stereoselective oxidation at C12 in the biosynthetic pathway towards PSTs.