Light regulation on growth, development, and secondary metabolism of marine-derived filamentous fungi

Effects of different light conditions on development, growth, and secondary metabolism of three marine-derived filamentous fungi were investigated. Darkness irritated sexual development of Aspergillus glaucus HB1-19, while white, red, and blue lights improved its asexual behavior. The red and blue lights improved asexual stroma formation of Xylaria sp. (no. 2508), but the darkness and white light inhibited it. Differently, development of Halorosellinia sp. (no. 1403) turned out to be insensitive to any tested light irradiation. Upon the experimental data, no regularity was observed linking development with secondary metabolism. However, fungal growth showed inversely correlation with productions of major bioactive compounds (aspergiolide A, 1403C, and xyloketal B) from various strains. The results indicated that aspergiolide A biosynthesis favored blue light illumination, while 1403C and xyloketal B preferred red light irradiation. With the favorite light sensing conditions, productions of aspergiolide A, 1403C, and xyloketal B were enhanced by 32.9, 21.9, and 30.8 % compared with those in the dark, respectively. The phylogenetic analysis comparing the light-responding proteins of A. glaucus HB 1-19 with those in other systems indicated that A. glaucus HB 1-19 was closely related to Aspergillus spp. especially A. nidulans in spite of its role of marine-derived fungus. It indicated that marine fungi might conserve its light response system when adapting the marine environment. This work also offers useful information for process optimization involving light regulation on growth and metabolism for drug candidate production from light-sensitive marine fungi.     

Seed priming with sorghum extracts and benzyl aminopurine improves the tolerance against salt stress in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Salt stress impedes the productivity of wheat (Triticum aestivum L.) in many parts of the world. This study evaluated the potential role of benzyl aminopurine (BAP) and sorghum water extract (SWE) in improving the wheat performance under saline conditions. Seeds were primed with BAP (5 mg L^?1), SWE (5% v/v), BAP + SWE, and distilled water (hydropriming). Soil filled pots maintained at the soil salinity levels of 4 and 10 dS m^?1 were used for the sowing of primed and non-primed seeds. Salt stress suppressed the wheat growth; seed priming treatments significantly improved the wheat growth under optimal and suboptimal conditions. Total phenolics, total soluble sugars and proteins, α-amylase activity, chlorophyll contents, and tissue potassium ion (K⁺) contents were increased by seed priming under salt stress; while, tissue sodium ion (Na⁺) contents were decreased. Seed priming with SWE + BAP was the most effective in this regard. Under salt stress, the tissue Na⁺ contents were reduced by 5.78, 28.3, 32.2, 36.7% by hydropriming, seed priming with SWE, seed priming with BAP, and seed priming with SWE + BAP, respectively over the non-primed control. Effectiveness of seed priming techniques followed the order SWE + BAP > BAP > SWE > Hydropriming. In conclusion, seed priming with SWE + BAP may be opted to improve the tolerance against salt stress in wheat.     

Assessment of the preventive effect of vermicompost on salinity resistance in tomato (<Emphasis Type="Italic">Solanum lycopersicum</Emphasis> cv. Ailsa Craig)

To determine the effects of vermicompost leachate (VCL) on resistance to salt stress in plants, young tomato seedlings (Solanum lycopersicum, cv. Ailsa Craig) were exposed to salinity (150 mM NaCl addition to nutrient solution) for 7 days after or during 6 mL L^??1 VCL application. Salt stress significantly decreased leaf fresh and dry weights, reduced leaf water content, significantly increased root and leaf Na⁺ concentrations, and decreased K⁺ concentrations. Salt stress decreased stomatal conductance (g_s), net photosynthesis (A), instantaneous transpiration (E), maximal efficiency of PSII photochemistry in the dark-adapted state (F_v/F_m), photochemical quenching (qP), and actual PSII photochemical efficiency (ΦPSII). VCL applied during salt stress increased leaf fresh weight and g_s, but did not reduce leaf osmotic potential, despite increased proline content in salt-treated plants. VCL reduced Na⁺ concentrations in leaves (by 21.4%), but increased them in roots (by 16.9%). VCL pre-treatment followed by salt stress was more efficient than VCL concomitant to salt stress, since VCL pre-treatment provided the greatest osmotic adjustment recorded, with maintenance of net photosynthesis and K⁺/Na⁺ ratios following salt stress. VCL pre-treatment also led to the highest proline content in leaves (50 µmol g^??1 FW) and the highest sugar content in roots (9.2 µmol g^??1 FW). Fluorescence-related parameters confirmed that VCL pre-treatment of salt-stressed plants showed higher PSII stability and efficiency compared to plants under concomitant VCL and salt stress. Therefore, VCL represents an efficient protective agent for improvement of salt-stress resistance in tomato.     

Synergistic Interactions Between Salt-tolerant Rhizobia and Arbuscular Mycorrhizal Fungi on Salinity Tolerance of <Emphasis Type="Italic">Sesbania cannabina</Emphasis> Plants

Legumes can host rhizobia and mycorrhizal fungi, and this triple symbiosis might be exploited to improve saline soil fertility. Therefore, a greater understanding of the interaction of rhizobia and arbuscular mycorrhizal fungus during legume growth in saline soil is required. We investigated the efficiency of salt tolerance conferred by rhizobia in mycorrhizal Sesbania cannabina. Greenhouse experiments were conducted in which S. cannabina plants inoculated with Glomus mosseae BGC NM03D (GM), and two rhizobia strains Agrobacterium pusense YIC4105 (4105) and Neorhizobium huautlense YIC4083 (4083), were exposed to 100 and 200 mM NaCl. Under 200 mM NaCl stress, plants inoculated with 4105, rather than 4083, showed significant increases in shoot and root dry mass compared with non-inoculated plants. Simultaneously, a significant increase over GM-inoculated plants in mycorrhizal colonization and dependency was recorded for 4105 + GM-inoculated plants compared with 4083 + GM-inoculated plants. In addition, under NaCl stress, significant increases in the number and mass of nodules, nitrogenase activity, and leghemoglobin content of nodules occurred in 4105 + GM-inoculated plants compared with 4083 + GM-inoculated plants. Furthermore, the activities of antioxidant enzymes in rhizobia-inoculated plants were significantly higher in the GM + 4105 group than the 4083 + GM group. The malondialdehyde content of plants from the 4105 + GM group was significantly lower than in the 4083 + GM group. Thus, the results revealed a synergistic relationship among the 4105 and GM in alleviating salt stress in S. cannabina. Salt-tolerant rhizobia might improve the salinity tolerance of S. cannabina by enhancing the antioxidant system.     

Indigenous salt-tolerant rhizobacterium <Emphasis Type="Italic">Pantoea dispersa</Emphasis> (PSB3) reduces sodium uptake and mitigates the effects of salt stress on growth and yield of chickpea

Salt stress has multiple damaging effects on plants including physiological damage, reduced growth, and productivity. Plant growth-promoting rhizobacteria (PGPR) are one of the valuable options to mitigate the negative effects of this stress. In the present study, native bacteria from chickpea’s rhizosphere were isolated, and checked for their salt tolerance and plant growth-promoting attributes (phosphate (P) solubilization, siderophores, indole-3-acetic acid (IAA) production, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase production). One isolate, subsequently identified as Pantoea dispersa, showed appreciable production of IAA (218.3 µg/ml) and siderophores (60.33% SU), P-solubilization (3.64 µg/ml) and ACC deaminase activity (207.45 nmol/mg/h) in the presence of 150 mM NaCl, under laboratory conditions. Salt stress in uninoculated chickpea (GPF2 cultivar) plants induced high accumulation of Na⁺ ions (3.86 mg g^?1 dw) in the leaves, along with significant reduction in K⁺ uptake, membrane integrity, chlorophyll concentration, and leaf water content, thus resulting in impaired growth of the plant and yield (pods and seeds) in a salt concentration-dependent manner. The damage due to salt stress was restored significantly in plants inoculated with P. dispersa. A significant improvement in biomass (32–34%), pods number (31–34.5%), seeds number (32–35.7%), pods weight (30–32.6%), and seeds weight (27–35%) per plant occurred in salt stress-affected plants, which was associated with significant reduction in Na⁺ uptake, reduced membrane damage, significantly improved leaf water content, chlorophyll content, and K⁺ uptake. This study suggests for the first time that native P. dispersa strain PSB3 can be used to alleviate the negative effects of salt stress on chickpea plants and holds the potential to be used as a biofertilizer.     

盐胁迫下花生种子萌发期代谢组学分析

盐碱地高盐分会降低种子活力、抑制萌发出苗,严重制约盐碱地区花生生产和产业发展。种子萌发过程中物质代谢对种子发芽及植株形态建成至关重要,逐渐成为评价种子活力和品质的重要指标。以不同萌发期花生种子为研究对象,利用生理指标和高效液相色谱串联质谱（LC-MS/MS）分析方法,研究了盐胁迫下花生种子不同萌发期主要营养物质含量和差异代谢物的变化。种子吸水萌发促进了脂肪、蛋白质、可溶性糖代谢,随萌发时间延长,脂肪和可溶性糖含量逐渐降低,可溶性蛋白质含量呈先降后升的变化趋势。主成分分析和偏最小二乘法判别分析表明盐胁迫与对照组间代谢物差异较大,暗示盐胁迫对花生种子萌发期物质代谢影响较大。利用VIP值分析和KEGG pathway预测分析显示：正常条件下,花生种子吸水膨胀期的差异代谢物较少,未鉴定到富集的KEGG pathway;而胚根伸长期差异代谢物主要富集于12个KEGG pathway,表明萌发后期物质代谢较前期旺盛。盐处理显著提高多种差异代谢物表达水平,其中渗透保护物甜菜碱和脯氨酸差异明显;另外,盐胁迫下吸水膨胀和胚根伸长两时段的差异代谢物显著增多,分别富集到26和31个KEGG pathway。盐胁迫显著促进了能量代谢、甘油磷脂代谢、谷胱甘肽代谢以及芥子油苷生物合成途径等相关通路,推测其与盐胁迫下花生种子萌发期抗逆有关。甜菜碱和脯氨酸可能是花生种子萌发期适应盐胁迫的关键代谢物,甘油磷脂代谢、谷胱甘肽代谢以及芥子油苷生物合成等途径可能是重要的代谢调控通路。试验结果可为促进盐胁迫下花生种子萌发出苗探索新途径、新方法,以及提高盐碱地花生出苗率提供理论依据和参考价值。     

Transcriptome Analysis of the Heritable Salt Tolerance of Prairie Cordgrass (<Emphasis Type="Italic">Spartina pectinata Link</Emphasis>)

The salt-tolerant capability of the candidate bioenergy crop prairie cordgrass greatly surpasses that of previously characterized prairie grass species and most other plants. To understand the mechanism of inherited salt tolerance, we compared phenotypic and genetic qualities in half-sib families of prairie cordgrass after salt treatment. Each family was treated with a 400 mM NaCl solution or a water control and then measured for various health phenotypes. Phenotypes associated with salt tolerance were shown to be moderately heritable between parent and offspring. RNA-seq analysis revealed differential regulation in unique pathways including metabolism, signaling, photosynthesis, and the circadian rhythm. The studies herein suggest that alternative regulation of the photosynthetic pathway could confer increased salt resistance in halophytes and can be monitored phenotypically or genetically in breeding programs. The improvement of salt-tolerant traits in prairie cordgrass would increase its potential to be grown as a bioenergy crop on lands that are not suitable for the growth of food crops.     

Photosynthetic physiological performance and proteomic profiling of the oleaginous algae <Emphasis Type="Italic">Scenedesmus acuminatus</Emphasis> reveal the mechanism of lipid accumulation under low and high nitrogen supplies

In this study, we presented cellular morphological changes, time-resolved biochemical composition, photosynthetic performance and proteomic profiling to capture the photosynthetic physiological response of Scenedesmus acuminatus under low nitrogen (3.6 mM NaNO₃, N^?) and high nitrogen supplies (18.0 mM NaNO₃, N⁺). S. acuminatus cells showed extensive lipid accumulation (53.7% of dry weight) and were enriched in long-chain fatty acids (C16 & C18) under low nitrogen supply. The activity of PSII and photosynthetic rate decreases, whereas non-photochemical quenching and dark respiration rates were increased in the N^? group. In addition, the results indicated a redistribution of light excitation energy between PSII and PSI in S. acuminatus exists before lipid accumulation. The iTRAQ results showed that, under high nitrogen supply, protein abundance of the chlorophyll biosynthesis, the Calvin cycle and ribosomal proteins decreased in S. acuminatus. In contrast, proteins associated with the photosynthetic machinery, except for F-type ATPase, were increased in the N⁺ group (N⁺, 3 vs. 9 days and 3 days, N⁺ vs. N^?). Under low nitrogen supply, proteins involved in central carbon metabolism, fatty acid synthesis and branched-chain amino acid metabolism were increased, whereas the abundance of proteins of the photosynthetic machinery had decreased, with exception of PSI (N^?, 3 vs. 9 days and 9 days, N⁺ vs. N^?). Collectively, the current study has provided a basis for the metabolic engineering of S. acuminatus for biofuel production.     

Effect of varying NaCl doses on flavonoid production in suspension cells of Ginkgo biloba: relationship to chlorophyll fluorescence,ion homeostasis,antioxidant system and ultrastructure

Ginkgo suspension cells were used to investigate the mechanism that governs the shift between primary and secondary metabolism under NaCl elicitation. The production of three flavonol glycosides, chlorophyll fluorescence, ion content, the antioxidant system, and the cellular ultrastructure in the presence of NaCl doses from 5 to 175 mM were examined. At low salt doses (5–50 mM), cell growth and flavonol glycosides accumulation were stimulated without damaging cell structure or inducing oxidative stress by maintaining high K⁺ and chlorophyll content. At moderate salt doses (75–125 mM), the cells could withstand the salt stress without an impact on survival by changing internal cellular structure, maintaining high levels of K⁺ and Ca²⁺ and increasing anti-oxidative enzyme activities rather than flavonol glycosides to counteract the inhibition of the photosystem II, the accumulation of Na⁺ and hydrogen peroxide (H₂O₂) in the cells. This allowed cells to divert their metabolism from growth to defense-related pathways and tolerate NaCl stress. At higher salinity (150–175 mM), the cellular structure was damaged, and the high Na⁺ and low K⁺ content led to osmotic stress, and therefore, the stimulation of peroxidase (POD) and catalase (CAT) was not enough to cope with high H₂O₂ accumulation. The high production of flavonol glycosides may be a response of elicitation stimulation to serious damage at 175 mM NaCl. In conclusion, the use of 175 mM NaCl may be desirable for the induction of flavonol glycoside production in Ginkgo suspension cells.     

海绵体动物中trans-AT聚酮合成酶来源的聚酮化合物的生物合成

海绵体动物分离到的聚酮类化合物很多是由其共生或附生微生物体内的trans-AT聚酮合成酶催化产生的。利用宏基因组技术克隆具有生物活性的聚酮化合物的生物合成基因簇,不但能阐明活性化合物的生物合成路径,而且可以通过异源表达获得目标化合物。本文综述了海绵体动物来源的trans-AT聚酮合成酶产生的聚酮化合物生物合成及其基因簇的研究进展。     

Arbuscular mycorrhiza and salt tolerance of plants

Although salt has detrimental effects on spore germination of arbuscular mycorrhizal fungi (AMF), their hyphal growth and the colonization rate of plants under laboratory conditions, many salt tolerant plants (the halophytes) are strongly colonized by AMF in their natural habitats. AMF spores in several saline soils consist of to up to 80 % of one single species, Glomus geosporum. In contrast, roots of halophytes are mostly colonized by fungi of the Glomus intraradices group, of which many are as yet uncultured. Salt stress is intimately related to drought in saline habitats. Molecular analyses of genes expressed upon salt stress indicate that aquaporins which facilitate the transfer of water across membranes play a major role in alleviating salt stress in plants. In AMF, genes serving to scavenge reactive oxygen species (ROS) are expressed upon exposure to salt, indicating that fungi have to develop an enhanced oxidative defence. The development of AMF inocula that confer sustained salt tolerance to plants would have enormous practical applications. Many positive reports on salt stress alleviation by AMF exist. However, the state of the art has not yet reached field applications. In contrast to other recent reviews, the present article focuses on ecological aspects of the symbiosis between AMF and halophytes. It also emphasizes the complexity of the interactions between salt and drought stress as well as the role of AMF in alleviating salt stress.     

Characterization of salt stress-enhanced phosphoenolpyruvate carboxylase kinase activity in leaves of <Emphasis Type="Italic">Sorghum</Emphasis><Emphasis Type="Italic">vulgare</Emphasis>: independence from osmotic stress,involvement of ion toxicity and significance of dark phosphorylation

C(4) phosphoenolpyruvate carboxylase (PEPCase: EC 4.1.1.31) is subjected to in vivo regulatory phosphorylation by a light up-regulated, calcium-independent protein kinase. Salt stress greatly enhanced phosphoenolpyruvate carboxylase-kinase (PEPCase-k) activity in leaves of Sorghum. The increase in PEPCase-k anticipated the time course of proline accumulation thereby suggesting that water stress was not involved in the kinase response to salt. Moreover, osmotic stress seemed not to be the main factor implicated, as demonstrated by the lack of effect when water availability was restricted by mannitol. In contrast, LiCl (at a concentration of 10 mM in short-term treatment of both excised leaves and whole plants) mimicked the effects of 172 mM NaCl salt-acclimation, indicating that the rise in PEPCase-k activity resulted primarily from the ionic stress. Both NaCl and LiCl treatments increased the activity of a Ca(2+)-independent, 35 kDa kinase, as demonstrated by an in-gel phosphorylation experiment. Short-term treatment of excised leaves with NaCl or LiCl partially reproduces the effects of whole plant treatments. Finally, salinization also increased PEPCase-k activity and the phosphorylation state of PEPCase in darkened Sorghum leaves. This fact, together with increased malate production during the dark period, suggests a shift towards mixed C(4) and crassulacean acid metabolism types of photosynthesis in response to salt stress.     

Phytochrome-mediated Carotenoids Biosynthesis in Ripening Tomatoes

Red light induced and far red light inhibited carotenoid biosynthesis in ripening tomatoes (Lycopersicon esculentum Mill.) when compared to controls kept in the dark. Red illumination following far red illumination reversed the inhibitory action of far red light on carotenoid biosynthesis, suggesting a phytochrome-mediated process. Quantitation of individual carotenoids favored the hypothesis of two separate carotenoid biosynthetic pathways in tomatoes.